[omChauhanDev]

Problem

LLM.chat() translates a forced tool_choice the same way for every model: "required" becomes {"type": "any"} and a named function becomes {"type": "tool", "name": ...}. Claude Opus 5.5, Sonnet 5.5, Fable 5.1 and Mythos 5.1 don't support forced tool use (Opus 5.5, Sonnet 5.5, Fable 5.1 and Mythos 5.1 migration guides), so on these models every such request fails with a 400: tool_choice: type "tool" and "any" are not supported for this model. AMD and keyterm detection force "required" on their own, so they fail on these models even when the app never sets a tool choice.

Changes

For these four models a forced choice is now sent as {"type": "auto"}, keeping disable_parallel_tool_use when it's set, and the plugin logs a warning once per LLM instance. Requests for all other models are unchanged. These models have no forced mode, so the model may now answer without calling a tool, or call a different tool than the one named.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[toni-anthropic]

Thanks for this fix. One addition to consider before it merges: Claude Sonnet 5.5 (claude-sonnet-5-5) rejects a forced tool_choice the same way (migration guide, "Forced tool use is not supported"). I ran this branch (862a936) against the live API: through LLM.chat() with tool_choice="required", which AMD and keyterm detection use, Sonnet 5.5 still gets {"type": "any"} and the API returns:

400 invalid_request_error: tool_choice: type "tool" and "any" are not supported for this model.

With "claude-sonnet-5-5" added to _NO_FORCED_TOOL_CHOICE_PATTERNS, the request goes out as auto and the model calls the tool. claude-sonnet-5, claude-haiku-5-5 and claude-sonnet-4-6 still accept any and call the tool, so the entry doesn't need to be wider. #7631 makes the same change for the Bedrock plugin.

Happy to test the branch again once it's updated.

[toni-anthropic]

Re-tested at e6fc2ad against the live API, with tool_choice="required" and with a named function. On main (f548149), Sonnet 5.5, Opus 5.5 and Fable 5.1 all return the 400. With this PR, all three send auto and call the tool. Sonnet 5 and Haiku 5.5 still send the forced choice, as before. Thanks for adding Sonnet 5.5.