Source Intelligence

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 v2.1.221 Home All releases olderv2.1.220 v2.1.222newer

Tools can declare a fail-closed permission posture

You'll notice
Useful3 Signal0
Permissions

If a tool's permission check crashes in plan mode, the action is now denied instead of quietly allowed.

What

A new optional tool hook decides what happens when a tool's own permission check throws, instead of the previous behaviour of logging the failure and carrying on.

Details
  • The hook is permissionCheckFailureDecision, consulted whenever a tool's permission check raises.
  • If a tool declares one, its decision replaces the log-and-continue fallback; if the hook itself throws, the call is denied.
  • The Artifact tool uses it so that a crashed permission check in plan mode denies the action rather than letting it past the consent floor.
Evidence

Plan-mode artifact consent floor fails closed when its permission check cannot complete

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

See this entry in the whole of v2.1.221 →