Add OIDC back-channel logout with session indexes

- Add a uv workspace at the repository root covering all packages/kaya-* members
- Replace pip-compile requirements files with a committed uv.lock
- Remove redundant per-package dev extras
- Build and publish artifacts with uv build and uv publish in CI
- Update the README with uv sync/run/build commands

.gitea/workflows/build.yaml

@@ -5,7 +5,7 @@ on:
       - 'release/*'
 jobs:
   build_pip_package:
-    name: "Build Pip package"
+    name: "Build and publish packages"
     runs-on: hostinger
     timeout-minutes: 30
     container:
@@ -18,12 +18,14 @@ jobs:
           fetch-tags: true
       - uses: actions/setup-python@v6
         with:
-          python-version: '3.14.6' 
+          python-version-file: '.python-version'
-          cache: 'pip'
+      - name: Install uv
+        uses: astral-sh/setup-uv@v10
+        with:
+          version: '0.13.4'
+          enable-cache: true
       - name: Install dependencies
-        run: |
+        run: uv sync --locked
-          python -m venv .venv
-          .venv/bin/pip install -r requirements-dev.txt
       - name: Check kaya-core
         run: |
           .venv/bin/python -m mypy -p kaya.core
@@ -48,51 +50,99 @@ jobs:
         run: |
           .venv/bin/python -m mypy -p kaya.oidc
           .venv/bin/python -m unittest discover -s packages/kaya-oidc/tests
+      - name: Check kaya-openapi
+        run: |
+          .venv/bin/python -m mypy -p kaya.openapi
+          .venv/bin/python -m unittest discover -s packages/kaya-openapi/tests
+      - name: Check kaya-cors
+        run: |
+          .venv/bin/python -m mypy -p kaya.cors
+          .venv/bin/python -m unittest discover -s packages/kaya-cors/tests
+      - name: Check kaya-forwarded
+        run: |
+          .venv/bin/python -m mypy -p kaya.forwarded
+          .venv/bin/python -m unittest discover -s packages/kaya-forwarded/tests
+      - name: Check kaya-otel
+        run: |
+          .venv/bin/python -m mypy -p kaya.otel
+          .venv/bin/python -m unittest discover -s packages/kaya-otel/tests
       - name: Publish kaya-core artifacts
         env:
-          TWINE_REPOSITORY_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
-          TWINE_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
-          TWINE_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
         run: |
-          .venv/bin/pyproject-build packages/kaya-core
+          uv build --package kaya-core --out-dir packages/kaya-core/dist --no-sources
-          .venv/bin/twine upload --repository gitea packages/kaya-core/dist/*.whl packages/kaya-core/dist/*.tar.gz
+          uv publish packages/kaya-core/dist/*.whl packages/kaya-core/dist/*.tar.gz
       - name: Publish kaya-rsgi artifacts
         env:
-          TWINE_REPOSITORY_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
-          TWINE_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
-          TWINE_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
         run: |
-          .venv/bin/pyproject-build packages/kaya-rsgi
+          uv build --package kaya-rsgi --out-dir packages/kaya-rsgi/dist --no-sources
-          .venv/bin/twine upload --repository gitea packages/kaya-rsgi/dist/*.whl packages/kaya-rsgi/dist/*.tar.gz
+          uv publish packages/kaya-rsgi/dist/*.whl packages/kaya-rsgi/dist/*.tar.gz
       - name: Publish kaya-session artifacts
         env:
-          TWINE_REPOSITORY_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
-          TWINE_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
-          TWINE_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
         run: |
-          .venv/bin/pyproject-build packages/kaya-session
+          uv build --package kaya-session --out-dir packages/kaya-session/dist --no-sources
-          .venv/bin/twine upload --repository gitea packages/kaya-session/dist/*.whl packages/kaya-session/dist/*.tar.gz
+          uv publish packages/kaya-session/dist/*.whl packages/kaya-session/dist/*.tar.gz
       - name: Publish kaya-session-memcache artifacts
         env:
-          TWINE_REPOSITORY_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
-          TWINE_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
-          TWINE_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
         run: |
-          .venv/bin/pyproject-build packages/kaya-session-memcache
+          uv build --package kaya-session-memcache --out-dir packages/kaya-session-memcache/dist --no-sources
-          .venv/bin/twine upload --repository gitea packages/kaya-session-memcache/dist/*.whl packages/kaya-session-memcache/dist/*.tar.gz
+          uv publish packages/kaya-session-memcache/dist/*.whl packages/kaya-session-memcache/dist/*.tar.gz
       - name: Publish kaya-session-redis artifacts
         env:
-          TWINE_REPOSITORY_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
-          TWINE_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
-          TWINE_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
         run: |
-          .venv/bin/pyproject-build packages/kaya-session-redis
+          uv build --package kaya-session-redis --out-dir packages/kaya-session-redis/dist --no-sources
-          .venv/bin/twine upload --repository gitea packages/kaya-session-redis/dist/*.whl packages/kaya-session-redis/dist/*.tar.gz
+          uv publish packages/kaya-session-redis/dist/*.whl packages/kaya-session-redis/dist/*.tar.gz
       - name: Publish kaya-oidc artifacts
         env:
-          TWINE_REPOSITORY_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
-          TWINE_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
-          TWINE_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
         run: |
-          .venv/bin/pyproject-build packages/kaya-oidc
+          uv build --package kaya-oidc --out-dir packages/kaya-oidc/dist --no-sources
-          .venv/bin/twine upload --repository gitea packages/kaya-oidc/dist/*.whl packages/kaya-oidc/dist/*.tar.gz
+          uv publish packages/kaya-oidc/dist/*.whl packages/kaya-oidc/dist/*.tar.gz
+      - name: Publish kaya-openapi artifacts
+        env:
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+        run: |
+          uv build --package kaya-openapi --out-dir packages/kaya-openapi/dist --no-sources
+          uv publish packages/kaya-openapi/dist/*.whl packages/kaya-openapi/dist/*.tar.gz
+      - name: Publish kaya-cors artifacts
+        env:
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+        run: |
+          uv build --package kaya-cors --out-dir packages/kaya-cors/dist --no-sources
+          uv publish packages/kaya-cors/dist/*.whl packages/kaya-cors/dist/*.tar.gz
+      - name: Publish kaya-forwarded artifacts
+        env:
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+        run: |
+          uv build --package kaya-forwarded --out-dir packages/kaya-forwarded/dist --no-sources
+          uv publish packages/kaya-forwarded/dist/*.whl packages/kaya-forwarded/dist/*.tar.gz
+      - name: Publish kaya-otel artifacts
+        env:
+          UV_PUBLISH_URL: ${{ vars.PYPI_REGISTRY_URL }}
+          UV_PUBLISH_USERNAME: ${{ vars.PUBLISHER_USERNAME }}
+          UV_PUBLISH_PASSWORD: ${{ secrets.PUBLISHER_TOKEN }}
+        run: |
+          uv build --package kaya-otel --out-dir packages/kaya-otel/dist --no-sources
+          uv publish packages/kaya-otel/dist/*.whl packages/kaya-otel/dist/*.tar.gz

.python-version

@@ -0,0 +1 @@
+3.14.6

README.md

@@ -12,58 +12,70 @@ This repository is a monorepo for the Kaya framework. The code is split into ind
 - **kaya-session-redis** — Redis-backed session storage (`packages/kaya-session-redis/`)
 - **kaya-session-memcache** — memcached-backed session storage (`packages/kaya-session-memcache/`)
 - **kaya-oidc** — OpenID Connect authentication (`packages/kaya-oidc/`)
+- **kaya-openapi** — automatic OpenAPI specification generation (`packages/kaya-openapi/`)
+- **kaya-cors** — CORS (Cross-Origin Resource Sharing) support (`packages/kaya-cors/`)
+- **kaya-forwarded** — trusted-proxy `Forwarded`/`X-Forwarded-*` client address resolution (`packages/kaya-forwarded/`)
+- **kaya-otel** — OpenTelemetry tracing and metrics (`packages/kaya-otel/`)
 
-Additional `kaya-*` packages can be added as new directories under `packages/`.
+Additional `kaya-*` packages can be added as new directories under `packages/`. When adding a new package, also add it to the root `pyproject.toml` dependencies and `[tool.uv.sources]` so `uv sync` installs it.
 
 ## Build & run locally
 
-Install dev dependencies:
+This project uses [uv](https://docs.astral.sh/uv/) for dependency management. From the repository root:
 
 ```bash
-pip install --index-url https://gitea.woggioni.net/api/packages/woggioni/pypi/simple --extra-index-url https://pypi.org/simple -r requirements-dev.txt
+uv sync
 ```
 
-Install the packages in development mode:
+This creates `.venv`, installs all workspace packages in editable mode, and installs the dev dependency group from `uv.lock`. Use `uv lock` after changing dependencies, and commit the updated `uv.lock`.
-
-```bash
-pip install -e packages/kaya-core -e packages/kaya-rsgi -e packages/kaya-session -e packages/kaya-session-redis -e packages/kaya-session-memcache -e packages/kaya-oidc
-```
 
 Run the example:
 
 ```bash
-python example/hello.py
+uv run python example/hello.py
 ```
 
 ## Tests
 
 ```bash
-python -m unittest discover -s packages/kaya-core/tests
+uv run python -m unittest discover -s packages/kaya-core/tests
-python -m unittest discover -s packages/kaya-rsgi/tests
+uv run python -m unittest discover -s packages/kaya-rsgi/tests
-python -m unittest discover -s packages/kaya-session/tests
+uv run python -m unittest discover -s packages/kaya-session/tests
-python -m unittest discover -s packages/kaya-session-redis/tests
+uv run python -m unittest discover -s packages/kaya-session-redis/tests
-python -m unittest discover -s packages/kaya-session-memcache/tests
+uv run python -m unittest discover -s packages/kaya-session-memcache/tests
-python -m unittest discover -s packages/kaya-oidc/tests
+uv run python -m unittest discover -s packages/kaya-oidc/tests
+uv run python -m unittest discover -s packages/kaya-openapi/tests
+uv run python -m unittest discover -s packages/kaya-cors/tests
+uv run python -m unittest discover -s packages/kaya-forwarded/tests
+uv run python -m unittest discover -s packages/kaya-otel/tests
 ```
 
 ## Static analysis
 
 ```bash
-mypy -p kaya.core
+uv run mypy -p kaya.core
-mypy -p kaya.rsgi
+uv run mypy -p kaya.rsgi
-mypy -p kaya.session
+uv run mypy -p kaya.session
-mypy -p kaya.session_redis
+uv run mypy -p kaya.session.redis
-mypy -p kaya.session_memcache
+uv run mypy -p kaya.session.memcache
-mypy -p kaya.oidc
+uv run mypy -p kaya.oidc
+uv run mypy -p kaya.openapi
+uv run mypy -p kaya.cors
+uv run mypy -p kaya.forwarded
+uv run mypy -p kaya.otel
 ```
 
 ## Building packages
 
 ```bash
-python -m build packages/kaya-core
+uv build --package kaya-core --out-dir packages/kaya-core/dist
-python -m build packages/kaya-rsgi
+uv build --package kaya-rsgi --out-dir packages/kaya-rsgi/dist
-python -m build packages/kaya-session
+uv build --package kaya-session --out-dir packages/kaya-session/dist
-python -m build packages/kaya-session-redis
+uv build --package kaya-session-redis --out-dir packages/kaya-session-redis/dist
-python -m build packages/kaya-session-memcache
+uv build --package kaya-session-memcache --out-dir packages/kaya-session-memcache/dist
-python -m build packages/kaya-oidc
+uv build --package kaya-oidc --out-dir packages/kaya-oidc/dist
+uv build --package kaya-openapi --out-dir packages/kaya-openapi/dist
+uv build --package kaya-cors --out-dir packages/kaya-cors/dist
+uv build --package kaya-forwarded --out-dir packages/kaya-forwarded/dist
+uv build --package kaya-otel --out-dir packages/kaya-otel/dist
 ```

example/openapi.py

@@ -0,0 +1,32 @@
+from kaya.core import HttpContext, KayaApp
+from kaya.openapi import OpenAPIMixin, operation
+
+app = KayaApp(mixins=[OpenAPIMixin(
+    title='Greeting API',
+    version='1.0.0',
+    description='Example API documented with kaya-openapi',
+)])
+
+
+@app.GET('/hello')
+async def hello(ctx: HttpContext) -> None:
+    """Say hello to the world."""
+    await ctx.send_str(200, 'Hello World')
+
+
+@app.GET('/hello/${name}')
+@operation(summary='Greet someone',
+           tags=['greetings'],
+           responses={200: {'description': 'A personalized greeting'}})
+async def hello_name(ctx: HttpContext, name: str) -> None:
+    await ctx.send_str(200, f'Hello {name}')
+
+
+@app.GET('/square/${x:int}')
+@operation(summary='Compute the square of a number', tags=['math'])
+async def square(ctx: HttpContext, x: int) -> None:
+    await ctx.send_str(200, str(x * x))
+
+# serve with an ASGI/RSGI server, e.g.:
+#   granian --interface rsgi example.openapi:app
+# then open http://localhost:8000/docs to browse the API

packages/kaya-core/pyproject.toml

@@ -26,11 +26,6 @@ dependencies = [
     "typing-extensions",
 ]
 
-[project.optional-dependencies]
-dev = [
-    "build", "mypy", "ipdb", "twine", "httpx", "httpx-ws"
-]
-
 [project.urls]
 "Homepage" = "https://github.com/woggioni/kaya"
 "Bug Tracker" = "https://github.com/woggioni/kaya/issues"

packages/kaya-core/src/kaya/core/__init__.py

@@ -4,7 +4,7 @@ from ._http_context import HttpContext
 from ._mixin import KayaMixin
 from ._tree import Tree, PathIterator
 from ._path_handler import PathHandler, Matches
-from ._websocket import WebSocket, WebSocketMessage
+from ._websocket import WebSocket, WebSocketDisconnect, WebSocketMessage
 
 
 __all__ = [
@@ -18,5 +18,6 @@ __all__ = [
     'Matches',
     'PathIterator',
     'WebSocket',
+    'WebSocketDisconnect',
     'WebSocketMessage'
 ]

packages/kaya-core/src/kaya/core/_app.py

@@ -9,7 +9,7 @@ from ._http_method import HttpMethod
 from ._mixin import KayaMixin
 from ._path_handler import Context
 from ._types import StrOrStrings
-from ._websocket import WebSocket, WebSocketMessage
+from ._websocket import WebSocket, WebSocketDisconnect, WebSocketMessage
 from ._asgi import AsgiContext, AsgiWebSocket
 from ._tree import Tree
 from ._types.asgi import LifespanScope, HTTPScope as ASGIHTTPScope, WebSocketScope as ASGIWebSocketScope
@@ -145,6 +145,9 @@ class KayaApp(AbstractKayaApp):
                 await handler.handle_request(ctx, captured)
             else:
                 await ctx.send_empty(404)
+        except Exception as exc:
+            ctx.exception = exc
+            raise
         finally:
             for hook in reversed(self._after_request_hooks):
                 await hook(ctx)
@@ -161,6 +164,15 @@ class KayaApp(AbstractKayaApp):
                 await handler.handle_request(ws, captured)
             else:
                 await ws.close(1000)
+        except WebSocketDisconnect:
+            # The peer went away while the handler was using the websocket
+            # (e.g. sending on a vanished transport). This is normal
+            # termination, not an application error, so it is not recorded
+            # on the socket nor re-raised.
+            pass
+        except Exception as exc:
+            ws.exception = exc
+            raise
         finally:
             for hook in reversed(self._after_websocket_hooks):
                 await hook(ws)
@@ -173,6 +185,10 @@ class KayaApp(AbstractKayaApp):
         for mixin in self._mixins:
             mixin.shutdown(loop)
 
+    def route_template(self, url: str, method: HttpMethod = HttpMethod.GET) -> Optional[str]:
+        """Return the registered route template that would handle ``url``."""
+        return self._tree.route_template(url, method)
+
     def route(self,
               paths: StrOrStrings,
               methods: Optional[HttpMethod | Sequence[HttpMethod]] = None,

packages/kaya-core/src/kaya/core/_asgi.py

@@ -17,7 +17,7 @@ from pwo import Maybe
 from pathlib import Path
 from ._http_method import HttpMethod
 from ._http_context import HttpContext
-from ._websocket import WebSocket, WebSocketMessage
+from ._websocket import WebSocket, WebSocketDisconnect, WebSocketMessage
 from ._types import StrOrStrings
 from ._types.asgi import HTTPScope, WebSocketScope
 
@@ -179,7 +179,16 @@ class AsgiWebSocket(WebSocket):
             # Emit a list rather than a tuple: wsproto's AcceptConnection (used
             # by httpx_ws and others) requires list concatenation.
             message['headers'] = list(encode_headers(headers))
-        await self._send(message)
+        await self._send_message(message)
+
+    async def _send_message(self, message: Mapping[str, Any]) -> None:
+        try:
+            await self._send(message)
+        except OSError as exc:
+            # ASGI servers (e.g. uvicorn) report a vanished peer with an
+            # OSError subclass; surface it as a kaya-level disconnect so
+            # handlers do not need to know about server internals.
+            raise WebSocketDisconnect(code=1006) from exc
 
     async def receive(self) -> WebSocketMessage:
         message = await self._receive()
@@ -200,13 +209,13 @@ class AsgiWebSocket(WebSocket):
             return WebSocketMessage(kind='close')
 
     async def send_text(self, data: str) -> None:
-        await self._send({'type': 'websocket.send', 'text': data})
+        await self._send_message({'type': 'websocket.send', 'text': data})
 
     async def send_bytes(self, data: bytes) -> None:
-        await self._send({'type': 'websocket.send', 'bytes': data})
+        await self._send_message({'type': 'websocket.send', 'bytes': data})
 
     async def close(self, code: int = 1000) -> None:
-        await self._send({'type': 'websocket.close', 'code': code})
+        await self._send_message({'type': 'websocket.close', 'code': code})
 
     async def __anext__(self) -> WebSocketMessage:
         message = await self.receive()

packages/kaya-core/src/kaya/core/_http_context.py

@@ -29,6 +29,7 @@ class HttpContext(ABC):
     server: Optional[Tuple[str, Optional[int]]]
     request_body: AsyncIterator[bytes]
     session: Optional[Any] = None
+    exception: Optional[BaseException] = None
 
     @abstractmethod
     async def stream_body(self,

packages/kaya-core/src/kaya/core/_mixin.py

@@ -29,9 +29,22 @@ class KayaMixin(ABC):
         pass
 
     def setup(self, loop: AbstractEventLoop) -> None:
-        """Called on lifespan startup (default: no-op)."""
+        """Called on lifespan startup (default: no-op).
+
+        Under RSGI (granian) the loop is NOT yet running when this is
+        called: schedule work on the passed ``loop`` (e.g.
+        ``loop.create_task``) instead of calling
+        ``asyncio.get_running_loop()``, which raises ``RuntimeError``
+        there. Under ASGI the lifespan runs inside a coroutine, so a
+        running loop happens to be available — do not rely on that.
+        """
         pass
 
     def shutdown(self, loop: AbstractEventLoop) -> None:
-        """Called on lifespan shutdown (default: no-op)."""
+        """Called on lifespan shutdown (default: no-op).
+
+        As with :meth:`setup`, use the passed ``loop``; it may already be
+        stopped under RSGI, so ``asyncio.get_running_loop()`` is not
+        reliable here either.
+        """
         pass

packages/kaya-core/src/kaya/core/_tree.py

@@ -92,6 +92,16 @@ class Tree:
                 result = child
         key = leaf
         while key is not None:
+            existing = self._find_equivalent_matcher(result, key)
+            if existing is not None:
+                result = existing
+                key = next(it, None)
+                continue
+            child = result.children.get(key)
+            if child is not None:
+                result = child
+                key = next(it, None)
+                continue
             new_node = self.parse(key, result)
             if isinstance(new_node, Node):
                 result.children[key] = new_node
@@ -109,6 +119,44 @@ class Tree:
     def _supports_method(node: Node | PathMatcher, method: HttpMethod) -> bool:
         return None in node.supported_methods or method in node.supported_methods
 
+    @staticmethod
+    def _matcher_identity(leaf: str) -> Optional[Tuple[str, str]]:
+        start = index_of_with_escape(leaf, '${', '\\', 0)
+        if start >= 0:
+            start += 2
+            end = leaf.index('}', start + 2)
+            definition = leaf[start:end]
+            try:
+                colon = definition.index(':')
+            except ValueError:
+                colon = None
+            if colon is None:
+                name = definition
+                kind = 'str'
+            else:
+                name = definition[:colon]
+                kind = definition[colon + 1:]
+            if kind not in ('str', 'int'):
+                raise ValueError(f"Unknown kind: '{kind}'")
+            return (kind, name)
+        if index_of_with_escape(leaf, '*', '\\', 0) >= 0:
+            return ('glob', leaf)
+        return None
+
+    def _find_equivalent_matcher(self, node: Node | PathMatcher, leaf: str) -> Optional[PathMatcher]:
+        identity = self._matcher_identity(leaf)
+        if identity is None:
+            return None
+        kind, key = identity
+        for existing in node.path_matchers:
+            if kind == 'str' and isinstance(existing, StrMatcher) and existing.name == key:
+                return existing
+            if kind == 'int' and isinstance(existing, IntMatcher) and existing.name == key:
+                return existing
+            if kind == 'glob' and isinstance(existing, GlobMatcher) and existing.pattern == key:
+                return existing
+        return None
+
     def _check_matcher_conflict(self, node: Node | PathMatcher, method: Optional[HttpMethod]) -> None:
         new_is_generic = method is None
         for existing in node.path_matchers:
@@ -138,16 +186,27 @@ class Tree:
                  callback: Callable[[Context, Unpack[Any]], Awaitable[None]],
                  recursive: bool) -> None:
         class Handler(PathHandler):
+            """PathHandler created by :meth:`Tree.register`.
+
+            The original user callback is exposed through the ``callback``
+            attribute so that extensions (e.g. ``kaya-openapi``) can inspect
+            it for metadata such as docstrings or decorator attributes.
+            """
+
+            callback: Callable[[Context, Unpack[Any]], Awaitable[None]]
 
             async def handle_request(self, ctx: Context, captured: Matches) -> None:
                 args = Maybe.of_nullable(captured.path).map(lambda it: [it]).or_else([])
-                await callback(ctx, *args, **captured.kwargs)
+                await self.callback(ctx, *args, **captured.kwargs)
 
             @property
             def recursive(self) -> bool:
                 return recursive
 
         handler = Handler()
+        # assigned as an instance attribute (not a class attribute) so that
+        # the function descriptor protocol does not turn it into a bound method
+        handler.callback = callback
         self.add((p for p in PathIterator(path)), method, handler)
 
     def find_node(self, path: Generator[str, None, None], method: HttpMethod = HttpMethod.GET) \
@@ -178,6 +237,37 @@ class Tree:
             #     return (handler, unmatched)
         return None
 
+    def route_template(self, url: str, method: HttpMethod = HttpMethod.GET) -> Optional[str]:
+        """Return the registered route template that would handle ``url``.
+
+        Static segments are returned verbatim, ``${name}``/``${name:int}``
+        parameter matchers are reconstructed from the matched nodes, and glob
+        matchers keep their pattern. Returns ``None`` when no route (including
+        recursive fallback routes) would handle the request.
+        """
+        result = self.find_node((p for p in PathIterator(urlparse(url).path)), method)
+        if result is None:
+            return None
+        node, captured = result
+        if len(captured.unmatched_paths) > 0 and not any(handler.recursive for handler in node.handlers):
+            return None
+
+        parts: List[str] = []
+        current: Optional[Node | PathMatcher] = node
+        while current is not None:
+            if isinstance(current, Node):
+                key = current.key
+                if not isinstance(key, HttpMethod) and key != '/':
+                    parts.append(str(key))
+            elif isinstance(current, IntMatcher):
+                parts.append('${%s:int}' % current.name)
+            elif isinstance(current, StrMatcher):
+                parts.append('${%s}' % current.name)
+            elif isinstance(current, GlobMatcher):
+                parts.append(current.pattern)
+            current = current.parent
+        return '/' + '/'.join(reversed(parts)) if parts else '/'
+
     def parse(self, leaf: str, parent: Optional[Node | PathMatcher]) -> Node | PathMatcher:
         start = 0
         result = index_of_with_escape(leaf, '${', '\\', 0)

packages/kaya-core/src/kaya/core/_websocket.py

@@ -13,6 +13,41 @@ class WebSocketMessage:
     data: WebSocketData = None
 
 
+class WebSocketDisconnect(Exception):
+    """Raised when using a websocket whose peer has disconnected.
+
+    Concrete websocket implementations raise this from ``send_text()`` and
+    ``send_bytes()`` when the transport reports that the peer is gone (for
+    example when a browser tab is closed without a close handshake), so
+    handlers can catch it and stop producing output:
+
+    .. code-block:: python
+
+        try:
+            await ws.send_text('hello')
+        except WebSocketDisconnect:
+            pass
+
+    Reading from a disconnected websocket is not an error: ``receive()``
+    reports a ``close`` message and iterating with ``async for`` simply ends,
+    which is what most handlers should rely on instead.
+
+    ``code`` is a websocket close code; ``1006`` means the connection was
+    closed abnormally, without a close handshake.
+    """
+
+    code: int
+    reason: str
+
+    def __init__(self, code: int = 1006, reason: str = '') -> None:
+        self.code = code
+        self.reason = reason
+        message = f'WebSocket disconnected (code={code})'
+        if reason:
+            message = f'{message}: {reason}'
+        super().__init__(message)
+
+
 class WebSocket(ABC):
     path: str
     query_string: str
@@ -21,6 +56,7 @@ class WebSocket(ABC):
     client: Optional[Tuple[str, int]]
     server: Optional[Tuple[str, Optional[int]]]
     session: Optional[Any] = None
+    exception: Optional[BaseException] = None
 
     @abstractmethod
     async def accept(self, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:

packages/kaya-core/tests/test_asgi.py

@@ -190,3 +190,92 @@ class AsgiTest(unittest.TestCase):
                 'employee_id': 101325
             }, response)
 
+    @async_test
+    async def test_nested_param_routes(self):
+        app = KayaApp()
+
+        @app.GET('/restaurants/${id}')
+        async def restaurant(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"restaurant:{id}")
+
+        @app.GET('/restaurants/${id}/menu')
+        async def menu(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"menu:{id}")
+
+        transport = httpx.ASGITransport(app=app)
+
+        async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as client:
+            r = await client.get("/restaurants/42")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("restaurant:42", r.text)
+
+            r = await client.get("/restaurants/42/menu")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("menu:42", r.text)
+
+            r = await client.get("/restaurants/42/unknown")
+            self.assertEqual(404, r.status_code)
+
+    @async_test
+    async def test_nested_param_routes_multiple_methods(self):
+        app = KayaApp()
+
+        @app.GET('/restaurants/${id}')
+        async def restaurant(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"restaurant:{id}")
+
+        @app.GET('/restaurants/${id}/menu')
+        async def menu_get(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"menu_get:{id}")
+
+        @app.POST('/restaurants/${id}/menu')
+        async def menu_post(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"menu_post:{id}")
+
+        transport = httpx.ASGITransport(app=app)
+
+        async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as client:
+            r = await client.get("/restaurants/42")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("restaurant:42", r.text)
+
+            r = await client.get("/restaurants/42/menu")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("menu_get:42", r.text)
+
+            r = await client.post("/restaurants/42/menu")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("menu_post:42", r.text)
+
+            r = await client.put("/restaurants/42/menu")
+            self.assertEqual(404, r.status_code)
+
+    def test_route_template(self):
+        self.assertEqual('/employee/${employee_id}',
+                         self.app.route_template('/employee/101325', HttpMethod.GET))
+        self.assertEqual('/square/${x:int}', self.app.route_template('/square/30', HttpMethod.GET))
+        self.assertIsNone(self.app.route_template('/unknown', HttpMethod.GET))
+
+    @async_test
+    async def test_exception_exposed_to_after_hooks(self):
+        app = KayaApp()
+        seen = []
+
+        async def after_request(ctx: HttpContext) -> None:
+            seen.append(ctx.exception)
+
+        app.add_after_request_hook(after_request)
+
+        @app.GET('/raises')
+        async def raises(ctx: HttpContext) -> None:
+            raise RuntimeError('boom')
+
+        transport = httpx.ASGITransport(app=app)
+        async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as client:
+            with self.assertRaises(RuntimeError):
+                await client.get('/raises')
+
+        self.assertEqual(1, len(seen))
+        self.assertIsInstance(seen[0], RuntimeError)
+        self.assertEqual('boom', str(seen[0]))
+

packages/kaya-core/tests/test_tree.py

@@ -80,11 +80,39 @@ class TreeTest(unittest.TestCase):
                 self.assertIs(Maybe.of(handler_num).map(self.handlers.__getitem__).or_none(),
                               Maybe.of_nullable(res).map(lambda it: it[0]).or_none())
 
+    def test_route_template(self):
+        cases: Tuple[Tuple[str, HttpMethod, Optional[str]], ...] = (
+            ('/home/something', HttpMethod.GET, '/home/something'),
+            ('/home/something_else', HttpMethod.POST, '/home/something_else'),
+            ('/home/README.md', HttpMethod.GET, '/home/*.md'),
+            ('/home/something/ciao/blah/README.md', HttpMethod.GET, '/home/something/*/blah/*.md'),
+            ('/home/bar/ciao/blah/README.md', HttpMethod.GET, '/home/bar/*'),
+            ('/unknown', HttpMethod.GET, None),
+        )
+        for url, method, expected in cases:
+            with self.subTest(f'{method} {url}'):
+                self.assertEqual(expected, self.tree.route_template(url, method))
+
+    def test_route_template_with_params(self):
+        tree = Tree()
+        tree.add((p for p in ('foo', '${id:int}')), HttpMethod.PUT, self.handlers[0])
+        tree.add((p for p in ('foo', '${name}')), HttpMethod.GET, self.handlers[1])
+        self.assertEqual('/foo/${id:int}', tree.route_template('/foo/42', HttpMethod.PUT))
+        self.assertEqual('/foo/${name}', tree.route_template('/foo/bar', HttpMethod.GET))
+        self.assertIsNone(tree.route_template('/foo/bar', HttpMethod.DELETE))
+
     def test_two_method_agnostic_matchers_raise(self):
         tree = Tree()
         tree.add((p for p in ('foo', '*')), None, self.handlers[0])
         with self.assertRaises(ValueError):
-            tree.add((p for p in ('foo', '*')), None, self.handlers[1])
+            tree.add((p for p in ('foo', '*.md')), None, self.handlers[1])
+
+    def test_identical_method_agnostic_matchers_reuse(self):
+        tree = Tree()
+        tree.add((p for p in ('foo', '*')), None, self.handlers[0])
+        tree.add((p for p in ('foo', '*')), None, self.handlers[1])
+        handler = Maybe.of_nullable(tree.get_handler('/foo/bar', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], handler)
 
     def test_two_overlapping_method_specific_matchers_raise(self):
         tree = Tree()
@@ -101,3 +129,81 @@ class TreeTest(unittest.TestCase):
         self.assertIs(self.handlers[0], put_handler)
         self.assertIs(self.handlers[1], get_handler)
 
+    def test_nested_routes_with_same_param_allowed(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id}')), HttpMethod.GET, self.handlers[0])
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.GET, self.handlers[1])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+
+    def test_nested_routes_same_param_reverse_order(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.GET, self.handlers[1])
+        tree.add((p for p in ('restaurants', '${id}')), HttpMethod.GET, self.handlers[0])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+
+    def test_nested_routes_with_same_int_param_allowed(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id:int}')), HttpMethod.GET, self.handlers[0])
+        tree.add((p for p in ('restaurants', '${id:int}', 'menu')), HttpMethod.GET, self.handlers[1])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+
+    def test_nested_routes_method_agnostic_reuses_matcher(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id}')), HttpMethod.GET, self.handlers[0])
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), None, self.handlers[1])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.POST)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+
+    def test_different_param_names_still_raise(self):
+        tree = Tree()
+        tree.add((p for p in ('a', '${id}')), HttpMethod.GET, self.handlers[0])
+        with self.assertRaises(ValueError):
+            tree.add((p for p in ('a', '${name}', 'x')), HttpMethod.GET, self.handlers[1])
+
+    def test_different_param_kinds_still_raise(self):
+        tree = Tree()
+        tree.add((p for p in ('a', '${id}')), HttpMethod.GET, self.handlers[0])
+        with self.assertRaises(ValueError):
+            tree.add((p for p in ('a', '${id:int}', 'x')), HttpMethod.GET, self.handlers[1])
+
+    def test_nested_routes_different_methods_share_subtree(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.GET, self.handlers[0])
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.POST, self.handlers[1])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.POST)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+
+    def test_nested_routes_different_methods_reverse_order(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.POST, self.handlers[1])
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.GET, self.handlers[0])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.POST)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+
+    def test_nested_routes_combined_detail_and_menu_methods(self):
+        tree = Tree()
+        tree.add((p for p in ('restaurants', '${id}')), HttpMethod.GET, self.handlers[0])
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.GET, self.handlers[1])
+        tree.add((p for p in ('restaurants', '${id}', 'menu')), HttpMethod.POST, self.handlers[2])
+        h0 = Maybe.of_nullable(tree.get_handler('/restaurants/42', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h1 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.GET)).map(lambda it: it[0]).or_none()
+        h2 = Maybe.of_nullable(tree.get_handler('/restaurants/42/menu', HttpMethod.POST)).map(lambda it: it[0]).or_none()
+        self.assertIs(self.handlers[0], h0)
+        self.assertIs(self.handlers[1], h1)
+        self.assertIs(self.handlers[2], h2)
+

packages/kaya-core/tests/test_websocket.py

@@ -1,9 +1,9 @@
 import unittest
 import httpx
 from pwo import async_test
-from httpx_ws import aconnect_ws, WebSocketDisconnect
+from httpx_ws import aconnect_ws, WebSocketDisconnect as HttpxWebSocketDisconnect
 from httpx_ws.transport import ASGIWebSocketTransport
-from kaya.core import KayaApp, WebSocket
+from kaya.core import KayaApp, WebSocket, WebSocketDisconnect, WebSocketMessage
 from kaya.core._asgi import AsgiWebSocket
 
 
@@ -66,7 +66,7 @@ class WebSocketTest(unittest.TestCase):
         transport = ASGIWebSocketTransport(app=self.app)
 
         async with httpx.AsyncClient(transport=transport, base_url="http://testserver") as client:
-            with self.assertRaises(WebSocketDisconnect) as cm:
+            with self.assertRaises(HttpxWebSocketDisconnect) as cm:
                 async with aconnect_ws("/unknown", client) as ws:
                     pass
 
