fix(mcplocal): stream chat SSE through the proxy instead of buffering it #109

Merged
michal merged 2 commits from fix/chat-sse-streaming into main 2026-08-10 21:28:00 +00:00

2 Commits

Author SHA1 Message Date
Michal
bbd2195c64 test(mcplocal): prove chat SSE streams live through the proxy, not buffered
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`mcpctl chat reviewer` showed nothing until the turn finished, then dumped
the whole answer at once. mcpd streams token deltas and the CLI renders
them incrementally — the sole buffering point was mcplocal's catch-all
/api/v1/* proxy reading the whole SSE body via res.text() before replying.
The previous commit (cherry-picked from feat/agentic-teams) pipes the body
through instead; this one adds the cover that was missing:

- proxy-long-running.test.ts: a progressive-delivery test in which the
  stand-in mcpd withholds its final frame until the client has observed the
  first delta through the proxy. A buffering proxy cannot satisfy that
  ordering — verified: the test fails in 3s (no hang) against a res.text()
  proxy and passes against the piped one. The existing SSE test used
  inject(), which collects the whole body and so passes either way.

- agent-chat.smoke.test.ts: a live smoke that posts through mcplocal on
  localhost:3200 (the path `mcpctl chat` actually takes — every other chat
  smoke uses --direct and bypasses the proxy entirely) and asserts delta
  frames arrive spread across the generation window, not in one burst at
  stream end. Uses its own agent: the shared smoke agent pins replies to a
  single token, too short to tell live streaming from a buffer dump.

Also settles the strict-boolean-expressions lint on the auth-header check
the streaming split touched.

Local: workspace 2546 passed, proxy suite 10/10, smoke file loads + self-skips.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dNpnBqyyz9GxfznVcX2sP
2026-08-10 22:27:21 +01:00
Michal
5a8185d7c9 fix(mcplocal): stop the 30s proxy timeout killing agent turns
`mcpctl chat <agent>` failed with

    HTTP 503 {"error":"service_unavailable","message":"Cannot reach mcpd daemon. Is it running?"}

while mcpd was answering /healthz in 32ms. The message was wrong in a way that
cost real debugging time: mcplocal was reaching mcpd fine and giving up after
30s. journalctl shows the signature plainly — statusCode 503 with
responseTime 30003.87 on POST /api/v1/agents/reviewer/chat.

This blocks the agentic-teams epic outright. An agent turn is a multi-turn
tool-use loop that runs for minutes by design, so a 30s ceiling on the chat path
is not a safety net, it is a guaranteed failure for every non-trivial turn.

Three defects, all in the same path:

1. One blanket budget for every forwarded route. DEFAULT_TIMEOUT_MS = 30_000 is
   right for CRUD and wrong for chat. Chat, project chat, llm infer and
   inference-task streams now get LONG_RUNNING_TIMEOUT_MS (600_000, override
   with MCPLOCAL_LONG_TIMEOUT_MS) — matching STREAM_TIMEOUT_MS, which the CLI
   already allowed. mcplocal in the middle was the binding constraint.

2. Timeouts were reported as connection failures. Split UpstreamTimeoutError
   out of ConnectionError and map it to 504 with an accurate message that says
   the daemon IS reachable. ConnectionError still means unreachable and still
   returns 503. Verified nothing else branches on ConnectionError.

3. SSE was buffered. `forward()` reads the whole body through res.text(), so
   even turns that finished in time arrived as one blob and the CLI's live
   token output never appeared. Streaming routes now use forwardStream() and
   pipe the body straight through, preserving content-type and
   x-accel-buffering (dropping the latter lets intermediaries re-buffer and
   reintroduces the stall).

Also closes the escape that produced the sibling `500 code:23` failure: the body
read in forward() was outside the try, so when mcpd had already written SSE
headers the raw DOMException reached Fastify unhandled.

Tests: 9 new proxy tests. The two that matter — "does not abort an agent chat
that outlives the CRUD budget" and "streams SSE through instead of buffering" —
were confirmed to FAIL against the pre-fix behaviour and pass after. Three
existing mcpd-client tests asserted the old taxonomy and were updated to assert
the new one deliberately.

Local: build clean, workspace 2375 passed, lint unchanged at 869.

NOT YET LIVE: mcplocal runs from the installed RPM, so this needs a package
rebuild + `systemctl --user restart mcplocal` to take effect.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4wNHWf7xSwnZCWpJcyv9p
2026-08-10 22:19:56 +01:00