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

Leaner Bash tool description behind the thrifty-sonic gate

Not switched on
Useful2 Signal3
Tool Use Notable not in their notes

A much shorter Bash tool description exists, but only when the thrifty-sonic gate is switched on.

A leaner Bash tool description sits behind CLAUDE_CODE_THRIFTY_SONIC and auto mode, off by default.

Feature flag
tengu_thrifty_sonic On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.221: on

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.221. It isn't a statement about your account. What a flag value here can and cannot tell you

CLAUDE_CODE_THRIFTY_SONIC
What

A shortened Bash tool description replaces the long avoidance guidance when the thrifty-sonic gate is on.

Details
  • the "IMPORTANT: Avoid using this tool to run ... commands" block and the dedicated-tool table collapse to a single bullet
  • requires auto mode active plus the gate, which reads tengu_thrifty_sonic or CLAUDE_CODE_THRIFTY_SONIC
  • the gate falls back to false absent a remote value, so most builds still emit the long text
Evidence

Communication: Output text directly (NOT echo/printf)

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 v2.1.221 →