vava-nessa/free-coding-models v0.5.56

on GitHub

Fixed

• 🔁 Router stream-stall failover after partial response (#137) — previously, if a model streamed some data then stalled (per-chunk timeout), the client received a truncated response with no automatic retry. Now the router:

  1. Emits a synthetic SSE error event in OpenAI format (code: fcm_stream_failover) so the client knows the stream was truncated and that failover is happening.
  2. Returns failoverToNext: true to the outer retry loop, which tries the next model on a fresh upstream connection.
  3. The new model's chunks are appended to the same response object — the client sees one continuous stream with a clear mid-stream error marker.
  4. On a mid-stream failover the router skips res.writeHead() (headers were already sent by the previous model) and emits an SSE comment : fcm-router-failover-from=<oldKey> so debuggers can see which model served which segment.

  Scope of the fix: only stream_stall_timeout and timeout errors trigger mid-stream failover. Generic upstream errors (malformed JSON, connection reset, destroy) still close cleanly with no failover — their partial data is more likely to be invalid, so re-streaming from another model wouldn't help.

Maintenance

• 🧪 +1 regression test (test/test.js) locking in the new failover behavior with a stalled-stream mock provider. The existing "does not retry after partial output" test still passes — it uses res.destroy() which is not a stall, so it correctly keeps the old behaviour.
• 🧪 591/591 tests pass (pnpm test).
• 🧹 vite build succeeds.

How clients see this

A streaming request that stalls now produces something like:

data: {"choices":[{"delta":{"content":"partial"}}]}

data: {"error":{"message":"Stream truncated by router due to upstream stream_stall_timeout; failing over to next model.","type":"stream_error","code":"fcm_stream_failover","reason":"stream_stall_timeout"}}

data: {"choices":[{"delta":{"content":"fresh answer from fallback"}}]}

data: [DONE]

Plus an SSE comment marker on each failover segment.