The ChatGPT Codex backend (chatgpt.com/backend-api/codex) has historically
silently dropped certain model requests: the connection is accepted but no
stream events are emitted and no error is raised. PR #31967 lowered the
implicit stale-call default from 300s to 90s so fallbacks kick in faster,
but users still see an opaque "No response from provider for 90s
(non-streaming, ...)" message that gives no path forward.
This patch adds a narrow heuristic — gpt-5.5 family on the Codex backend
via codex_responses api_mode — that substitutes the generic timeout
message with actionable text naming the gpt-5.4-codex workaround and
pointing at #21444 for symptom history.
Changes:
- run_agent.py — new ``AIAgent._codex_silent_hang_hint(model=...)`` method.
Returns ``None`` for any request that does not match all three guards
(codex_responses api_mode, openai-codex provider or chatgpt.com Codex
base URL, gpt-5.5-family model name with word-boundary regex anchoring
to avoid false-positives on e.g. ``gpt-5.50``).
- agent/chat_completion_helpers.py — the non-stream stale-call site
consults the hint via ``getattr(...)`` so the call site stays robust
if the helper is ever removed or stubbed in tests. Hint is appended to
both the ``_emit_status`` warning and the ``TimeoutError`` message so
the user sees it in their terminal AND it lands in any retry-loop
diagnostics.
- tests/run_agent/test_codex_silent_hang_hint.py — 10 regression tests
covering positive cases (bare gpt-5.5, vendor-prefixed openai/gpt-5.5,
gpt-5.5-codex SKU, model=None fallback to self.model) and negative
cases (gpt-5.4-codex workaround, gpt-5.50 false-positive guard,
non-codex api_mode, non-codex provider, empty/None model, unrelated
models on Codex).
Does NOT fix the backend-side issue (that's an upstream OpenAI/ChatGPT
problem we cannot patch from here). Only converts an opaque timeout into
text that names the workaround so users do not have to dig through logs
or wait for a forum post to learn what to do.
Closes#22046