@@ -151,3 +151,113 @@ class WebSocketTest(unittest.TestCase):
         }
         ws = AsgiWebSocket(scope, receive, send)
         self.assertEqual('ws', ws.scheme)
+
+
+class FakeWebSocket(WebSocket):
+    """Minimal in-memory websocket for exercising ``KayaApp`` directly."""
+
+    def __init__(self, path: str) -> None:
+        self.path = path
+        self.query_string = ''
+        self.scheme = 'ws'
+        self.headers: dict[str, list[str]] = {}
+        self.client = ('127.0.0.1', 12345)
+        self.server = ('127.0.0.1', 80)
+        self.closed: list[int] = []
+
+    async def accept(self, headers=None) -> None:
+        pass
+
+    async def receive(self) -> WebSocketMessage:
+        return WebSocketMessage(kind='close')
+
+    async def send_text(self, data: str) -> None:
+        pass
+
+    async def send_bytes(self, data: bytes) -> None:
+        pass
+
+    async def close(self, code: int = 1000) -> None:
+        self.closed.append(code)
+
+    async def __anext__(self) -> WebSocketMessage:
+        raise StopAsyncIteration
+
+
+class WebSocketDisconnectTest(unittest.TestCase):
+
+    def setUp(self):
+        self.app = KayaApp()
+
+        @self.app.websocket('/disconnect')
+        async def disconnect(ws: WebSocket) -> None:
+            await ws.accept()
+            await ws.send_text('before')
+            raise WebSocketDisconnect()
+
+        @self.app.websocket('/failure')
+        async def failure(ws: WebSocket) -> None:
+            await ws.accept()
+            raise RuntimeError('boom')
+
+    @async_test
+    async def test_disconnect_terminates_quietly(self):
+        after_hook_calls = []
+
+        async def after(ws: WebSocket) -> None:
+            after_hook_calls.append(ws)
+
+        self.app.add_after_websocket_hook(after)
+        ws = FakeWebSocket('/disconnect')
+        await self.app.handle_websocket(ws)
+        self.assertEqual([ws], after_hook_calls)
+        self.assertIsNone(ws.exception)
+
+    @async_test
+    async def test_other_errors_are_recorded_and_reraised(self):
+        ws = FakeWebSocket('/failure')
+        with self.assertRaises(RuntimeError):
+            await self.app.handle_websocket(ws)
+        self.assertIsInstance(ws.exception, RuntimeError)
+
+    @async_test
+    async def test_asgi_send_after_disconnect_raises_websocket_disconnect(self):
+        async def send(message):
+            raise OSError('client gone')
+
+        async def receive():
+            return {'type': 'websocket.disconnect', 'code': 1006}
+
+        ws = AsgiWebSocket(self._scope(), receive, send)
+        with self.assertRaises(WebSocketDisconnect) as ctx:
+            await ws.send_text('hello')
+        self.assertEqual(1006, ctx.exception.code)
+        with self.assertRaises(WebSocketDisconnect):
+            await ws.send_bytes(b'hello')
+        with self.assertRaises(WebSocketDisconnect):
+            await ws.close()
+
+    @async_test
+    async def test_asgi_accept_after_disconnect_raises_websocket_disconnect(self):
+        async def send(message):
+            raise OSError('client gone')
+
+        async def receive():
+            return {'type': 'websocket.connect'}
+
+        ws = AsgiWebSocket(self._scope(), receive, send)
+        with self.assertRaises(WebSocketDisconnect) as ctx:
+            await ws.accept()
+        self.assertEqual(1006, ctx.exception.code)
+
+    @staticmethod
+    def _scope() -> dict:
+        return {
+            'type': 'websocket',
+            'path': '/echo',
+            'query_string': b'',
+            'scheme': 'ws',
+            'client': ('127.0.0.1', 12345),
+            'server': ('127.0.0.1', 80),
+            'headers': [],
+        }

packages/kaya-cors/README.md

@@ -0,0 +1,63 @@
+# kaya-cors
+
+CORS (Cross-Origin Resource Sharing) support for the Kaya web framework.
+
+Provides `CorsMixin`, a `KayaMixin` that adds CORS response headers to outgoing
+responses and answers CORS preflight (`OPTIONS`) requests, with the same
+configuration parameters and semantics as FastAPI/Starlette's `CORSMiddleware`.
+
+## Usage
+
+```python
+from kaya.core import KayaApp, HttpContext
+from kaya.cors import CorsMixin
+
+app = KayaApp(mixins=[
+    CorsMixin(
+        allow_origins=['https://example.com'],
+        allow_methods=('GET', 'POST'),
+        allow_headers=('X-Custom-Header',),
+        allow_credentials=True,
+        max_age=600,
+    )
+])
+
+@app.GET('/')
+async def home(ctx: HttpContext):
+    await ctx.send_str(200, 'Hello World!')
+```
+
+## Parameters
+
+- `allow_origins`: list of origins allowed to make cross-origin requests.
+  Use `['*']` to allow any origin.
+- `allow_origin_regex`: optional regex string matched (fullmatch) against the
+  request origin.
+- `allow_methods`: HTTP methods allowed for cross-origin requests
+  (default `('GET',)`); use `'*'` to allow all standard methods.
+- `allow_headers`: request headers allowed in cross-origin requests
+  (default `()`); use `'*'` to mirror back any requested headers.
+- `allow_credentials`: allow cookies/credentials in cross-origin requests
+  (default `False`). When enabled, the allowed origin is always echoed
+  explicitly instead of `'*'`.
+- `expose_headers`: response headers made accessible to the browser.
+- `max_age`: seconds browsers may cache the preflight response
+  (default `600`).
+
+## Behavior
+
+- Requests without an `Origin` header pass through untouched.
+- Simple cross-origin requests with an allowed origin get
+  `Access-Control-Allow-Origin` (plus `Access-Control-Allow-Credentials` and
+  `Access-Control-Expose-Headers` when configured) added to the response.
+  Headers already set by the handler are never overwritten.
+- Preflight requests (`OPTIONS` with `Origin` and
+  `Access-Control-Request-Method` headers) are answered directly by the mixin
+  with `200 OK` (or `400` with a `Disallowed CORS ...` body when the origin,
+  method or headers are not allowed). The preflight response is the only one
+  delivered to the client: if the routing tree matches the request anyway
+  (including user-registered `OPTIONS` handlers or the 404 fallback), its
+  output is discarded.
+
+`CorsMixin` is a `KayaMixin`, so the app stays a `KayaApp` and both ASGI and
+RSGI keep working.

packages/kaya-cors/pyproject.toml

@@ -0,0 +1,51 @@
+[build-system]
+requires = ["setuptools>=61.0", "setuptools-scm>=8"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "kaya-cors"
+dynamic = ["version"]
+authors = [
+  { name="Walter Oggioni", email="oggioni.walter@gmail.com" },
+]
+description = "CORS support for the Kaya lightweight ASGI web framework"
+readme = "README.md"
+requires-python = ">=3.10"
+license = "MIT"
+classifiers = [
+        'Development Status :: 3 - Alpha',
+        'Topic :: Utilities',
+        'Intended Audience :: System Administrators',
+        'Intended Audience :: Developers',
+        'Environment :: Console',
+        'Programming Language :: Python :: 3',
+]
+
+dependencies = [
+    "kaya-core",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/woggioni/kaya"
+"Bug Tracker" = "https://github.com/woggioni/kaya/issues"
+
+[tool.setuptools.packages.find]
+where = ["src"]
+namespaces = true
+
+[tool.mypy]
+python_version = "3.12"
+disallow_untyped_defs = true
+show_error_codes = true
+no_implicit_optional = true
+warn_return_any = true
+warn_unused_ignores = true
+exclude = ["scripts", "docs", "test"]
+strict = true
+
+[tool.setuptools_scm]
+root = "../.."
+version_file = "src/kaya/cors/_version.py"
+
+[tool.setuptools_scm.tag]
+prefix = "release/"

packages/kaya-cors/src/kaya/cors/__init__.py

@@ -0,0 +1,10 @@
+from pkgutil import extend_path
+
+__path__ = extend_path(__path__, __name__)
+
+from ._mixin import CorsMixin
+
+
+__all__ = [
+    'CorsMixin',
+]

packages/kaya-cors/src/kaya/cors/_mixin.py

@@ -0,0 +1,274 @@
+import re
+from pathlib import Path
+from typing import (
+    Any,
+    AsyncGenerator,
+    Dict,
+    List,
+    Mapping,
+    Optional,
+    Sequence,
+    Tuple,
+)
+
+from kaya.core import HttpContext, HttpMethod, KayaApp, KayaMixin
+from kaya.core._types import StrOrStrings
+
+ALL_METHODS: Tuple[str, ...] = ("DELETE", "GET", "HEAD", "OPTIONS", "PATCH", "POST", "PUT", "QUERY")
+SAFELISTED_HEADERS = frozenset({"Accept", "Accept-Language", "Content-Language", "Content-Type"})
+
+
+def _first_header(headers: Mapping[str, Sequence[str]], name: str) -> Optional[str]:
+    values = headers.get(name)
+    if not values:
+        return None
+    return values[0]
+
+
+def _merge_headers(headers: Optional[Mapping[str, StrOrStrings]],
+                   cors_headers: Mapping[str, str]) -> Mapping[str, StrOrStrings]:
+    """Merge CORS headers into the response headers.
+
+    Header names are matched case-insensitively; headers already set by the
+    handler are never overwritten. A CORS ``Vary`` value is appended to an
+    existing ``Vary`` header when not already present.
+    """
+    result: Dict[str, StrOrStrings] = dict(headers) if headers else {}
+    key_by_lower: Dict[str, str] = {k.lower(): k for k in result}
+    for key, value in cors_headers.items():
+        existing_key = key_by_lower.get(key.lower())
+        if existing_key is None:
+            result[key] = value
+            key_by_lower[key.lower()] = key
+        elif key.lower() == 'vary':
+            previous = result[existing_key]
+            previous_values = [previous] if isinstance(previous, str) else list(previous)
+            present = {v.strip().lower() for part in previous_values for v in part.split(',')}
+            if value.lower() not in present:
+                if isinstance(previous, str):
+                    result[existing_key] = f"{previous}, {value}"
+                else:
+                    result[existing_key] = (*previous_values, value)
+    return result
+
+
+class CorsHttpContext(HttpContext):
+    """HttpContext wrapper that injects CORS headers into response headers.
+
+    Works with any concrete ``HttpContext`` (ASGI or RSGI) because it only
+    relies on the abstract send methods, which all implementations share.
+    Attributes not explicitly overridden are delegated to the wrapped context
+    via ``__getattr__``, so protocol-specific fields (``pathsend``,
+    ``receive``/``send`` for ASGI, ``protocol`` for RSGI, etc.) are passed
+    through transparently.
+    """
+
+    def __init__(self, ctx: HttpContext, cors_headers: Mapping[str, str]) -> None:
+        object.__setattr__(self, '_ctx', ctx)
+        object.__setattr__(self, 'session', ctx.session)
+        object.__setattr__(self, '_cors_headers', cors_headers)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ctx':
+            raise AttributeError(name)
+        return getattr(self._ctx, name)
+
+    def _merge(self, headers: Optional[Mapping[str, StrOrStrings]]) -> Mapping[str, StrOrStrings]:
+        return _merge_headers(headers, self._cors_headers)
+
+    async def stream_body(self,
+                          status: int,
+                          body_generator: AsyncGenerator[bytes, None],
+                          headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.stream_body(status, body_generator, self._merge(headers))
+
+    async def send_bytes(self, status: int, body: bytes, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_bytes(status, body, self._merge(headers))
+
+    async def send_str(self, status: int, body: str, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_str(status, body, self._merge(headers))
+
+    async def send_file(self, status: int, path: Path, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_file(status, path, self._merge(headers))
+
+    async def send_empty(self, status: int, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_empty(status, self._merge(headers))
+
+
+class _SwallowedHttpContext(HttpContext):
+    """HttpContext wrapper whose send methods are no-ops.
+
+    Returned by the CORS hook after a preflight response has already been sent,
+    so that routing (or the 404 fallback) does not attempt to send a second
+    response for the same request.
+    """
+
+    def __init__(self, ctx: HttpContext) -> None:
+        object.__setattr__(self, '_ctx', ctx)
+        object.__setattr__(self, 'session', ctx.session)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ctx':
+            raise AttributeError(name)
+        return getattr(self._ctx, name)
+
+    async def stream_body(self,
+                          status: int,
+                          body_generator: AsyncGenerator[bytes, None],
+                          headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        pass
+
+    async def send_bytes(self, status: int, body: bytes, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        pass
+
+    async def send_file(self, status: int, path: Path, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        pass
+
+    async def send_empty(self, status: int, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        pass
+
+
+class CorsMixin(KayaMixin):
+    """Kaya mixin adding CORS headers to responses, modeled after
+    FastAPI/Starlette's ``CORSMiddleware``.
+
+    Registers a before-request hook that:
+
+    - answers CORS preflight requests (``OPTIONS`` requests carrying ``Origin``
+      and ``Access-Control-Request-Method`` headers) directly: ``200 OK`` when
+      the origin, method and headers are allowed, ``400`` with a
+      ``Disallowed CORS ...`` body otherwise. The preflight response is the
+      only one delivered to the client; if the routing tree matches the
+      request anyway, its output is discarded;
+    - wraps the request context in a :class:`CorsHttpContext` for simple
+      cross-origin requests, injecting ``Access-Control-Allow-Origin`` (and
+      the configured credentials/expose headers) into the response.
+
+    Requests without an ``Origin`` header pass through untouched. Because the
+    app stays a ``KayaApp``, both ASGI and RSGI keep working.
+
+    Example::
+
+        app = KayaApp(mixins=[
+            CorsMixin(
+                allow_origins=['https://example.com'],
+                allow_methods=('GET', 'POST'),
+                allow_headers=('X-Custom-Header',),
+                allow_credentials=True,
+            )
+        ])
+    """
+
+    def __init__(self,
+                 allow_origins: Sequence[str] = (),
+                 allow_methods: Sequence[str] = ('GET',),
+                 allow_headers: Sequence[str] = (),
+                 allow_credentials: bool = False,
+                 allow_origin_regex: Optional[str] = None,
+                 expose_headers: Sequence[str] = (),
+                 max_age: int = 600) -> None:
+        methods: Sequence[str] = ALL_METHODS if '*' in allow_methods else allow_methods
+        self._allow_origin_regex = re.compile(allow_origin_regex) if allow_origin_regex is not None else None
+        self._allow_all_origins = '*' in allow_origins
+        self._allow_all_headers = '*' in allow_headers
+        self._allow_credentials = allow_credentials
+        self._allow_origins = tuple(allow_origins)
+        self._allow_methods = tuple(methods)
+        sorted_allow_headers = sorted(SAFELISTED_HEADERS | set(allow_headers))
+        self._allow_headers = [h.lower() for h in sorted_allow_headers]
+        self._preflight_explicit_allow_origin = not self._allow_all_origins or allow_credentials
+
+        simple_headers: Dict[str, str] = {}
+        if self._allow_all_origins:
+            simple_headers['Access-Control-Allow-Origin'] = '*'
+        if allow_credentials:
+            simple_headers['Access-Control-Allow-Credentials'] = 'true'
+        if expose_headers:
+            simple_headers['Access-Control-Expose-Headers'] = ', '.join(expose_headers)
+        self._simple_headers = simple_headers
+
+        preflight_headers: Dict[str, str] = {}
+        if self._preflight_explicit_allow_origin:
+            # the origin value is set dynamically in _preflight_response()
+            preflight_headers['Vary'] = 'Origin'
+        else:
+            preflight_headers['Access-Control-Allow-Origin'] = '*'
+        preflight_headers['Access-Control-Allow-Methods'] = ', '.join(self._allow_methods)
+        preflight_headers['Access-Control-Max-Age'] = str(max_age)
+        if sorted_allow_headers and not self._allow_all_headers:
+            preflight_headers['Access-Control-Allow-Headers'] = ', '.join(sorted_allow_headers)
+        if allow_credentials:
+            preflight_headers['Access-Control-Allow-Credentials'] = 'true'
+        self._preflight_headers = preflight_headers
+
+    def apply(self, app: KayaApp) -> None:
+        app.add_before_request_hook(self._before_request)
+
+    def _is_allowed_origin(self, origin: str) -> bool:
+        if self._allow_all_origins:
+            return True
+        if self._allow_origin_regex is not None and self._allow_origin_regex.fullmatch(origin):
+            return True
+        return origin in self._allow_origins
+
+    def _simple_response_headers(self, origin: str) -> Mapping[str, str]:
+        headers = dict(self._simple_headers)
+        if self._allow_all_origins and self._allow_credentials:
+            # credentials require the specific origin instead of '*'
+            headers['Access-Control-Allow-Origin'] = origin
+            headers['Vary'] = 'Origin'
+        elif not self._allow_all_origins and self._is_allowed_origin(origin):
+            # specific origins must be mirrored back in the response
+            headers['Access-Control-Allow-Origin'] = origin
+            headers['Vary'] = 'Origin'
+        return headers
+
+    def _preflight_response(self,
+                            request_headers: Mapping[str, Sequence[str]],
+                            origin: str) -> Tuple[int, str, Mapping[str, str]]:
+        requested_method = _first_header(request_headers, 'access-control-request-method')
+        requested_headers = _first_header(request_headers, 'access-control-request-headers')
+
+        headers = dict(self._preflight_headers)
+        failures: List[str] = []
+
+        if self._is_allowed_origin(origin):
+            if self._preflight_explicit_allow_origin:
+                # the "else" case is already accounted for in self._preflight_headers
+                # and the value would be '*'
+                headers['Access-Control-Allow-Origin'] = origin
+        else:
+            failures.append('origin')
+
+        if requested_method not in self._allow_methods:
+            failures.append('method')
+
+        # if we allow all headers, then we have to mirror back any requested
+        # headers in the response
+        if self._allow_all_headers and requested_headers is not None:
+            headers['Access-Control-Allow-Headers'] = requested_headers
+        elif requested_headers is not None:
+            for header in [h.lower() for h in requested_headers.split(',')]:
+                if header.strip() not in self._allow_headers:
+                    failures.append('headers')
+                    break
+
+        # we don't strictly need to use 400 responses here, since it's up to
+        # the browser to enforce the CORS policy, but it's more informative
+        # if we do
+        if failures:
+            return 400, 'Disallowed CORS ' + ', '.join(failures), headers
+        return 200, 'OK', headers
+
+    async def _before_request(self, ctx: HttpContext) -> Optional[HttpContext]:
+        origin = _first_header(ctx.headers, 'origin')
+        if origin is None:
+            return None
+        if ctx.method == HttpMethod.OPTIONS \
+                and _first_header(ctx.headers, 'access-control-request-method') is not None:
+            status, body, headers = self._preflight_response(ctx.headers, origin)
+            response_headers: Dict[str, StrOrStrings] = {'Content-Type': 'text/plain; charset=utf-8'}
+            response_headers.update(headers)
+            await ctx.send_str(status, body, response_headers)
+            return _SwallowedHttpContext(ctx)
+        return CorsHttpContext(ctx, self._simple_response_headers(origin))

packages/kaya-cors/tests/test_cors.py

@@ -0,0 +1,246 @@
+import asyncio
+import unittest
+from typing import Any, Optional
+
+import httpx
+from pwo import async_test
+
+from kaya.core import HttpContext, KayaApp
+from kaya.cors import CorsMixin
+
+
+def make_app(**cors_kwargs: Any) -> KayaApp:
+    app = KayaApp(mixins=[CorsMixin(**cors_kwargs)])
+
+    @app.GET('/hello')
+    async def hello(ctx: HttpContext) -> None:
+        await ctx.send_str(200, 'Hello World!')
+
+    return app
+
+
+async def request(app: KayaApp,
+                  method: str,
+                  path: str = '/hello',
+                  headers: Optional[dict[str, str]] = None) -> httpx.Response:
+    transport = httpx.ASGITransport(app=app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as client:
+        return await client.request(method, path, headers=headers)
+
+
+class CorsSimpleRequestTest(unittest.TestCase):
+
+    @async_test
+    async def test_allowed_origin(self):
+        app = make_app(allow_origins=['https://example.com'])
+        r = await request(app, 'GET', headers={'Origin': 'https://example.com'})
+        self.assertEqual(200, r.status_code)
+        self.assertEqual('Hello World!', r.text)
+        self.assertEqual('https://example.com', r.headers.get('Access-Control-Allow-Origin'))
+        self.assertEqual('Origin', r.headers.get('Vary'))
+
+    @async_test
+    async def test_disallowed_origin(self):
+        app = make_app(allow_origins=['https://example.com'])
+        r = await request(app, 'GET', headers={'Origin': 'https://evil.com'})
+        self.assertEqual(200, r.status_code)
+        self.assertNotIn('Access-Control-Allow-Origin', r.headers)
+
+    @async_test
+    async def test_wildcard_origin(self):
+        app = make_app(allow_origins=['*'])
+        r = await request(app, 'GET', headers={'Origin': 'https://anything.example.com'})
+        self.assertEqual('*', r.headers.get('Access-Control-Allow-Origin'))
+
+    @async_test
+    async def test_wildcard_origin_with_credentials_echoes_origin(self):
+        app = make_app(allow_origins=['*'], allow_credentials=True)
+        r = await request(app, 'GET', headers={'Origin': 'https://example.com'})
+        self.assertEqual('https://example.com', r.headers.get('Access-Control-Allow-Origin'))
+        self.assertEqual('true', r.headers.get('Access-Control-Allow-Credentials'))
+        self.assertEqual('Origin', r.headers.get('Vary'))
+
+    @async_test
+    async def test_origin_regex(self):
+        app = make_app(allow_origin_regex=r'https://.*\.example\.com')
+        r = await request(app, 'GET', headers={'Origin': 'https://api.example.com'})
+        self.assertEqual('https://api.example.com', r.headers.get('Access-Control-Allow-Origin'))
+        r = await request(app, 'GET', headers={'Origin': 'https://example.com.evil.org'})
+        self.assertNotIn('Access-Control-Allow-Origin', r.headers)
+
+    @async_test
+    async def test_no_origin_header(self):
+        app = make_app(allow_origins=['*'])
+        r = await request(app, 'GET')
+        self.assertEqual(200, r.status_code)
+        self.assertNotIn('Access-Control-Allow-Origin', r.headers)
+
+    @async_test
+    async def test_expose_headers(self):
+        app = make_app(allow_origins=['*'], expose_headers=['X-Total-Count'])
+        r = await request(app, 'GET', headers={'Origin': 'https://example.com'})
+        self.assertEqual('X-Total-Count', r.headers.get('Access-Control-Expose-Headers'))
+
+    @async_test
+    async def test_handler_set_cors_header_not_overwritten(self):
+        app = KayaApp(mixins=[CorsMixin(allow_origins=['*'])])
+
+        @app.GET('/custom')
+        async def custom(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'custom', headers={'Access-Control-Allow-Origin': 'https://custom.example.com'})
+
+        r = await request(app, 'GET', '/custom', headers={'Origin': 'https://example.com'})
+        self.assertEqual('https://custom.example.com', r.headers.get('Access-Control-Allow-Origin'))
+
+
+class CorsPreflightTest(unittest.TestCase):
+
+    @staticmethod
+    def preflight_headers(origin: str = 'https://example.com',
+                          method: str = 'POST',
+                          headers: Optional[str] = None) -> dict[str, str]:
+        result = {
+            'Origin': origin,
+            'Access-Control-Request-Method': method,
+        }
+        if headers is not None:
+            result['Access-Control-Request-Headers'] = headers
+        return result
+
+    @async_test
+    async def test_preflight_allowed(self):
+        app = make_app(allow_origins=['https://example.com'],
+                       allow_methods=('GET', 'POST'),
+                       allow_credentials=True)
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers())
+        self.assertEqual(200, r.status_code)
+        self.assertEqual('OK', r.text)
+        self.assertEqual('https://example.com', r.headers.get('Access-Control-Allow-Origin'))
+        self.assertEqual('GET, POST', r.headers.get('Access-Control-Allow-Methods'))
+        self.assertEqual('600', r.headers.get('Access-Control-Max-Age'))
+        self.assertEqual('true', r.headers.get('Access-Control-Allow-Credentials'))
+        self.assertEqual('Origin', r.headers.get('Vary'))
+
+    @async_test
+    async def test_preflight_wildcard_origin(self):
+        app = make_app(allow_origins=['*'], allow_methods=('GET', 'POST'))
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers())
+        self.assertEqual(200, r.status_code)
+        self.assertEqual('*', r.headers.get('Access-Control-Allow-Origin'))
+
+    @async_test
+    async def test_preflight_disallowed_origin(self):
+        app = make_app(allow_origins=['https://example.com'], allow_methods=('GET', 'POST'))
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers(origin='https://evil.com'))
+        self.assertEqual(400, r.status_code)
+        self.assertEqual('Disallowed CORS origin', r.text)
+
+    @async_test
+    async def test_preflight_disallowed_method(self):
+        app = make_app(allow_origins=['https://example.com'], allow_methods=('GET',))
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers(method='DELETE'))
+        self.assertEqual(400, r.status_code)
+        self.assertEqual('Disallowed CORS method', r.text)
+
+    @async_test
+    async def test_preflight_disallowed_headers(self):
+        app = make_app(allow_origins=['https://example.com'], allow_methods=('GET', 'POST'))
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers(headers='X-Custom'))
+        self.assertEqual(400, r.status_code)
+        self.assertEqual('Disallowed CORS headers', r.text)
+
+    @async_test
+    async def test_preflight_safelisted_headers_allowed(self):
+        app = make_app(allow_origins=['https://example.com'], allow_methods=('GET', 'POST'))
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers(headers='Content-Type'))
+        self.assertEqual(200, r.status_code)
+
+    @async_test
+    async def test_preflight_allow_all_headers_mirrors_request(self):
+        app = make_app(allow_origins=['*'], allow_methods=('GET', 'POST'), allow_headers=['*'])
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers(headers='X-Custom, X-Other'))
+        self.assertEqual(200, r.status_code)
+        self.assertEqual('X-Custom, X-Other', r.headers.get('Access-Control-Allow-Headers'))
+
+    @async_test
+    async def test_preflight_configured_allow_headers(self):
+        app = make_app(allow_origins=['https://example.com'],
+                       allow_methods=('GET', 'POST'),
+                       allow_headers=('X-Custom',))
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers(headers='X-Custom'))
+        self.assertEqual(200, r.status_code)
+        allow_headers = r.headers.get('Access-Control-Allow-Headers')
+        self.assertIsNotNone(allow_headers)
+        assert allow_headers is not None
+        self.assertIn('X-Custom', allow_headers)
+
+    @async_test
+    async def test_preflight_response_not_overwritten_by_handler(self):
+        # even when a user-registered OPTIONS handler matches, the preflight
+        # response sent by the mixin is the only one delivered to the client
+        app = KayaApp(mixins=[CorsMixin(allow_origins=['https://example.com'], allow_methods=('GET', 'POST'))])
+
+        @app.GET('/hello')
+        async def hello(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'Hello World!')
+
+        @app.OPTIONS('/hello')
+        async def options(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'custom OPTIONS handler')
+
+        r = await request(app, 'OPTIONS', headers=self.preflight_headers())
+        self.assertEqual(200, r.status_code)
+        self.assertEqual('OK', r.text)
+
+    @async_test
+    async def test_options_without_preflight_headers_routes_normally(self):
+        app = KayaApp(mixins=[CorsMixin(allow_origins=['https://example.com'])])
+
+        @app.OPTIONS('/hello')
+        async def options(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'custom OPTIONS handler')
+
+        # an OPTIONS request without Access-Control-Request-Method is not a
+        # preflight request and is routed normally
+        r = await request(app, 'OPTIONS', headers={'Origin': 'https://example.com'})
+        self.assertEqual(200, r.status_code)
+        self.assertEqual('custom OPTIONS handler', r.text)
+        self.assertEqual('https://example.com', r.headers.get('Access-Control-Allow-Origin'))
+
+
+class CorsRsgiTest(unittest.TestCase):
+
+    def test_rsgi_context_header_injection(self):
+        from kaya.rsgi import RsgiContext
+
+        class FakeScope:
+            scheme = 'http'
+            method = 'GET'
+            path = '/'
+            query_string = ''
+            headers = {'origin': 'https://example.com'}
+            client = '127.0.0.1:12345'
+            server = '127.0.0.1:80'
+
+        class FakeProtocol:
+            def __init__(self) -> None:
+                self.responses = []
+
+            def response_str(self, status: int, headers: list, body: str) -> None:
+                self.responses.append((status, dict(headers), body))
+
+        mixin = CorsMixin(allow_origins=['https://example.com'])
+        protocol = FakeProtocol()
+        ctx = RsgiContext(FakeScope(), protocol)  # type: ignore[arg-type]
+
+        async def run() -> None:
+            wrapped = await mixin._before_request(ctx)
+            assert wrapped is not None
+            await wrapped.send_str(200, 'hi')
+
+        asyncio.run(run())
+        self.assertEqual(1, len(protocol.responses))
+        status, headers, body = protocol.responses[0]
+        self.assertEqual(200, status)
+        self.assertEqual('https://example.com', headers.get('Access-Control-Allow-Origin'))
+        self.assertEqual('Origin', headers.get('Vary'))

packages/kaya-forwarded/README.md

@@ -0,0 +1,61 @@
+# kaya-forwarded
+
+Trusted-proxy forwarded header handling for the Kaya web framework.
+
+Without this package, Kaya exposes the raw socket peer address as
+`ctx.client` / `ws.client` and ignores `Forwarded` / `X-Forwarded-*` headers
+entirely (they are client-controllable and trivially spoofable when the app is
+directly exposed).
+
+`ForwardedHeadersMixin` opts the application into honoring those headers, but
+only when the direct socket peer is a trusted proxy, identified by a list of
+trusted CIDRs/IPs.
+
+## Usage
+
+```python
+from kaya.core import KayaApp, HttpContext
+from kaya.forwarded import ForwardedHeadersMixin
+
+app = KayaApp(mixins=[
+    ForwardedHeadersMixin(trusted_proxies=['127.0.0.1', '::1', '10.0.0.0/8'])
+])
+
+@app.GET('/whoami')
+async def whoami(ctx: HttpContext):
+    host, port = ctx.client
+    await ctx.send_str(200, f'{host}:{port}')
+```
+
+## How it works
+
+When a request arrives:
+
+1. If the socket peer IP does not belong to any trusted CIDR (or there is no
+   peer address), the mixin leaves the context untouched — `client` remains
+   the socket peer and all proxy headers are ignored.
+2. Otherwise the client address is resolved from the headers, in order:
+   - `Forwarded` (RFC 7239): the `for=` entries are walked **from right to
+     left**, skipping entries that are themselves trusted proxies (and
+     `unknown`); the first untrusted entry is the client. This defeats
+     spoofing when the edge proxy *appends* to the header (e.g. nginx with
+     `$proxy_add_x_forwarded_for`), because attacker-supplied leftmost entries
+     are never selected. A `:port` in the selected `for=` value also
+     populates the port.
+   - `X-Forwarded-For`: same right-to-left trusted-proxy walk; the port comes
+     from `X-Forwarded-Port` when present and valid.
+   - `X-Forwarded-Host`: first entry; port from `X-Forwarded-Port` as above.
+3. If none of the headers are present or usable, the socket peer is kept.
+
+If every entry in the chain is a trusted proxy, the leftmost entry is used
+(the whole chain is trusted, so the leftmost is the original client).
+
+The resolved address is exposed by wrapping the request context /
+websocket (the same pattern as `kaya-session`), so both ASGI and RSGI keep
+working and `ctx.session` from other mixins is preserved.
+
+## Note
+
+Even with this mixin, the edge proxy should still strip or overwrite inbound
+`Forwarded` / `X-Forwarded-*` headers from clients — the mixin protects the
+application, the proxy protects the chain.

packages/kaya-forwarded/pyproject.toml

@@ -0,0 +1,51 @@
+[build-system]
+requires = ["setuptools>=61.0", "setuptools-scm>=8"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "kaya-forwarded"
+dynamic = ["version"]
+authors = [
+  { name="Walter Oggioni", email="oggioni.walter@gmail.com" },
+]
+description = "Trusted-proxy forwarded header handling for the Kaya lightweight ASGI web framework"
+readme = "README.md"
+requires-python = ">=3.10"
+license = "MIT"
+classifiers = [
+        'Development Status :: 3 - Alpha',
+        'Topic :: Utilities',
+        'Intended Audience :: System Administrators',
+        'Intended Audience :: Developers',
+        'Environment :: Console',
+        'Programming Language :: Python :: 3',
+]
+
+dependencies = [
+    "kaya-core",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/woggioni/kaya"
+"Bug Tracker" = "https://github.com/woggioni/kaya/issues"
+
+[tool.setuptools.packages.find]
+where = ["src"]
+namespaces = true
+
+[tool.mypy]
+python_version = "3.12"
+disallow_untyped_defs = true
+show_error_codes = true
+no_implicit_optional = true
+warn_return_any = true
+warn_unused_ignores = true
+exclude = ["scripts", "docs", "test"]
+strict = true
+
+[tool.setuptools_scm]
+root = "../.."
+version_file = "src/kaya/forwarded/_version.py"
+
+[tool.setuptools_scm.tag]
+prefix = "release/"

packages/kaya-forwarded/src/kaya/forwarded/__init__.py

@@ -0,0 +1,10 @@
+from pkgutil import extend_path
+
+__path__ = extend_path(__path__, __name__)
+
+from ._mixin import ForwardedHeadersMixin
+
+
+__all__ = [
+    'ForwardedHeadersMixin',
+]

packages/kaya-forwarded/src/kaya/forwarded/_mixin.py

@@ -0,0 +1,237 @@
+from ipaddress import ip_address, ip_network, IPv4Address, IPv4Network, IPv6Address, IPv6Network
+from pathlib import Path
+from typing import (
+    Any,
+    AsyncGenerator,
+    List,
+    Mapping,
+    Optional,
+    Sequence,
+    Tuple,
+    Union,
+)
+
+from kaya.core import HttpContext, KayaApp, KayaMixin, WebSocket, WebSocketMessage
+from kaya.core._types import StrOrStrings
+
+_IPAddress = Union[IPv4Address, IPv6Address]
+_IPNetwork = Union[IPv4Network, IPv6Network]
+
+
+def _split_host_port(value: str) -> Tuple[str, Optional[int]]:
+    if value.startswith('['):
+        # bracketed IPv6 address, optionally followed by :port
+        closing = value.find(']')
+        if closing == -1:
+            return value, None
+        host = value[1:closing]
+        rest = value[closing + 1:]
+        if rest.startswith(':'):
+            try:
+                return host, int(rest[1:])
+            except ValueError:
+                return host, None
+        return host, None
+    if value.count(':') == 1:
+        host, _, port_str = value.rpartition(':')
+        try:
+            return host, int(port_str)
+        except ValueError:
+            return value, None
+    return value, None
+
+
+def _parse_forwarded_entries(headers: Mapping[str, Sequence[str]]) -> List[Tuple[str, Optional[int]]]:
+    """Extract the (host, port) `for=` entries of the RFC 7239 `Forwarded` header,
+    flattened across all header values, in chain order (leftmost = original client).
+    """
+    entries: List[Tuple[str, Optional[int]]] = []
+    for raw_value in headers.get('forwarded', ()):
+        for element in raw_value.split(','):
+            for param in element.split(';'):
+                key, sep, value = param.partition('=')
+                if sep and key.strip().lower() == 'for':
+                    for_value = value.strip().strip('"')
+                    if for_value and for_value.lower() != 'unknown':
+                        entries.append(_split_host_port(for_value))
+                    break
+    return entries
+
+
+def _first_header_value(headers: Mapping[str, Sequence[str]], name: str) -> Optional[str]:
+    values = headers.get(name)
+    if not values:
+        return None
+    first = values[0].split(',')[0].strip()
+    return first or None
+
+
+class _ForwardedHttpContext(HttpContext):
+    """HttpContext wrapper that exposes the forwarded client address.
+
+    Everything except ``client`` is delegated to the wrapped context via
+    ``__getattr__``, so it works with any concrete ``HttpContext`` (ASGI or
+    RSGI) and preserves attributes set by other mixins (e.g. ``session``).
+    """
+
+    def __init__(self, ctx: HttpContext, client: Tuple[str, int]) -> None:
+        object.__setattr__(self, '_ctx', ctx)
+        object.__setattr__(self, 'session', ctx.session)
+        object.__setattr__(self, 'client', client)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ctx':
+            raise AttributeError(name)
+        return getattr(self._ctx, name)
+
+    async def stream_body(self,
+                          status: int,
+                          body_generator: AsyncGenerator[bytes, None],
+                          headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.stream_body(status, body_generator, headers)
+
+    async def send_bytes(self, status: int, body: bytes, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_bytes(status, body, headers)
+
+    async def send_str(self, status: int, body: str, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_str(status, body, headers)
+
+    async def send_file(self, status: int, path: Path, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_file(status, path, headers)
+
+    async def send_empty(self, status: int, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ctx.send_empty(status, headers)
+
+
+class _ForwardedWebSocket(WebSocket):
+    """WebSocket wrapper that exposes the forwarded client address.
+
+    Everything except ``client`` is delegated to the wrapped socket via
+    ``__getattr__``, so it works with any concrete ``WebSocket`` (ASGI or
+    RSGI) and preserves attributes set by other mixins (e.g. ``session``).
+    """
+
+    def __init__(self, ws: WebSocket, client: Tuple[str, int]) -> None:
+        object.__setattr__(self, '_ws', ws)
+        object.__setattr__(self, 'session', ws.session)
+        object.__setattr__(self, 'client', client)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ws':
+            raise AttributeError(name)
+        return getattr(self._ws, name)
+
+    async def accept(self, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ws.accept(headers)
+
+    async def receive(self) -> WebSocketMessage:
+        return await self._ws.receive()
+
+    async def send_text(self, data: str) -> None:
+        await self._ws.send_text(data)
+
+    async def send_bytes(self, data: bytes) -> None:
+        await self._ws.send_bytes(data)
+
+    async def close(self, code: int = 1000) -> None:
+        await self._ws.close(code)
+
+    async def __anext__(self) -> WebSocketMessage:
+        return await self._ws.__anext__()
+
+
+class ForwardedHeadersMixin(KayaMixin):
+    """Kaya mixin that resolves the client address from proxy headers
+    (``Forwarded``, ``X-Forwarded-For``, ``X-Forwarded-Host``), but only when
+    the direct socket peer is a trusted proxy.
+
+    Without this mixin, Kaya exposes the raw socket peer as ``ctx.client`` /
+    ``ws.client`` and ignores forwarded headers entirely. With the mixin
+    applied, forwarded headers are honored only if the socket peer IP belongs
+    to one of the ``trusted_proxies`` CIDRs; otherwise the context is left
+    untouched.
+
+    When the peer is trusted, the address chain is walked from right to left
+    and entries that are themselves trusted proxies are skipped, so a client
+    that prepends a spoofed entry cannot fool the resolution when the edge
+    proxy appends to the header (e.g. nginx with ``$proxy_add_x_forwarded_for``).
+
+    Example::
+
+        app = KayaApp(mixins=[
+            ForwardedHeadersMixin(trusted_proxies=['127.0.0.1', '::1', '10.0.0.0/8'])
+        ])
+    """
+
+    def __init__(self, trusted_proxies: Sequence[str] = ()) -> None:
+        self._trusted_networks: Tuple[_IPNetwork, ...] = tuple(
+            ip_network(cidr, strict=False) for cidr in trusted_proxies
+        )
+
+    def apply(self, app: KayaApp) -> None:
+        app.add_before_request_hook(self._before_request)
+        app.add_before_websocket_hook(self._before_websocket)
+
+    def _is_trusted(self, host: str) -> bool:
+        try:
+            addr: _IPAddress = ip_address(host)
+        except ValueError:
+            return False
+        return any(addr.version == network.version and addr in network
+                   for network in self._trusted_networks)
+
+    def _select_forwarded_entry(self, entries: List[Tuple[str, Optional[int]]]) -> Optional[Tuple[str, Optional[int]]]:
+        """Walk the chain right-to-left skipping trusted proxies; the first
+        untrusted entry is the client. If every entry is trusted, the leftmost
+        (original client) is returned.
+        """
+        for entry in reversed(entries):
+            if not self._is_trusted(entry[0]):
+                return entry
+        return entries[0] if entries else None
+
+    def _forwarded_port(self, headers: Mapping[str, Sequence[str]], socket_port: int) -> int:
+        forwarded_port = _first_header_value(headers, 'x-forwarded-port')
+        if forwarded_port is not None:
+            try:
+                return int(forwarded_port)
+            except ValueError:
+                pass
+        return socket_port
+
+    def _resolve(self,
+                 headers: Mapping[str, Sequence[str]],
+                 client: Optional[Tuple[str, int]]) -> Optional[Tuple[str, int]]:
+        if client is None or not self._is_trusted(client[0]):
+            return client
+        socket_port = client[1]
+
+        selected = self._select_forwarded_entry(_parse_forwarded_entries(headers))
+        if selected is not None:
+            host, port = selected
+            return host, port if port is not None else socket_port
+
+        xff_values = headers.get('x-forwarded-for')
+        if xff_values:
+            xff_entries = [entry.strip() for value in xff_values for entry in value.split(',') if entry.strip()]
+            selected_host = self._select_forwarded_entry([(entry, None) for entry in xff_entries])
+            if selected_host is not None:
+                return selected_host[0], self._forwarded_port(headers, socket_port)
+
+        xfh = _first_header_value(headers, 'x-forwarded-host')
+        if xfh is not None:
+            return xfh, self._forwarded_port(headers, socket_port)
+
+        return client
+
+    async def _before_request(self, ctx: HttpContext) -> Optional[HttpContext]:
+        resolved = self._resolve(ctx.headers, ctx.client)
+        if resolved is None or resolved is ctx.client:
+            return None
+        return _ForwardedHttpContext(ctx, resolved)
+
+    async def _before_websocket(self, ws: WebSocket) -> Optional[WebSocket]:
+        resolved = self._resolve(ws.headers, ws.client)
+        if resolved is None or resolved is ws.client:
+            return None
+        return _ForwardedWebSocket(ws, resolved)

