fix(auth): get_access_token reflects current request in stateful sessions

[Epochex]

Fixes #2208.

Stateful Streamable HTTP sessions start the server task group on the first request. Anyio copies the request contextvars into that long-lived task, so get_access_token() could keep returning the token from the session-creating request even when later requests send a different Authorization header.

This change pushes the authenticated user into the auth contextvar at request-dispatch time (using the ServerMessageMetadata.request_context threaded through the transport), and resets it after the handler returns.

Tests:

• uv run python -m pytest tests/server/auth/middleware/test_auth_context.py tests/server/auth/test_get_access_token_streamable_http.py

[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/mcp/server/runner.py">

<violation number="1" location="src/mcp/server/runner.py:231">
P2: Notification handlers in a stateful Streamable HTTP session can still read the session-creating request's token after a later authenticated notification. Scope `push_auth_context_from_request(ctx.request)`/`pop_auth_context()` around `_on_notify`'s middleware call too, so `get_access_token()` matches that notification's HTTP request.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Notification handlers in a stateful Streamable HTTP session can still read the session-creating request's token after a later authenticated notification. Scope push_auth_context_from_request(ctx.request)/pop_auth_context() around _on_notify's middleware call too, so get_access_token() matches that notification's HTTP request.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At src/mcp/server/runner.py, line 231:

<comment>Notification handlers in a stateful Streamable HTTP session can still read the session-creating request's token after a later authenticated notification. Scope `push_auth_context_from_request(ctx.request)`/`pop_auth_context()` around `_on_notify`'s middleware call too, so `get_access_token()` matches that notification's HTTP request.</comment>

<file context>
@@ -227,7 +228,11 @@ async def _inner(ctx: ServerRequestContext[LifespanT, Any]) -> HandlerResult:
         # including its response envelope. The pipeline never patches it up after
         # the fact.
-        result = _dump_result(await call(ctx))
+        auth_token = push_auth_context_from_request(ctx.request)
+        try:
+            result = _dump_result(await call(ctx))
</file context>