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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

← All of v2.1.251 Home All releases ←olderv2.1.250
Claude Code v2.1.251

Capability list handed to the model is now explicitly closed

Under the hood
Useful2 Signal3
System Prompt

The model is told its capability list is complete, so it stops claiming absent ones.

What

The prompt that tells the model which capabilities it may declare now states that the list is complete and that anything absent is unavailable to you, and separates capabilities needing an explicit declaration from built-ins that are always on.

Details
  • The contents vary by context, since the capability set is passed in per user and page rather than fixed.
  • Reworded in this release; the block itself is not new.
Evidence

the complete set of capability names you may declare. Anything not listed is unavailable to this user.

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

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.251 →