packages/kaya-forwarded/tests/test_forwarded.py

@@ -0,0 +1,244 @@
+import asyncio
+import json
+import unittest
+from typing import Optional
+
+import httpx
+from pwo import async_test
+
+from kaya.core import HttpContext, KayaApp
+from kaya.core._asgi import AsgiWebSocket
+from kaya.forwarded import ForwardedHeadersMixin
+
+TRUSTED = ['127.0.0.1', '::1', '10.0.0.0/8']
+
+
+def make_app(trusted_proxies=TRUSTED) -> KayaApp:
+    mixins = [ForwardedHeadersMixin(trusted_proxies=trusted_proxies)] if trusted_proxies is not None else []
+    app = KayaApp(mixins=mixins)
+
+    @app.GET('/client')
+    async def client(ctx: HttpContext) -> None:
+        host, port = ctx.client if ctx.client is not None else (None, None)
+        await ctx.send_str(200, json.dumps({'host': host, 'port': port}))
+
+    return app
+
+
+async def request(app: KayaApp,
+                  headers: Optional[dict[str, str]] = None,
+                  client: tuple[str, int] = ('127.0.0.1', 123)) -> dict:
+    transport = httpx.ASGITransport(app=app, client=client)
+    async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as http_client:
+        r = await http_client.get('/client', headers=headers)
+        assert r.status_code == 200
+        return json.loads(r.text)
+
+
+class TrustedPeerTest(unittest.TestCase):
+
+    @async_test
+    async def test_no_headers_returns_socket_peer(self):
+        app = make_app()
+        result = await request(app)
+        self.assertEqual({'host': '127.0.0.1', 'port': 123}, result)
+
+    @async_test
+    async def test_forwarded_header_with_port(self):
+        app = make_app()
+        result = await request(app, headers={'Forwarded': 'for=203.0.113.5:1234'})
+        self.assertEqual({'host': '203.0.113.5', 'port': 1234}, result)
+
+    @async_test
+    async def test_forwarded_header_bracketed_ipv6(self):
+        app = make_app()
+        result = await request(app, headers={'Forwarded': 'for="[2001:db8::1]:4711"'})
+        self.assertEqual({'host': '2001:db8::1', 'port': 4711}, result)
+
+    @async_test
+    async def test_forwarded_header_without_port_keeps_socket_port(self):
+        app = make_app()
+        result = await request(app, headers={'Forwarded': 'for=203.0.113.5'})
+        self.assertEqual({'host': '203.0.113.5', 'port': 123}, result)
+
+    @async_test
+    async def test_forwarded_unknown_entry_skipped(self):
+        app = make_app()
+        result = await request(app, headers={'Forwarded': 'for=unknown, for=203.0.113.5'})
+        self.assertEqual('203.0.113.5', result['host'])
+
+    @async_test
+    async def test_forwarded_rightmost_untrusted_wins(self):
+        # attacker-controlled leftmost entry is skipped: the rightmost
+        # untrusted entry (appended by the trusted edge proxy) is the client
+        app = make_app()
+        result = await request(app, headers={'Forwarded': 'for=1.2.3.4, for=5.6.7.8, for=10.0.0.2'})
+        self.assertEqual('5.6.7.8', result['host'])
+
+    @async_test
+    async def test_x_forwarded_for_spoofed_leftmost_entry_skipped(self):
+        # XFF = "<attacker-supplied>, <real client>" as appended by the proxy
+        app = make_app()
+        result = await request(app, headers={'X-Forwarded-For': '1.2.3.4, 5.6.7.8'})
+        self.assertEqual('5.6.7.8', result['host'])
+
+    @async_test
+    async def test_x_forwarded_for_all_trusted_chain_uses_leftmost(self):
+        app = make_app()
+        result = await request(app, headers={'X-Forwarded-For': '10.0.0.5, 10.0.0.2'})
+        self.assertEqual('10.0.0.5', result['host'])
+
+    @async_test
+    async def test_x_forwarded_port(self):
+        app = make_app()
+        result = await request(app, headers={
+            'X-Forwarded-For': '203.0.113.5',
+            'X-Forwarded-Port': '8443',
+        })
+        self.assertEqual({'host': '203.0.113.5', 'port': 8443}, result)
+
+    @async_test
+    async def test_invalid_x_forwarded_port_ignored(self):
+        app = make_app()
+        result = await request(app, headers={
+            'X-Forwarded-For': '203.0.113.5',
+            'X-Forwarded-Port': 'not-a-port',
+        })
+        self.assertEqual({'host': '203.0.113.5', 'port': 123}, result)
+
+    @async_test
+    async def test_forwarded_takes_precedence_over_x_forwarded_for(self):
+        app = make_app()
+        result = await request(app, headers={
+            'Forwarded': 'for=203.0.113.5',
+            'X-Forwarded-For': '198.51.100.7',
+        })
+        self.assertEqual('203.0.113.5', result['host'])
+
+    @async_test
+    async def test_x_forwarded_host_fallback(self):
+        app = make_app()
+        result = await request(app, headers={'X-Forwarded-Host': '198.51.100.7'})
+        self.assertEqual('198.51.100.7', result['host'])
+
+    @async_test
+    async def test_ipv6_cidr_trust(self):
+        app = make_app(trusted_proxies=['2001:db8::/32'])
+        result = await request(app,
+                               headers={'X-Forwarded-For': '203.0.113.5'},
+                               client=('2001:db8::10', 9999))
+        self.assertEqual({'host': '203.0.113.5', 'port': 9999}, result)
+
+
+class UntrustedPeerTest(unittest.TestCase):
+
+    @async_test
+    async def test_untrusted_peer_ignores_forwarded_headers(self):
+        app = make_app()
+        result = await request(app,
+                               headers={'Forwarded': 'for=1.2.3.4', 'X-Forwarded-For': '1.2.3.4'},
+                               client=('203.0.113.99', 4567))
+        self.assertEqual({'host': '203.0.113.99', 'port': 4567}, result)
+
+    @async_test
+    async def test_empty_trusted_proxies_ignores_everything(self):
+        app = make_app(trusted_proxies=[])
+        result = await request(app, headers={'X-Forwarded-For': '1.2.3.4'})
+        self.assertEqual({'host': '127.0.0.1', 'port': 123}, result)
+
+    @async_test
+    async def test_invalid_cidr_fails_fast(self):
+        with self.assertRaises(ValueError):
+            ForwardedHeadersMixin(trusted_proxies=['not-a-cidr'])
+
+
+class OptOutTest(unittest.TestCase):
+
+    @async_test
+    async def test_without_mixin_headers_are_ignored(self):
+        app = KayaApp()
+
+        @app.GET('/client')
+        async def client(ctx: HttpContext) -> None:
+            host, port = ctx.client if ctx.client is not None else (None, None)
+            await ctx.send_str(200, json.dumps({'host': host, 'port': port}))
+
+        result = await request(app, headers={'Forwarded': 'for=1.2.3.4', 'X-Forwarded-For': '1.2.3.4'})
+        self.assertEqual({'host': '127.0.0.1', 'port': 123}, result)
+
+
+class WebSocketTest(unittest.TestCase):
+
+    @staticmethod
+    def _make_ws(headers):
+        async def send(message):
+            pass
+
+        async def receive():
+            return {'type': 'websocket.connect'}
+
+        scope = {
+            'type': 'websocket',
+            'path': '/ws',
+            'query_string': b'',
+            'scheme': 'ws',
+            'client': ('127.0.0.1', 12345),
+            'server': ('127.0.0.1', 80),
+            'headers': headers,
+        }
+        return AsgiWebSocket(scope, receive, send)
+
+    @async_test
+    async def test_websocket_trusted_peer(self):
+        mixin = ForwardedHeadersMixin(trusted_proxies=TRUSTED)
+        ws = self._make_ws([(b'x-forwarded-for', b'1.2.3.4, 5.6.7.8')])
+        wrapped = await mixin._before_websocket(ws)
+        assert wrapped is not None
+        self.assertEqual(('5.6.7.8', 12345), wrapped.client)
+
+    @async_test
+    async def test_websocket_untrusted_peer(self):
+        mixin = ForwardedHeadersMixin(trusted_proxies=['10.0.0.0/8'])
+        ws = self._make_ws([(b'x-forwarded-for', b'1.2.3.4')])
+        wrapped = await mixin._before_websocket(ws)
+        self.assertIsNone(wrapped)
+        self.assertEqual(('127.0.0.1', 12345), ws.client)
+
+
+class RsgiTest(unittest.TestCase):
+
+    def test_rsgi_context(self):
+        from kaya.rsgi import RsgiContext
+
+        class FakeScope:
+            scheme = 'http'
+            method = 'GET'
+            path = '/'
+            query_string = ''
+            headers = {'x-forwarded-for': '1.2.3.4, 5.6.7.8'}
+            client = '127.0.0.1:12345'
+            server = '127.0.0.1:80'
+
+        mixin = ForwardedHeadersMixin(trusted_proxies=TRUSTED)
+        ctx = RsgiContext(FakeScope(), object())  # type: ignore[arg-type]
+        wrapped = asyncio.run(mixin._before_request(ctx))
+        assert wrapped is not None
+        self.assertEqual(('5.6.7.8', 12345), wrapped.client)
+
+    def test_rsgi_context_untrusted_peer(self):
+        from kaya.rsgi import RsgiContext
+
+        class FakeScope:
+            scheme = 'http'
+            method = 'GET'
+            path = '/'
+            query_string = ''
+            headers = {'x-forwarded-for': '1.2.3.4'}
+            client = '192.0.2.1:12345'
+            server = '127.0.0.1:80'
+
+        mixin = ForwardedHeadersMixin(trusted_proxies=TRUSTED)
+        ctx = RsgiContext(FakeScope(), object())  # type: ignore[arg-type]
+        wrapped = asyncio.run(mixin._before_request(ctx))
+        self.assertIsNone(wrapped)
+        self.assertEqual(('192.0.2.1', 12345), ctx.client)

packages/kaya-oidc/README.md

@@ -40,20 +40,219 @@ async def profile(ctx: HttpContext):
 `OIDCMixin` depends on `SessionMixin`; passing only `oidc` to `KayaApp(mixins=...)`
 also works because the app applies mixin dependencies automatically.
 
+## Multiple providers
+
+Use `OIDCProviders` to run several OIDC providers in one application. Each
+config's `provider` becomes a route segment under `base_path`
+(`/auth/{provider}/login`, `/auth/{provider}/callback` and
+`/auth/{provider}/logout`), and all providers share a single `SessionMixin`:
+
+```python
+from kaya.oidc import OIDCConfig, OIDCProviders
+
+session = SessionMixin(InMemorySessionStore())
+oidc = OIDCProviders(
+    [
+        OIDCConfig(
+            issuer='https://accounts.google.com',
+            client_id=os.environ['GOOGLE_CLIENT_ID'],
+            client_secret=os.environ['GOOGLE_CLIENT_SECRET'],
+            redirect_uri='http://localhost:8000/auth/google/callback',
+            provider='google',
+        ),
+        OIDCConfig(
+            issuer='https://github.com/login/oauth',  # or any OIDC issuer
+            client_id=os.environ['GITHUB_CLIENT_ID'],
+            client_secret=os.environ['GITHUB_CLIENT_SECRET'],
+            redirect_uri='http://localhost:8000/auth/github/callback',
+            provider='github',
+        ),
+    ],
+    session=session,
+    base_path='/auth',  # optional
+)
+app = KayaApp(mixins=[session, oidc])
+
+@app.GET('/google-profile')
+@oidc.require_auth('google')
+async def google_profile(ctx: HttpContext):
+    user = oidc.get_user(ctx, 'google')
+    await ctx.send_str(200, f"Hello {user.email or user.sub}")
+
+@app.GET('/who')
+async def who(ctx: HttpContext):
+    users = oidc.get_users(ctx)                     # {provider: OIDCUser}
+    providers = oidc.logged_in_providers(ctx)       # ['google', ...]
+    await ctx.send_str(200, ', '.join(users))
+```
+
+Each provider's session state is namespaced as `oidc:{provider}:...`. Make sure
+each config's `redirect_uri` points at that provider's derived callback path.
+
+### Identity strategy
+
+`strategy` controls how many identities may coexist in the shared session:
+
+- `'single-identity'` (default): completing a login evicts every other
+  provider's identity and tokens, so the session holds exactly one user — last
+  login wins, like Spring Security. After a GitHub login, `get_user(ctx,
+  'google')` returns `None` and `require_auth('google')` redirects to the Google
+  login.
+- `'multi-identity'`: each provider stays logged in independently. Use it for
+  linked accounts, aggregating several provider APIs, or step-up flows. Logging
+  out of one provider keeps the shared session alive while another provider is
+  still logged in.
+
+```python
+oidc = OIDCProviders([google_config, github_config], session=session,
+                     strategy='multi-identity')
+```
+
+Ephemeral flow keys (`state`, `nonce`, `code_verifier`) are never evicted, so
+logins already in flight can still complete; under `'single-identity'` the last
+callback to finish wins. Under either strategy, `get_users(ctx)` only reports
+providers actually present in the session.
+
+The composable alternative is to create one `OIDCMixin` per provider, pointing
+each at distinct `login_path`/`callback_path`/`logout_path` values and sharing
+the same `SessionMixin`. The same `strategy` keyword is accepted and defaults to
+`'single-identity'`:
+
+```python
+google = OIDCMixin(google_config, session=session)
+github = OIDCMixin(github_config, session=session, strategy='multi-identity')
+app = KayaApp(mixins=[session, google, github])
+```
+
+> **Upgrading:** session keys are now prefixed with `oidc:{provider}:` (the
+> default provider is `default`). Existing logged-in users are signed out once
+> and simply re-authenticate.
+
+## Back-channel logout
+
+Set `backchannel_logout_path` to accept OIDC Back-Channel Logout tokens from
+the provider:
+
+```python
+OIDCConfig(
+    issuer=os.environ['OIDC_ISSUER'],
+    client_id=os.environ['OIDC_CLIENT_ID'],
+    client_secret=os.environ['OIDC_CLIENT_SECRET'],
+    redirect_uri='https://example.com/auth/callback',
+    backchannel_logout_path='/auth/backchannel-logout',
+)
+```
+
+Register the corresponding absolute URL (for example
+`https://example.com/auth/backchannel-logout`) as the client's back-channel
+logout URI with the provider. This registration happens at the provider; it is
+not part of OIDC discovery. With `OIDCProviders`, enabling the option derives
+`{base_path}/{provider}/backchannel-logout` for that provider.
+
+The endpoint accepts form-encoded `POST` requests containing `logout_token`.
+It validates the JWT signature against the provider JWKS, the `logout+jwt`
+type, issuer, audience, `iat`, `jti`, and the back-channel logout event, and
+rejects tokens containing `nonce`. A token with `sid` logs out sessions for
+that provider session; without `sid`, `sub` logs out all sessions for that
+subject. Under `multi-identity`, only the named provider's identity is removed
+from a shared session. Valid requests return `200` with
+`Cache-Control: no-store`, including when the session is already gone. Invalid
+requests return `400`.
+
+Back-channel logout requires a session store with index support. All built-in
+stores (`InMemorySessionStore`, `RedisSessionStore`, and
+`MemcacheSessionStore`) support it. `OIDCMixin` raises immediately if the
+configured store does not. Sessions created before upgrading are indexed on
+their next request.
+
+Logout tokens must be asymmetrically signed; unsigned tokens, HMAC signatures,
+and encrypted logout tokens (JWE) are not supported. `jti` is required, but no
+replay cache is maintained: repeating a valid logout request is idempotent.
+`backchannel_logout_leeway` controls the allowed clock skew (60 seconds by
+default). For a templated Microsoft Entra issuer, the logout token must carry
+`tid`, just as for ID token validation.
+
+## Pushed authorization requests (PAR)
+
+`OIDCConfig.par` controls RFC 9126 Pushed Authorization Requests:
+
+- `'never'` (default): the authorization request travels as query parameters,
+  as before.
+- `'auto'`: push the request whenever the provider advertises a
+  `pushed_authorization_request_endpoint`; otherwise fall back to the plain
+  redirect.
+- `'always'`: always push; login raises a `RuntimeError` if the provider does
+  not support PAR.
+
+```python
+OIDCConfig(..., par='auto')
+```
+
+A provider that advertises `require_pushed_authorization_requests: true` must be
+configured with `par='auto'` or `par='always'`. With `par='never'` the login
+fails fast with a clear error instead of issuing a redirect the provider would
+reject.
+
+The same parameters as the plain authorization request (PKCE challenge,
+`state`, `nonce`, scopes, ...) are POSTed directly to the provider, and the
+browser is redirected with only `client_id` and the single-use `request_uri`.
+Request parameters therefore no longer travel through the user agent. PKCE,
+`state`, and `nonce` are still used and protect against request URI swapping.
+
+Client authentication follows the token endpoint: HTTP Basic when
+`client_secret` is set, or none for public clients. PAR with other client
+authentication methods (`private_key_jwt`, mTLS) is not supported.
+
 ## Features
 
 - Generic OIDC discovery
 - Authorization Code Flow with PKCE (S256)
 - ID token signature validation with JWKS
+- Issuer validation against discovery metadata, including support for
+  Microsoft Entra ID `{tenantid}` issuer templates
+- Refreshed ID token validation on token refresh
 - `state` and `nonce` protection
 - Session fixation defense via `regenerate_id()` after login
 - Optional userinfo endpoint fetch
 - Refresh token support
 - RP-initiated logout (when provider advertises `end_session_endpoint`)
+- Back-channel logout (`sid` and `sub` session invalidation)
+- Pushed Authorization Requests (RFC 9126) via `OIDCConfig.par`
+- Multiple providers in one app via `OIDCProviders` (or several `OIDCMixin` instances)
+- `single-identity` (default) or `multi-identity` session strategy
 - Composable with any other `KayaMixin` (RSGI, MCP, etc.)
 
+## Microsoft Entra ID
+
+Entra ID v2 ID tokens carry an `iss` claim of the form
+`https://login.microsoftonline.com/<tenant-id>/v2.0`, while the discovery
+metadata for the multi-tenant endpoints advertises the templated issuer
+`https://login.microsoftonline.com/{tenantid}/v2.0`. `kaya-oidc` validates the
+`iss` claim against the discovered metadata and substitutes the token's `tid`
+claim into `{tenantid}`, so both tenant-specific and multi-tenant issuers work:
+
+```python
+OIDCConfig(
+    issuer='https://login.microsoftonline.com/<tenant-id-or-domain>/v2.0',
+    client_id=os.environ['OIDC_CLIENT_ID'],
+    client_secret=os.environ['OIDC_CLIENT_SECRET'],
+    redirect_uri='https://example.com/auth/callback',
+)
+```
+
+Use a tenant-specific issuer (the tenant GUID or a verified domain name) to
+restrict logins to that tenant. The `common` and `organizations` aliases are
+multi-tenant: any tenant in that cloud can obtain an ID token that passes
+validation. If you build a multi-tenant application, check the `tid` claim
+against the tenants you trust.
+
 ## Security notes
 
+- The `iss` claim is validated against the `issuer` value of the provider's
+  discovery document, not against `OIDCConfig.issuer` (they can differ, for
+  example for Entra ID multi-tenant endpoints).
+- Refreshed ID tokens are validated before being stored; the `nonce` is also
+  checked when the refreshed token carries one.
 - The `none` signing algorithm is rejected by default.
 - Only algorithms listed in `OIDCConfig.allowed_id_token_algorithms` are accepted.
 - Always use HTTPS for `redirect_uri` in production.

packages/kaya-oidc/pyproject.toml

@@ -28,11 +28,6 @@ dependencies = [
     "PyJWT[crypto]",
 ]
 
-[project.optional-dependencies]
-dev = [
-    "build", "mypy", "ipdb", "twine", "httpx", "httpx-ws"
-]
-
 [project.urls]
 "Homepage" = "https://github.com/woggioni/kaya"
 "Bug Tracker" = "https://github.com/woggioni/kaya/issues"

packages/kaya-oidc/src/kaya/oidc/__init__.py

@@ -1,11 +1,15 @@
 from ._client import OIDCClient
-from ._config import OIDCConfig
+from ._config import OIDCConfig, PARPolicy
-from ._mixin import OIDCMixin, OIDCUser
+from ._mixin import IdentityStrategy, OIDCMixin, OIDCUser
+from ._providers import OIDCProviders
 
 
 __all__ = [
+    'IdentityStrategy',
     'OIDCClient',
     'OIDCConfig',
     'OIDCMixin',
+    'OIDCProviders',
     'OIDCUser',
+    'PARPolicy',
 ]

packages/kaya-oidc/src/kaya/oidc/_client.py

@@ -1,3 +1,4 @@
+import re
 from typing import Any, Mapping, Optional, Sequence, cast
 from urllib.parse import urlencode
 
@@ -5,9 +6,13 @@ import httpx
 import jwt
 from jwt import PyJWK
 
-from ._config import OIDCConfig
+from ._config import PARPolicy, OIDCConfig
 from ._utils import generate_nonce, generate_pkce, generate_state
 
+_TENANT_ID_PLACEHOLDER = re.compile(r'\{tenantid\}', re.IGNORECASE)
+_BACKCHANNEL_LOGOUT_EVENT = 'http://schemas.openid.net/event/backchannel-logout'
+_LOGOUT_TOKEN_TYPES = frozenset({'logout+jwt', 'application/logout+jwt'})
+
 
 class OIDCClient:
     """Low-level OIDC client implementing discovery, PKCE, and token validation."""
@@ -42,8 +47,14 @@ class OIDCClient:
         async with httpx.AsyncClient() as client:
             return await client.request(method, url, **kwargs)
 
-    async def build_authorization_url(self) -> tuple[str, str, str, str]:
+    async def build_authorization_url(self, par: PARPolicy = 'never') -> tuple[str, str, str, str]:
-        """Return (authorization_url, state, nonce, code_verifier)."""
+        """Return (authorization_url, state, nonce, code_verifier).
+
+        When ``par`` selects Pushed Authorization Requests (RFC 9126), the
+        authorization request parameters are POSTed to the provider's PAR
+        endpoint first and the returned URL carries only ``client_id`` and
+        ``request_uri``.
+        """
         metadata = await self._ensure_metadata()
         authorization_endpoint = metadata.get('authorization_endpoint')
         if not isinstance(authorization_endpoint, str):
@@ -54,7 +65,6 @@ class OIDCClient:
         code_verifier, code_challenge = generate_pkce()
 
         params = {
-            'client_id': self._config.client_id,
             'response_type': 'code',
             'scope': ' '.join(self._config.scopes),
             'redirect_uri': self._config.redirect_uri,
@@ -63,9 +73,67 @@ class OIDCClient:
             'code_challenge': code_challenge,
             'code_challenge_method': 'S256',
         }
-        url = authorization_endpoint + '?' + urlencode(params)
+
+        if self._use_par(metadata, par):
+            request_uri = await self._push_authorization_request(metadata, params)
+            redirect_params = {'client_id': self._config.client_id, 'request_uri': request_uri}
+        else:
+            redirect_params = {'client_id': self._config.client_id, **params}
+
+        url = authorization_endpoint + '?' + urlencode(redirect_params)
         return url, state, nonce, code_verifier
 
+    def _use_par(self, metadata: Mapping[str, Any], policy: PARPolicy) -> bool:
+        endpoint = metadata.get('pushed_authorization_request_endpoint')
+        required = metadata.get('require_pushed_authorization_requests') is True
+
+        if required:
+            if not isinstance(endpoint, str):
+                raise RuntimeError(
+                    'OIDC provider requires pushed authorization requests but does not '
+                    'advertise a pushed_authorization_request_endpoint'
+                )
+            if policy == 'never':
+                raise RuntimeError(
+                    "OIDC provider requires pushed authorization requests; set par to "
+                    "'auto' or 'always'"
+                )
+            return True
+
+        if policy == 'always':
+            if not isinstance(endpoint, str):
+                raise RuntimeError(
+                    'OIDC provider does not advertise a pushed_authorization_request_endpoint'
+                )
+            return True
+
+        return policy == 'auto' and isinstance(endpoint, str)
+
+    async def _push_authorization_request(
+        self, metadata: Mapping[str, Any], params: Mapping[str, str]
+    ) -> str:
+        endpoint = metadata.get('pushed_authorization_request_endpoint')
+        if not isinstance(endpoint, str):
+            raise RuntimeError(
+                'OIDC provider does not advertise a pushed_authorization_request_endpoint'
+            )
+
+        # RFC 9126 section 2.1: client_id is required in the body even when the
+        # client authenticates with the Authorization header.
+        data = {'client_id': self._config.client_id, **params}
+        resp = await self._request('POST', endpoint, data=data, auth=self._client_auth())
+        resp.raise_for_status()
+        body = resp.json()
+        request_uri = body.get('request_uri') if isinstance(body, Mapping) else None
+        if not isinstance(request_uri, str):
+            raise RuntimeError('PAR endpoint response is missing request_uri')
+        return request_uri
+
+    def _client_auth(self) -> Optional[tuple[str, str]]:
+        if self._config.client_secret is None:
+            return None
+        return (self._config.client_id, self._config.client_secret)
+
     async def fetch_token(self, code: str, code_verifier: str) -> Mapping[str, Any]:
         metadata = await self._ensure_metadata()
         token_endpoint = metadata.get('token_endpoint')
@@ -79,11 +147,8 @@ class OIDCClient:
             'client_id': self._config.client_id,
             'code_verifier': code_verifier,
         }
-        auth: Optional[tuple[str, str]] = None
-        if self._config.client_secret is not None:
-            auth = (self._config.client_id, self._config.client_secret)
 
-        resp = await self._request('POST', token_endpoint, data=data, auth=auth)
+        resp = await self._request('POST', token_endpoint, data=data, auth=self._client_auth())
         resp.raise_for_status()
         return cast(Mapping[str, Any], resp.json())
 
@@ -98,15 +163,89 @@ class OIDCClient:
             'refresh_token': refresh_token,
             'client_id': self._config.client_id,
         }
-        auth: Optional[tuple[str, str]] = None
-        if self._config.client_secret is not None:
-            auth = (self._config.client_id, self._config.client_secret)
 
-        resp = await self._request('POST', token_endpoint, data=data, auth=auth)
+        resp = await self._request('POST', token_endpoint, data=data, auth=self._client_auth())
         resp.raise_for_status()
         return cast(Mapping[str, Any], resp.json())
 
     async def validate_id_token(self, id_token: str, nonce: str) -> Mapping[str, Any]:
+        payload = await self._decode_id_token(id_token)
+        if payload.get('nonce') != nonce:
+            raise ValueError('ID token nonce mismatch')
+        return payload
+
+    async def validate_refreshed_id_token(
+        self,
+        id_token: str,
+        expected_nonce: Optional[str] = None,
+    ) -> Mapping[str, Any]:
+        """Validate an ID token returned by the refresh token grant.
+
+        Unlike the authorization code flow, the provider may omit the ``nonce``
+        claim; when it is present and the original nonce is known, the two must
+        match (OIDC Core 12.2).
+        """
+        payload = await self._decode_id_token(id_token)
+        token_nonce = payload.get('nonce')
+        if token_nonce is not None and expected_nonce is not None and token_nonce != expected_nonce:
+            raise ValueError('ID token nonce mismatch')
+        return payload
+
+    async def validate_logout_token(self, logout_token: str) -> Mapping[str, Any]:
+        """Validate an OIDC Back-Channel Logout token and return its claims."""
+        header = jwt.get_unverified_header(logout_token)
+        typ = header.get('typ')
+        if not isinstance(typ, str) or typ.lower() not in _LOGOUT_TOKEN_TYPES:
+            raise ValueError('Logout token typ must be logout+jwt')
+
+        alg = header.get('alg')
+        if not isinstance(alg, str):
+            raise ValueError('Logout token header is missing alg')
+        if alg == 'none' or alg.startswith('HS'):
+            raise ValueError('Logout tokens must use an asymmetric signature')
+        if alg not in self._config.allowed_id_token_algorithms:
+            raise ValueError(f'Logout token algorithm {alg} is not allowed')
+
+        metadata_issuer = await self._get_metadata_issuer()
+        jwks = await self._ensure_jwks()
+        signing_key = self._get_signing_key(jwks, header.get('kid'), alg)
+        payload = jwt.decode(
+            logout_token,
+            signing_key.key,
+            algorithms=[alg],
+            audience=self._config.client_id,
+            leeway=self._config.backchannel_logout_leeway,
+            options={
+                'require': ['iss', 'aud', 'iat', 'jti', 'events'],
+                'verify_exp': True,
+                'verify_iat': True,
+                'verify_nbf': True,
+            },
+        )
+        if not isinstance(payload, dict):
+            raise ValueError('Logout token payload is not a JSON object')
+        self._validate_issuer(payload, metadata_issuer)
+
+        if not isinstance(payload.get('jti'), str):
+            raise ValueError('Logout token jti must be a string')
+        events = payload.get('events')
+        if (not isinstance(events, Mapping)
+                or not isinstance(events.get(_BACKCHANNEL_LOGOUT_EVENT), Mapping)):
+            raise ValueError('Logout token is missing the back-channel logout event')
+        if 'nonce' in payload:
+            raise ValueError('Logout token must not contain a nonce')
+
+        sub = payload.get('sub')
+        sid = payload.get('sid')
+        if sub is not None and not isinstance(sub, str):
+            raise ValueError('Logout token sub must be a string')
+        if sid is not None and not isinstance(sid, str):
+            raise ValueError('Logout token sid must be a string')
+        if sub is None and sid is None:
+            raise ValueError('Logout token must contain sub or sid')
+        return payload
+
+    async def _decode_id_token(self, id_token: str) -> Mapping[str, Any]:
         header = jwt.get_unverified_header(id_token)
         alg = header.get('alg')
         if not isinstance(alg, str):
@@ -115,29 +254,59 @@ class OIDCClient:
         if alg == 'none':
             if not self._config.allow_unsigned_id_tokens:
                 raise ValueError('Unsigned ID tokens are not allowed')
+            metadata_issuer = await self._get_metadata_issuer()
             payload = jwt.decode(
                 id_token,
-                options={'verify_signature': False},
+                audience=self._config.client_id,
+                options={
+                    'verify_signature': False,
+                    'verify_aud': True,
+                    'verify_exp': True,
+                    'verify_iat': True,
+                    'verify_nbf': True,
+                },
             )
         else:
             if alg not in self._config.allowed_id_token_algorithms:
                 raise ValueError(f'ID token algorithm {alg} is not allowed')
+            metadata_issuer = await self._get_metadata_issuer()
             jwks = await self._ensure_jwks()
             signing_key = self._get_signing_key(jwks, header.get('kid'), alg)
             payload = jwt.decode(
                 id_token,
                 signing_key.key,
                 algorithms=[alg],
-                issuer=self._config.issuer,
                 audience=self._config.client_id,
             )
 
         if not isinstance(payload, dict):
             raise ValueError('ID token payload is not a JSON object')
-        if payload.get('nonce') != nonce:
+        self._validate_issuer(payload, metadata_issuer)
-            raise ValueError('ID token nonce mismatch')
         return payload
 
+    async def _get_metadata_issuer(self) -> str:
+        metadata = await self._ensure_metadata()
+        issuer = metadata.get('issuer')
+        if not isinstance(issuer, str):
+            raise RuntimeError('OIDC provider does not advertise an issuer')
+        return issuer
+
+    @staticmethod
+    def _validate_issuer(payload: Mapping[str, Any], metadata_issuer: str) -> None:
+        iss = payload.get('iss')
+        if not isinstance(iss, str):
+            raise jwt.MissingRequiredClaimError('iss')
+
+        expected = metadata_issuer
+        if _TENANT_ID_PLACEHOLDER.search(expected):
+            tenant_id = payload.get('tid')
+            if not isinstance(tenant_id, str):
+                raise jwt.InvalidIssuerError('Invalid issuer')
+            expected = _TENANT_ID_PLACEHOLDER.sub(tenant_id, expected, count=1)
+
+        if iss != expected:
+            raise jwt.InvalidIssuerError('Invalid issuer')
+
     def _get_signing_key(self, jwks: Mapping[str, Any], kid: Optional[str], alg: str) -> PyJWK:
         keys = jwks.get('keys')
         if not isinstance(keys, Sequence):

packages/kaya-oidc/src/kaya/oidc/_config.py

@@ -1,13 +1,37 @@
+import re
 from dataclasses import dataclass, field
-from typing import Any, Optional, Sequence
+from typing import Any, Literal, Optional, Sequence
 
 import httpx
 
+_PROVIDER_PATTERN = re.compile(r'^[A-Za-z0-9_-]+$')
+
+type PARPolicy = Literal['never', 'auto', 'always']
+
+_PAR_POLICIES: tuple[PARPolicy, ...] = ('never', 'auto', 'always')
+
 
 @dataclass
 class OIDCConfig:
     """Configuration for an OpenID Connect provider.
 
