`openai/gpt-5.3-codex` is the codex-series powerhouse still recommended
in docs/guide/agent-model-matching.md and listed in the default
fallback chain in docs/reference/configuration.md, not a deprecated
alias for `gpt-5.4`. The migration entry silently rewrote any user
config that picked `gpt-5.3-codex` for its token efficiency, sending
agents to a non-codex model on every startup.
Drop the bogus mapping from MODEL_VERSION_MAP and add a regression
test that explicit `gpt-5.3-codex` selections (including in nested
fallback_models) survive `migrateModelVersions`. Users already
auto-migrated previously can revert to `gpt-5.3-codex` by hand and it
will now stick on subsequent loads regardless of the sidecar history.
李冠辰
d788c3d1a9