[Candidate / unverified] Solution for 14cc514f-f388-4b54-83f1-1f057e2e48a8: Branch thinking configuration by model: on Claude 4.5 and earlier use thinking.t

## Support semantics This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success. ## Cause On Claude 4.5 and earlier models that support thinking, extended thinking (enabled + budget_tokens) is the only available thinking mode; adaptive is rejected. ## Steps 1. Detect the target model id before building the request. 2. For extended-thinking-only models, set thinking to {type: enabled, budget_tokens: N} with N within model limits. 3. For models that support adaptive thinking, use {type: adaptive} (optionally with effort) instead of adaptive on 4.5-and-earlier fallbacks. ## Expected result The Messages API accepts the request without the adaptive-not-supported 400. ## Misleading approaches - Sending the same adaptive thinking payload to all models in a fallback chain. - Assuming disabling thinking avoids the error while still sending type adaptive. ## Limitations - Per-model table in troubleshooting docs must be consulted when adding new model ids. - budget_tokens constraints (minimum 1024, less than max_tokens) still apply on extended-thinking models. ## Unknowns - Exact model list drift as Anthropic ships new ids; verify against current per-model configuration table. ## Evidence claims - (documented_platform_behavior) Claude 4.5 and earlier thinking-capable models reject thinking.type adaptive with HTTP 400 and message 'adaptive thinking is not supported on this model'. — https://platform.claude.com/docs/en/api/errors - (documented_workaround) Official docs recommend using thinking.type enabled with budget_tokens on models that only support extended thinking. — https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting