Counted the thinking block exactly via /tokenize. Server default stops it at
4095 tokens; a client sending reasoning_budget=16384 still gets 4095, so it
cannot be raised per request. Changing it means editing the compose file.
It truncates mid-derivation on a moderately hard problem, but the model
recovered and answered correctly (empty solution set, verified by brute
force), so there is no evidence 4096 is actually damaging output.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
