Files
hermes-agent/tools
Teknium a565e2d493 fix(mcp): widen the SSE fallback trigger and harden its guards (salvage #53764)
Relocated onto the decomposed module layout and hardened:

- Trigger covers the rejection CLASS, not just literal 400: SSE-only
  servers' load balancers answer the chunked Streamable HTTP initialize
  POST with 400/405/406/411, and the mcp>=2.0 SDK surfaces many such
  rejections as an opaque -32603 'Server returned an error response'
  (error class per #104363 by @RohithPariki). Timeouts and 5xx never
  trigger the fallback: they are not transport mismatches.
- Reconnect exclusion via _ever_connected instead of _ready: run()
  clears _ready before re-entering the transport, so the original guard
  also fired on reconnects after a proven session.
- Successful fallback latches _sse_fallback so reconnects go straight
  to SSE, and logs a warning suggesting the user pin transport: sse.
- Both transports failing raises a ConnectionError naming both errors
  and suggesting transport: sse / checking the URL.
- No fallback with strict_redirect_headers (SSE cannot enforce that
  boundary) or when transport is explicitly configured.
- Tests trimmed to 3 invariant contracts (proven red on base): fallback
  connects + latches; no fallback on reconnect/timeout/5xx; both-fail
  error is actionable.

The extracted SSE path reuses _sse_transport/_serve_transport from main,
preserving the bounded handshake timeout and reconnect-retry semantics.

Fixes #53676
2026-09-12 21:05:29 -07:00
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