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Garry TanandClaude Fable 5 73c96f9c12 feat(codex): model round-trip probe — an unusable configured model fails fast with guidance (#2477)
The auth probe accepts 'auth exists' as readiness, but a ChatGPT account
with a stale model pin in ~/.codex/config.toml passes it and then EVERY
mode dies with an HTTP 400 ('The <model> model is not supported when using
Codex with a ChatGPT account') and no pointer to where the model came from
— one report burned ~40 minutes and four invocations plus a strings dump
of the binary before finding the one-line config fix.

bin/gstack-codex-probe gains _gstack_codex_model_probe: a short
codex exec 'reply OK' round trip with the configured model, gated behind
the cheap auth probe at all three preflight sites (codex Step 0.5, the
shared codexPreflight in scripts/resolvers/constants.ts — which grows a
model_unusable CODEX_MODE branch — and autoplan's availability chain).
Verdicts: MODEL_OK (cached 1h, keyed on config.toml + auth.json mtimes so
a pin edit or re-login re-probes immediately), MODEL_UNUSABLE (exit 1,
prints the rejection plus HINTs at the model= pin and the
[notice.model_migrations] table), MODEL_PROBE_INCONCLUSIVE (timeout or
transient: FAIL-OPEN so network luck never wedges codex mode).

The 'Model not supported (HTTP 400)' Error Handling entry already shipped
in v1.64.0.0; Step 0.5's prose now routes MODEL_UNUSABLE to it.

test/codex-model-probe.test.ts drives all four behaviors against a stubbed
codex binary (invocation-counted cache hit, hint content, fail-open
polarity, mtime invalidation).

Fixes #2477

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-08-16 10:59:35 -07:00
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