+    ``provider`` is a stable identifier for this provider. It namespaces the
+    session state (``oidc:{provider}:...``) so several providers can be used in
+    the same application without interfering with each other.
+
+    ``par`` selects when to use Pushed Authorization Requests (RFC 9126):
+    ``'never'`` uses a plain query-string authorization request, ``'auto'``
+    pushes the request whenever the provider advertises a
+    ``pushed_authorization_request_endpoint``, and ``'always'`` requires PAR.
+    A provider that sets ``require_pushed_authorization_requests`` is always
+    treated as requiring PAR.
+
+    ``backchannel_logout_path`` enables OIDC Back-Channel Logout when set to
+    an application path. Register the corresponding absolute URL with the
+    provider. It requires a session store with index support.
+    ``backchannel_logout_leeway`` is the clock-skew allowance, in seconds,
+    used when validating logout tokens.
+
     ``client_secret`` is optional; omit it for public clients.
     ``fetch_userinfo`` controls whether the userinfo endpoint is queried after
     token exchange.
@@ -35,8 +59,28 @@ class OIDCConfig:
         'EdDSA',
     ))
     http_client: Optional[httpx.AsyncClient] = None
+    provider: str = 'default'
+    par: PARPolicy = 'never'
+    backchannel_logout_path: Optional[str] = None
+    backchannel_logout_leeway: int = 60
 
     def __post_init__(self) -> None:
+        if not self.provider or _PROVIDER_PATTERN.match(self.provider) is None:
+            raise ValueError(
+                'provider must be a non-empty string of letters, digits, '
+                "underscores or hyphens (got "
+                f'{self.provider!r})'
+            )
+        if self.par not in _PAR_POLICIES:
+            raise ValueError(
+                f'par must be one of {", ".join(map(repr, _PAR_POLICIES))} '
+                f'(got {self.par!r})'
+            )
+        if (self.backchannel_logout_path is not None
+                and not self.backchannel_logout_path.startswith('/')):
+            raise ValueError('backchannel_logout_path must start with "/"')
+        if self.backchannel_logout_leeway < 0:
+            raise ValueError('backchannel_logout_leeway must be non-negative')
         scopes_list = list(self.scopes)
         if 'openid' not in scopes_list:
             self.scopes = ('openid', *scopes_list)

packages/kaya-oidc/src/kaya/oidc/_mixin.py

@@ -1,5 +1,6 @@
-from typing import Any, Awaitable, Callable, Mapping, Optional, Sequence
+from typing import Any, Awaitable, Callable, Literal, Mapping, Optional, Sequence, cast
 
+import jwt
 from kaya.core import HttpContext, KayaApp, KayaMixin
 from kaya.session import Session, SessionMixin
 from urllib.parse import parse_qs
@@ -10,6 +11,14 @@ from ._config import OIDCConfig
 
 type HttpHandler = Callable[..., Awaitable[None]]
 
+type IdentityStrategy = Literal['single-identity', 'multi-identity']
+
+_SESSION_NAMESPACE = 'oidc'
+_USER_SUFFIX = 'user'
+_IDENTITY_FIELDS = frozenset({'user', 'id_token', 'access_token', 'refresh_token', 'sid'})
+_IDENTITY_STRATEGIES: tuple[IdentityStrategy, ...] = ('single-identity', 'multi-identity')
+_BACKCHANNEL_BODY_LIMIT = 64 * 1024
+
 
 class OIDCUser(Mapping[str, Any]):
     """Read-only view of the OIDC userinfo / ID token claims."""
@@ -28,7 +37,7 @@ class OIDCUser(Mapping[str, Any]):
 
     @property
     def sub(self) -> str:
-        return self._data['sub']
+        return cast(str, self._data['sub'])
 
     @property
     def email(self) -> Optional[str]:
@@ -56,6 +65,21 @@ class OIDCMixin(KayaMixin):
     - ``callback_path`` (default ``/auth/callback``): handles the provider callback.
     - ``logout_path`` (default ``/auth/logout``): logs the user out.
 
+    When ``backchannel_logout_path`` is configured, a POST route accepting
+    OIDC Back-Channel Logout tokens is registered as well. This requires an
+    index-capable session store.
+
+    Session state is namespaced by ``OIDCConfig.provider`` as
+    ``oidc:{provider}:...`` so several providers can share one session. Use one
+    ``OIDCMixin`` per provider (with distinct route paths), or
+    :class:`~kaya.oidc.OIDCProviders` to wire several at once.
+
+    ``strategy`` controls how many identities may coexist in the session. The
+    default ``'single-identity'`` evicts every other provider's identity after a
+    successful login, so the session has exactly one user (last login wins).
+    ``'multi-identity'`` keeps each provider logged in independently, which is
+    useful for linked accounts, provider API aggregation, and step-up flows.
+
     Example::
 
         session = SessionMixin(InMemorySessionStore())
@@ -69,23 +93,115 @@ class OIDCMixin(KayaMixin):
             ...
     """
 
-    def __init__(self, config: OIDCConfig, session: SessionMixin) -> None:
+    def __init__(
+        self,
+        config: OIDCConfig,
+        session: SessionMixin,
+        strategy: IdentityStrategy = 'single-identity',
+    ) -> None:
+        if strategy not in _IDENTITY_STRATEGIES:
+            raise ValueError(
+                'strategy must be one of '
+                f'{", ".join(map(repr, _IDENTITY_STRATEGIES))} (got {strategy!r})'
+            )
         self._config = config
         self._session = session
         self._client = OIDCClient(config)
+        self._strategy = strategy
+        self._prefix = f'{_SESSION_NAMESPACE}:{config.provider}:'
+        if (config.backchannel_logout_path is not None
+                and not session.store.supports_indexes):
+            raise ValueError(
+                'backchannel_logout_path requires a session store with index support'
+            )
+
+    @property
+    def provider(self) -> str:
+        return self._config.provider
+
+    @property
+    def strategy(self) -> IdentityStrategy:
+        return self._strategy
+
+    def _key(self, name: str) -> str:
+        return f'{self._prefix}{name}'
+
+    def _index_name(self, claim: str, provider: Optional[str] = None) -> str:
+        return f'{_SESSION_NAMESPACE}:{provider or self.provider}:{claim}'
+
+    def _apply_identity_indexes(
+        self,
+        session: Session,
+        sub: str,
+        sid: Optional[str],
+    ) -> None:
+        session.add_index(self._index_name('sub'), sub)
+        if sid is not None:
+            session.add_index(self._index_name('sid'), sid)
+        session[self._key('indexed')] = True
+
+    def _remove_identity_indexes(
+        self,
+        session: Session,
+        provider: Optional[str] = None,
+    ) -> None:
+        prefix = f'{_SESSION_NAMESPACE}:{provider or self.provider}:'
+        user = session.get(f'{prefix}user')
+        if isinstance(user, Mapping):
+            sub = user.get('sub')
+            if isinstance(sub, str):
+                session.remove_index(self._index_name('sub', provider), sub)
+        sid = session.get(f'{prefix}sid')
+        if isinstance(sid, str):
+            session.remove_index(self._index_name('sid', provider), sid)
+
+    def _backfill_identity_indexes(self, session: Session) -> None:
+        """Index an authenticated session created before index support."""
+        user = session.get(self._key('user'))
+        if not isinstance(user, Mapping) or self._key('indexed') in session:
+            return
+        sub = user.get('sub')
+        if not isinstance(sub, str):
+            return
+
+        sid = session.get(self._key('sid'))
+        if not isinstance(sid, str):
+            id_token = session.get(self._key('id_token'))
+            if isinstance(id_token, str):
+                try:
+                    claims = jwt.decode(
+                        id_token,
+                        options={'verify_signature': False},
+                    )
+                    candidate = claims.get('sid')
+                    if isinstance(candidate, str):
+                        sid = candidate
+                        session[self._key('sid')] = candidate
+                except jwt.PyJWTError:
+                    pass
+        self._apply_identity_indexes(
+            session,
+            sub,
+            sid if isinstance(sid, str) else None,
+        )
 
     @property
     def dependencies(self) -> Sequence[KayaMixin]:
         return [self._session]
 
     def apply(self, app: KayaApp) -> None:
+        if self._config.backchannel_logout_path is not None:
+            app.add_before_request_hook(self._before_request)
+
         @app.GET(self._config.login_path)
         async def login(ctx: HttpContext) -> None:
-            auth_url, state, nonce, code_verifier = await self._client.build_authorization_url()
+            auth_url, state, nonce, code_verifier = await self._client.build_authorization_url(
+                par=self._config.par
+            )
             session = self._session_of(ctx)
-            session['oidc_state'] = state
+            session[self._key('state')] = state
-            session['oidc_nonce'] = nonce
+            session[self._key('nonce')] = nonce
-            session['oidc_code_verifier'] = code_verifier
+            session[self._key('code_verifier')] = code_verifier
             await ctx.send_empty(302, {'Location': auth_url})
 
         @app.GET(self._config.callback_path)
@@ -108,13 +224,13 @@ class OIDCMixin(KayaMixin):
                 return
 
             session = self._session_of(ctx)
-            expected_state = session.get('oidc_state')
+            expected_state = session.get(self._key('state'))
             if state != expected_state:
                 await ctx.send_str(400, 'Invalid state')
                 return
 
-            nonce = session.get('oidc_nonce', '')
+            nonce = session.get(self._key('nonce'), '')
-            code_verifier = session.get('oidc_code_verifier', '')
+            code_verifier = session.get(self._key('code_verifier'), '')
 
             try:
                 token_response = await self._client.fetch_token(code, code_verifier)
@@ -124,6 +240,12 @@ class OIDCMixin(KayaMixin):
                     return
 
                 claims = await self._client.validate_id_token(id_token, nonce)
+                sub = claims.get('sub')
+                if not isinstance(sub, str):
+                    raise ValueError('ID token is missing a valid sub claim')
+                sid = claims.get('sid')
+                if sid is not None and not isinstance(sid, str):
+                    raise ValueError('ID token sid must be a string')
 
                 user: dict[str, Any] = dict(claims)
                 access_token = token_response.get('access_token')
@@ -131,31 +253,151 @@ class OIDCMixin(KayaMixin):
                     userinfo = await self._client.fetch_userinfo(access_token)
                     user.update(userinfo)
 
-                session.pop('oidc_state', None)
+                session.pop(self._key('state'), None)
-                session.pop('oidc_nonce', None)
+                session.pop(self._key('code_verifier'), None)
-                session.pop('oidc_code_verifier', None)
+                # Keep this provider's nonce so refreshed ID tokens can be
+                # checked for nonce continuity (OIDC Core 12.2).
 
-                session['oidc_user'] = user
+                self._remove_identity_indexes(session)
-                session['oidc_id_token'] = id_token
+                session[self._key('user')] = user
+                session[self._key('id_token')] = id_token
+                session.pop(self._key('sid'), None)
+                if sid is not None:
+                    session[self._key('sid')] = sid
+                self._apply_identity_indexes(session, sub, sid)
                 if isinstance(access_token, str):
-                    session['oidc_access_token'] = access_token
+                    session[self._key('access_token')] = access_token
                 if 'refresh_token' in token_response:
-                    session['oidc_refresh_token'] = token_response['refresh_token']
+                    session[self._key('refresh_token')] = token_response['refresh_token']
+
+                if self._strategy == 'single-identity':
+                    self._strip_other_identities(session)
 
                 session.regenerate_id()
                 await ctx.send_empty(302, {'Location': self._config.post_login_redirect})
-            except ValueError as exc:
+            except (ValueError, jwt.PyJWTError) as exc:
                 await ctx.send_str(400, f'Authentication failed: {exc}')
 
         @app.GET(self._config.logout_path)
         async def logout(ctx: HttpContext) -> None:
             session = self._session_of(ctx)
-            id_token = session.get('oidc_id_token')
+            id_token = session.get(self._key('id_token'))
-            session.invalidate()
+            self._logout_session(session)
             logout_url = await self._client.build_logout_url(id_token if isinstance(id_token, str) else None)
             location = logout_url if logout_url is not None else self._config.post_logout_redirect
             await ctx.send_empty(302, {'Location': location})
 
+        backchannel_path = self._config.backchannel_logout_path
+        if backchannel_path is not None:
+            @app.POST(backchannel_path)
+            async def backchannel_logout(ctx: HttpContext) -> None:
+                # This endpoint is server-to-server. Never persist a browser
+                # session that happens to accompany the request.
+                ctx.session = Session()
+                try:
+                    logout_token = await self._read_logout_token(ctx)
+                    claims = await self._client.validate_logout_token(logout_token)
+                except (ValueError, jwt.PyJWTError):
+                    await ctx.send_str(
+                        400,
+                        'Invalid logout token',
+                        {'Cache-Control': 'no-store'},
+                    )
+                    return
+
+                await self._invalidate_by_logout_token(claims)
+                await ctx.send_empty(200, {'Cache-Control': 'no-store'})
+
+    def _logout_session(self, session: Session) -> None:
+        """Drop this provider's session state.
+
+        The shared session is only invalidated when no other provider remains
+        logged in, so logging out of one provider does not sign the user out of
+        the others.
+        """
+        self._remove_identity_indexes(session)
+        for key in [key for key in session if key.startswith(self._prefix)]:
+            del session[key]
+        if not any(_is_user_key(key) for key in session):
+            session.invalidate()
+
+    def _strip_other_identities(self, session: Session) -> None:
+        """Remove every other provider's identity and tokens from the session.
+
+        Only identity keys are dropped; ephemeral flow keys (``state``,
+        ``nonce``, ``code_verifier``) are left alone so logins already in flight
+        can still complete. Under this strategy the last callback to finish
+        wins.
+        """
+        other_providers = {
+            _provider_of_user_key(key)
+            for key in session
+            if _is_user_key(key) and not key.startswith(self._prefix)
+        }
+        for provider in other_providers:
+            self._remove_identity_indexes(session, provider)
+        for key in [key for key in session
+                    if _is_identity_key(key) and not key.startswith(self._prefix)]:
+            del session[key]
+
+    async def _before_request(self, ctx: HttpContext) -> Optional[HttpContext]:
+        session = ctx.session
+        if isinstance(session, Session):
+            self._backfill_identity_indexes(session)
+        return None
+
+    async def _read_logout_token(self, ctx: HttpContext) -> str:
+        content_type_values = ctx.headers.get('content-type')
+        if isinstance(content_type_values, str):
+            content_type = content_type_values
+        elif content_type_values:
+            content_type = content_type_values[0]
+        else:
+            content_type = ''
+        if content_type.split(';', 1)[0].strip().lower() != 'application/x-www-form-urlencoded':
+            raise ValueError('Back-channel logout requires a form-encoded request')
+
+        body = bytearray()
+        async for chunk in ctx.request_body:
+            body.extend(chunk)
+            if len(body) > _BACKCHANNEL_BODY_LIMIT:
+                raise ValueError('Back-channel logout request is too large')
+        form = parse_qs(body.decode('utf-8'), keep_blank_values=True)
+        logout_token = self._first_value(form.get('logout_token'))
+        if logout_token is None:
+            raise ValueError('Missing logout_token')
+        return logout_token
+
+    async def _invalidate_by_logout_token(self, claims: Mapping[str, Any]) -> None:
+        store = self._session.store
+        sub = claims.get('sub')
+        sid = claims.get('sid')
+        if isinstance(sid, str):
+            session_ids = await store.find_sessions(self._index_name('sid'), sid)
+        elif isinstance(sub, str):
+            session_ids = await store.find_sessions(self._index_name('sub'), sub)
+        else:
+            return
+
+        for session_id in session_ids:
+            session = await store.load(session_id)
+            if session is None:
+                continue
+            if isinstance(sid, str) and isinstance(sub, str):
+                user = session.get(self._key('user'))
+                if not isinstance(user, Mapping) or user.get('sub') != sub:
+                    continue
+
+            # A session can hold several provider identities. Remove only this
+            # provider's identity and delete the whole session when it was the
+            # last one, mirroring the local logout behavior.
+            self._logout_session(session)
+            if session.invalidated:
+                await store.delete(session_id)
+            else:
+                await store.save(session_id, session, self._session.max_age)
+                session.commit_indexes()
+
     @staticmethod
     def _session_of(ctx: HttpContext) -> Session:
         session = ctx.session
@@ -169,14 +411,31 @@ class OIDCMixin(KayaMixin):
         return None
 
     def is_authenticated(self, ctx: HttpContext) -> bool:
-        return 'oidc_user' in self._session_of(ctx)
+        return self._key('user') in self._session_of(ctx)
 
     def get_user(self, ctx: HttpContext) -> Optional[OIDCUser]:
-        user = self._session_of(ctx).get('oidc_user')
+        user = self._session_of(ctx).get(self._key('user'))
         if user is None or not isinstance(user, Mapping):
             return None
         return OIDCUser(user)
 
+    def logged_in_providers(self, ctx: HttpContext) -> list[str]:
+        """Return the names of every provider with a user in this session."""
+        return [_provider_of_user_key(key)
+                for key in self._session_of(ctx) if _is_user_key(key)]
+
+    def get_users(self, ctx: HttpContext) -> dict[str, OIDCUser]:
+        """Return the users of every provider logged into this session."""
+        session = self._session_of(ctx)
+        users: dict[str, OIDCUser] = {}
+        for key in session:
+            if not _is_user_key(key):
+                continue
+            data = session.get(key)
+            if isinstance(data, Mapping):
+                users[_provider_of_user_key(key)] = OIDCUser(data)
+        return users
+
     def require_auth(self, handler: HttpHandler) -> HttpHandler:
         async def wrapper(ctx: HttpContext, *args: Any, **kwargs: Any) -> None:
             if not self.is_authenticated(ctx):
@@ -186,18 +445,53 @@ class OIDCMixin(KayaMixin):
         return wrapper
 
     async def refresh_access_token(self, session: Session) -> Optional[str]:
-        refresh_token = session.get('oidc_refresh_token')
+        refresh_token = session.get(self._key('refresh_token'))
         if not isinstance(refresh_token, str):
             return None
         try:
             token_response = await self._client.refresh_token(refresh_token)
             access_token = token_response.get('access_token')
+            id_token = token_response.get('id_token')
+            if isinstance(id_token, str):
+                stored_nonce = session.get(self._key('nonce'))
+                claims = await self._client.validate_refreshed_id_token(
+                    id_token,
+                    stored_nonce if isinstance(stored_nonce, str) else None,
+                )
+                user = session.get(self._key('user'))
+                original_sub = user.get('sub') if isinstance(user, Mapping) else None
+                if isinstance(original_sub, str) and claims.get('sub') != original_sub:
+                    raise ValueError('ID token subject mismatch')
+
+                refreshed_sid = claims.get('sid')
+                stored_sid = session.get(self._key('sid'))
+                if (isinstance(refreshed_sid, str)
+                        and refreshed_sid != stored_sid):
+                    if isinstance(stored_sid, str):
+                        session.remove_index(self._index_name('sid'), stored_sid)
+                    session[self._key('sid')] = refreshed_sid
+                    session.add_index(self._index_name('sid'), refreshed_sid)
+
             if isinstance(access_token, str):
-                session['oidc_access_token'] = access_token
+                session[self._key('access_token')] = access_token
-            if 'id_token' in token_response:
+            if isinstance(id_token, str):
-                session['oidc_id_token'] = token_response['id_token']
+                session[self._key('id_token')] = id_token
             if 'refresh_token' in token_response:
-                session['oidc_refresh_token'] = token_response['refresh_token']
+                session[self._key('refresh_token')] = token_response['refresh_token']
             return access_token if isinstance(access_token, str) else None
         except Exception:
             return None
+
+
+def _is_user_key(key: str) -> bool:
+    return key.startswith(f'{_SESSION_NAMESPACE}:') and key.endswith(f':{_USER_SUFFIX}')
+
+
+def _is_identity_key(key: str) -> bool:
+    return (key.startswith(f'{_SESSION_NAMESPACE}:')
+            and key.rsplit(':', 1)[-1] in _IDENTITY_FIELDS)
+
+
+def _provider_of_user_key(key: str) -> str:
+    return key[len(_SESSION_NAMESPACE) + 1:-(len(_USER_SUFFIX) + 1)]
+

packages/kaya-oidc/src/kaya/oidc/_providers.py

@@ -0,0 +1,141 @@
+from dataclasses import replace
+from types import MappingProxyType
+from typing import Callable, Mapping, Optional, Sequence
+
+from kaya.core import HttpContext, KayaApp, KayaMixin
+from kaya.session import Session, SessionMixin
+
+from ._config import OIDCConfig
+from ._mixin import (
+    _IDENTITY_STRATEGIES,
+    HttpHandler,
+    IdentityStrategy,
+    OIDCMixin,
+    OIDCUser,
+)
+
+
+class OIDCProviders(KayaMixin):
+    """Wire several OpenID Connect providers into one application.
+
+    Each config's ``provider`` becomes a route segment under ``base_path``:
+    ``{base_path}/{provider}/login``, ``{base_path}/{provider}/callback`` and
+    ``{base_path}/{provider}/logout``. Providers that enable back-channel
+    logout also get ``{base_path}/{provider}/backchannel-logout``. All
+    providers share the supplied
+    :class:`~kaya.session.SessionMixin` and namespace their session state by
+    provider.
+
+    ``strategy`` controls how many identities may coexist in the session. The
+    default ``'single-identity'`` evicts every other provider's identity after a
+    successful login (last login wins). ``'multi-identity'`` keeps each provider
+    logged in independently, so logging out of one provider does not sign the
+    user out of the others.
+
+    Example::
+
+        session = SessionMixin(InMemorySessionStore())
+        oidc = OIDCProviders([google_config, github_config], session=session)
+        app = KayaApp(mixins=[session, oidc])
+
+        @app.GET('/profile')
+        @oidc.require_auth('google')
+        async def profile(ctx: HttpContext):
+            user = oidc.get_user(ctx, 'google')
+            ...
+    """
+
+    def __init__(
+        self,
+        configs: Sequence[OIDCConfig],
+        session: SessionMixin,
+        base_path: str = '/auth',
+        strategy: IdentityStrategy = 'single-identity',
+    ) -> None:
+        if not configs:
+            raise ValueError('At least one OIDCConfig is required')
+        if not base_path.startswith('/'):
+            raise ValueError('base_path must start with "/"')
+        if strategy not in _IDENTITY_STRATEGIES:
+            raise ValueError(
+                'strategy must be one of '
+                f'{", ".join(map(repr, _IDENTITY_STRATEGIES))} (got {strategy!r})'
+            )
+
+        self._session = session
+        self._strategy = strategy
+        self._base_path = base_path.rstrip('/')
+        self._providers: dict[str, OIDCMixin] = {}
+        for config in configs:
+            name = config.provider
+            if name in self._providers:
+                raise ValueError(f'Duplicate OIDC provider {name!r}')
+            backchannel_path = (
+                f'{self._base_path}/{name}/backchannel-logout'
+                if config.backchannel_logout_path is not None else None
+            )
+            self._providers[name] = OIDCMixin(
+                replace(
+                    config,
+                    login_path=f'{self._base_path}/{name}/login',
+                    callback_path=f'{self._base_path}/{name}/callback',
+                    logout_path=f'{self._base_path}/{name}/logout',
+                    backchannel_logout_path=backchannel_path,
+                ),
+                session=session,
+                strategy=strategy,
+            )
+
+    @property
+    def base_path(self) -> str:
+        return self._base_path
+
+    @property
+    def strategy(self) -> IdentityStrategy:
+        return self._strategy
+
+    @property
+    def providers(self) -> Mapping[str, OIDCMixin]:
+        return MappingProxyType(self._providers)
+
+    def provider(self, name: str) -> OIDCMixin:
+        try:
+            return self._providers[name]
+        except KeyError:
+            raise KeyError(f'Unknown OIDC provider {name!r}') from None
+
+    def __getitem__(self, name: str) -> OIDCMixin:
+        return self.provider(name)
+
+    @property
+    def dependencies(self) -> Sequence[KayaMixin]:
+        return [self._session]
+
+    def apply(self, app: KayaApp) -> None:
+        for mixin in self._providers.values():
+            mixin.apply(app)
+
+    def is_authenticated(self, ctx: HttpContext, provider: str) -> bool:
+        return self.provider(provider).is_authenticated(ctx)
+
+    def get_user(self, ctx: HttpContext, provider: str) -> Optional[OIDCUser]:
+        return self.provider(provider).get_user(ctx)
+
+    def get_users(self, ctx: HttpContext) -> dict[str, OIDCUser]:
+        """Return the user of every provider with a session on ``ctx``."""
+        users: dict[str, OIDCUser] = {}
+        for name, mixin in self._providers.items():
+            user = mixin.get_user(ctx)
+            if user is not None:
+                users[name] = user
+        return users
+
+    def logged_in_providers(self, ctx: HttpContext) -> list[str]:
+        """Return the names of the providers logged into ``ctx``."""
+        return [name for name, mixin in self._providers.items() if mixin.is_authenticated(ctx)]
+
+    def require_auth(self, provider: str) -> Callable[[HttpHandler], HttpHandler]:
+        return self.provider(provider).require_auth
+
+    async def refresh_access_token(self, session: Session, provider: str) -> Optional[str]:
+        return await self.provider(provider).refresh_access_token(session)

packages/kaya-oidc/tests/test_backchannel_logout.py

@@ -0,0 +1,427 @@
+import unittest
+from time import time
+from typing import Any, Optional
+from urllib.parse import parse_qs, urlparse
+
+import httpx
+import jwt
+from cryptography.hazmat.primitives.asymmetric import rsa
+from pwo import async_test
+from test_oidc import MockOIDCProvider, MockTransport
+
+from kaya.core import HttpContext, KayaApp
+from kaya.oidc import OIDCConfig, OIDCMixin, OIDCProviders
+from kaya.session import InMemorySessionStore, SessionMixin
+
+_EVENT = 'http://schemas.openid.net/event/backchannel-logout'
+
+
+class BackchannelProvider(MockOIDCProvider):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
+        self.sid: Optional[str] = None
+
+    def issue_id_token(self, *args: Any, **kwargs: Any) -> str:
+        token = super().issue_id_token(*args, **kwargs)
+        if self.sid is None:
+            return token
+        payload = jwt.decode(token, options={'verify_signature': False})
+        payload['sid'] = self.sid
+        return jwt.encode(
+            payload,
+            self.private_key,
+            algorithm='RS256',
+            headers={'kid': self.kid},
+        )
+
+
+class BackchannelLogoutTest(unittest.TestCase):
+
+    def setUp(self) -> None:
+        self.provider = BackchannelProvider()
+        self.http_client = httpx.AsyncClient(transport=MockTransport(self.provider))
+        self.store = InMemorySessionStore()
+        self.session = SessionMixin(self.store)
+        self.oidc = OIDCMixin(
+            OIDCConfig(
+                issuer=self.provider.issuer,
+                client_id='client',
+                client_secret='secret',
+                redirect_uri='http://localhost:8000/auth/callback',
+                backchannel_logout_path='/auth/backchannel-logout',
+                http_client=self.http_client,
+            ),
+            session=self.session,
+        )
+        self.app = KayaApp(mixins=[self.session, self.oidc])
+        self.transport = httpx.ASGITransport(app=self.app)
+
+        @self.app.GET('/profile')
+        @self.oidc.require_auth
+        async def profile(ctx: HttpContext) -> None:
+            user = self.oidc.get_user(ctx)
+            assert user is not None
+            await ctx.send_str(200, user.sub)
+
+        @self.app.GET('/refresh')
+        @self.oidc.require_auth
+        async def refresh(ctx: HttpContext) -> None:
+            token = await self.oidc.refresh_access_token(ctx.session)
+            await ctx.send_str(200, token or 'no-token')
+
+    def _client(self) -> httpx.AsyncClient:
+        return httpx.AsyncClient(transport=self.transport, base_url='http://127.0.0.1:80')
+
+    async def _login(self, client: httpx.AsyncClient, sid: str) -> None:
+        self.provider.sid = sid
+        response = await client.get('/auth/login', follow_redirects=False)
+        self.assertEqual(302, response.status_code)
+        query = parse_qs(urlparse(response.headers['Location']).query)
+        self.provider.nonce = query['nonce'][0]
+        response = await client.get(
+            '/auth/callback',
+            params={'code': 'mock-code', 'state': query['state'][0]},
+            follow_redirects=False,
+        )
+        self.assertEqual(302, response.status_code)
+
+    def _claims(self, **overrides: Any) -> dict[str, Any]:
+        claims: dict[str, Any] = {
+            'iss': self.provider.issuer,
+            'aud': 'client',
+            'iat': time(),
+            'jti': 'logout-token-id',
+            'events': {_EVENT: {}},
+            'sub': self.provider.sub,
+        }
+        claims.update(overrides)
+        return claims
+
+    def _token(
+        self,
+        claims: dict[str, Any],
+        *,
+        typ: str = 'logout+jwt',
+        key: Any = None,
+        algorithm: str = 'RS256',
+    ) -> str:
+        return jwt.encode(
+            claims,
+            self.provider.private_key if key is None else key,
+            algorithm=algorithm,
+            headers={'kid': self.provider.kid, 'typ': typ},
+        )
+
+    async def _post_logout(self, token: str) -> httpx.Response:
+        async with self._client() as client:
+            return await client.post(
+                '/auth/backchannel-logout',
+                data={'logout_token': token},
+            )
+
+    async def _profile_status(self, client: httpx.AsyncClient) -> int:
+        response = await client.get('/profile', follow_redirects=False)
+        return response.status_code
+
+    @async_test
+    async def test_logout_by_sid_only_invalidates_matching_session(self) -> None:
+        async with self._client() as first, self._client() as second:
+            await self._login(first, 'sid-a')
+            await self._login(second, 'sid-b')
+
+            response = await self._post_logout(self._token(self._claims(sid='sid-a')))
+            self.assertEqual(200, response.status_code)
+            self.assertEqual('no-store', response.headers['Cache-Control'])
+            self.assertNotIn('Set-Cookie', response.headers)
+            self.assertEqual(302, await self._profile_status(first))
+            self.assertEqual(200, await self._profile_status(second))
+            self.assertEqual([], await self.store.find_sessions('oidc:default:sid', 'sid-a'))
+            self.assertEqual(
+                [second.cookies['session_id']],
+                await self.store.find_sessions('oidc:default:sid', 'sid-b'),
+            )
+
+    @async_test
+    async def test_logout_by_sub_invalidates_all_user_sessions(self) -> None:
+        async with self._client() as first, self._client() as second, self._client() as other:
+            await self._login(first, 'sid-a')
+            await self._login(second, 'sid-b')
+            self.provider.sub = 'bob'
+            await self._login(other, 'sid-c')
+
+            response = await self._post_logout(self._token(self._claims(sub='user123')))
+            self.assertEqual(200, response.status_code)
+            self.assertEqual(302, await self._profile_status(first))
+            self.assertEqual(302, await self._profile_status(second))
+            self.assertEqual(200, await self._profile_status(other))
+
+    @async_test
+    async def test_sid_logout_verifies_sub_when_both_are_present(self) -> None:
+        async with self._client() as client:
+            await self._login(client, 'sid-a')
+            response = await self._post_logout(
+                self._token(self._claims(sub='someone-else', sid='sid-a'))
+            )
+            self.assertEqual(200, response.status_code)
+            self.assertEqual(200, await self._profile_status(client))
+
+    @async_test
+    async def test_unknown_session_is_idempotent(self) -> None:
+        response = await self._post_logout(self._token(self._claims(sid='unknown')))
+        self.assertEqual(200, response.status_code)
+
+    @async_test
+    async def test_invalid_logout_tokens_are_rejected(self) -> None:
+        other_key = rsa.generate_private_key(public_exponent=65537, key_size=2048)
+        missing_iat = self._claims(sid='sid-a')
+        del missing_iat['iat']
+        missing_jti = self._claims(sid='sid-a')
+        del missing_jti['jti']
+        missing_events = self._claims(sid='sid-a')
+        del missing_events['events']
+        missing_subject = self._claims()
+        del missing_subject['sub']
+
+        invalid_tokens = [
+            self._token(self._claims(sid='sid-a'), typ='JWT'),
+            jwt.encode(
+                self._claims(sid='sid-a'),
+                None,
+                algorithm='none',
+                headers={'typ': 'logout+jwt'},
+            ),
+            self._token(self._claims(sid='sid-a'), key=other_key),
+            self._token(self._claims(iss='https://evil.local', sid='sid-a')),
+            self._token(self._claims(aud='other-client', sid='sid-a')),
+            self._token(missing_iat),
+            self._token(missing_jti),
+            self._token(missing_events),
+            self._token(self._claims(events={'wrong-event': {}}, sid='sid-a')),
+            self._token(self._claims(events={_EVENT: None}, sid='sid-a')),
+            self._token(self._claims(nonce='forbidden', sid='sid-a')),
+            self._token(missing_subject),
+            self._token(self._claims(exp=time() - 3600, sid='sid-a')),
+            self._token(self._claims(sid='sid-a'), key='x' * 32, algorithm='HS256'),
+        ]
+
+        async with self._client() as client:
+            await self._login(client, 'sid-a')
+            for token in invalid_tokens:
+                response = await self._post_logout(token)
+                self.assertEqual(400, response.status_code)
+            self.assertEqual(200, await self._profile_status(client))
+
+    @async_test
+    async def test_invalid_requests_are_rejected(self) -> None:
+        async with self._client() as client:
+            response = await client.post('/auth/backchannel-logout', data={})
+            self.assertEqual(400, response.status_code)
+            response = await client.post(
+                '/auth/backchannel-logout',
+                content='logout_token=abc',
+                headers={'Content-Type': 'text/plain'},
+            )
+            self.assertEqual(400, response.status_code)
+            response = await client.post(
+                '/auth/backchannel-logout',
+                content='x' * (64 * 1024 + 1),
+                headers={'Content-Type': 'application/x-www-form-urlencoded'},
+            )
+            self.assertEqual(400, response.status_code)
+
+    @async_test
+    async def test_local_logout_removes_indexes(self) -> None:
+        async with self._client() as client:
+            await self._login(client, 'sid-a')
+            self.assertEqual(
+                [client.cookies['session_id']],
+                await self.store.find_sessions('oidc:default:sub', 'user123'),
+            )
+            await client.get('/auth/logout', follow_redirects=False)
+            self.assertEqual([], await self.store.find_sessions('oidc:default:sub', 'user123'))
+            self.assertEqual([], await self.store.find_sessions('oidc:default:sid', 'sid-a'))
+
+    @async_test
+    async def test_relogin_replaces_old_sid_index(self) -> None:
+        async with self._client() as client:
+            await self._login(client, 'sid-a')
+            await self._login(client, 'sid-b')
+            self.assertEqual([], await self.store.find_sessions('oidc:default:sid', 'sid-a'))
+            self.assertEqual(
+                [client.cookies['session_id']],
+                await self.store.find_sessions('oidc:default:sid', 'sid-b'),
+            )
+
+    @async_test
+    async def test_refresh_updates_changed_sid_index(self) -> None:
+        async with self._client() as client:
+            await self._login(client, 'sid-a')
+            self.provider.sid = 'sid-b'
+            response = await client.get('/refresh')
+            self.assertEqual(200, response.status_code)
+            self.assertNotEqual('no-token', response.text)
+            self.assertEqual([], await self.store.find_sessions('oidc:default:sid', 'sid-a'))
+            self.assertEqual(
+                [client.cookies['session_id']],
+                await self.store.find_sessions('oidc:default:sid', 'sid-b'),
+            )
+
+    @async_test
+    async def test_existing_session_is_backfilled(self) -> None:
+        async with self._client() as client:
+            await self._login(client, 'sid-a')
+            session_id = client.cookies['session_id']
+            self.store._data[session_id].pop('oidc:default:indexed')
+            self.store._session_indexes.pop(session_id, None)
+            for session_ids in self.store._index_sessions.values():
+                session_ids.discard(session_id)
+            self.assertEqual([], await self.store.find_sessions('oidc:default:sid', 'sid-a'))
+
+            self.assertEqual(200, await self._profile_status(client))
+            self.assertEqual(
+                [session_id],
+                await self.store.find_sessions('oidc:default:sid', 'sid-a'),
+            )
+
+    @async_test
+    async def test_index_capable_store_is_required(self) -> None:
+        class LegacyStore(InMemorySessionStore):
+            supports_indexes = False
+
+        with self.assertRaises(ValueError):
+            OIDCMixin(
+                OIDCConfig(
+                    issuer=self.provider.issuer,
+                    client_id='client',
+                    redirect_uri='http://localhost:8000/auth/callback',
+                    backchannel_logout_path='/auth/backchannel-logout',
+                ),
+                session=SessionMixin(LegacyStore()),
+            )
+
+
+class MultiProviderBackchannelLogoutTest(unittest.TestCase):
+
+    def setUp(self) -> None:
+        self.google = BackchannelProvider('google', sub='shared-sub', email='g@example.com')
+        self.github = BackchannelProvider('github', sub='shared-sub', email='h@example.com')
+        self.store = InMemorySessionStore()
+        self.session = SessionMixin(self.store)
+        self.oidc = OIDCProviders(
+            [
+                self._config(self.google, 'google'),
+                self._config(self.github, 'github'),
+            ],
+            session=self.session,
+            strategy='multi-identity',
+        )
+        self.app = KayaApp(mixins=[self.session, self.oidc])
+        self.transport = httpx.ASGITransport(app=self.app)
+
+        @self.app.GET('/google-profile')
+        @self.oidc.require_auth('google')
+        async def google_profile(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'google')
+
+        @self.app.GET('/github-profile')
+        @self.oidc.require_auth('github')
+        async def github_profile(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'github')
+
+    @staticmethod
+    def _config(provider: BackchannelProvider, name: str) -> OIDCConfig:
+        return OIDCConfig(
+            issuer=provider.issuer,
+            client_id='client',
+            client_secret='secret',
+            redirect_uri=f'http://localhost:8000/auth/{name}/callback',
+            provider=name,
+            backchannel_logout_path=f'/auth/{name}/backchannel-logout',
+            http_client=httpx.AsyncClient(transport=MockTransport(provider)),
+        )
+
+    async def _login(
+        self,
+        client: httpx.AsyncClient,
+        provider: BackchannelProvider,
+        name: str,
+        sid: str,
+    ) -> None:
+        provider.sid = sid
+        response = await client.get(f'/auth/{name}/login', follow_redirects=False)
+        query = parse_qs(urlparse(response.headers['Location']).query)
+        provider.nonce = query['nonce'][0]
+        await client.get(
+            f'/auth/{name}/callback',
+            params={'code': 'mock-code', 'state': query['state'][0]},
+            follow_redirects=False,
+        )
+
+    @async_test
+    async def test_single_identity_eviction_removes_old_provider_indexes(self) -> None:
+        session = SessionMixin(self.store)
+        oidc = OIDCProviders(
+            [
+                self._config(self.google, 'google'),
+                self._config(self.github, 'github'),
+            ],
+            session=session,
+            strategy='single-identity',
+        )
+        app = KayaApp(mixins=[session, oidc])
+        transport = httpx.ASGITransport(app=app)
+        async with httpx.AsyncClient(
+            transport=transport,
+            base_url='http://127.0.0.1:80',
+        ) as client:
+            await self._login(client, self.google, 'google', 'google-sid')
+            self.assertEqual(
+                [client.cookies['session_id']],
+                await self.store.find_sessions('oidc:google:sid', 'google-sid'),
+            )
+            await self._login(client, self.github, 'github', 'github-sid')
+            self.assertEqual(
+                [],
+                await self.store.find_sessions('oidc:google:sid', 'google-sid'),
+            )
+            self.assertEqual(
+                [client.cookies['session_id']],
+                await self.store.find_sessions('oidc:github:sid', 'github-sid'),
+            )
+
+    @async_test
+    async def test_provider_logout_is_isolated(self) -> None:
+        async with httpx.AsyncClient(
+            transport=self.transport,
+            base_url='http://127.0.0.1:80',
+        ) as client:
+            await self._login(client, self.google, 'google', 'google-sid')
+            await self._login(client, self.github, 'github', 'github-sid')
+            token = jwt.encode(
+                {
+                    'iss': self.google.issuer,
+                    'aud': 'client',
+                    'iat': time(),
+                    'jti': 'google-logout',
+                    'events': {_EVENT: {}},
+                    'sub': 'shared-sub',
+                    'sid': 'google-sid',
+                },
+                self.google.private_key,
+                algorithm='RS256',
+                headers={'kid': self.google.kid, 'typ': 'logout+jwt'},
+            )
+            response = await client.post(
+                '/auth/google/backchannel-logout',
+                data={'logout_token': token},
+            )
+            self.assertEqual(200, response.status_code)
+
+            response = await client.get('/google-profile', follow_redirects=False)
+            self.assertEqual(302, response.status_code)
+            response = await client.get('/github-profile', follow_redirects=False)
+            self.assertEqual(200, response.status_code)
+
+
+if __name__ == '__main__':
+    unittest.main()

