The gpt-account (Codex) turn built its function tools with strict:null. The
Responses API expects strict to be a boolean or omitted; null is malformed,
so the endpoint dropped the whole tool list — leaving the model with nothing
to call. That is exactly the "model returned no tool calls" failure on the
GPT-account path. Omit strict when null; keep the boolean otherwise. Locked
with a test, alongside the Bedrock/Gemini forced-tool-choice encoding.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
ZacharyZhang-NYandClaude Opus 4.8
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