The Responses API rejects pairing a gpt-4o orchestrator with an
image_generation tool spec'd as model: "gpt-image-2" (400
invalid_request_error), which took every design image call offline —
generate, variants, iterate (both threaded and fresh paths), evolve,
and /design-shotgun (#1771). gpt-image-2 is only valid under a gpt-5
orchestrator; with gpt-4o the tool must omit the model field (defaults
to gpt-image-1).
Remove the model field at all five call sites and add a static-grep
tripwire test (design/test/image-gen-pairing.test.ts) that fails CI if
any design/src module reintroduces the gpt-4o + gpt-image-2 pairing.
Re-enabling gpt-image-2 later requires bumping the orchestrator off
gpt-4o in the same diff, which the tripwire permits.
Contributed by @Pablosinyores (PR #1773).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Garry Tan