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Claude Code v2.1.208

set_max_thinking_tokens: null or omitted now resets to session default

What

When calling set_max_thinking_tokens with max_thinking_tokens omitted or null, thinking now resets to the session default rather than keeping the previously-set mid-session override. This makes it possible to undo a thinking budget adjustment without restarting the session.

Details
  • Previously, max_thinking_tokens: null had ambiguous behavior
  • Now: omitting or setting to null clears any mid-session budget override back to the spawn-time budget
  • For sessions where thinking is disabled, this keeps thinking disabled
  • max_thinking_tokens must be an integer (or null); non-integer numbers are now rejected
Evidence

Updated set_max_thinking_tokens description (search for "When max_thinking_tokens is omitted or null, thinking resets to the session default")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.208 →