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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.

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Claude Code v2.1.251

A confined evaluation mode, set by Claude Code on itself

Under the hood
Useful2 Signal4
Plugin Eval Notable not in their notes

A confined evaluation mode exists that Claude Code only sets on its own eval subprocesses.

CLAUDE_CODE_EVAL_CONFINED
What

A new environment variable, CLAUDE_CODE_EVAL_CONFINED, appears 26 times in this build and not at all in the previous one. Claude Code sets it to 1 on subprocesses it spawns for evaluation runs rather than reading it from your settings, so every branch it controls is inert in an ordinary session.

Details
  • Gates git-source teleport refusals, hard-link checks on files, forced permission denials, and network fetch confinement.
  • Added to the three lists of environment variables preserved when spawning privileged worker and background subprocesses.
  • Set alongside CLAUDE_CODE_EVAL_ARTIFACT_STUB_DIR on the same spawn.
Evidence

CLAUDE_CODE_EVAL_CONFINED, v.CLAUDE_CODE_EVAL_CONFINED = "1"

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 →