packages/kaya-openapi/README.md

@@ -0,0 +1,136 @@
+# kaya-openapi
+
+Automatic [OpenAPI](https://www.openapis.org/) specification generation for the
+[Kaya](https://github.com/woggioni/kaya) lightweight ASGI web framework.
+
+The package provides an `OpenAPIMixin` that inspects a `KayaApp`'s routing
+tree and serves:
+
+- an OpenAPI 3.1 JSON document (default: `GET /openapi.json`)
+- a Swagger UI page to browse it interactively (default: `GET /docs`)
+
+## Usage
+
+```python
+from kaya.core import HttpContext, KayaApp
+from kaya.openapi import OpenAPIMixin, operation
+
+app = KayaApp(mixins=[OpenAPIMixin(title='My API', version='1.0.0')])
+
+
+@app.GET('/users/${user_id:int}')
+@operation(summary='Get a user',
+           tags=['users'],
+           responses={
+               200: {'description': 'The user'},
+               404: {'description': 'User not found'},
+           })
+async def get_user(ctx: HttpContext, user_id: int) -> None:
+    ...
+```
+
+Run the app with any ASGI/RSGI server and open `http://localhost:8000/docs`.
+
+## How routes are mapped
+
+- Static segments and parameters are converted to OpenAPI path templating:
+  - `/users/${user_id}` → `/users/{user_id}` (string path parameter)
+  - `/users/${user_id:int}` → `/users/{user_id}` (integer path parameter)
+- Wildcard routes (`*`) are **skipped**: they cannot be expressed in OpenAPI
+  path syntax.
+- Websocket routes are **skipped**: OpenAPI does not model websockets.
+- Method-agnostic routes (registered with `app.route(path)` without methods)
+  are documented under **all** standard HTTP methods, since they respond to
+  all of them.
+- The mixin's own endpoints are excluded from the document unless
+  `include_self=True`.
+
+The document is generated on every request to the spec endpoint, so routes
+registered after the mixin is applied are always included.
+
+## Operation metadata
+
+The `@operation` decorator attaches OpenAPI metadata to a route handler.
+All fragments are plain dicts merged verbatim into the generated operation
+object, so any valid OpenAPI 3.1 construct can be used:
+
+```python
+@operation(summary='...',            # operation summary
+           description='...',        # defaults to the handler docstring
+           tags=['users'],
+           operation_id='getUser',
+           request_body={...},       # OpenAPI requestBody object
+           responses={200: {...}},   # per-status-code response objects
+           parameters=[...],         # extra/overriding parameter objects
+           deprecated=False,
+           hidden=False)             # exclude from the document
+```
+
+`parameters` entries whose `name` and `in` match an auto-generated path
+parameter override it; all others are appended.
+
+## Reusable schemas (`components`)
+
+Schemas can be defined once and referenced from operation fragments: pass a
+`components` mapping to the mixin and use `schema_ref` in `@operation`.
+
+```python
+from kaya.openapi import OpenAPIMixin, operation, schema_ref
+
+USER = {
+    'type': 'object',
+    'required': ['id'],
+    'properties': {'id': {'type': 'integer'}, 'name': {'type': 'string'}},
+}
+USER_PAGE = {
+    'type': 'object',
+    'properties': {'results': {'type': 'array', 'items': schema_ref('User')}},
+}
+
+app = KayaApp(mixins=[OpenAPIMixin(
+    title='My API',
+    version='1.0.0',
+    components={'schemas': {'User': USER, 'UserPage': USER_PAGE}},
+)])
+
+
+@app.GET('/users')
+@operation(summary='List users',
+           responses={200: {
+               'description': 'A page of users',
+               'content': {'application/json': {'schema': schema_ref('UserPage')}},
+           }})
+async def list_users(ctx: HttpContext) -> None:
+    ...
+```
+
+`components` is merged verbatim (as a copy) into the generated document under
+`components`, so Swagger UI lists the named schemas. Every
+`#/components/<section>/<name>` reference — in operations or between
+components — is validated when the document is generated: a missing section or
+entry raises `ValueError`. Reflected references (`./other.json#/...`, absolute
+URLs) are left alone.
+
+## Configuration
+
+```python
+OpenAPIMixin(
+    title='My API',                # info.title (required)
+    version='1.0.0',               # info.version (required)
+    description='',                # info.description
+    spec_path='/openapi.json',     # where the JSON document is served
+    docs_path='/docs',             # where Swagger UI is served
+    servers=[{'url': 'https://api.example.com'}],
+    openapi_version='3.1.0',
+    include_self=False,            # include spec/docs endpoints in the document
+    components=None,               # reusable OpenAPI components (e.g. schemas)
+)
+```
+
+The document can also be generated programmatically without serving it:
+
+```python
+from kaya.openapi import generate_spec
+
+spec = generate_spec(app, title='My API', version='1.0.0')
+```

packages/kaya-openapi/pyproject.toml

@@ -0,0 +1,51 @@
+[build-system]
+requires = ["setuptools>=61.0", "setuptools-scm>=8"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "kaya-openapi"
+dynamic = ["version"]
+authors = [
+  { name="Walter Oggioni", email="oggioni.walter@gmail.com" },
+]
+description = "Automatic OpenAPI specification generation for the Kaya lightweight ASGI web framework"
+readme = "README.md"
+requires-python = ">=3.10"
+license = "MIT"
+classifiers = [
+        'Development Status :: 3 - Alpha',
+        'Topic :: Utilities',
+        'Intended Audience :: System Administrators',
+        'Intended Audience :: Developers',
+        'Environment :: Console',
+        'Programming Language :: Python :: 3',
+]
+
+dependencies = [
+    "kaya-core",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/woggioni/kaya"
+"Bug Tracker" = "https://github.com/woggioni/kaya/issues"
+
+[tool.setuptools.packages.find]
+where = ["src"]
+namespaces = true
+
+[tool.mypy]
+python_version = "3.12"
+disallow_untyped_defs = true
+show_error_codes = true
+no_implicit_optional = true
+warn_return_any = true
+warn_unused_ignores = true
+exclude = ["scripts", "docs", "test"]
+strict = true
+
+[tool.setuptools_scm]
+root = "../.."
+version_file = "src/kaya/openapi/_version.py"
+
+[tool.setuptools_scm.tag]
+prefix = "release/"

packages/kaya-openapi/src/kaya/openapi/__init__.py

@@ -0,0 +1,11 @@
+from ._metadata import operation
+from ._mixin import OpenAPIMixin
+from ._spec import generate_spec, schema_ref
+
+
+__all__ = [
+    'OpenAPIMixin',
+    'generate_spec',
+    'operation',
+    'schema_ref',
+]

packages/kaya-openapi/src/kaya/openapi/_metadata.py

@@ -0,0 +1,86 @@
+from typing import Any, Awaitable, Callable, Mapping, Optional, Sequence, TypeVar
+
+F = TypeVar('F', bound=Callable[..., Awaitable[None]])
+
+METADATA_ATTR = '__kaya_openapi__'
+
+#: Metadata attached to route handler functions by :func:`operation`.
+#: Values are raw OpenAPI fragments (plain dicts) merged verbatim into the
+#: generated operation object.
+type OperationMetadata = Mapping[str, Any]
+
+
+def operation(summary: Optional[str] = None,
+              description: Optional[str] = None,
+              tags: Optional[Sequence[str]] = None,
+              request_body: Optional[Mapping[str, Any]] = None,
+              responses: Optional[Mapping[int | str, Mapping[str, Any]]] = None,
+              parameters: Optional[Sequence[Mapping[str, Any]]] = None,
+              operation_id: Optional[str] = None,
+              deprecated: bool = False,
+              hidden: bool = False) -> Callable[[F], F]:
+    """Attach OpenAPI metadata to a Kaya route handler.
+
+    The metadata is stored on the function itself and picked up by
+    :class:`~kaya.openapi.OpenAPIMixin` when generating the specification.
+
+    All schema fragments are plain dicts inserted verbatim into the generated
+    OpenAPI document, so any valid OpenAPI 3.1 construct can be used. ``$ref``
+    fragments may point at the reusable schemas registered through the
+    ``components`` argument of :class:`~kaya.openapi.OpenAPIMixin`.
+
+    Example::
+
+        @app.GET('/users/${user_id:int}')
+        @operation(summary='Get a user',
+                   tags=['users'],
+                   responses={200: {'description': 'The user'},
+                              404: {'description': 'User not found'}})
+        async def get_user(ctx: HttpContext, user_id: int) -> None:
+            ...
+
+    :param summary: short summary of the operation
+    :param description: longer description (defaults to the handler docstring)
+    :param tags: list of OpenAPI tags
+    :param request_body: OpenAPI ``requestBody`` object
+    :param responses: mapping of status code (or ``'default'``) to OpenAPI
+        response objects
+    :param parameters: extra OpenAPI parameter objects merged with the
+        auto-generated path parameters (entries whose ``name`` matches a path
+        parameter override the auto-generated one)
+    :param operation_id: explicit OpenAPI ``operationId``
+    :param deprecated: mark the operation as deprecated
+    :param hidden: exclude the operation from the generated specification
+    """
+    def decorator(func: F) -> F:
+        metadata: dict[str, Any] = {}
+        if summary is not None:
+            metadata['summary'] = summary
+        if description is not None:
+            metadata['description'] = description
+        if tags is not None:
+            metadata['tags'] = list(tags)
+        if request_body is not None:
+            metadata['request_body'] = dict(request_body)
+        if responses is not None:
+            metadata['responses'] = {str(k): dict(v) for k, v in responses.items()}
+        if parameters is not None:
+            metadata['parameters'] = [dict(p) for p in parameters]
+        if operation_id is not None:
+            metadata['operation_id'] = operation_id
+        if deprecated:
+            metadata['deprecated'] = True
+        if hidden:
+            metadata['hidden'] = True
+        setattr(func, METADATA_ATTR, metadata)
+        return func
+
+    return decorator
+
+
+def get_metadata(handler: Any) -> OperationMetadata:
+    """Return the metadata attached by :func:`operation`, or an empty mapping."""
+    metadata = getattr(handler, METADATA_ATTR, None)
+    if isinstance(metadata, Mapping):
+        return metadata
+    return {}

packages/kaya-openapi/src/kaya/openapi/_mixin.py

@@ -0,0 +1,118 @@
+import json
+from html import escape
+from typing import Any, Mapping, Optional, Sequence
+
+from kaya.core import HttpContext, KayaApp, KayaMixin
+
+from ._spec import generate_spec
+
+_DOCS_PAGE = """<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title>{title} - API documentation</title>
+    <link rel="stylesheet" href="https://unpkg.com/swagger-ui-dist@5/swagger-ui.css" />
+  </head>
+  <body>
+    <div id="swagger-ui"></div>
+    <script src="https://unpkg.com/swagger-ui-dist@5/swagger-ui-bundle.js" crossorigin></script>
+    <script>
+      window.onload = () => {{
+        window.ui = SwaggerUIBundle({{
+          url: '{spec_path}',
+          dom_id: '#swagger-ui',
+        }});
+      }};
+    </script>
+  </body>
+</html>
+"""
+
+
+class OpenAPIMixin(KayaMixin):
+    """Kaya mixin serving an auto-generated OpenAPI specification.
+
+    Registers two routes on the app:
+
+    - ``spec_path`` (default ``/openapi.json``): the OpenAPI document,
+      generated on each request from the application's routing tree so that
+      routes registered after the mixin are always included.
+    - ``docs_path`` (default ``/docs``): a Swagger UI page rendering the
+      specification (assets are loaded from a CDN).
+
+    Routes are converted as follows:
+
+    - ``${name}`` path segments become ``{name}`` string path parameters,
+      ``${name:int}`` become integer path parameters;
+    - wildcard (``*``) and websocket routes are skipped, since they cannot be
+      expressed in OpenAPI;
+    - method-agnostic routes (registered with ``app.route(path)``) are
+      documented under all standard HTTP methods;
+    - the mixin's own routes are excluded unless ``include_self`` is true.
+
+    Use :func:`~kaya.openapi.operation` to attach summaries, tags, request
+    bodies and response schemas to individual handlers; the handler docstring
+    is used as the operation description when no explicit one is given.
+
+    Reusable schemas are supplied through ``components`` and referenced from
+    operation fragments with :func:`~kaya.openapi.schema_ref`; every
+    ``#/components/...`` reference is validated when the document is
+    generated.
+
+    Example::
+
+        openapi = OpenAPIMixin(title='My API', version='1.0.0')
+        app = KayaApp(mixins=[openapi])
+
+        @app.GET('/users/${user_id:int}')
+        @operation(summary='Get a user', tags=['users'])
+        async def get_user(ctx: HttpContext, user_id: int) -> None:
+            ...
+    """
+
+    def __init__(self,
+                 title: str,
+                 version: str,
+                 description: str = '',
+                 spec_path: str = '/openapi.json',
+                 docs_path: str = '/docs',
+                 servers: Optional[Sequence[Mapping[str, Any]]] = None,
+                 openapi_version: str = '3.1.0',
+                 include_self: bool = False,
+                 components: Optional[Mapping[str, Any]] = None) -> None:
+        self._title = title
+        self._version = version
+        self._description = description
+        self._spec_path = spec_path
+        self._docs_path = docs_path
+        self._servers = servers
+        self._openapi_version = openapi_version
+        self._include_self = include_self
+        self._components = components
+
+    def apply(self, app: KayaApp) -> None:
+        @app.GET(self._spec_path)
+        async def openapi_spec(ctx: HttpContext) -> None:
+            spec = self.generate_spec(app)
+            await ctx.send_str(200,
+                               json.dumps(spec, indent=2),
+                               {'Content-Type': 'application/json'})
+
+        @app.GET(self._docs_path)
+        async def openapi_docs(ctx: HttpContext) -> None:
+            page = _DOCS_PAGE.format(title=escape(self._title), spec_path=self._spec_path)
+            await ctx.send_str(200, page, {'Content-Type': 'text/html; charset=utf-8'})
+
+    def generate_spec(self, app: KayaApp) -> Mapping[str, Any]:
+        """Generate the OpenAPI document for ``app`` (also used by the
+        ``spec_path`` endpoint on every request)."""
+        exclude_paths = frozenset() if self._include_self else frozenset((self._spec_path, self._docs_path))
+        return generate_spec(app,
+                             title=self._title,
+                             version=self._version,
+                             description=self._description,
+                             servers=self._servers,
+                             exclude_paths=exclude_paths,
+                             openapi_version=self._openapi_version,
+                             components=self._components)

packages/kaya-openapi/src/kaya/openapi/_spec.py

@@ -0,0 +1,248 @@
+from copy import deepcopy
+from dataclasses import dataclass
+from inspect import getdoc
+from typing import AbstractSet, Any, Dict, Iterator, Mapping, Optional, Sequence
+
+from kaya.core import HttpMethod, KayaApp
+from kaya.core._path_handler import PathHandler
+from kaya.core._path_matcher import GlobMatcher, IntMatcher, Node, PathMatcher, StrMatcher
+
+from ._metadata import get_metadata
+
+#: HTTP methods documented for method-agnostic routes
+#: (registered with ``app.route(path)`` without explicit methods).
+STANDARD_METHODS: Sequence[HttpMethod] = (
+    HttpMethod.GET,
+    HttpMethod.PUT,
+    HttpMethod.POST,
+    HttpMethod.DELETE,
+    HttpMethod.OPTIONS,
+    HttpMethod.HEAD,
+    HttpMethod.PATCH,
+)
+
+
+def schema_ref(name: str) -> Dict[str, str]:
+    """Return a reference to the component schema ``name``.
+
+    The reference resolves to ``#/components/schemas/<name>`` in the
+    generated document; the schema itself is supplied through the
+    ``components`` argument of :func:`generate_spec` (or
+    :class:`~kaya.openapi.OpenAPIMixin`).
+    """
+    return {'$ref': f'#/components/schemas/{name}'}
+
+
+@dataclass
+class _Route:
+    raw_path: str
+    openapi_path: str
+    method: Optional[HttpMethod]
+    params: Sequence[Mapping[str, Any]]
+    handlers: Sequence[PathHandler]
+
+
+def _walk(node: Node | PathMatcher,
+          raw_path: str,
+          openapi_path: str,
+          params: Sequence[Mapping[str, Any]],
+          routes: list[_Route]) -> None:
+    if node.handlers:
+        routes.append(_Route(raw_path or '/', openapi_path or '/', None, params, list(node.handlers)))
+    for key, child in node.children.items():
+        if isinstance(key, HttpMethod):
+            if key is not HttpMethod.WS and child.handlers:
+                routes.append(_Route(raw_path or '/', openapi_path or '/', key, params, list(child.handlers)))
+        else:
+            _walk(child, f'{raw_path}/{key}', f'{openapi_path}/{key}', params, routes)
+    for matcher in node.path_matchers:
+        if isinstance(matcher, GlobMatcher):
+            # Wildcard routes cannot be expressed in OpenAPI path syntax
+            continue
+        if isinstance(matcher, IntMatcher):
+            raw_segment = f'${{{matcher.name}:int}}'
+            schema: Mapping[str, Any] = {'type': 'integer'}
+        elif isinstance(matcher, StrMatcher):
+            raw_segment = f'${{{matcher.name}}}'
+            schema = {'type': 'string'}
+        else:
+            continue
+        param: dict[str, Any] = {
+            'name': matcher.name,
+            'in': 'path',
+            'required': True,
+            'schema': dict(schema),
+        }
+        _walk(matcher,
+              f'{raw_path}/{raw_segment}',
+              f'{openapi_path}/{{{matcher.name}}}',
+              (*params, param),
+              routes)
+
+
+def _merge_parameters(params: Sequence[Mapping[str, Any]],
+                      extra: Any) -> list[Mapping[str, Any]]:
+    merged: list[Mapping[str, Any]] = [dict(p) for p in params]
+    if not isinstance(extra, Sequence) or isinstance(extra, (str, bytes)):
+        return merged
+    for candidate in extra:
+        if not isinstance(candidate, Mapping):
+            continue
+        for i, existing in enumerate(merged):
+            if existing.get('name') == candidate.get('name') and existing.get('in') == candidate.get('in'):
+                merged[i] = candidate
+                break
+        else:
+            merged.append(candidate)
+    return merged
+
+
+def _build_operation(params: Sequence[Mapping[str, Any]],
+                     handler: PathHandler) -> Optional[dict[str, Any]]:
+    callback = getattr(handler, 'callback', None)
+    metadata = get_metadata(callback) if callback is not None else {}
+    if metadata.get('hidden'):
+        return None
+    operation: dict[str, Any] = {}
+    operation_id = metadata.get('operation_id')
+    if operation_id is not None:
+        operation['operationId'] = operation_id
+    summary = metadata.get('summary')
+    if summary is not None:
+        operation['summary'] = summary
+    description = metadata.get('description')
+    if description is None and callback is not None:
+        description = getdoc(callback)
+    if description is not None:
+        operation['description'] = description
+    tags = metadata.get('tags')
+    if tags is not None:
+        operation['tags'] = tags
+    if metadata.get('deprecated'):
+        operation['deprecated'] = True
+    parameters = _merge_parameters(params, metadata.get('parameters'))
+    if parameters:
+        operation['parameters'] = parameters
+    request_body = metadata.get('request_body')
+    if request_body is not None:
+        operation['requestBody'] = request_body
+    responses = metadata.get('responses')
+    operation['responses'] = responses if responses is not None else {
+        'default': {'description': 'Successful response'},
+    }
+    return operation
+
+
+def _unescape_pointer_token(token: str) -> str:
+    """Decode one JSON Pointer reference token (``~1`` → ``/``, ``~0`` → ``~``)."""
+    return token.replace('~1', '/').replace('~0', '~')
+
+
+def _iter_refs(node: Any) -> Iterator[str]:
+    """Yield every ``$ref`` string found anywhere under ``node``."""
+    if isinstance(node, Mapping):
+        ref = node.get('$ref')
+        if isinstance(ref, str):
+            yield ref
+        for value in node.values():
+            yield from _iter_refs(value)
+    elif isinstance(node, (list, tuple)):
+        for value in node:
+            yield from _iter_refs(value)
+
+
+def _validate_component_refs(spec: Mapping[str, Any]) -> None:
+    """Fail fast on references to missing ``components`` entries.
+
+    Every ``#/components/<section>/<name>`` reference found in the operations
+    or in the components themselves must resolve against the document;
+    references in any other form (relative files, absolute URLs, other
+    pointers) are ignored. Raises :class:`ValueError` naming the offending
+    reference and the operation it appears in.
+    """
+    components = spec.get('components')
+    known: Mapping[str, Any] = components if isinstance(components, Mapping) else {}
+
+    def check(node: Any, location: str) -> None:
+        for ref in _iter_refs(node):
+            if not ref.startswith('#/components/'):
+                continue
+            parts = [_unescape_pointer_token(part) for part in ref[len('#/components/'):].split('/')]
+            if len(parts) < 2:
+                raise ValueError(f'invalid component reference {ref!r} in {location}')
+            section, name = parts[0], parts[1]
+            bucket = known.get(section)
+            if not isinstance(bucket, Mapping) or name not in bucket:
+                raise ValueError(f'unknown component reference {ref!r} in {location}')
+
+    paths = spec.get('paths')
+    if isinstance(paths, Mapping):
+        for path, item in paths.items():
+            if not isinstance(item, Mapping):
+                continue
+            for method, operation in item.items():
+                check(operation, f'{method.upper()} {path}')
+    if isinstance(components, Mapping):
+        check(components, 'components')
+
+
+def generate_spec(app: KayaApp,
+                  title: str,
+                  version: str,
+                  description: str = '',
+                  servers: Optional[Sequence[Mapping[str, Any]]] = None,
+                  exclude_paths: AbstractSet[str] = frozenset(),
+                  openapi_version: str = '3.1.0',
+                  components: Optional[Mapping[str, Any]] = None) -> Mapping[str, Any]:
+    """Generate an OpenAPI specification document from a :class:`KayaApp`.
+
+    The application's routing tree is walked and every route is converted to
+    an OpenAPI path item:
+
+    - static segments and ``${name}`` / ``${name:int}`` parameters are mapped
+      to OpenAPI path templating (``{name}``);
+    - wildcard (``*``) and websocket routes are skipped;
+    - method-agnostic routes are documented under all standard HTTP methods;
+    - routes whose Kaya path is in ``exclude_paths`` are skipped.
+
+    :param app: the application to inspect
+    :param title: value of ``info.title``
+    :param version: value of ``info.version``
+    :param description: value of ``info.description``
+    :param servers: list of OpenAPI server objects
+    :param exclude_paths: Kaya paths (e.g. ``/openapi.json``) to omit
+    :param openapi_version: OpenAPI version to declare
+    :param components: OpenAPI ``components`` object merged verbatim into the
+        document; references to ``#/components/<section>/<name>`` must resolve
+        against it (e.g. :func:`schema_ref` for reusable schemas)
+    :return: the OpenAPI document as a JSON-serializable mapping
+    """
+    routes: list[_Route] = []
+    _walk(app._tree.root, '', '', (), routes)
+
+    paths: dict[str, dict[str, Any]] = {}
+    for route in sorted(routes, key=lambda it: it.openapi_path):
+        if route.raw_path in exclude_paths or not route.handlers:
+            continue
+        operation = _build_operation(route.params, route.handlers[0])
+        if operation is None:
+            continue
+        path_item = paths.setdefault(route.openapi_path, {})
+        methods = STANDARD_METHODS if route.method is None else (route.method,)
+        for method in methods:
+            path_item[method.value.lower()] = deepcopy(operation)
+
+    info: dict[str, Any] = {'title': title, 'version': version}
+    if description:
+        info['description'] = description
+    spec: dict[str, Any] = {
+        'openapi': openapi_version,
+        'info': info,
+        'paths': paths,
+    }
+    if servers:
+        spec['servers'] = [dict(server) for server in servers]
+    if components:
+        spec['components'] = deepcopy(dict(components))
+    _validate_component_refs(spec)
+    return spec

packages/kaya-openapi/tests/test_openapi.py

@@ -0,0 +1,289 @@
+import json
+import unittest
+from typing import Any, Mapping, Sequence
+
+import httpx
+from pwo import async_test
+
+from kaya.core import HttpContext, HttpMethod, KayaApp, WebSocket
+from kaya.openapi import OpenAPIMixin, generate_spec, operation, schema_ref
+
+
+class OpenAPITest(unittest.TestCase):
+    app: KayaApp
+
+    def setUp(self) -> None:
+        self.app = KayaApp(mixins=[OpenAPIMixin(title='Test API', version='1.2.3')])
+
+        @self.app.GET('/hello')
+        async def hello(ctx: HttpContext) -> None:
+            """Say hello."""
+            await ctx.send_str(200, 'Hello World!')
+
+        @self.app.GET('/users/${user_id:int}')
+        @operation(summary='Get a user',
+                   tags=['users'],
+                   responses={
+                       200: {'description': 'The user'},
+                       404: {'description': 'User not found'},
+                   })
+        async def get_user(ctx: HttpContext, user_id: int) -> None:
+            await ctx.send_str(200, str(user_id))
+
+        @self.app.POST('/users/${name}')
+        async def create_user(ctx: HttpContext, name: str) -> None:
+            await ctx.send_str(201, name)
+
+        @self.app.route('/ping')
+        async def ping(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'pong')
+
+        @self.app.GET('/files/*', recursive=True)
+        async def serve_file(ctx: HttpContext, path: Sequence[str]) -> None:
+            await ctx.send_str(200, '/'.join(path))
+
+        @self.app.GET('/internal/health')
+        @operation(hidden=True)
+        async def health(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'ok')
+
+        @self.app.websocket('/echo')
+        async def echo(ws: WebSocket) -> None:
+            await ws.accept()
+            await ws.close()
+
+    async def _get_spec(self) -> Mapping[str, Any]:
+        transport = httpx.ASGITransport(app=self.app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            response = await client.get('/openapi.json')
+            self.assertEqual(200, response.status_code)
+            self.assertEqual('application/json', response.headers['Content-Type'])
+            return json.loads(response.text)
+
+    @async_test
+    async def test_spec_endpoint(self) -> None:
+        spec = await self._get_spec()
+        self.assertEqual('3.1.0', spec['openapi'])
+        self.assertEqual({'title': 'Test API', 'version': '1.2.3'}, spec['info'])
+        self.assertIn('paths', spec)
+
+    @async_test
+    async def test_static_route_with_docstring(self) -> None:
+        spec = await self._get_spec()
+        hello = spec['paths']['/hello']['get']
+        self.assertEqual('Say hello.', hello['description'])
+        self.assertIn('responses', hello)
+
+    @async_test
+    async def test_int_path_parameter(self) -> None:
+        spec = await self._get_spec()
+        operation = spec['paths']['/users/{user_id}']['get']
+        self.assertEqual('Get a user', operation['summary'])
+        self.assertEqual(['users'], operation['tags'])
+        self.assertEqual({
+            '200': {'description': 'The user'},
+            '404': {'description': 'User not found'},
+        }, operation['responses'])
+        self.assertEqual(
+            [{'name': 'user_id', 'in': 'path', 'required': True, 'schema': {'type': 'integer'}}],
+            operation['parameters'])
+
+    @async_test
+    async def test_str_path_parameter(self) -> None:
+        spec = await self._get_spec()
+        operation = spec['paths']['/users/{name}']['post']
+        self.assertEqual(
+            [{'name': 'name', 'in': 'path', 'required': True, 'schema': {'type': 'string'}}],
+            operation['parameters'])
+
+    @async_test
+    async def test_method_agnostic_route(self) -> None:
+        spec = await self._get_spec()
+        path_item = spec['paths']['/ping']
+        for method in ('get', 'put', 'post', 'delete', 'options', 'head', 'patch'):
+            self.assertIn(method, path_item)
+
+    @async_test
+    async def test_excluded_routes(self) -> None:
+        spec = await self._get_spec()
+        paths = spec['paths']
+        # wildcard routes cannot be expressed in OpenAPI
+        self.assertNotIn('/files/*', paths)
+        self.assertFalse(any('files' in path for path in paths))
+        # websocket routes are not part of OpenAPI
+        self.assertNotIn('/echo', paths)
+        # hidden operations are skipped
+        self.assertNotIn('/internal/health', paths)
+        # the mixin's own endpoints are excluded by default
+        self.assertNotIn('/openapi.json', paths)
+        self.assertNotIn('/docs', paths)
+
+    @async_test
+    async def test_docs_endpoint(self) -> None:
+        transport = httpx.ASGITransport(app=self.app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            response = await client.get('/docs')
+            self.assertEqual(200, response.status_code)
+            self.assertEqual('text/html; charset=utf-8', response.headers['Content-Type'])
+            self.assertIn('swagger-ui', response.text)
+            self.assertIn('/openapi.json', response.text)
+
+    @async_test
+    async def test_late_registered_routes_are_included(self) -> None:
+        @self.app.GET('/late')
+        async def late(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'late')
+
+        spec = await self._get_spec()
+        self.assertIn('/late', spec['paths'])
+
+    @async_test
+    async def test_custom_paths_and_self_inclusion(self) -> None:
+        app = KayaApp(mixins=[OpenAPIMixin(title='Custom',
+                                           version='0.1.0',
+                                           spec_path='/spec.json',
+                                           docs_path='/swagger',
+                                           include_self=True)])
+
+        @app.route('/items/${item_id:int}', HttpMethod.DELETE)
+        async def delete_item(ctx: HttpContext, item_id: int) -> None:
+            await ctx.send_empty(204)
+
+        transport = httpx.ASGITransport(app=app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            response = await client.get('/spec.json')
+            self.assertEqual(200, response.status_code)
+            spec = json.loads(response.text)
+            self.assertIn('delete', spec['paths']['/items/{item_id}'])
+            self.assertIn('/spec.json', spec['paths'])
+            self.assertIn('/swagger', spec['paths'])
+
+            response = await client.get('/swagger')
+            self.assertEqual(200, response.status_code)
+            self.assertIn('/spec.json', response.text)
+
+
+class ComponentsTest(unittest.TestCase):
+    """Reusable schemas through ``components`` and ``schema_ref``."""
+
+    async def _spec_of(self, app: KayaApp) -> Mapping[str, Any]:
+        transport = httpx.ASGITransport(app=app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            response = await client.get('/openapi.json')
+            self.assertEqual(200, response.status_code)
+            return json.loads(response.text)
+
+    def test_schema_ref_helper(self) -> None:
+        self.assertEqual({'$ref': '#/components/schemas/User'}, schema_ref('User'))
+
+    @async_test
+    async def test_components_merged_and_refs_preserved(self) -> None:
+        user = {'type': 'object', 'properties': {'id': {'type': 'integer'}}}
+        page = {'type': 'object',
+                'properties': {'results': {'type': 'array', 'items': schema_ref('User')}}}
+        app = KayaApp(mixins=[OpenAPIMixin(
+            title='Components API',
+            version='1.0.0',
+            components={'schemas': {'User': user, 'UserPage': page}},
+        )])
+
+        @app.GET('/users')
+        @operation(responses={200: {
+            'description': 'A page of users',
+            'content': {'application/json': {'schema': schema_ref('UserPage')}},
+        }})
+        async def list_users(ctx: HttpContext) -> None:
+            await ctx.send_str(200, '[]')
+
+        spec = await self._spec_of(app)
+        self.assertEqual({'schemas': {'User': user, 'UserPage': page}}, spec['components'])
+        schema = spec['paths']['/users']['get']['responses']['200']['content']['application/json']['schema']
+        self.assertEqual(schema_ref('UserPage'), schema)
+
+    @async_test
+    async def test_request_body_ref_preserved(self) -> None:
+        app = KayaApp(mixins=[OpenAPIMixin(
+            title='Components API',
+            version='1.0.0',
+            components={'schemas': {'User': {'type': 'object'}}},
+        )])
+
+        @app.POST('/users')
+        @operation(request_body={'required': True,
+                                 'content': {'application/json': {'schema': schema_ref('User')}}},
+                   responses={201: {'description': 'Created'}})
+        async def create_user(ctx: HttpContext) -> None:
+            await ctx.send_str(201, '{}')
+
+        spec = await self._spec_of(app)
+        schema = spec['paths']['/users']['post']['requestBody']['content']['application/json']['schema']
+        self.assertEqual(schema_ref('User'), schema)
+
+    @async_test
+    async def test_default_spec_has_no_components(self) -> None:
+        app = KayaApp(mixins=[OpenAPIMixin(title='Plain API', version='1.0.0')])
+
+        @app.GET('/plain')
+        async def plain(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'ok')
+
+        spec = await self._spec_of(app)
+        self.assertNotIn('components', spec)
+
+    def test_unknown_schema_ref_raises(self) -> None:
+        app = KayaApp()
+
+        @app.GET('/broken')
+        @operation(responses={200: {
+            'description': 'x',
+            'content': {'application/json': {'schema': schema_ref('Missing')}},
+        }})
+        async def broken(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'x')
+
+        with self.assertRaises(ValueError) as caught:
+            generate_spec(app, title='Broken', version='1.0.0',
+                          components={'schemas': {'User': {}}})
+        message = str(caught.exception)
+        self.assertIn('#/components/schemas/Missing', message)
+        self.assertIn('GET /broken', message)
+
+    def test_component_to_component_ref_validates(self) -> None:
+        app = KayaApp()
+        spec = generate_spec(app, title='Nested', version='1.0.0', components={'schemas': {
+            'User': {'type': 'object'},
+            'Page': {'type': 'object',
+                     'properties': {'results': {'type': 'array', 'items': schema_ref('User')}}},
+        }})
+        self.assertIn('components', spec)
+
+    def test_external_refs_are_ignored(self) -> None:
+        app = KayaApp()
+
+        @app.GET('/external')
+        @operation(responses={200: {
+            'description': 'x',
+            'content': {'application/json': {'schema': {'$ref': './other.json#/Thing'}}},
+        }})
+        async def external(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'x')
+
+        spec = generate_spec(app, title='External', version='1.0.0')
+        self.assertNotIn('components', spec)
+
+    def test_generic_component_section_validated(self) -> None:
+        app = KayaApp()
+
+        @app.GET('/p')
+        @operation(parameters=[{'name': 'q', 'in': 'query',
+                                'schema': {'$ref': '#/components/parameters/Missing'}}])
+        async def p(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'x')
+
+        with self.assertRaises(ValueError) as caught:
+            generate_spec(app, title='P', version='1.0.0', components={'parameters': {}})
+        self.assertIn('#/components/parameters/Missing', str(caught.exception))
+
+
+if __name__ == '__main__':
+    unittest.main()

packages/kaya-otel/README.md

@@ -0,0 +1,89 @@
+# kaya-otel
+
+OpenTelemetry tracing and metrics for the Kaya web framework.
+
+Provides `OTelMixin`, a `KayaMixin` that instruments HTTP requests and
+WebSocket connections with OpenTelemetry spans and exports HTTP server
+metrics, shipping everything to an OTLP/HTTP collector.
+
+## Usage
+
+```python
+from kaya.core import KayaApp, HttpContext
+from kaya.otel import OTelMixin
+
+app = KayaApp(mixins=[
+    OTelMixin(
+        service_name='my-service',
+        endpoint='http://localhost:4318',
+    )
+])
+
+@app.GET('/')
+async def home(ctx: HttpContext):
+    await ctx.send_str(200, 'Hello World!')
+```
+
+## Parameters
+
+- `service_name`: value of the `service.name` resource attribute.
+- `endpoint`: base URL of an OTLP/HTTP collector; the signal paths
+  `/v1/traces` and `/v1/metrics` are appended. When `None`, the exporters
+  use their own defaults, including the standard
+  `OTEL_EXPORTER_OTLP_ENDPOINT` environment variable.
+- `headers`: extra HTTP headers sent to the collector (e.g. authentication).
+- `metric_export_interval_millis`: metric export interval
+  (default `60000`).
+- `tracer_provider` / `meter_provider`: inject custom providers (e.g. with
+  in-memory exporters for tests) instead of the OTLP defaults. The mixin
+  only shuts down providers it created itself.
+- `resource_attributes`: extra resource attributes merged with
+  `service.name` when the mixin creates the providers.
+- `excluded_paths` / `excluded_path_regexes`: skip tracing and metrics for
+  matching paths (useful for health checks and metrics endpoints).
+- `capture_request_headers` / `capture_response_headers`: opt-in HTTP header
+  capture as `http.request.header.<name>` / `http.response.header.<name>`
+  span attributes. Header names are normalized to lowercase with `-`
+  replaced by `_`; values are captured as string lists.
+- `sanitize_headers`: headers captured as `REDACTED` (default:
+  `authorization`, `proxy-authorization`, `cookie`, `set-cookie`).
+- `server_request_hook` / `server_response_hook` / `websocket_connect_hook` /
+  `websocket_close_hook`: optional synchronous callbacks invoked with the
+  span and the Kaya context/websocket at the corresponding lifecycle point.
+  Hook exceptions are logged and do not fail the request.
+- `metrics_include_raw_path`: when `True`, metrics use raw `url.path`
+  attributes (legacy, potentially high cardinality). The default `False`
+  keeps metrics low-cardinality by using `http.route` when Kaya can resolve
+  a route template.
+- `websocket_error_close_codes`: close codes that mark a websocket span as
+  failed. Defaults to protocol/application error codes such as `1002`,
+  `1003` and `1007`-`1011`.
+
+## Behavior
+
+- Every HTTP request gets a `SERVER` span named `<METHOD> <path>` with the
+  usual HTTP semantic attributes (`http.request.method`, `url.path`,
+  `client.address`, `server.address`, ...). When Kaya resolves a route
+  template, the span name is updated to `<METHOD> <route template>` and
+  `http.route` is set. The response status code is recorded as
+  `http.response.status_code` when the handler sends the response; 5xx
+  statuses mark the span as failed. Exceptions escaping the handler are
+  recorded on the span and also mark it as failed.
+- Every WebSocket connection gets one span for its whole lifetime, carrying
+  the applicable standard attributes: `url.scheme`, `url.path`, `url.query`,
+  `network.protocol.name` (`websocket`), `network.transport`,
+  `client.address`/`client.port` and `server.address`/`server.port`. The
+  close code is recorded as `kaya.websocket.close_code`; exceptions and
+  configured error close codes mark the span as failed and set `error.type`
+  (the exception class name, or the close code).
+- W3C `traceparent`/`tracestate` headers on incoming requests are honored,
+  so traces propagate from upstream services.
+- Metrics:
+  - `http.server.request.duration` (histogram, seconds), with
+    `http.request.method`, `http.route` when known and
+    `http.response.status_code` attributes.
+  - `http.server.active_requests` (up-down counter), with
+    `http.request.method` attributes.
+
+`OTelMixin` is a `KayaMixin`, so the app stays a `KayaApp` and both ASGI and
+RSGI keep working.

