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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 v2.1.242

Cloud-supplied hook templates run as vetted python3 scripts

Not switched on
Useful2 Signal3
Hooks

Cloud-supplied hook scripts run through a vetted python3 wrapper that rechecks their checksum.

A hardened template runner exists inside the disabled cloud hook-template path.

Feature flag
tengu_violin_wood Off in both readings

The flag server returned off for the account this site reads and for the anonymous baseline. A reading of off cannot rule out a rollout these two readings sit outside of.

This account: off · anonymous baseline: off · compiled default in v2.1.242: on

tengu_violin_amati Off in both readings

The flag server returned off for the account this site reads and for the anonymous baseline. A reading of off cannot rule out a rollout these two readings sit outside of.

This account: off · anonymous baseline: off · compiled default in v2.1.242: not a boolean we can read

Read once, for one account on one subscription tier, against v2.1.242. It isn't a statement about your account. What a flag value here can and cannot tell you

What

A new runner executes hook scripts supplied by the cloud session. It picks the first absolute interpreter it can vet from a fixed list, writes the script to a per-process directory, and runs it through a wrapper that re-reads the file, enforces a size cap and re-checks its SHA-256 before executing. A mismatch exits with code 86 and is reported as an integrity failure.

Details
  • The spawn clears environment variables matching LD_, DYLD_, GCONV_PATH, PYTHON and sets only CLAUDE_PROJECT_DIR. It runs detached in its own process group, which is killed on timeout or abort.
  • Registration and upload require two account flags together, tengu_violin_wood and tengu_violin_amati. If neither has been served yet the request answers "hook_forwarding_not_ready: feature flags not yet available; retry".
  • Policy settings that restrict hooks to plugins, disable customization, allow only managed hooks, or disable hooks entirely clear the registry first.
  • None of these strings exist in 2.1.241.
Evidence

device hook template integrity check failed:

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 v2.1.242 →