What
The guidance for running Opus 5 with thinking turned off previously gave separate fixes for two problems: a tool call written out as plain text that silently never runs, and internal thinking tags leaking into the answer. They are now one combined instruction.
Details
- The combined rule allows a preamble sentence, tells the model to say so when no available tool fits the request, and forbids internal XML tags in general rather than naming a specific tag.
- The existing rule against naming thinking tags in the prompt is kept and restated in the checklist.
Evidence
If no tool can express what the user asked for, say so instead of guessing.
Strings lifted out of the shipped bundle, so the claim above can be checked against them.