packages/kaya-otel/pyproject.toml

@@ -0,0 +1,53 @@
+[build-system]
+requires = ["setuptools>=61.0", "setuptools-scm>=8"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "kaya-otel"
+dynamic = ["version"]
+authors = [
+  { name="Walter Oggioni", email="oggioni.walter@gmail.com" },
+]
+description = "OpenTelemetry tracing and metrics for the Kaya lightweight ASGI web framework"
+readme = "README.md"
+requires-python = ">=3.10"
+license = "MIT"
+classifiers = [
+        'Development Status :: 3 - Alpha',
+        'Topic :: Utilities',
+        'Intended Audience :: System Administrators',
+        'Intended Audience :: Developers',
+        'Environment :: Console',
+        'Programming Language :: Python :: 3',
+]
+
+dependencies = [
+    "kaya-core",
+    "opentelemetry-sdk",
+    "opentelemetry-exporter-otlp-proto-http",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/woggioni/kaya"
+"Bug Tracker" = "https://github.com/woggioni/kaya/issues"
+
+[tool.setuptools.packages.find]
+where = ["src"]
+namespaces = true
+
+[tool.mypy]
+python_version = "3.12"
+disallow_untyped_defs = true
+show_error_codes = true
+no_implicit_optional = true
+warn_return_any = true
+warn_unused_ignores = true
+exclude = ["scripts", "docs", "test"]
+strict = true
+
+[tool.setuptools_scm]
+root = "../.."
+version_file = "src/kaya/otel/_version.py"
+
+[tool.setuptools_scm.tag]
+prefix = "release/"

packages/kaya-otel/src/kaya/otel/__init__.py

@@ -0,0 +1,10 @@
+from pkgutil import extend_path
+
+__path__ = extend_path(__path__, __name__)
+
+from ._mixin import OTelMixin
+
+
+__all__ = [
+    'OTelMixin',
+]

packages/kaya-otel/src/kaya/otel/_mixin.py

@@ -0,0 +1,518 @@
+import re
+import time
+from asyncio import AbstractEventLoop
+from logging import getLogger
+from pathlib import Path
+from typing import (
+    Any,
+    AsyncGenerator,
+    Callable,
+    Dict,
+    Mapping,
+    Optional,
+    Sequence,
+    Tuple,
+)
+
+from kaya.core import HttpContext, KayaApp, KayaMixin, WebSocket, WebSocketMessage
+from kaya.core._types import StrOrStrings
+from opentelemetry import context as otel_context
+from opentelemetry import trace
+from opentelemetry.context import Context
+from opentelemetry.exporter.otlp.proto.http.metric_exporter import OTLPMetricExporter
+from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
+from opentelemetry.metrics import Histogram, UpDownCounter
+from opentelemetry.propagators.textmap import Getter
+from opentelemetry.sdk.metrics import MeterProvider
+from opentelemetry.sdk.metrics.export import PeriodicExportingMetricReader
+from opentelemetry.sdk.resources import Resource
+from opentelemetry.sdk.trace import TracerProvider
+from opentelemetry.sdk.trace.export import BatchSpanProcessor
+from opentelemetry.trace import Span, SpanKind, Status, StatusCode, Tracer
+from opentelemetry.trace.propagation.tracecontext import TraceContextTextMapPropagator
+
+log = getLogger(__name__)
+
+RequestHook = Callable[[Span, HttpContext], None]
+WebSocketHook = Callable[[Span, WebSocket], None]
+
+_DEFAULT_SANITIZE_HEADERS = (
+    'authorization',
+    'proxy-authorization',
+    'cookie',
+    'set-cookie',
+)
+_DEFAULT_WEBSOCKET_ERROR_CLOSE_CODES = frozenset((1002, 1003, 1007, 1008, 1009, 1010, 1011))
+
+
+class _HeadersGetter(Getter[Mapping[str, Sequence[str]]]):
+    """Extract propagation headers from a kaya request/websocket context.
+
+    Kaya header mappings have lowercase names with one or more values each,
+    which is all the W3C trace-context propagator needs.
+    """
+
+    def get(self, carrier: Mapping[str, Sequence[str]], key: str) -> Optional[list[str]]:
+        values = carrier.get(key.lower())
+        if not values:
+            return None
+        return list(values)
+
+    def keys(self, carrier: Mapping[str, Sequence[str]]) -> list[str]:
+        return list(carrier.keys())
+
+
+_PROPAGATOR = TraceContextTextMapPropagator()
+_GETTER = _HeadersGetter()
+
+
+def _server_attributes(ctx: HttpContext) -> Dict[str, Any]:
+    attributes: Dict[str, Any] = {
+        'http.request.method': str(ctx.method),
+        'url.scheme': ctx.scheme,
+        'url.path': ctx.path,
+    }
+    if ctx.query_string:
+        attributes['url.query'] = ctx.query_string
+    if ctx.client is not None:
+        attributes['client.address'] = ctx.client[0]
+        attributes['client.port'] = ctx.client[1]
+    if ctx.server is not None:
+        attributes['server.address'] = ctx.server[0]
+        if ctx.server[1] is not None:
+            attributes['server.port'] = ctx.server[1]
+    return attributes
+
+
+def _websocket_attributes(ws: WebSocket) -> Dict[str, Any]:
+    """Standard attributes applicable to a websocket connection span.
+
+    OpenTelemetry defines no websocket-specific conventions; these are the
+    general URL, network and peer attributes that apply to the connection.
+    """
+    attributes: Dict[str, Any] = {
+        'url.scheme': ws.scheme,
+        'url.path': ws.path,
+        'network.protocol.name': 'websocket',
+        'network.transport': 'tcp',
+    }
+    if ws.query_string:
+        attributes['url.query'] = ws.query_string
+    if ws.client is not None:
+        attributes['client.address'] = ws.client[0]
+        attributes['client.port'] = ws.client[1]
+    if ws.server is not None:
+        attributes['server.address'] = ws.server[0]
+        if ws.server[1] is not None:
+            attributes['server.port'] = ws.server[1]
+    return attributes
+
+
+def _normalize_header_name(name: str) -> str:
+    return name.lower().replace('-', '_')
+
+
+def _header_values(value: StrOrStrings | Sequence[str]) -> list[str]:
+    if isinstance(value, str):
+        return [value]
+    return list(value)
+
+
+class _SpanHolder:
+    """Mutable per-request slot shared by the tracing hooks and wrappers."""
+
+    __slots__ = ('span', 'token', 'status_code', 'start_ns', 'active_attributes', 'close_code')
+
+    def __init__(self, span: Span, token: object, active_attributes: Dict[str, Any]) -> None:
+        self.span = span
+        self.token = token
+        self.status_code: Optional[int] = None
+        self.start_ns = time.perf_counter_ns()
+        self.active_attributes = active_attributes
+        self.close_code: Optional[int] = None
+
+
+class _TracedHttpContext(HttpContext):
+    """HttpContext wrapper that records the response status code on the span.
+
+    Attributes not explicitly overridden are delegated to the wrapped context
+    via ``__getattr__``, so it works with any concrete ``HttpContext`` (ASGI
+    or RSGI) and preserves attributes set by other mixins (e.g. ``session``).
+    """
+
+    def __init__(self, ctx: HttpContext, holder: _SpanHolder, mixin: 'OTelMixin') -> None:
+        object.__setattr__(self, '_ctx', ctx)
+        object.__setattr__(self, 'session', ctx.session)
+        object.__setattr__(self, '_holder', holder)
+        object.__setattr__(self, '_mixin', mixin)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ctx':
+            raise AttributeError(name)
+        return getattr(self._ctx, name)
+
+    def _sent(self, status: int, headers: Optional[Mapping[str, StrOrStrings]]) -> None:
+        self._holder.status_code = status
+        self._holder.span.set_attribute('http.response.status_code', status)
+        self._mixin._capture_response_headers(self._holder.span, headers)
+
+    async def stream_body(self,
+                          status: int,
+                          body_generator: AsyncGenerator[bytes, None],
+                          headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        self._sent(status, headers)
+        await self._ctx.stream_body(status, body_generator, headers)
+
+    async def send_bytes(self, status: int, body: bytes, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        self._sent(status, headers)
+        await self._ctx.send_bytes(status, body, headers)
+
+    async def send_str(self, status: int, body: str, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        self._sent(status, headers)
+        await self._ctx.send_str(status, body, headers)
+
+    async def send_file(self, status: int, path: Path, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        self._sent(status, headers)
+        await self._ctx.send_file(status, path, headers)
+
+    async def send_empty(self, status: int, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        self._sent(status, headers)
+        await self._ctx.send_empty(status, headers)
+
+
+class _TracedWebSocket(WebSocket):
+    """WebSocket wrapper that keeps the connection span reachable.
+
+    Everything is delegated to the wrapped socket via ``__getattr__``, so it
+    works with any concrete ``WebSocket`` (ASGI or RSGI) and preserves
+    attributes set by other mixins (e.g. ``session``).
+    """
+
+    def __init__(self, ws: WebSocket, holder: _SpanHolder) -> None:
+        object.__setattr__(self, '_ws', ws)
+        object.__setattr__(self, 'session', ws.session)
+        object.__setattr__(self, '_holder', holder)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ws':
+            raise AttributeError(name)
+        return getattr(self._ws, name)
+
+    async def accept(self, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
+        await self._ws.accept(headers)
+
+    async def receive(self) -> WebSocketMessage:
+        return await self._ws.receive()
+
+    async def send_text(self, data: str) -> None:
+        await self._ws.send_text(data)
+
+    async def send_bytes(self, data: bytes) -> None:
+        await self._ws.send_bytes(data)
+
+    async def close(self, code: int = 1000) -> None:
+        self._holder.close_code = code
+        await self._ws.close(code)
+
+    async def __anext__(self) -> WebSocketMessage:
+        return await self._ws.__anext__()
+
+
+class OTelMixin(KayaMixin):
+    """Kaya mixin adding OpenTelemetry tracing and metrics.
+
+    HTTP requests get a ``SERVER`` span named ``<METHOD> <path>`` carrying the
+    usual HTTP semantic attributes; the response status code is recorded when
+    the handler sends the response and 5xx statuses mark the span as failed.
+    Exceptions escaping the handler are recorded and mark the span as failed.
+    WebSocket connections get one span for the whole connection lifetime,
+    carrying the applicable standard websocket URL, network and peer
+    attributes (``url.scheme``, ``url.path``, ``network.protocol.name``,
+    ``client.address``/``server.address``, ...); exceptions and configured
+    error close codes set ``error.type`` and mark the span as failed.
+    W3C ``traceparent``/``tracestate`` headers on incoming requests are
+    honored, so traces propagate from upstream services.
+
+    Metrics exported on the meter provider:
+
+    - ``http.server.request.duration`` (histogram, seconds), with
+      ``http.request.method``, ``http.route`` when known and
+      ``http.response.status_code`` attributes;
+    - ``http.server.active_requests`` (up-down counter), with
+      ``http.request.method`` attributes.
+
+    Example::
+
+        app = KayaApp(mixins=[
+            OTelMixin(
+                service_name='my-service',
+                endpoint='http://localhost:4318',
+            )
+        ])
+
+    ``endpoint`` is the base URL of an OTLP/HTTP collector (the signal paths
+    ``/v1/traces`` and ``/v1/metrics`` are appended); when ``None`` the
+    exporters fall back to their own defaults, including the standard
+    ``OTEL_EXPORTER_OTLP_ENDPOINT`` environment variable. Custom
+    ``tracer_provider``/``meter_provider`` instances (e.g. with in-memory
+    exporters for tests) can be injected instead of the OTLP defaults; the
+    mixin only shuts down providers it created itself.
+    """
+
+    def __init__(self,
+                 service_name: str,
+                 endpoint: Optional[str] = None,
+                 headers: Optional[Mapping[str, str]] = None,
+                 metric_export_interval_millis: float = 60000,
+                 tracer_provider: Optional[TracerProvider] = None,
+                 meter_provider: Optional[MeterProvider] = None,
+                 resource_attributes: Optional[Mapping[str, Any]] = None,
+                 excluded_paths: Sequence[str] = (),
+                 excluded_path_regexes: Sequence[str] = (),
+                 capture_request_headers: Sequence[str] = (),
+                 capture_response_headers: Sequence[str] = (),
+                 sanitize_headers: Sequence[str] = _DEFAULT_SANITIZE_HEADERS,
+                 server_request_hook: Optional[RequestHook] = None,
+                 server_response_hook: Optional[RequestHook] = None,
+                 websocket_connect_hook: Optional[WebSocketHook] = None,
+                 websocket_close_hook: Optional[WebSocketHook] = None,
+                 metrics_include_raw_path: bool = False,
+                 websocket_error_close_codes: Optional[Sequence[int]] = None) -> None:
+        self._owns_tracer_provider = tracer_provider is None
+        self._owns_meter_provider = meter_provider is None
+        if tracer_provider is None:
+            tracer_provider = TracerProvider(resource=self._create_resource(service_name, resource_attributes))
+            span_exporter = OTLPSpanExporter(
+                endpoint=f'{endpoint}/v1/traces' if endpoint else None,
+                headers=dict(headers) if headers else None,
+            )
+            tracer_provider.add_span_processor(BatchSpanProcessor(span_exporter))
+        if meter_provider is None:
+            meter_provider = MeterProvider(
+                resource=self._create_resource(service_name, resource_attributes),
+                metric_readers=[
+                    PeriodicExportingMetricReader(
+                        OTLPMetricExporter(
+                            endpoint=f'{endpoint}/v1/metrics' if endpoint else None,
+                            headers=dict(headers) if headers else None,
+                        ),
+                        export_interval_millis=metric_export_interval_millis,
+                    )
+                ],
+            )
+        self._tracer_provider = tracer_provider
+        self._meter_provider = meter_provider
+        self._tracer: Tracer = tracer_provider.get_tracer('kaya.otel')
+        meter = meter_provider.get_meter('kaya.otel')
+        self._request_duration: Histogram = meter.create_histogram(
+            'http.server.request.duration',
+            unit='s',
+            description='Duration of HTTP server requests',
+        )
+        self._active_requests: UpDownCounter = meter.create_up_down_counter(
+            'http.server.active_requests',
+            unit='{request}',
+            description='Number of in-flight HTTP server requests',
+        )
+        self._app: Optional[KayaApp] = None
+        self._excluded_paths = frozenset(excluded_paths)
+        self._excluded_path_regexes = tuple(re.compile(regex) for regex in excluded_path_regexes)
+        self._request_headers_to_capture = tuple(capture_request_headers)
+        self._response_headers_to_capture = tuple(capture_response_headers)
+        self._sanitize_headers = frozenset(name.lower() for name in sanitize_headers)
+        self._server_request_hook = server_request_hook
+        self._server_response_hook = server_response_hook
+        self._websocket_connect_hook = websocket_connect_hook
+        self._websocket_close_hook = websocket_close_hook
+        self._metrics_include_raw_path = metrics_include_raw_path
+        self._websocket_error_close_codes = (
+            frozenset(websocket_error_close_codes)
+            if websocket_error_close_codes is not None
+            else _DEFAULT_WEBSOCKET_ERROR_CLOSE_CODES
+        )
+        # Live spans keyed by the id of the (wrapped) context/websocket the
+        # after hooks receive; entries are removed when the span ends.
+        self._spans: Dict[int, _SpanHolder] = {}
+
+    @staticmethod
+    def _create_resource(service_name: str,
+                         resource_attributes: Optional[Mapping[str, Any]]) -> Resource:
+        attributes: Dict[str, Any] = {'service.name': service_name}
+        if resource_attributes:
+            attributes.update(resource_attributes)
+        return Resource.create(attributes)
+
+    def apply(self, app: KayaApp) -> None:
+        self._app = app
+        app.add_before_request_hook(self._before_request)
+        app.add_after_request_hook(self._after_request)
+        app.add_before_websocket_hook(self._before_websocket)
+        app.add_after_websocket_hook(self._after_websocket)
+
+    def _is_excluded(self, path: str) -> bool:
+        if path in self._excluded_paths:
+            return True
+        return any(regex.search(path) is not None for regex in self._excluded_path_regexes)
+
+    @staticmethod
+    def _call_hook(hook: Optional[Callable[[Span, Any], None]], span: Span, value: Any) -> None:
+        if hook is None:
+            return
+        try:
+            hook(span, value)
+        except Exception:
+            log.exception('OpenTelemetry span hook failed')
+
+    def _capture_headers(self,
+                         span: Span,
+                         headers: Mapping[str, StrOrStrings | Sequence[str]],
+                         configured: Sequence[str],
+                         prefix: str) -> None:
+        if not configured:
+            return
+        lower_headers = {name.lower(): value for name, value in headers.items()}
+        for name in configured:
+            key = name.lower()
+            if key not in lower_headers:
+                continue
+            values = _header_values(lower_headers[key])
+            if key in self._sanitize_headers:
+                values = ['REDACTED'] * len(values)
+            span.set_attribute(f'{prefix}.{_normalize_header_name(name)}', values)
+
+    def _capture_request_headers(self, span: Span, headers: Mapping[str, Sequence[str]]) -> None:
+        self._capture_headers(span, headers, self._request_headers_to_capture, 'http.request.header')
+
+    def _capture_response_headers(self,
+                                  span: Span,
+                                  headers: Optional[Mapping[str, StrOrStrings]]) -> None:
+        if headers is None:
+            return
+        self._capture_headers(span, headers, self._response_headers_to_capture, 'http.response.header')
+
+    def _start_span(self, name: str, attributes: Mapping[str, Any],
+                    headers: Mapping[str, Sequence[str]]) -> _SpanHolder:
+        parent: Context = _PROPAGATOR.extract(carrier=headers, getter=_GETTER)
+        span = self._tracer.start_span(
+            name,
+            context=parent,
+            kind=SpanKind.SERVER,
+            attributes=dict(attributes),
+        )
+        self._capture_request_headers(span, headers)
+        token = otel_context.attach(trace.set_span_in_context(span, parent))
+        return _SpanHolder(span, token, {})
+
+    @staticmethod
+    def _finish_span(holder: _SpanHolder, error: bool) -> None:
+        if error:
+            holder.span.set_status(Status(StatusCode.ERROR))
+        holder.span.end()
+        otel_context.detach(holder.token)  # type: ignore[arg-type]
+
+    def _pop_holder(self, obj: Any) -> Optional[_SpanHolder]:
+        """Find and remove the span holder for a context/websocket.
+
+        The before hooks key holders by the id of the context they received,
+        but after hooks run on the outermost wrapper (later mixins may have
+        wrapped the context again), so the id may not match. In that case the
+        holder is reachable through the wrapper delegation chain as
+        ``_holder`` and the stale dict entry is reaped by identity.
+        """
+        holder = self._spans.pop(id(obj), None)
+        if holder is not None:
+            return holder
+        candidate = getattr(obj, '_holder', None)
+        if not isinstance(candidate, _SpanHolder):
+            return None
+        for key, value in list(self._spans.items()):
+            if value is candidate:
+                del self._spans[key]
+        return candidate
+
+    def _route_template(self, ctx: HttpContext) -> Optional[str]:
+        if self._app is None:
+            return None
+        return self._app.route_template(ctx.path, ctx.method)
+
+    async def _before_request(self, ctx: HttpContext) -> Optional[HttpContext]:
+        if self._is_excluded(ctx.path):
+            return None
+        holder = self._start_span(
+            f'{ctx.method} {ctx.path}',
+            _server_attributes(ctx),
+            ctx.headers,
+        )
+        holder.active_attributes = {'http.request.method': str(ctx.method)}
+        if self._metrics_include_raw_path:
+            holder.active_attributes['url.path'] = ctx.path
+        self._spans[id(ctx)] = holder
+        self._active_requests.add(1, holder.active_attributes)
+        self._call_hook(self._server_request_hook, holder.span, ctx)
+        return _TracedHttpContext(ctx, holder, self)
+
+    async def _after_request(self, ctx: HttpContext) -> None:
+        holder = self._pop_holder(ctx)
+        if holder is None:
+            return
+        status_code = holder.status_code
+        exception = getattr(ctx, 'exception', None)
+        error = status_code is not None and status_code >= 500
+        if isinstance(exception, BaseException):
+            holder.span.record_exception(exception)
+            error = True
+        route_template = self._route_template(ctx)
+        if route_template is not None:
+            holder.span.update_name(f'{ctx.method} {route_template}')
+            holder.span.set_attribute('http.route', route_template)
+        self._call_hook(self._server_response_hook, holder.span, ctx)
+        self._finish_span(holder, error)
+        self._active_requests.add(-1, holder.active_attributes)
+        metric_attributes: Dict[str, Any] = {
+            'http.request.method': str(ctx.method),
+        }
+        if self._metrics_include_raw_path:
+            metric_attributes['url.path'] = ctx.path
+        elif route_template is not None:
+            metric_attributes['http.route'] = route_template
+        if status_code is not None:
+            metric_attributes['http.response.status_code'] = status_code
+        duration = (time.perf_counter_ns() - holder.start_ns) / 1e9
+        self._request_duration.record(duration, metric_attributes)
+
+    async def _before_websocket(self, ws: WebSocket) -> Optional[WebSocket]:
+        if self._is_excluded(ws.path):
+            return None
+        holder = self._start_span(f'WS {ws.path}', _websocket_attributes(ws), ws.headers)
+        self._spans[id(ws)] = holder
+        self._call_hook(self._websocket_connect_hook, holder.span, ws)
+        return _TracedWebSocket(ws, holder)
+
+    async def _after_websocket(self, ws: WebSocket) -> None:
+        holder = self._pop_holder(ws)
+        if holder is None:
+            return
+        exception = getattr(ws, 'exception', None)
+        error = isinstance(exception, BaseException)
+        if isinstance(exception, BaseException):
+            holder.span.record_exception(exception)
+            holder.span.set_attribute('error.type', type(exception).__qualname__)
+        close_code = holder.close_code
+        if close_code is not None:
+            holder.span.set_attribute('kaya.websocket.close_code', close_code)
+            if close_code in self._websocket_error_close_codes:
+                error = True
+                if not isinstance(exception, BaseException):
+                    # Mirror the HTTP conventions, where server-side error
+                    # statuses are recorded as ``error.type`` values.
+                    holder.span.set_attribute('error.type', str(close_code))
+        self._call_hook(self._websocket_close_hook, holder.span, ws)
+        self._finish_span(holder, error)
+
+    def shutdown(self, loop: AbstractEventLoop) -> None:
+        # Only providers created by this mixin are shut down; injected ones
+        # stay under the caller's control.
+        if self._owns_tracer_provider:
+            self._tracer_provider.shutdown()
+        if self._owns_meter_provider:
+            self._meter_provider.shutdown()

packages/kaya-otel/tests/test_otel.py

@@ -0,0 +1,420 @@
+import json
+import unittest
+from typing import Any, Optional, Tuple
+
+import httpx
+from pwo import async_test
+
+from kaya.core import HttpContext, KayaApp
+from kaya.core._asgi import AsgiWebSocket
+from kaya.otel import OTelMixin
+from opentelemetry.sdk.metrics import MeterProvider
+from opentelemetry.sdk.metrics.export import InMemoryMetricReader
+from opentelemetry.sdk.resources import Resource
+from opentelemetry.sdk.trace import TracerProvider
+from opentelemetry.sdk.trace.export import SimpleSpanProcessor
+from opentelemetry.sdk.trace.export.in_memory_span_exporter import InMemorySpanExporter
+from opentelemetry.trace import StatusCode
+
+TRACEPARENT = '00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01'
+
+
+def make_mixin(**kwargs) -> Tuple[OTelMixin, InMemorySpanExporter, InMemoryMetricReader]:
+    resource = Resource.create({'service.name': 'test-service'})
+    span_exporter = InMemorySpanExporter()
+    tracer_provider = TracerProvider(resource=resource)
+    tracer_provider.add_span_processor(SimpleSpanProcessor(span_exporter))
+    metric_reader = InMemoryMetricReader()
+    meter_provider = MeterProvider(resource=resource, metric_readers=[metric_reader])
+    mixin = OTelMixin(
+        service_name='test-service',
+        tracer_provider=tracer_provider,
+        meter_provider=meter_provider,
+        **kwargs,
+    )
+    return mixin, span_exporter, metric_reader
+
+
+def make_app(mixin: OTelMixin) -> KayaApp:
+    app = KayaApp(mixins=[mixin])
+
+    @app.GET('/hello')
+    async def hello(ctx: HttpContext) -> None:
+        await ctx.send_str(200, json.dumps({'ok': True}))
+
+    @app.GET('/boom')
+    async def boom(ctx: HttpContext) -> None:
+        await ctx.send_str(500, 'boom')
+
+    return app
+
+
+async def request(app: KayaApp, path: str = '/hello', headers: Optional[dict[str, str]] = None) -> httpx.Response:
+    transport = httpx.ASGITransport(app=app, client=('127.0.0.1', 123))
+    async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as http_client:
+        return await http_client.get(path, headers=headers)
+
+
+class HttpTracingTest(unittest.TestCase):
+
+    @async_test
+    async def test_request_produces_server_span(self):
+        mixin, span_exporter, _ = make_mixin()
+        app = make_app(mixin)
+        r = await request(app)
+        self.assertEqual(200, r.status_code)
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        span = spans[0]
+        self.assertEqual('GET /hello', span.name)
+        assert span.attributes is not None
+        self.assertEqual('GET', span.attributes['http.request.method'])
+        self.assertEqual('/hello', span.attributes['url.path'])
+        self.assertEqual(200, span.attributes['http.response.status_code'])
+        self.assertEqual(StatusCode.UNSET, span.status.status_code)
+
+    @async_test
+    async def test_5xx_marks_span_as_error(self):
+        mixin, span_exporter, _ = make_mixin()
+        app = make_app(mixin)
+        r = await request(app, '/boom')
+        self.assertEqual(500, r.status_code)
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual(500, spans[0].attributes['http.response.status_code'])  # type: ignore[index]
+        self.assertEqual(StatusCode.ERROR, spans[0].status.status_code)
+
+    @async_test
+    async def test_traceparent_header_propagates(self):
+        mixin, span_exporter, _ = make_mixin()
+        app = make_app(mixin)
+        await request(app, headers={'traceparent': TRACEPARENT})
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        span = spans[0]
+        self.assertEqual(0x4bf92f3577b34da6a3ce929d0e0e4736, span.context.trace_id)  # type: ignore[union-attr]
+        assert span.parent is not None
+        self.assertEqual(0x00f067aa0ba902b7, span.parent.span_id)
+
+    @async_test
+    async def test_unmatched_route_still_traced(self):
+        mixin, span_exporter, _ = make_mixin()
+        app = make_app(mixin)
+        r = await request(app, '/nowhere')
+        self.assertEqual(404, r.status_code)
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual(404, spans[0].attributes['http.response.status_code'])  # type: ignore[index]
+
+    @async_test
+    async def test_no_leaked_spans_after_requests(self):
+        mixin, span_exporter, _ = make_mixin()
+        app = make_app(mixin)
+        await request(app)
+        await request(app, '/boom')
+        self.assertEqual(0, len(mixin._spans))
+        self.assertEqual(2, len(span_exporter.get_finished_spans()))
+
+
+    @async_test
+    async def test_exception_marks_span_as_error(self):
+        mixin, span_exporter, _ = make_mixin()
+        app = KayaApp(mixins=[mixin])
+
+        @app.GET('/raises')
+        async def raises(ctx: HttpContext) -> None:
+            raise RuntimeError('boom')
+
+        transport = httpx.ASGITransport(app=app, client=('127.0.0.1', 123))
+        async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as http_client:
+            with self.assertRaises(RuntimeError):
+                await http_client.get('/raises')
+
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        span = spans[0]
+        self.assertEqual(StatusCode.ERROR, span.status.status_code)
+        self.assertTrue(any(event.name == 'exception' for event in span.events))
+        self.assertEqual(0, len(mixin._spans))
+
+    @async_test
+    async def test_excluded_path_skips_tracing_and_metrics(self):
+        mixin, span_exporter, metric_reader = make_mixin(excluded_paths=('/health',))
+        app = KayaApp(mixins=[mixin])
+
+        @app.GET('/health')
+        async def health(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'ok')
+
+        @app.GET('/hello')
+        async def hello(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'hello')
+
+        await request(app, '/health')
+        await request(app, '/hello')
+
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual('GET /hello', spans[0].name)
+
+        metrics = MetricsTest._metric_names(metric_reader)
+        duration_points = list(metrics['http.server.request.duration'].data.data_points)
+        self.assertEqual(1, len(duration_points))
+        self.assertEqual(1, duration_points[0].count)
+
+    @async_test
+    async def test_route_template_used_for_span_name_and_metrics(self):
+        mixin, span_exporter, metric_reader = make_mixin()
+        app = KayaApp(mixins=[mixin])
+
+        @app.GET('/items/${item_id:int}')
+        async def item(ctx: HttpContext, item_id: int) -> None:
+            await ctx.send_str(200, str(item_id))
+
+        r = await request(app, '/items/123')
+        self.assertEqual(200, r.status_code)
+
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        span = spans[0]
+        self.assertEqual('GET /items/${item_id:int}', span.name)
+        assert span.attributes is not None
+        self.assertEqual('/items/${item_id:int}', span.attributes['http.route'])
+        self.assertEqual('/items/123', span.attributes['url.path'])
+
+        metrics = MetricsTest._metric_names(metric_reader)
+        duration_points = list(metrics['http.server.request.duration'].data.data_points)
+        self.assertEqual(1, len(duration_points))
+        duration_attributes = dict(duration_points[0].attributes)
+        self.assertEqual('GET', duration_attributes['http.request.method'])
+        self.assertEqual('/items/${item_id:int}', duration_attributes['http.route'])
+        self.assertEqual(200, duration_attributes['http.response.status_code'])
+        self.assertNotIn('url.path', duration_attributes)
+
+        active_points = list(metrics['http.server.active_requests'].data.data_points)
+        self.assertEqual(1, len(active_points))
+        self.assertEqual({'http.request.method': 'GET'}, dict(active_points[0].attributes))
+
+    @async_test
+    async def test_header_capture_and_sanitization(self):
+        mixin, span_exporter, _ = make_mixin(
+            capture_request_headers=('X-Request-Id', 'Authorization'),
+            capture_response_headers=('X-Response-Id', 'Set-Cookie'),
+        )
+        app = KayaApp(mixins=[mixin])
+
+        @app.GET('/headers')
+        async def headers(ctx: HttpContext) -> None:
+            await ctx.send_str(200, 'ok', {
+                'X-Response-Id': 'res-1',
+                'Set-Cookie': 'sid=secret',
+            })
+
+        r = await request(app, '/headers', headers={
+            'X-Request-Id': 'req-1',
+            'Authorization': 'Bearer secret',
+        })
+        self.assertEqual(200, r.status_code)
+
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        attributes = spans[0].attributes
+        assert attributes is not None
+        self.assertEqual(['req-1'], list(attributes['http.request.header.x_request_id']))
+        self.assertEqual(['REDACTED'], list(attributes['http.request.header.authorization']))
+        self.assertEqual(['res-1'], list(attributes['http.response.header.x_response_id']))
+        self.assertEqual(['REDACTED'], list(attributes['http.response.header.set_cookie']))
+
+    @async_test
+    async def test_http_hooks_are_called(self):
+        calls = []
+
+        def request_hook(span: Any, ctx: HttpContext) -> None:
+            calls.append(('request', ctx.path))
+            span.set_attribute('test.request_hook', True)
+
+        def response_hook(span: Any, ctx: HttpContext) -> None:
+            calls.append(('response', ctx.path))
+            span.set_attribute('test.response_hook', True)
+
+        mixin, span_exporter, _ = make_mixin(
+            server_request_hook=request_hook,
+            server_response_hook=response_hook,
+        )
+        app = make_app(mixin)
+        await request(app)
+
+        self.assertEqual([('request', '/hello'), ('response', '/hello')], calls)
+        attributes = span_exporter.get_finished_spans()[0].attributes
+        assert attributes is not None
+        self.assertTrue(attributes['test.request_hook'])
+        self.assertTrue(attributes['test.response_hook'])
+
+
+class MetricsTest(unittest.TestCase):
+
+    @staticmethod
+    def _metric_names(metric_reader: InMemoryMetricReader) -> dict:
+        data = metric_reader.get_metrics_data()
+        return {m.name: m for rm in data.resource_metrics for m in rm.scope_metrics[0].metrics
+                if rm.scope_metrics}
+
+    @async_test
+    async def test_duration_histogram_and_active_requests(self):
+        mixin, _, metric_reader = make_mixin()
+        app = make_app(mixin)
+        await request(app)
+        metrics = self._metric_names(metric_reader)
+        self.assertIn('http.server.request.duration', metrics)
+        self.assertIn('http.server.active_requests', metrics)
+        duration_points = list(metrics['http.server.request.duration'].data.data_points)
+        self.assertEqual(1, len(duration_points))
+        self.assertEqual(1, duration_points[0].count)
+        self.assertGreaterEqual(duration_points[0].sum, 0)
+        active_points = list(metrics['http.server.active_requests'].data.data_points)
+        self.assertEqual(1, len(active_points))
+        self.assertEqual(0, active_points[0].value)
+
+
+class WebSocketTracingTest(unittest.TestCase):
+
+    @staticmethod
+    def _make_ws(headers=(), query_string: bytes = b''):
+        async def send(message):
+            pass
+
+        async def receive():
+            return {'type': 'websocket.connect'}
+
+        scope = {
+            'type': 'websocket',
+            'path': '/ws/games/abc',
+            'query_string': query_string,
+            'scheme': 'ws',
+            'client': ('127.0.0.1', 12345),
+            'server': ('127.0.0.1', 80),
+            'headers': headers,
+        }
+        return AsgiWebSocket(scope, receive, send)
+
+    @async_test
+    async def test_websocket_lifecycle_produces_span(self):
+        mixin, span_exporter, _ = make_mixin()
+        ws = self._make_ws()
+        wrapped = await mixin._before_websocket(ws)
+        self.assertIsNotNone(wrapped)
+        self.assertEqual(1, len(mixin._spans))
+        await mixin._after_websocket(wrapped)  # type: ignore[arg-type]
+        self.assertEqual(0, len(mixin._spans))
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        span = spans[0]
+        self.assertEqual('WS /ws/games/abc', span.name)
+        assert span.attributes is not None
+        self.assertEqual('ws', span.attributes['url.scheme'])
+        self.assertEqual('/ws/games/abc', span.attributes['url.path'])
+        self.assertNotIn('url.query', span.attributes)
+        self.assertEqual('websocket', span.attributes['network.protocol.name'])
+        self.assertEqual('tcp', span.attributes['network.transport'])
+        self.assertEqual('127.0.0.1', span.attributes['client.address'])
+        self.assertEqual(12345, span.attributes['client.port'])
+        self.assertEqual('127.0.0.1', span.attributes['server.address'])
+        self.assertEqual(80, span.attributes['server.port'])
+
+    @async_test
+    async def test_websocket_query_string_recorded(self):
+        mixin, span_exporter, _ = make_mixin()
+        ws = self._make_ws(query_string=b'room=1&token=abc')
+        wrapped = await mixin._before_websocket(ws)
+        await mixin._after_websocket(wrapped)  # type: ignore[arg-type]
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        assert spans[0].attributes is not None
+        self.assertEqual('room=1&token=abc', spans[0].attributes['url.query'])
+
+    @async_test
+    async def test_websocket_traceparent_propagates(self):
+        mixin, span_exporter, _ = make_mixin()
+        ws = self._make_ws(headers=[(b'traceparent', TRACEPARENT.encode())])
+        wrapped = await mixin._before_websocket(ws)
+        await mixin._after_websocket(wrapped)  # type: ignore[arg-type]
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual(0x4bf92f3577b34da6a3ce929d0e0e4736, spans[0].context.trace_id)  # type: ignore[union-attr]
+
+    @async_test
+    async def test_wrapped_websocket_delegates(self):
+        mixin, _, _ = make_mixin()
+        ws = self._make_ws()
+        wrapped = await mixin._before_websocket(ws)
+        assert wrapped is not None
+        self.assertEqual('/ws/games/abc', wrapped.path)
+        self.assertEqual(('127.0.0.1', 12345), wrapped.client)
+        await mixin._after_websocket(wrapped)
+
+    @async_test
+    async def test_websocket_error_close_code_marks_span_error(self):
+        mixin, span_exporter, _ = make_mixin()
+        ws = self._make_ws()
+        wrapped = await mixin._before_websocket(ws)
+        assert wrapped is not None
+        await wrapped.close(1011)
+        await mixin._after_websocket(wrapped)
+
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual(StatusCode.ERROR, spans[0].status.status_code)
+        assert spans[0].attributes is not None
+        self.assertEqual(1011, spans[0].attributes['kaya.websocket.close_code'])
+        self.assertEqual('1011', spans[0].attributes['error.type'])
+
+    @async_test
+    async def test_websocket_exception_marks_span_error(self):
+        mixin, span_exporter, _ = make_mixin()
+        ws = self._make_ws()
+        wrapped = await mixin._before_websocket(ws)
+        assert wrapped is not None
+        wrapped.exception = RuntimeError('ws boom')
+        await mixin._after_websocket(wrapped)
+
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual(StatusCode.ERROR, spans[0].status.status_code)
+        self.assertTrue(any(event.name == 'exception' for event in spans[0].events))
+        assert spans[0].attributes is not None
+        self.assertEqual('RuntimeError', spans[0].attributes['error.type'])
+
+    @async_test
+    async def test_websocket_hooks_are_called(self):
+        calls = []
+
+        def connect_hook(span: Any, ws: Any) -> None:
+            calls.append(('connect', ws.path))
+            span.set_attribute('test.websocket_connect_hook', True)
+
+        def close_hook(span: Any, ws: Any) -> None:
+            calls.append(('close', ws.path))
+            span.set_attribute('test.websocket_close_hook', True)
+
+        mixin, span_exporter, _ = make_mixin(
+            websocket_connect_hook=connect_hook,
+            websocket_close_hook=close_hook,
+        )
+        ws = self._make_ws()
+        wrapped = await mixin._before_websocket(ws)
+        assert wrapped is not None
+        await wrapped.close(1000)
+        await mixin._after_websocket(wrapped)
+
+        self.assertEqual([('connect', '/ws/games/abc'), ('close', '/ws/games/abc')], calls)
+        spans = span_exporter.get_finished_spans()
+        self.assertEqual(1, len(spans))
+        self.assertEqual(StatusCode.UNSET, spans[0].status.status_code)
+        assert spans[0].attributes is not None
+        self.assertNotIn('error.type', spans[0].attributes)
+        self.assertTrue(spans[0].attributes['test.websocket_connect_hook'])
+        self.assertTrue(spans[0].attributes['test.websocket_close_hook'])
+
+
+if __name__ == '__main__':
+    unittest.main()

