LibreChat/api/server
Helge Wiethoff 61b9b1daa7
🩹 fix(SSE): Treat responseCode === 0 as Transport Failure, Not Server Error (#12834)
* fix(sse): treat responseCode===0 as transport failure, not server error

When a long-running model response (e.g. gpt-5.4 with web_search:true)
takes longer than the browser's idle connection timeout, the SSE transport
drops and sse.js fires an error event with responseCode=0 and e.data set
to the raw response buffer (non-JSON SSE text).

The previous guard `!responseCode` is truthy for both 0 (transport drop)
and undefined (genuine server-sent error event), so the client incorrectly
entered the server-error branch, tried to JSON.parse raw SSE text, logged
"Failed to parse server error", and showed the user a red error banner --
even though the backend continued processing and delivered the final answer
seconds later.

Fix 1 (client): change guard from `!responseCode` to `responseCode == null`
so that only undefined/null (no HTTP status at all) triggers the server-error
parse path. responseCode===0 now correctly falls through to the reconnect path.

Fix 2 (backend): after res.flushHeaders() the response is already committed
as SSE. The fallback branch that wrote res.status(404).json() was an HTTP/SSE
protocol violation. Replace with an SSE-conformant event:error frame + res.end().

* fix(sse): use onError helper on subscribe failure + add regression tests

Replace silent res.end() with onError('Failed to subscribe to stream')
so the client receives a parseable SSE error event instead of a stream
that closes with no signal. The previous res.end() left the UI stuck
in "submitting" state because no error/abort/final event ever fired.

Also adds two missing test cases for the responseCode guard change:
- responseCode === 0 with raw SSE buffer data must NOT call errorHandler
  (transport failure should reconnect, not display garbage)
- responseCode == null with JSON error data MUST call errorHandler
  (server-sent error events should still surface to the user)

---------

Co-authored-by: Danny Avila <danny@librechat.ai>
2026-04-29 10:05:51 +09:00
..
controllers 🧹 fix: Graceful MCP OAuth Revoke Cleanup When Tokens Are Missing (#12825) 2026-04-29 09:11:12 +09:00
middleware 🧬 feat: Scaffold Skills CRUD with ACL Sharing and File Schema (#12613) 2026-04-25 04:01:59 -04:00
routes 🩹 fix(SSE): Treat responseCode === 0 as Transport Failure, Not Server Error (#12834) 2026-04-29 10:05:51 +09:00
services 🛡️ fix: Filter user_provided Sentinel in Tool Credential Loading (#12840) 2026-04-29 09:09:54 +09:00
utils 📜 feat: Skills UI + Initial E2E CRUD / Sharing (#12580) 2026-04-25 04:02:00 -04:00
cleanup.js 🧹 refactor: Tighten Config Schema Typing and Remove Deprecated Fields (#12452) 2026-03-29 01:10:57 -04:00
experimental.js 🧬 feat: Scaffold Skills CRUD with ACL Sharing and File Schema (#12613) 2026-04-25 04:01:59 -04:00
index.js 🧬 feat: Scaffold Skills CRUD with ACL Sharing and File Schema (#12613) 2026-04-25 04:01:59 -04:00
index.spec.js 🚦 fix: 404 JSON Responses for Unmatched API Routes (#11976) 2026-02-27 22:49:54 -05:00
socialLogins.js 🔐 feat: Admin Auth Support for SAML and Social OAuth Providers (#12472) 2026-03-30 22:49:44 -04:00