Critical: the MCP SDK auto-enables DNS-rebinding protection when its host
parameter is left at the 127.0.0.1 default, hard-coding a loopback-only Host
allow-list. Every remote client (the only deployment this feature targets) was
refused with HTTP 421 before auth or the tool ran. Now driven by a new
MCP_ALLOWED_HOSTS setting, with '*' as an explicit, logged opt-out.
Also bounds query/top_k to match AskRequest (top_k is amplified 4x downstream,
so an unbounded value was a resource-exhaustion vector), decodes the
Authorization header as latin-1 per the ASGI spec instead of raising a 500 on
malformed bytes, and returns WWW-Authenticate on 401 per RFC 7235.
Moves the psycopg2 import guard into backend/tests/conftest.py: duplicated
across four test modules, it only worked because of alphabetical collection
order, and any earlier-sorting package would have reintroduced a live
connection attempt against the production database.
Registers the mcp module in the authoritative backend architecture doc.
84 backend tests pass. Verified against a live server: allowed remote Host
returns a valid initialize result, unknown Host returns 421, missing token
returns 401 with WWW-Authenticate.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
- New backend/app/mcp/ module: MCPServer instance with a single
search_regulations tool backed by the existing AgentConversationService.
- MCPAuthMiddleware reuses existing JWT auth (no new auth mechanism).
- Mounted at /mcp/ in api/main.py via Streamable HTTP transport; wired the
MCP session manager into the existing lifespan() via AsyncExitStack
(app.mount() does not propagate nested ASGI lifespans automatically).
- Fixed a doubled /mcp/mcp path by setting streamable_http_path to "/"
(MCPServer.streamable_http_app() defaults to registering its own /mcp route).
- Verified end-to-end with the real mcp Python client: list_tools() returns
search_regulations, auth correctly 401s without or with an invalid token.
- 7 new tests, 76 total (up from 69), all passing.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Fix 1 (bootstrap.py): wrap store.flush() in asyncio.to_thread() inside the
periodic _flush_loop() to avoid blocking the async event loop every 60s.
Synchronous signatures of _start/_stop_model_usage_persistence() and the
one-time seed/shutdown flushes are left unchanged per review scope.
Fix 2 (test_stream_chat_usage_capture.py): add the two-line stream_options
assertion to test_qwen_vl_stream_chat_returns_usage_from_trailing_chunk,
matching the identical check already present in the DeepSeek and Qwen tests.
Fix 3 (design doc): note the single-worker assumption in A3's write strategy
section — multi-worker deployments get last-writer-wins per-row semantics.
Tests: 69 passed, 0 failed (python -m pytest backend/tests -q)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