packages/kaya-rsgi/pyproject.toml

@@ -27,11 +27,6 @@ dependencies = [
     "pwo",
 ]
 
-[project.optional-dependencies]
-dev = [
-    "build", "mypy", "ipdb", "twine"
-]
-
 [project.urls]
 "Homepage" = "https://github.com/woggioni/kaya"
 "Bug Tracker" = "https://github.com/woggioni/kaya/issues"

packages/kaya-rsgi/src/kaya/rsgi/_rsgi.py

@@ -17,13 +17,21 @@ from typing import (
 from granian._granian import (  # type: ignore[attr-defined]
     RSGIHTTPProtocol,
     RSGIHTTPScope,
+    RSGIProtocolClosed,
     RSGIWebsocketProtocol,
     RSGIWebsocketScope,
     RSGIWebsocketTransport,
 )
 from pwo import Maybe
 
-from kaya.core import AbstractKayaApp, HttpContext, HttpMethod, WebSocket, WebSocketMessage
+from kaya.core import (
+    AbstractKayaApp,
+    HttpContext,
+    HttpMethod,
+    WebSocket,
+    WebSocketDisconnect,
+    WebSocketMessage,
+)
 from kaya.core._types import StrOrStrings
 
 
@@ -109,6 +117,7 @@ class RsgiContext(HttpContext):
 class RsgiWebSocket(WebSocket):
     _protocol: RSGIWebsocketProtocol
     _transport: Optional[RSGIWebsocketTransport]
+    _closed: bool
     scheme: str
     path: str
     query_string: str
@@ -124,6 +133,7 @@ class RsgiWebSocket(WebSocket):
             )
         self._protocol = protocol
         self._transport = None
+        self._closed = False
         self.scheme = scope.scheme
         self.path = scope.path
         self.query_string = scope.query_string
@@ -144,13 +154,28 @@ class RsgiWebSocket(WebSocket):
     async def accept(self, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
         # RSGI's websocket accept() takes no arguments (https://github.com/emmett-framework/granian/blob/master/docs/spec/RSGI.md),
         # so handshake headers (e.g. Set-Cookie) cannot be sent on RSGI; they are silently ignored here.
-        self._transport = await self._protocol.accept()
+        try:
+            self._transport = await self._protocol.accept()
+        except RSGIProtocolClosed as exc:
+            self._closed = True
+            raise WebSocketDisconnect(code=1006) from exc
 
     async def receive(self) -> WebSocketMessage:
         if self._transport is None:
             raise RuntimeError('WebSocket connection has not been accepted yet')
-        message = await self._transport.receive()
+        if self._closed:
+            return WebSocketMessage(kind='close')
+        try:
+            message = await self._transport.receive()
+        except RSGIProtocolClosed:
+            # Granian raises this when the peer is gone without a close
+            # handshake (browser tab closed, network dropped, ...). Surface it
+            # as a close message so receive loops terminate normally instead
+            # of seeing an exception.
+            self._closed = True
+            return WebSocketMessage(kind='close')
         if message.kind == 0:
+            self._closed = True
             return WebSocketMessage(kind='close')
         elif message.kind == 1:
             return WebSocketMessage(kind='binary', data=message.data)
@@ -162,15 +187,32 @@ class RsgiWebSocket(WebSocket):
     async def send_text(self, data: str) -> None:
         if self._transport is None:
             raise RuntimeError('WebSocket connection has not been accepted yet')
-        await self._transport.send_str(data)
+        if self._closed:
+            raise WebSocketDisconnect(code=1006)
+        try:
+            await self._transport.send_str(data)
+        except RSGIProtocolClosed as exc:
+            self._closed = True
+            raise WebSocketDisconnect(code=1006) from exc
 
     async def send_bytes(self, data: bytes) -> None:
         if self._transport is None:
             raise RuntimeError('WebSocket connection has not been accepted yet')
-        await self._transport.send_bytes(data)
+        if self._closed:
+            raise WebSocketDisconnect(code=1006)
+        try:
+            await self._transport.send_bytes(data)
+        except RSGIProtocolClosed as exc:
+            self._closed = True
+            raise WebSocketDisconnect(code=1006) from exc
 
     async def close(self, code: int = 1000) -> None:
-        self._protocol.close(code)
+        if self._closed:
+            return
+        try:
+            self._protocol.close(code)
+        except RSGIProtocolClosed:
+            self._closed = True
 
     async def __anext__(self) -> WebSocketMessage:
         message = await self.receive()

packages/kaya-rsgi/tests/test_rsgi.py

@@ -1,22 +1,150 @@
 import unittest
+from types import SimpleNamespace
+from typing import Any
+
+from granian.rsgi import ProtocolClosed
+from pwo import async_test
+
+from kaya.core import WebSocketDisconnect
 from kaya.rsgi import RsgiWebSocket
 
 
+class FakeScope:
+    scheme = 'ws'
+    path = '/ws'
+    query_string = ''
+    headers: dict[str, list[str]] = {}
+    client = '127.0.0.1:12345'
+    server = '127.0.0.1:80'
+
+
+class FakeTransport:
+    """A transport whose peer vanished without a close handshake."""
+
+    def __init__(self) -> None:
+        self.receive_calls = 0
+        self.sent: list[Any] = []
+
+    async def receive(self) -> Any:
+        self.receive_calls += 1
+        raise ProtocolClosed()
+
+    async def send_str(self, data: str) -> None:
+        self.sent.append(data)
+        raise ProtocolClosed()
+
+    async def send_bytes(self, data: bytes) -> None:
+        self.sent.append(data)
+        raise ProtocolClosed()
+
+
+class CleanCloseTransport(FakeTransport):
+    """A transport that reports a close message (kind 0)."""
+
+    async def receive(self) -> Any:
+        self.receive_calls += 1
+        return SimpleNamespace(kind=0, data=None)
+
+
+class FakeProtocol:
+    def __init__(self, transport: FakeTransport) -> None:
+        self._transport = transport
+        self.closed: list[int] = []
+
+    async def accept(self) -> FakeTransport:
+        return self._transport
+
+    def close(self, code: int) -> None:
+        self.closed.append(code)
+
+
+class ClosedOnAcceptProtocol(FakeProtocol):
+    """A protocol whose peer vanished during the handshake."""
+
+    async def accept(self) -> FakeTransport:
+        raise ProtocolClosed()
+
+
 class RsgiWebSocketTest(unittest.TestCase):
 
     def test_misconfigured_granian(self):
-        class FakeScope:
+        class FakeProtocolWithoutWebsockets:
-            scheme = 'ws'
-            path = '/ws'
-            query_string = ''
-            headers = {}
-            client = '127.0.0.1:12345'
-            server = '127.0.0.1:80'
-
-        class FakeProtocol:
             pass
 
         with self.assertRaises(RuntimeError) as ctx:
-            RsgiWebSocket(FakeScope(), FakeProtocol())  # type: ignore[arg-type]
+            RsgiWebSocket(FakeScope(), FakeProtocolWithoutWebsockets())  # type: ignore[arg-type]
 
         self.assertIn('Granian was not configured for websockets', str(ctx.exception))
+
+    async def _socket(self, transport: FakeTransport) -> tuple[RsgiWebSocket, FakeProtocol]:
+        protocol = FakeProtocol(transport)
+        ws = RsgiWebSocket(FakeScope(), protocol)  # type: ignore[arg-type]
+        await ws.accept()
+        return ws, protocol
+
+    @async_test
+    async def test_receive_returns_close_when_transport_is_gone(self):
+        ws, _ = await self._socket(FakeTransport())
+        message = await ws.receive()
+        self.assertEqual('close', message.kind)
+
+    @async_test
+    async def test_iteration_ends_when_transport_is_gone(self):
+        ws, _ = await self._socket(FakeTransport())
+        messages = [message async for message in ws]
+        self.assertEqual([], messages)
+
+    @async_test
+    async def test_receive_remembers_the_close(self):
+        transport = FakeTransport()
+        ws, _ = await self._socket(transport)
+        self.assertEqual('close', (await ws.receive()).kind)
+        self.assertEqual('close', (await ws.receive()).kind)
+        self.assertEqual(1, transport.receive_calls)
+
+    @async_test
+    async def test_send_text_raises_disconnect_when_transport_is_gone(self):
+        ws, _ = await self._socket(FakeTransport())
+        with self.assertRaises(WebSocketDisconnect) as ctx:
+            await ws.send_text('hello')
+        self.assertEqual(1006, ctx.exception.code)
+
+    @async_test
+    async def test_send_bytes_raises_disconnect_when_transport_is_gone(self):
+        ws, _ = await self._socket(FakeTransport())
+        with self.assertRaises(WebSocketDisconnect) as ctx:
+            await ws.send_bytes(b'hello')
+        self.assertEqual(1006, ctx.exception.code)
+
+    @async_test
+    async def test_sends_after_disconnect_do_not_touch_the_transport(self):
+        transport = FakeTransport()
+        ws, _ = await self._socket(transport)
+        with self.assertRaises(WebSocketDisconnect):
+            await ws.send_text('first')
+        with self.assertRaises(WebSocketDisconnect):
+            await ws.send_text('second')
+        self.assertEqual(['first'], transport.sent)
+
+    @async_test
+    async def test_send_after_a_clean_close_raises_disconnect(self):
+        transport = CleanCloseTransport()
+        ws, _ = await self._socket(transport)
+        self.assertEqual('close', (await ws.receive()).kind)
+        with self.assertRaises(WebSocketDisconnect):
+            await ws.send_text('hello')
+        self.assertEqual([], transport.sent)
+
+    @async_test
+    async def test_accept_raises_disconnect_when_transport_is_gone(self):
+        ws = RsgiWebSocket(FakeScope(), ClosedOnAcceptProtocol(FakeTransport()))  # type: ignore[arg-type]
+        with self.assertRaises(WebSocketDisconnect) as ctx:
+            await ws.accept()
+        self.assertEqual(1006, ctx.exception.code)
+
+    @async_test
+    async def test_close_is_noop_once_the_transport_is_gone(self):
+        ws, protocol = await self._socket(FakeTransport())
+        await ws.receive()
+        await ws.close(1000)
+        self.assertEqual([], protocol.closed)

packages/kaya-session-memcache/README.md

@@ -13,7 +13,7 @@ import aiomcache
 
 from kaya.core import KayaApp, HttpContext
 from kaya.session import SessionMixin
-from kaya.session_memcache import MemcacheSessionStore
+from kaya.session.memcache import MemcacheSessionStore
 
 client = aiomcache.Client('127.0.0.1', 11211)
 session = SessionMixin(MemcacheSessionStore(client))
@@ -32,11 +32,25 @@ and slides on each access when the session mixin passes a `max_age`. TTLs
 larger than 30 days are automatically converted to absolute Unix timestamps,
 as required by the memcached protocol.
 
+## Session indexes
+
+`MemcacheSessionStore` supports `Session.add_index()`,
+`SessionStore.find_sessions()`, and `delete_by_index()`. Reverse memberships
+are stored as sets and updated with memcached CAS operations. Bucket keys use
+a SHA-256 digest of the index name and value, and stale members are pruned
+during lookups.
+
+Memcached's item-size limit (normally 1 MB) applies to each index bucket. Use
+the Redis store when one index value can have a very large number of active
+sessions.
+
 ## Serialization
 
 Session data is serialized with `pickle` by default, so arbitrary Python
-objects can be stored. A different serializer can be plugged in via the
+objects can be stored. The serialized value is an envelope containing the
-`dumps`/`loads` arguments:
+session dictionary and index metadata; legacy plain-dict values are still
+accepted. A different serializer can be plugged in via the `dumps`/`loads`
+arguments:
 
 ```python
 import json

packages/kaya-session-memcache/pyproject.toml

@@ -26,11 +26,6 @@ dependencies = [
     "aiomcache>=0.8",
 ]
 
-[project.optional-dependencies]
-dev = [
-    "build", "mypy", "ipdb", "twine"
-]
-
 [project.urls]
 "Homepage" = "https://github.com/woggioni/kaya"
 "Bug Tracker" = "https://github.com/woggioni/kaya/issues"
@@ -51,7 +46,7 @@ strict = true
 
 [tool.setuptools_scm]
 root = "../.."
-version_file = "src/kaya/session_memcache/_version.py"
+version_file = "src/kaya/session/memcache/_version.py"
 
 [tool.setuptools_scm.tag]
 prefix = "release/"

packages/kaya-session-memcache/src/kaya/session/memcache/_store.py

@@ -0,0 +1,199 @@
+import hashlib
+import pickle
+from time import time
+from typing import Any, Callable, Collection, Optional, Sequence
+
+import aiomcache
+
+from kaya.session import IndexKey, Session, SessionStore
+
+_THIRTY_DAYS = 30 * 24 * 60 * 60
+_INDEX_GRACE_PERIOD = 60
+_CAS_RETRIES = 5
+
+
+def _exptime(max_age: int, clock: Callable[[], float]) -> int:
+    """Convert a relative TTL to a memcached ``exptime`` value.
+
+    Memcached interprets ``exptime`` values larger than 30 days as absolute
+    Unix timestamps, so large TTLs must be converted explicitly.
+    """
+    if max_age > _THIRTY_DAYS:
+        return int(clock()) + max_age
+    return max_age
+
+
+class MemcacheSessionStore(SessionStore):
+    """Memcached-backed session store.
+
+    Suitable for multi-process and multi-host deployments: session data is
+    shared between all application instances connected to the same memcached
+    server.
+
+    Server-side expiry is delegated to memcached item expiration. When
+    ``max_age`` is provided, active sessions slide the expiry window on each
+    access. TTLs larger than 30 days are converted to absolute Unix
+    timestamps, as required by the memcached protocol.
+
+    Session data is serialized with ``pickle`` by default, so arbitrary
+    Python objects can be stored. Custom serializers can be plugged in via
+    the ``dumps``/``loads`` arguments. Only connect this store to a trusted
+    memcached server, as pickle deserialization of untrusted data is unsafe.
+
+    Reverse index buckets are pickled sets updated with memcached CAS
+    operations. Memcached's item-size limit applies to each bucket; Redis is a
+    better fit when one index value can have a very large number of sessions.
+    """
+
+    supports_indexes = True
+
+    def __init__(
+        self,
+        client: aiomcache.Client,
+        prefix: str = "kaya:session:",
+        dumps: Callable[[dict[str, Any]], bytes] = pickle.dumps,
+        loads: Callable[[bytes], dict[str, Any]] = pickle.loads,
+        clock: Callable[[], float] = time,
+    ) -> None:
+        self._client = client
+        self._prefix = prefix
+        self._dumps = dumps
+        self._loads = loads
+        self._clock = clock
+
+    def _key(self, session_id: str) -> bytes:
+        return f"{self._prefix}{session_id}".encode()
+
+    def _index_key(self, name: str, value: str) -> bytes:
+        digest = hashlib.sha256(f"{name}\0{value}".encode()).hexdigest()
+        return f"{self._prefix}idx:{digest}".encode()
+
+    def _index_exptime(self, max_age: Optional[int]) -> int:
+        if max_age is None:
+            return 0
+        return _exptime(max_age + _INDEX_GRACE_PERIOD, self._clock)
+
+    @staticmethod
+    def _decode_bucket(payload: bytes) -> tuple[set[str], Optional[int]]:
+        members, max_age = pickle.loads(payload)
+        return set(members), max_age
+
+    async def _update_bucket(
+        self,
+        index_key: bytes,
+        *,
+        add: Collection[str] = (),
+        remove: Collection[str] = (),
+        max_age: Optional[int] = None,
+    ) -> None:
+        for _ in range(_CAS_RETRIES):
+            payload, cas_token = await self._client.gets(index_key)
+            if cas_token is None:
+                if not add:
+                    return
+                members = set(add)
+                created = await self._client.add(
+                    index_key,
+                    pickle.dumps((members, max_age)),
+                    exptime=self._index_exptime(max_age),
+                )
+                if created:
+                    return
+                continue
+
+            assert payload is not None
+            members, stored_max_age = self._decode_bucket(payload)
+            updated = (members | set(add)) - set(remove)
+            if updated == members:
+                if not add:
+                    return
+                if await self._client.touch(
+                    index_key,
+                    self._index_exptime(max_age),
+                ):
+                    return
+                # The bucket may have expired between gets() and touch().
+                # Retry so it can be recreated instead of losing the index.
+                continue
+
+            effective_max_age = max_age if add else stored_max_age
+            if await self._client.cas(
+                index_key,
+                pickle.dumps((updated, effective_max_age)),
+                cas_token,
+                exptime=self._index_exptime(effective_max_age),
+            ):
+                return
+
+        raise RuntimeError('Could not update session index after repeated CAS conflicts')
+
+    async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
+        key = self._key(session_id)
+        payload = await self._client.get(key)
+        if payload is None:
+            return None
+
+        if max_age is not None:
+            await self._client.touch(key, _exptime(max_age, self._clock))
+
+        data = self._loads(payload)
+        return Session.from_payload(session_id, data)
+
+    async def save(self, session_id: str, session: Session, max_age: Optional[int] = None) -> None:
+        # Index first: if the session write subsequently fails, a stale index
+        # entry is harmless and will be pruned, while a live unindexed session
+        # would be invisible to index-based invalidation.
+        for name, value in session.indexes:
+            await self._update_bucket(
+                self._index_key(name, value),
+                add={session_id},
+                max_age=max_age,
+            )
+        for name, value in session.removed_indexes:
+            await self._update_bucket(
+                self._index_key(name, value),
+                remove={session_id},
+            )
+
+        payload = self._dumps(session.to_payload())
+        exptime = _exptime(max_age, self._clock) if max_age is not None else 0
+        await self._client.set(self._key(session_id), payload, exptime=exptime)
+
+    async def delete(self, session_id: str) -> None:
+        key = self._key(session_id)
+        payload = await self._client.get(key)
+        indexes: set[IndexKey] = set()
+        if payload is not None:
+            try:
+                indexes = set(Session.from_payload(
+                    session_id,
+                    self._loads(payload),
+                ).indexes)
+            except Exception:
+                # A corrupt payload must not prevent session deletion.
+                pass
+
+        await self._client.delete(key)
+        for name, value in indexes:
+            await self._update_bucket(
+                self._index_key(name, value),
+                remove={session_id},
+            )
+
+    async def find_sessions(self, name: str, value: str) -> Sequence[str]:
+        index_key = self._index_key(name, value)
+        payload = await self._client.get(index_key)
+        if payload is None:
+            return []
+
+        members, _ = self._decode_bucket(payload)
+        live: list[str] = []
+        stale: list[str] = []
+        for session_id in members:
+            if await self._client.get(self._key(session_id)) is None:
+                stale.append(session_id)
+            else:
+                live.append(session_id)
+        if stale:
+            await self._update_bucket(index_key, remove=stale)
+        return live

packages/kaya-session-memcache/src/kaya/session_memcache/_store.py

@@ -1,76 +0,0 @@
-import pickle
-from time import time
-from typing import Any, Callable, Optional
-
-import aiomcache
-
-from kaya.session import Session, SessionStore
-
-_THIRTY_DAYS = 30 * 24 * 60 * 60
-
-
-def _exptime(max_age: int, clock: Callable[[], float]) -> int:
-    """Convert a relative TTL to a memcached ``exptime`` value.
-
-    Memcached interprets ``exptime`` values larger than 30 days as absolute
-    Unix timestamps, so large TTLs must be converted explicitly.
-    """
-    if max_age > _THIRTY_DAYS:
-        return int(clock()) + max_age
-    return max_age
-
-
-class MemcacheSessionStore(SessionStore):
-    """Memcached-backed session store.
-
-    Suitable for multi-process and multi-host deployments: session data is
-    shared between all application instances connected to the same memcached
-    server.
-
-    Server-side expiry is delegated to memcached item expiration. When
-    ``max_age`` is provided, active sessions slide the expiry window on each
-    access. TTLs larger than 30 days are converted to absolute Unix
-    timestamps, as required by the memcached protocol.
-
-    Session data is serialized with ``pickle`` by default, so arbitrary
-    Python objects can be stored. Custom serializers can be plugged in via
-    the ``dumps``/``loads`` arguments. Only connect this store to a trusted
-    memcached server, as pickle deserialization of untrusted data is unsafe.
-    """
-
-    def __init__(
-        self,
-        client: aiomcache.Client,
-        prefix: str = "kaya:session:",
-        dumps: Callable[[dict[str, Any]], bytes] = pickle.dumps,
-        loads: Callable[[bytes], dict[str, Any]] = pickle.loads,
-        clock: Callable[[], float] = time,
-    ) -> None:
-        self._client = client
-        self._prefix = prefix
-        self._dumps = dumps
-        self._loads = loads
-        self._clock = clock
-
-    def _key(self, session_id: str) -> bytes:
-        return f"{self._prefix}{session_id}".encode()
-
-    async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
-        key = self._key(session_id)
-        payload = await self._client.get(key)
-        if payload is None:
-            return None
-
-        if max_age is not None:
-            await self._client.touch(key, _exptime(max_age, self._clock))
-
-        data = self._loads(payload)
-        return Session(session_id, data)
-
-    async def save(self, session_id: str, session: Session, max_age: Optional[int] = None) -> None:
-        payload = self._dumps(dict(session))
-        exptime = _exptime(max_age, self._clock) if max_age is not None else 0
-        await self._client.set(self._key(session_id), payload, exptime=exptime)
-
-    async def delete(self, session_id: str) -> None:
-        await self._client.delete(self._key(session_id))

packages/kaya-session-memcache/tests/test_indexes.py

@@ -0,0 +1,122 @@
+import pickle
+import unittest
+
+from pwo import async_test
+from test_store import FakeClock, StubMemcacheClient
+
+from kaya.session import Session
+from kaya.session.memcache import MemcacheSessionStore
+
+
+class MemcacheSessionIndexTest(unittest.TestCase):
+
+    def setUp(self) -> None:
+        self.clock = FakeClock()
+        self.client = StubMemcacheClient(self.clock)
+        self.store = MemcacheSessionStore(self.client, clock=self.clock)  # type: ignore[arg-type]
+
+    @async_test
+    async def test_save_load_and_find(self) -> None:
+        self.assertTrue(self.store.supports_indexes)
+        await self.store.save('abc', Session('abc', {'user': 'alice'}, indexes={('sub', 'alice')}))
+        loaded = await self.store.load('abc')
+        assert loaded is not None
+        self.assertEqual({'user': 'alice'}, dict(loaded))
+        self.assertEqual(frozenset({('sub', 'alice')}), loaded.indexes)
+        self.assertEqual(['abc'], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_rotation_preserves_index(self) -> None:
+        await self.store.save('old', Session('old', indexes={('sub', 'alice')}))
+        loaded = await self.store.load('old')
+        assert loaded is not None
+        loaded.set_id('new')
+        await self.store.delete('old')
+        await self.store.save('new', loaded)
+        self.assertEqual(['new'], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_delete_cleans_reverse_index(self) -> None:
+        await self.store.save('abc', Session('abc', indexes={('sub', 'alice')}))
+        await self.store.delete('abc')
+        self.assertEqual([], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_delete_by_index_deletes_all_sessions(self) -> None:
+        await self.store.save('a', Session('a', indexes={('sub', 'alice')}))
+        await self.store.save('b', Session('b', indexes={('sub', 'alice')}))
+        await self.store.save('c', Session('c', indexes={('sub', 'bob')}))
+        self.assertEqual(2, await self.store.delete_by_index('sub', 'alice'))
+        self.assertIsNone(await self.store.load('a'))
+        self.assertIsNone(await self.store.load('b'))
+        self.assertIsNotNone(await self.store.load('c'))
+
+    @async_test
+    async def test_stale_member_is_pruned(self) -> None:
+        await self.store.save('abc', Session('abc', indexes={('sub', 'alice')}))
+        await self.client.delete(b'kaya:session:abc')
+        self.assertEqual([], await self.store.find_sessions('sub', 'alice'))
+        index_key = self.store._index_key('sub', 'alice')
+        payload = await self.client.get(index_key)
+        assert payload is not None
+        members, _ = pickle.loads(payload)
+        self.assertEqual(set(), members)
+
+    @async_test
+    async def test_index_ttl_tracks_session_max_age(self) -> None:
+        await self.store.save(
+            'abc',
+            Session('abc', indexes={('sub', 'alice')}),
+            max_age=60,
+        )
+        index_key = self.store._index_key('sub', 'alice')
+        self.assertIn(index_key, self.client._expires)
+        self.clock.advance(61)
+        await self.store.save(
+            'abc',
+            Session('abc', indexes={('sub', 'alice')}),
+            max_age=60,
+        )
+        self.assertIsNotNone(await self.client.get(index_key))
+
+    @async_test
+    async def test_legacy_payload_is_upgraded_on_save(self) -> None:
+        await self.client.set(b'kaya:session:abc', pickle.dumps({'foo': 'bar'}))
+        loaded = await self.store.load('abc')
+        assert loaded is not None
+        self.assertEqual({'foo': 'bar'}, dict(loaded))
+        self.assertEqual(frozenset(), loaded.indexes)
+
+        loaded.add_index('sub', 'alice')
+        await self.store.save('abc', loaded)
+        raw = await self.client.get(b'kaya:session:abc')
+        assert raw is not None
+        payload = pickle.loads(raw)
+        self.assertEqual(1, payload['__kaya_session_v1__'])
+        self.assertEqual({'foo': 'bar'}, payload['data'])
+        self.assertEqual(['abc'], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_cas_conflict_is_retried(self) -> None:
+        await self.store.save('existing', Session('existing', indexes={('sub', 'alice')}))
+        original_cas = self.client.cas
+        attempts = 0
+
+        async def fail_once(key: bytes, value: bytes, cas_token: int, exptime: int = 0) -> bool:
+            nonlocal attempts
+            attempts += 1
+            if attempts == 1:
+                return False
+            return await original_cas(key, value, cas_token, exptime)
+
+        self.client.cas = fail_once  # type: ignore[method-assign]
+        await self.store.save('abc', Session('abc', indexes={('sub', 'alice')}))
+        self.assertEqual(
+            {'existing', 'abc'},
+            set(await self.store.find_sessions('sub', 'alice')),
+        )
+        self.assertGreaterEqual(attempts, 2)
+
+
+if __name__ == '__main__':
+    unittest.main()

packages/kaya-session-memcache/tests/test_store.py

@@ -7,7 +7,7 @@ from pwo import async_test
 
 from kaya.core import KayaApp, HttpContext
 from kaya.session import Session, SessionMixin
-from kaya.session_memcache import MemcacheSessionStore
+from kaya.session.memcache import MemcacheSessionStore
 
 
 class FakeClock:
@@ -28,6 +28,8 @@ class StubMemcacheClient:
         self._clock = clock
         self._data: dict[bytes, bytes] = {}
         self._expires: dict[bytes, float] = {}
+        self._cas: dict[bytes, int] = {}
+        self._next_cas = 1
         self.set_exptimes: list[int] = []
         self.touch_exptimes: list[int] = []
 
@@ -42,19 +44,46 @@ class StubMemcacheClient:
             return None
         return self._data.get(key)
 
-    async def set(self, key: bytes, value: bytes, exptime: int = 0) -> bool:
+    def _store(self, key: bytes, value: bytes, exptime: int) -> None:
-        self.set_exptimes.append(exptime)
         self._data[key] = value
+        self._cas[key] = self._next_cas
+        self._next_cas += 1
         if exptime > 0:
             self._expires[key] = self._clock() + exptime
         else:
             self._expires.pop(key, None)
+
+    async def set(self, key: bytes, value: bytes, exptime: int = 0) -> bool:
+        self.set_exptimes.append(exptime)
+        self._store(key, value, exptime)
+        return True
+
+    async def add(self, key: bytes, value: bytes, exptime: int = 0) -> bool:
+        if self._expired(key):
+            self._data.pop(key, None)
+            self._expires.pop(key, None)
+        if key in self._data:
+            return False
+        self._store(key, value, exptime)
+        return True
+
+    async def gets(self, key: bytes) -> tuple[Optional[bytes], Optional[int]]:
+        value = await self.get(key)
+        if value is None:
+            return None, None
+        return value, self._cas[key]
+
+    async def cas(self, key: bytes, value: bytes, cas_token: int, exptime: int = 0) -> bool:
+        if self._expired(key) or self._cas.get(key) != cas_token:
+            return False
+        self._store(key, value, exptime)
         return True
 
     async def delete(self, key: bytes) -> bool:
         existed = key in self._data
         self._data.pop(key, None)
         self._expires.pop(key, None)
+        self._cas.pop(key, None)
         return existed
 
     async def touch(self, key: bytes, exptime: int) -> bool:
@@ -169,7 +198,11 @@ class MemcacheSessionStoreTest(unittest.TestCase):
             clock=self.clock,
         )
         await store.save('abc', Session('abc', {'foo': 'bar'}))
-        self.assertEqual(b'{"foo": "bar"}', self.client._data[b'kaya:session:abc'])
+        self.assertEqual({
+            '__kaya_session_v1__': 1,
+            'data': {'foo': 'bar'},
+            'indexes': [],
+        }, json.loads(self.client._data[b'kaya:session:abc']))
         loaded = await store.load('abc')
         self.assertIsNotNone(loaded)
         assert loaded is not None

packages/kaya-session-redis/README.md

@@ -13,7 +13,7 @@ from redis.asyncio import Redis
 
 from kaya.core import KayaApp, HttpContext
 from kaya.session import SessionMixin
-from kaya.session_redis import RedisSessionStore
+from kaya.session.redis import RedisSessionStore
 
 client = Redis(host='localhost', port=6379)
 session = SessionMixin(RedisSessionStore(client))
@@ -30,11 +30,21 @@ Sessions are stored under keys with the prefix `kaya:session:` (configurable
 via the `prefix` argument). Server-side expiry uses Redis key TTLs and slides
 on each access when the session mixin passes a `max_age`.
 
+## Session indexes
+
+`RedisSessionStore` supports `Session.add_index()`,
+`SessionStore.find_sessions()`, and `delete_by_index()`. Reverse memberships
+are Redis sets updated in the same transactional pipeline as session saves.
+They are removed on deletion, and stale members are pruned during lookups.
+Bucket keys use a SHA-256 digest of the index name and value.
+
 ## Serialization
 
 Session data is serialized with `pickle` by default, so arbitrary Python
-objects can be stored. A different serializer can be plugged in via the
+objects can be stored. The serialized value is an envelope containing the
-`dumps`/`loads` arguments:
+session dictionary and index metadata; legacy plain-dict values are still
+accepted. A different serializer can be plugged in via the `dumps`/`loads`
+arguments:
 
 ```python
 import json

packages/kaya-session-redis/pyproject.toml

@@ -26,11 +26,6 @@ dependencies = [
     "redis>=5.0",
 ]
 
-[project.optional-dependencies]
-dev = [
-    "build", "mypy", "ipdb", "twine", "fakeredis"
-]
-
 [project.urls]
 "Homepage" = "https://github.com/woggioni/kaya"
 "Bug Tracker" = "https://github.com/woggioni/kaya/issues"
@@ -51,7 +46,7 @@ strict = true
 
 [tool.setuptools_scm]
 root = "../.."
-version_file = "src/kaya/session_redis/_version.py"
+version_file = "src/kaya/session/redis/_version.py"
 
