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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

Additional unnamed system-prompt section

Under the hood
Useful1 Signal3
System Prompt

The system prompt gained another section and computes Claude's identity block differently.

What

The system prompt is assembled from named sections, and a further one has been added next to an existing similarly named section, while the block that establishes Claude's identity is now computed through a different check.

Details
  • What the new section contains and what makes it appear are not determined by the surrounding code.
Evidence

yc("brook_heron", () => h8t(u))

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 →