DEFAULT_CODEX_MODELS shipped three slugs that the chatgpt.com Codex
backend rejects with HTTP 400 'The <slug> model is not supported when
using Codex with a ChatGPT account.' on every account tested live:
gpt-5.2-codex
gpt-5.1-codex-max
gpt-5.1-codex-mini
Live verified against https://chatgpt.com/backend-api/codex/models
which returns gpt-5.5, gpt-5.4, gpt-5.4-mini, gpt-5.3-codex,
gpt-5.3-codex-spark, gpt-5.2 for ChatGPT Pro accounts.
When _fetch_models_from_api fell back to DEFAULT_CODEX_MODELS (offline
first-run, transient API failure) the picker surfaced these dead slugs
and crashed on selection. The forward-compat synthesis table chained
them downstream too.
If OpenAI re-enables them on the OAuth-backed Codex backend, live
discovery will pick them up automatically — the defaults list is only
consulted when live discovery is unavailable.
Test fixture pivoted to use gpt-5.3-codex (templated by 4 entries) as
the synthesis driver so the forward-compat test still exercises the
synthesis path.
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