 [tool.setuptools_scm.tag]
 prefix = "release/"

packages/kaya-session-redis/src/kaya/session/redis/_store.py

@@ -0,0 +1,122 @@
+import hashlib
+import pickle
+from typing import Any, Callable, Optional, Sequence, cast
+
+from redis.asyncio import Redis
+
+from kaya.session import IndexKey, Session, SessionStore
+
+
+class RedisSessionStore(SessionStore):
+    """Redis-backed session store.
+
+    Suitable for multi-process and multi-host deployments: session data is
+    shared between all application instances connected to the same Redis
+    server.
+
+    Server-side expiry is delegated to Redis key TTLs. When ``max_age`` is
+    provided, active sessions slide the expiry window on each access.
+
+    Session data is serialized with ``pickle`` by default, so arbitrary
+    Python objects can be stored. Custom serializers can be plugged in via
+    the ``dumps``/``loads`` arguments. Only connect this store to a trusted
+    Redis server, as pickle deserialization of untrusted data is unsafe.
+
+    Reverse session indexes are stored as Redis sets. They are updated in the
+    same pipeline as session saves, cleaned on deletion, and pruned when stale
+    memberships are encountered during a lookup.
+    """
+
+    supports_indexes = True
+
+    def __init__(
+        self,
+        client: Redis,
+        prefix: str = "kaya:session:",
+        dumps: Callable[[dict[str, Any]], bytes] = pickle.dumps,
+        loads: Callable[[bytes], dict[str, Any]] = pickle.loads,
+    ) -> None:
+        self._client = client
+        self._prefix = prefix
+        self._dumps = dumps
+        self._loads = loads
+
+    def _key(self, session_id: str) -> str:
+        return f"{self._prefix}{session_id}"
+
+    def _index_key(self, name: str, value: str) -> str:
+        digest = hashlib.sha256(f"{name}\0{value}".encode()).hexdigest()
+        return f"{self._prefix}idx:{digest}"
+
+    async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
+        key = self._key(session_id)
+        payload = await self._client.get(key)
+        if payload is None:
+            return None
+
+        if max_age is not None:
+            await self._client.expire(key, max_age)
+
+        data = self._loads(cast(bytes, payload))
+        return Session.from_payload(session_id, data)
+
+    async def save(self, session_id: str, session: Session, max_age: Optional[int] = None) -> None:
+        payload = self._dumps(session.to_payload())
+        pipeline = self._client.pipeline(transaction=True)
+        pipeline.set(self._key(session_id), payload, ex=max_age)
+        for name, value in session.indexes:
+            index_key = self._index_key(name, value)
+            pipeline.sadd(index_key, session_id)
+            if max_age is None:
+                pipeline.persist(index_key)
+            else:
+                pipeline.expire(index_key, max_age + 60)
+        for name, value in session.removed_indexes:
+            pipeline.srem(self._index_key(name, value), session_id)
+        await pipeline.execute()
+
+    async def delete(self, session_id: str) -> None:
+        key = self._key(session_id)
+        payload = await self._client.get(key)
+        indexes: set[IndexKey] = set()
+        if payload is not None:
+            try:
+                indexes = set(Session.from_payload(
+                    session_id,
+                    self._loads(cast(bytes, payload)),
+                ).indexes)
+            except Exception:
+                # A corrupt payload must not prevent session deletion.
+                pass
+
+        pipeline = self._client.pipeline(transaction=True)
+        pipeline.delete(key)
+        for name, value in indexes:
+            pipeline.srem(self._index_key(name, value), session_id)
+        await pipeline.execute()
+
+    async def find_sessions(self, name: str, value: str) -> Sequence[str]:
+        index_key = self._index_key(name, value)
+        members = await self._client.smembers(index_key)
+        session_ids = [
+            member.decode() if isinstance(member, bytes) else str(member)
+            for member in members
+        ]
+        if not session_ids:
+            return []
+
+        pipeline = self._client.pipeline(transaction=False)
+        for session_id in session_ids:
+            pipeline.exists(self._key(session_id))
+        exists = await pipeline.execute()
+
+        live: list[str] = []
+        stale: list[str] = []
+        for session_id, found in zip(session_ids, exists):
+            if found:
+                live.append(session_id)
+            else:
+                stale.append(session_id)
+        if stale:
+            await self._client.srem(index_key, *stale)
+        return live

packages/kaya-session-redis/src/kaya/session_redis/_store.py

@@ -1,57 +0,0 @@
-import pickle
-from typing import Any, Callable, Optional, cast
-
-from redis.asyncio import Redis
-
-from kaya.session import Session, SessionStore
-
-
-class RedisSessionStore(SessionStore):
-    """Redis-backed session store.
-
-    Suitable for multi-process and multi-host deployments: session data is
-    shared between all application instances connected to the same Redis
-    server.
-
-    Server-side expiry is delegated to Redis key TTLs. When ``max_age`` is
-    provided, active sessions slide the expiry window on each access.
-
-    Session data is serialized with ``pickle`` by default, so arbitrary
-    Python objects can be stored. Custom serializers can be plugged in via
-    the ``dumps``/``loads`` arguments. Only connect this store to a trusted
-    Redis server, as pickle deserialization of untrusted data is unsafe.
-    """
-
-    def __init__(
-        self,
-        client: Redis,
-        prefix: str = "kaya:session:",
-        dumps: Callable[[dict[str, Any]], bytes] = pickle.dumps,
-        loads: Callable[[bytes], dict[str, Any]] = pickle.loads,
-    ) -> None:
-        self._client = client
-        self._prefix = prefix
-        self._dumps = dumps
-        self._loads = loads
-
-    def _key(self, session_id: str) -> str:
-        return f"{self._prefix}{session_id}"
-
-    async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
-        key = self._key(session_id)
-        payload = await self._client.get(key)
-        if payload is None:
-            return None
-
-        if max_age is not None:
-            await self._client.expire(key, max_age)
-
-        data = self._loads(cast(bytes, payload))
-        return Session(session_id, data)
-
-    async def save(self, session_id: str, session: Session, max_age: Optional[int] = None) -> None:
-        payload = self._dumps(dict(session))
-        await self._client.set(self._key(session_id), payload, ex=max_age)
-
-    async def delete(self, session_id: str) -> None:
-        await self._client.delete(self._key(session_id))

packages/kaya-session-redis/tests/test_indexes.py

@@ -0,0 +1,94 @@
+import pickle
+import unittest
+
+import fakeredis.aioredis
+from pwo import async_test
+
+from kaya.session import Session
+from kaya.session.redis import RedisSessionStore
+
+
+class RedisSessionIndexTest(unittest.TestCase):
+
+    def setUp(self) -> None:
+        self.client = fakeredis.aioredis.FakeRedis()
+        self.store = RedisSessionStore(self.client)
+
+    @async_test
+    async def test_save_load_and_find(self) -> None:
+        self.assertTrue(self.store.supports_indexes)
+        await self.store.save('abc', Session('abc', {'user': 'alice'}, indexes={('sub', 'alice')}))
+        loaded = await self.store.load('abc')
+        assert loaded is not None
+        self.assertEqual({'user': 'alice'}, dict(loaded))
+        self.assertEqual(frozenset({('sub', 'alice')}), loaded.indexes)
+        self.assertEqual(['abc'], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_rotation_preserves_index(self) -> None:
+        await self.store.save('old', Session('old', indexes={('sub', 'alice')}))
+        loaded = await self.store.load('old')
+        assert loaded is not None
+        loaded.set_id('new')
+        await self.store.delete('old')
+        await self.store.save('new', loaded)
+        self.assertEqual(['new'], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_delete_cleans_reverse_index(self) -> None:
+        await self.store.save('abc', Session('abc', indexes={('sub', 'alice')}))
+        index_key = self.store._index_key('sub', 'alice')
+        self.assertEqual({b'abc'}, await self.client.smembers(index_key))
+        await self.store.delete('abc')
+        self.assertEqual(set(), await self.client.smembers(index_key))
+
+    @async_test
+    async def test_delete_by_index_deletes_all_sessions(self) -> None:
+        await self.store.save('a', Session('a', indexes={('sub', 'alice')}))
+        await self.store.save('b', Session('b', indexes={('sub', 'alice')}))
+        await self.store.save('c', Session('c', indexes={('sub', 'bob')}))
+        self.assertEqual(2, await self.store.delete_by_index('sub', 'alice'))
+        self.assertIsNone(await self.store.load('a'))
+        self.assertIsNone(await self.store.load('b'))
+        self.assertIsNotNone(await self.store.load('c'))
+
+    @async_test
+    async def test_stale_member_is_pruned(self) -> None:
+        await self.store.save('abc', Session('abc', indexes={('sub', 'alice')}))
+        await self.client.delete('kaya:session:abc')
+        self.assertEqual([], await self.store.find_sessions('sub', 'alice'))
+        index_key = self.store._index_key('sub', 'alice')
+        self.assertEqual(set(), await self.client.smembers(index_key))
+
+    @async_test
+    async def test_index_ttl_tracks_session_max_age(self) -> None:
+        await self.store.save(
+            'abc',
+            Session('abc', indexes={('sub', 'alice')}),
+            max_age=60,
+        )
+        index_key = self.store._index_key('sub', 'alice')
+        ttl = await self.client.ttl(index_key)
+        self.assertGreater(ttl, 60)
+        self.assertLessEqual(ttl, 120)
+
+    @async_test
+    async def test_legacy_payload_is_upgraded_on_save(self) -> None:
+        await self.client.set('kaya:session:abc', pickle.dumps({'foo': 'bar'}))
+        loaded = await self.store.load('abc')
+        assert loaded is not None
+        self.assertEqual({'foo': 'bar'}, dict(loaded))
+        self.assertEqual(frozenset(), loaded.indexes)
+
+        loaded.add_index('sub', 'alice')
+        await self.store.save('abc', loaded)
+        raw = await self.client.get('kaya:session:abc')
+        assert raw is not None
+        payload = pickle.loads(raw)
+        self.assertEqual(1, payload['__kaya_session_v1__'])
+        self.assertEqual({'foo': 'bar'}, payload['data'])
+        self.assertEqual(['abc'], await self.store.find_sessions('sub', 'alice'))
+
+
+if __name__ == '__main__':
+    unittest.main()

packages/kaya-session-redis/tests/test_store.py

@@ -7,7 +7,7 @@ from pwo import async_test
 
 from kaya.core import KayaApp, HttpContext
 from kaya.session import Session, SessionMixin
-from kaya.session_redis import RedisSessionStore
+from kaya.session.redis import RedisSessionStore
 
 
 class RedisSessionStoreTest(unittest.TestCase):
@@ -89,7 +89,13 @@ class RedisSessionStoreTest(unittest.TestCase):
             loads=lambda b: json.loads(b.decode('utf-8')),
         )
         await store.save('abc', Session('abc', {'foo': 'bar'}))
-        self.assertEqual(b'{"foo": "bar"}', await self.client.get('kaya:session:abc'))
+        raw = await self.client.get('kaya:session:abc')
+        assert raw is not None
+        self.assertEqual({
+            '__kaya_session_v1__': 1,
+            'data': {'foo': 'bar'},
+            'indexes': [],
+        }, json.loads(raw))
         loaded = await store.load('abc')
         self.assertIsNotNone(loaded)
         assert loaded is not None

packages/kaya-session/README.md

@@ -66,6 +66,37 @@ session and creates a fresh empty one.
 Set `max_age=None` to disable server-side expiry (and the `Max-Age` cookie
 attribute) entirely.
 
+## Session indexes
+
+Authentication layers can attach reverse-index metadata to a session without
+adding it to the user-visible session dictionary:
+
+```python
+ctx.session.add_index('oidc:default:sub', 'user-123')
+```
+
+Index-capable stores persist these memberships on `save()` and maintain them
+across session ID rotation and deletion:
+
+```python
+session_ids = await store.find_sessions('oidc:default:sub', 'user-123')
+deleted = await store.delete_by_index('oidc:default:sub', 'user-123')
+```
+
+Use `session.remove_index(name, value)` to remove a membership while keeping
+the session. `SessionMixin.store` exposes the backing store for features such
+as back-channel logout.
+
+`InMemorySessionStore`, `RedisSessionStore`, and `MemcacheSessionStore` set
+`supports_indexes = True`. Custom stores can opt in by setting that flag,
+implementing `find_sessions()`, maintaining reverse memberships on `save()`,
+and removing them on `delete()`. `delete_by_index()` has a generic default
+implementation based on `find_sessions()` and `delete()`.
+
+Remote stores serialize an envelope containing both the session dictionary and
+its index metadata. Existing plain-dict payloads remain readable and are
+upgraded on the next save.
+
 ## Features
 
 - `Session`: dict-like session object with modification tracking
@@ -74,6 +105,7 @@ attribute) entirely.
 - `SessionMixin`: composable Kaya mixin managing session cookies and persistence
 - Session ID regeneration (`session.regenerate_id()`) and invalidation
   (`session.invalidate()`) for authentication layers
+- Reverse session indexes for looking up and invalidating sessions by metadata
 - WebSocket support: the session is exposed as `ws.session` in websocket
   handlers, loaded at connect time and persisted on close
 

packages/kaya-session/pyproject.toml

@@ -26,11 +26,6 @@ dependencies = [
     "pwo",
 ]
 
-[project.optional-dependencies]
-dev = [
-    "build", "mypy", "ipdb", "twine", "httpx", "httpx-ws"
-]
-
 [project.urls]
 "Homepage" = "https://github.com/woggioni/kaya"
 "Bug Tracker" = "https://github.com/woggioni/kaya/issues"

packages/kaya-session/src/kaya/session/__init__.py

@@ -1,10 +1,15 @@
+from pkgutil import extend_path
+
+__path__ = extend_path(__path__, __name__)
+
 from ._mixin import SessionMixin
-from ._session import Session
+from ._session import IndexKey, Session
 from ._store import InMemorySessionStore, SessionStore
 
 
 __all__ = [
     'InMemorySessionStore',
+    'IndexKey',
     'Session',
     'SessionMixin',
     'SessionStore',

packages/kaya-session/src/kaya/session/_mixin.py

@@ -183,6 +183,16 @@ class SessionMixin(KayaMixin):
         self._secure = secure
         self._samesite = samesite
 
+    @property
+    def store(self) -> SessionStore:
+        """Return the backing session store."""
+        return self._store
+
+    @property
+    def max_age(self) -> Optional[int]:
+        """Return the idle timeout used when persisting sessions."""
+        return self._max_age
+
     def apply(self, app: KayaApp) -> None:
         app.add_before_request_hook(self._before_request)
         app.add_after_request_hook(self._after_request)
@@ -273,3 +283,4 @@ class SessionMixin(KayaMixin):
 
         if session.id is not None:
             await self._store.save(session.id, session, self._max_age)
+            session.commit_indexes()

packages/kaya-session/src/kaya/session/_session.py

@@ -1,4 +1,10 @@
-from typing import Any, Iterator, Mapping, MutableMapping, Optional
+from typing import Any, Iterable, Iterator, Mapping, MutableMapping, Optional
+
+
+IndexKey = tuple[str, str]
+
+_PAYLOAD_MARKER = '__kaya_session_v1__'
+_PAYLOAD_VERSION = 1
 
 
 class Session(MutableMapping[str, Any]):
@@ -9,13 +15,21 @@ class Session(MutableMapping[str, Any]):
     it.
     """
 
-    def __init__(self, session_id: Optional[str] = None, data: Optional[Mapping[str, Any]] = None) -> None:
+    def __init__(
+        self,
+        session_id: Optional[str] = None,
+        data: Optional[Mapping[str, Any]] = None,
+        indexes: Iterable[IndexKey] = (),
+    ) -> None:
         self._id: Optional[str] = session_id
         self._old_id: Optional[str] = None
         self._data: dict[str, Any] = dict(data) if data else {}
         self._modified: bool = False
         self._regenerate: bool = False
         self._invalidated: bool = False
+        self._persisted_indexes: set[IndexKey] = set(indexes)
+        self._added_indexes: set[IndexKey] = set()
+        self._removed_indexes: set[IndexKey] = set()
 
     @property
     def id(self) -> Optional[str]:
@@ -60,6 +74,75 @@ class Session(MutableMapping[str, Any]):
     def mark_modified(self) -> None:
         self._modified = True
 
+    def add_index(self, name: str, value: str) -> None:
+        """Index this session under ``(name, value)`` when it is saved.
+
+        Index-capable stores can use this metadata to find and invalidate
+        sessions without knowing their IDs. Adding an already persisted index
+        is harmless and does not create a duplicate membership.
+        """
+        index = (name, value)
+        self._removed_indexes.discard(index)
+        if index not in self._persisted_indexes:
+            self._added_indexes.add(index)
+        self._modified = True
+
+    def remove_index(self, name: str, value: str) -> None:
+        """Remove an index membership when this session is saved."""
+        index = (name, value)
+        if index in self._added_indexes:
+            self._added_indexes.discard(index)
+        elif index in self._persisted_indexes:
+            self._removed_indexes.add(index)
+        self._modified = True
+
+    @property
+    def indexes(self) -> frozenset[IndexKey]:
+        """Return the index memberships that should be persisted."""
+        return frozenset(
+            (self._persisted_indexes - self._removed_indexes) | self._added_indexes
+        )
+
+    @property
+    def added_indexes(self) -> frozenset[IndexKey]:
+        """Return index memberships added since the last successful save."""
+        return frozenset(self._added_indexes)
+
+    @property
+    def removed_indexes(self) -> frozenset[IndexKey]:
+        """Return index memberships removed since the last successful save."""
+        return frozenset(self._removed_indexes)
+
+    def commit_indexes(self) -> None:
+        """Mark the current index memberships as persisted."""
+        self._persisted_indexes = set(self.indexes)
+        self._added_indexes.clear()
+        self._removed_indexes.clear()
+
+    def to_payload(self) -> dict[str, Any]:
+        """Return the serializable session payload used by remote stores."""
+        return {
+            _PAYLOAD_MARKER: _PAYLOAD_VERSION,
+            'data': dict(self),
+            'indexes': sorted(self.indexes),
+        }
+
+    @classmethod
+    def from_payload(cls, session_id: str, payload: Mapping[str, Any]) -> 'Session':
+        """Build a session from an envelope or a legacy plain-data payload."""
+        data = payload.get('data')
+        raw_indexes = payload.get('indexes')
+        if (payload.get(_PAYLOAD_MARKER) == _PAYLOAD_VERSION
+                and isinstance(data, Mapping)
+                and isinstance(raw_indexes, (list, tuple))):
+            indexes: set[IndexKey] = set()
+            for item in raw_indexes:
+                if (isinstance(item, (list, tuple)) and len(item) == 2
+                        and isinstance(item[0], str) and isinstance(item[1], str)):
+                    indexes.add((item[0], item[1]))
+            return cls(session_id, data, indexes=indexes)
+        return cls(session_id, payload)
+
     def __getitem__(self, key: str) -> Any:
         return self._data[key]
 

packages/kaya-session/src/kaya/session/_store.py

@@ -1,13 +1,21 @@
 from abc import ABC, abstractmethod
 from secrets import token_urlsafe
 from time import monotonic
-from typing import Any, Callable, Optional
+from typing import Any, Callable, ClassVar, Optional, Sequence
 
-from ._session import Session
+from ._session import IndexKey, Session
 
 
 class SessionStore(ABC):
-    """Pluggable backend for session persistence."""
+    """Pluggable backend for session persistence.
+
+    Stores with ``supports_indexes = True`` also maintain reverse indexes for
+    :class:`~kaya.session.Session` index metadata. They must add the session ID
+    to every effective index on ``save()``, apply pending removals, and remove
+    all of a session's index memberships on ``delete()``.
+    """
+
+    supports_indexes: ClassVar[bool] = False
 
     @abstractmethod
     async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
@@ -33,6 +41,23 @@ class SessionStore(ABC):
         """Remove the session from the store."""
         pass
 
+    async def find_sessions(self, name: str, value: str) -> Sequence[str]:
+        """Return live session IDs indexed under ``(name, value)``.
+
+        Only available on stores whose ``supports_indexes`` flag is true.
+        Implementations should prune stale index memberships encountered here.
+        """
+        raise NotImplementedError(
+            f'{type(self).__name__} does not support session indexes'
+        )
+
+    async def delete_by_index(self, name: str, value: str) -> int:
+        """Delete every live session indexed under ``(name, value)``."""
+        session_ids = await self.find_sessions(name, value)
+        for session_id in session_ids:
+            await self.delete(session_id)
+        return len(session_ids)
+
     def new_session_id(self) -> str:
         """Return a new opaque session identifier.
 
@@ -51,10 +76,26 @@ class InMemorySessionStore(SessionStore):
     inactivity. Active sessions slide the expiry window on each access.
     """
 
+    supports_indexes = True
+
     def __init__(self, clock: Callable[[], float] = monotonic) -> None:
         self._clock = clock
         self._data: dict[str, dict[str, Any]] = {}
         self._expires: dict[str, float] = {}
+        self._session_indexes: dict[str, set[IndexKey]] = {}
+        self._index_sessions: dict[IndexKey, set[str]] = {}
+
+    def _drop_session(self, session_id: str) -> None:
+        self._data.pop(session_id, None)
+        self._expires.pop(session_id, None)
+        indexes = self._session_indexes.pop(session_id, set())
+        for index in indexes:
+            session_ids = self._index_sessions.get(index)
+            if session_ids is None:
+                continue
+            session_ids.discard(session_id)
+            if not session_ids:
+                self._index_sessions.pop(index, None)
 
     async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
         data = self._data.get(session_id)
@@ -64,14 +105,17 @@ class InMemorySessionStore(SessionStore):
         expires = self._expires.get(session_id)
         now = self._clock()
         if expires is not None and now > expires:
-            self._data.pop(session_id, None)
+            self._drop_session(session_id)
-            self._expires.pop(session_id, None)
             return None
 
         if max_age is not None and expires is not None:
             self._expires[session_id] = now + max_age
 
-        return Session(session_id, data)
+        return Session(
+            session_id,
+            data,
+            indexes=self._session_indexes.get(session_id, ()),
+        )
 
     async def save(self, session_id: str, session: Session, max_age: Optional[int] = None) -> None:
         self._data[session_id] = dict(session)
@@ -80,6 +124,34 @@ class InMemorySessionStore(SessionStore):
         else:
             self._expires.pop(session_id, None)
 
+        for index in session.removed_indexes:
+            session_ids = self._index_sessions.get(index)
+            if session_ids is None:
+                continue
+            session_ids.discard(session_id)
+            if not session_ids:
+                self._index_sessions.pop(index, None)
+
+        indexes = set(session.indexes)
+        self._session_indexes[session_id] = indexes
+        for index in indexes:
+            self._index_sessions.setdefault(index, set()).add(session_id)
+
     async def delete(self, session_id: str) -> None:
-        self._data.pop(session_id, None)
+        self._drop_session(session_id)
-        self._expires.pop(session_id, None)
+
+    async def find_sessions(self, name: str, value: str) -> Sequence[str]:
+        session_ids = self._index_sessions.get((name, value))
+        if session_ids is None:
+            return []
+
+        now = self._clock()
+        live: list[str] = []
+        for session_id in list(session_ids):
+            expires = self._expires.get(session_id)
+            if (session_id not in self._data
+                    or (expires is not None and now > expires)):
+                self._drop_session(session_id)
+            else:
+                live.append(session_id)
+        return live

packages/kaya-session/tests/test_indexes.py

@@ -0,0 +1,169 @@
+import unittest
+
+import httpx
+from pwo import async_test
+
+from kaya.core import HttpContext, KayaApp
+from kaya.session import InMemorySessionStore, Session, SessionMixin
+
+
+class FakeClock:
+    def __init__(self, start: float = 0.0) -> None:
+        self._now = start
+
+    def __call__(self) -> float:
+        return self._now
+
+    def advance(self, seconds: float) -> None:
+        self._now += seconds
+
+
+class SessionIndexUnitTest(unittest.TestCase):
+
+    def test_add_and_remove_index(self) -> None:
+        session = Session()
+        session.add_index('sub', 'alice')
+        self.assertEqual(frozenset({('sub', 'alice')}), session.indexes)
+        self.assertEqual(frozenset({('sub', 'alice')}), session.added_indexes)
+        self.assertTrue(session.modified)
+
+        session.remove_index('sub', 'alice')
+        self.assertEqual(frozenset(), session.indexes)
+        self.assertEqual(frozenset(), session.added_indexes)
+        self.assertEqual(frozenset(), session.removed_indexes)
+
+    def test_remove_persisted_index(self) -> None:
+        session = Session(indexes={('sub', 'alice')})
+        self.assertFalse(session.modified)
+        session.remove_index('sub', 'alice')
+        self.assertEqual(frozenset(), session.indexes)
+        self.assertEqual(frozenset({('sub', 'alice')}), session.removed_indexes)
+
+        session.add_index('sub', 'alice')
+        self.assertEqual(frozenset({('sub', 'alice')}), session.indexes)
+        self.assertEqual(frozenset(), session.removed_indexes)
+
+    def test_payload_round_trip(self) -> None:
+        session = Session('abc', {'user': 'alice'}, indexes={('sub', 'alice')})
+        loaded = Session.from_payload('abc', session.to_payload())
+        self.assertEqual({'user': 'alice'}, dict(loaded))
+        self.assertEqual(frozenset({('sub', 'alice')}), loaded.indexes)
+
+    def test_legacy_payload(self) -> None:
+        loaded = Session.from_payload('abc', {'user': 'alice'})
+        self.assertEqual({'user': 'alice'}, dict(loaded))
+        self.assertEqual(frozenset(), loaded.indexes)
+
+
+class InMemorySessionIndexTest(unittest.TestCase):
+
+    @async_test
+    async def test_save_load_and_find(self) -> None:
+        store = InMemorySessionStore()
+        self.assertTrue(store.supports_indexes)
+        session = Session('abc', {'user': 'alice'})
+        session.add_index('sub', 'alice')
+        await store.save('abc', session)
+        session.commit_indexes()
+
+        loaded = await store.load('abc')
+        assert loaded is not None
+        self.assertEqual(frozenset({('sub', 'alice')}), loaded.indexes)
+        self.assertEqual(['abc'], await store.find_sessions('sub', 'alice'))
+        self.assertEqual([], await store.find_sessions('sub', 'bob'))
+
+    @async_test
+    async def test_delete_cleans_reverse_index(self) -> None:
+        store = InMemorySessionStore()
+        session = Session('abc', indexes={('sub', 'alice')})
+        await store.save('abc', session)
+        await store.delete('abc')
+        self.assertEqual([], await store.find_sessions('sub', 'alice'))
+        self.assertEqual({}, store._session_indexes)
+
+    @async_test
+    async def test_delete_by_index_deletes_all_sessions(self) -> None:
+        store = InMemorySessionStore()
+        await store.save('a', Session('a', indexes={('sub', 'alice')}))
+        await store.save('b', Session('b', indexes={('sub', 'alice')}))
+        await store.save('c', Session('c', indexes={('sub', 'bob')}))
+
+        self.assertEqual(2, await store.delete_by_index('sub', 'alice'))
+        self.assertIsNone(await store.load('a'))
+        self.assertIsNone(await store.load('b'))
+        self.assertIsNotNone(await store.load('c'))
+
+    @async_test
+    async def test_expiry_prunes_index(self) -> None:
+        clock = FakeClock()
+        store = InMemorySessionStore(clock=clock)
+        await store.save(
+            'abc',
+            Session('abc', indexes={('sub', 'alice')}),
+            max_age=60,
+        )
+        clock.advance(61)
+        self.assertEqual([], await store.find_sessions('sub', 'alice'))
+        self.assertEqual({}, store._session_indexes)
+
+    @async_test
+    async def test_removed_index_is_not_readded(self) -> None:
+        store = InMemorySessionStore()
+        session = Session('abc', indexes={('sub', 'alice')})
+        await store.save('abc', session)
+        session.commit_indexes()
+
+        session.remove_index('sub', 'alice')
+        await store.save('abc', session)
+        self.assertEqual([], await store.find_sessions('sub', 'alice'))
+        self.assertEqual(frozenset(), session.indexes)
+
+
+class SessionIndexIntegrationTest(unittest.TestCase):
+
+    def setUp(self) -> None:
+        self.store = InMemorySessionStore()
+        self.mixin = SessionMixin(self.store)
+        self.app = KayaApp(mixins=[self.mixin])
+
+        @self.app.GET('/login')
+        async def login(ctx: HttpContext) -> None:
+            ctx.session['user'] = 'alice'
+            ctx.session.add_index('sub', 'alice')
+            await ctx.send_str(200, 'ok')
+
+        @self.app.GET('/rotate')
+        async def rotate(ctx: HttpContext) -> None:
+            ctx.session.regenerate_id()
+            await ctx.send_str(200, 'ok')
+
+        @self.app.GET('/logout')
+        async def logout(ctx: HttpContext) -> None:
+            ctx.session.invalidate()
+            await ctx.send_str(200, 'ok')
+
+    @async_test
+    async def test_rotation_preserves_index(self) -> None:
+        self.assertIs(self.store, self.mixin.store)
+        transport = httpx.ASGITransport(app=self.app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            await client.get('/login')
+            old_id = client.cookies['session_id']
+            self.assertEqual([old_id], await self.store.find_sessions('sub', 'alice'))
+
+            await client.get('/rotate')
+            new_id = client.cookies['session_id']
+            self.assertNotEqual(old_id, new_id)
+            self.assertEqual([new_id], await self.store.find_sessions('sub', 'alice'))
+
+    @async_test
+    async def test_invalidation_cleans_index(self) -> None:
+        transport = httpx.ASGITransport(app=self.app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            await client.get('/login')
+            await client.get('/logout')
+            self.assertEqual([], await self.store.find_sessions('sub', 'alice'))
+
+
+if __name__ == '__main__':
+    unittest.main()

pyproject.toml

@@ -0,0 +1,51 @@
+[project]
+name = "kaya"
+version = "0.0.0"
+description = "Development workspace for the Kaya lightweight ASGI web framework"
+requires-python = ">=3.10"
+dependencies = [
+    "kaya-core",
+    "kaya-rsgi",
+    "kaya-session",
+    "kaya-session-redis",
+    "kaya-session-memcache",
+    "kaya-oidc",
+    "kaya-openapi",
+    "kaya-cors",
+    "kaya-forwarded",
+    "kaya-otel",
+]
+
+[dependency-groups]
+dev = [
+    "fakeredis",
+    "mypy",
+    "ipdb",
+    "httpx",
+    "httpx-ws",
+]
+
+[tool.uv]
+package = false
+required-version = ">=0.13"
+
+[tool.uv.workspace]
+members = ["packages/*"]
+
+[tool.uv.sources]
+kaya-core = { workspace = true }
+kaya-rsgi = { workspace = true }
+kaya-session = { workspace = true }
+kaya-session-redis = { workspace = true }
+kaya-session-memcache = { workspace = true }
+kaya-oidc = { workspace = true }
+kaya-openapi = { workspace = true }
+kaya-cors = { workspace = true }
+kaya-forwarded = { workspace = true }
+kaya-otel = { workspace = true }
+pwo = { index = "gitea" }
+
+[[tool.uv.index]]
+name = "gitea"
+url = "https://gitea.woggioni.net/api/packages/woggioni/pypi/simple"
+explicit = true

requirements-dev.in

@@ -1,13 +0,0 @@
-kaya-core @ file:./packages/kaya-core
-kaya-rsgi @ file:./packages/kaya-rsgi
-kaya-session @ file:./packages/kaya-session
-kaya-session-redis @ file:./packages/kaya-session-redis
-kaya-session-memcache @ file:./packages/kaya-session-memcache
-kaya-oidc @ file:./packages/kaya-oidc
-build
-fakeredis
-mypy
-ipdb
-twine
-httpx
-httpx-ws

requirements-dev.txt

@@ -1,205 +0,0 @@
-#
-# This file is autogenerated by pip-compile with Python 3.14
-# by the following command:
-#
-#    pip-compile --allow-unsafe --extra-index-url=https://pypi.org/simple --index-url=https://gitea.woggioni.net/api/packages/woggioni/pypi/simple --output-file=requirements-dev.txt requirements-dev.in
-#
---index-url https://gitea.woggioni.net/api/packages/woggioni/pypi/simple
---extra-index-url https://pypi.org/simple
-
-aiomcache==0.8.2
-    # via kaya-session-memcache
-anyio==4.14.2
-    # via
-    #   httpx
-    #   httpx-ws
-ast-serialize==0.6.0
-    # via mypy
-asttokens==3.0.2
-    # via stack-data
-build==1.5.0
-    # via -r requirements-dev.in
-certifi==2026.6.17
-    # via
-    #   httpcore
-    #   httpx
-    #   requests
-cffi==2.1.0
-    # via cryptography
-charset-normalizer==3.4.9
-    # via requests
-click==8.4.2
-    # via granian
-cryptography==49.0.0
-    # via
-    #   pyjwt
-    #   secretstorage
-decorator==5.3.1
-    # via
-    #   ipdb
-    #   ipython
-docutils==0.23
-    # via readme-renderer
-executing==2.2.1
-    # via stack-data
-fakeredis==2.36.2
-    # via -r requirements-dev.in
-granian==2.7.9
-    # via kaya-rsgi
-h11==0.16.0
-    # via
-    #   httpcore
-    #   wsproto
-httpcore==1.0.9
-    # via
-    #   httpx
-    #   httpx-ws
-httpx==0.28.1
-    # via
-    #   -r requirements-dev.in
-    #   httpx-ws
-    #   kaya-oidc
-httpx-ws==0.9.0
-    # via -r requirements-dev.in
-id==1.6.1
-    # via twine
-idna==3.18
-    # via
-    #   anyio
-    #   httpx
-    #   requests
-ipdb==0.13.13
-    # via -r requirements-dev.in
-ipython==9.15.0
-    # via ipdb
-ipython-pygments-lexers==1.1.1
-    # via ipython
-jaraco-classes==3.4.0
-    # via keyring
-jaraco-context==6.1.2
-    # via keyring
-jaraco-functools==4.6.0
-    # via keyring
-jedi==0.20.0
-    # via ipython
-jeepney==0.9.0
-    # via
-    #   keyring
-    #   secretstorage
-file:./packages/kaya-core
-    # via
-    #   -r requirements-dev.in
-    #   kaya-oidc
-    #   kaya-rsgi
-    #   kaya-session
-file:./packages/kaya-oidc
-    # via -r requirements-dev.in
-file:./packages/kaya-rsgi
-    # via -r requirements-dev.in
-file:./packages/kaya-session
-    # via
-    #   -r requirements-dev.in
-    #   kaya-oidc
-    #   kaya-session-memcache
-    #   kaya-session-redis
-file:./packages/kaya-session-memcache
-    # via -r requirements-dev.in
-file:./packages/kaya-session-redis
-    # via -r requirements-dev.in
-keyring==25.7.0
-    # via twine
-librt==0.13.0
-    # via mypy
-markdown-it-py==4.2.0
-    # via rich
-matplotlib-inline==0.2.2
-    # via ipython
-mdurl==0.1.2
-    # via markdown-it-py
-more-itertools==11.1.0
-    # via
-    #   jaraco-classes
-    #   jaraco-functools
-mypy==2.3.0
-    # via -r requirements-dev.in
-mypy-extensions==1.1.0
-    # via mypy
-nh3==0.3.6
-    # via readme-renderer
-packaging==26.2
-    # via
-    #   build
-    #   twine
-parso==0.8.7
-    # via jedi
-pathspec==1.1.1
-    # via mypy
-pexpect==4.9.0
-    # via ipython
-prompt-toolkit==3.0.52
-    # via ipython
-psutil==7.2.2
-    # via ipython
-ptyprocess==0.7.0
-    # via pexpect
-pure-eval==0.2.3
-    # via stack-data
-pwo==0.1.2
-    # via
-    #   kaya-core
-    #   kaya-rsgi
-    #   kaya-session
-pycparser==3.0
-    # via cffi
-pygments==2.20.0
-    # via
-    #   ipython
-    #   ipython-pygments-lexers
-    #   readme-renderer
-    #   rich
-pyjwt[crypto]==2.13.0
-    # via kaya-oidc
-pyproject-hooks==1.2.0
-    # via build
-readme-renderer==45.0
-    # via twine
-redis==8.0.1
-    # via
-    #   fakeredis
-    #   kaya-session-redis
-requests==2.34.2
-    # via
-    #   requests-toolbelt
-    #   twine
-requests-toolbelt==1.0.0
-    # via twine
-rfc3986==2.0.0
-    # via twine
-rich==15.0.0
-    # via twine
-secretstorage==3.5.0
-    # via keyring
-sortedcontainers==2.4.0
-    # via fakeredis
-stack-data==0.6.3
-    # via ipython
-traitlets==5.15.1
-    # via
-    #   ipython
-    #   matplotlib-inline
-twine==6.2.0
-    # via -r requirements-dev.in
-typing-extensions==4.16.0
-    # via
-    #   kaya-core
-    #   mypy
-    #   pwo
-urllib3==2.7.0
-    # via
-    #   id
-    #   requests
-    #   twine
-wcwidth==0.8.2
-    # via prompt-toolkit
-wsproto==1.3.2
-    # via httpx-ws