Flag reasoning support for DeepSeek-V4-Flash and Qwen3.6 models
Vendor research across the top router models: DeepSeek documents a hard
400 when reasoning_content is not passed back on tool-call turns (Flash
was the only Required-verdict model missing the flag; Pro already had
it), and the Qwen3.6 generation is trained for preserve_thinking with
documented accuracy loss in tool flows when reasoning is omitted.
gemma-4 stays unflagged deliberately: Google requires stripping thoughts
across completed turns.
