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 v2.1.248 Home All releases olderv2.1.247 v2.1.250newer
Claude Code v2.1.248

Tool descriptions can vary by proactive level, with streaming gates off

Not switched on
Useful2 Signal3
Tools

Tool descriptions can differ by session proactive level; the streaming behaviour behind it is off.

Fine-grained tool streaming is switched off in this build.

Feature flag
tengu_fgts 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 v2.1.248: on

tengu_structured_output_strict 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 v2.1.248: on

Read once, for one account on one subscription tier, against v2.1.248. It isn't a statement about your account. What a flag value here can and cannot tell you

What

The cache that stores generated tool descriptions now keys on the session's proactive level and one further mode, so one tool can present different instructions in different sessions. The fine-grained tool streaming behaviour behind this is switched off in this build.

Details
  • CLAUDE_CODE_ENABLE_FINE_GRAINED_TOOL_STREAMING is now read as a parsed boolean rather than a string comparison.
  • The two remote gates involved, tengu_fgts and tengu_structured_output_strict, both fall back to false here, so unless the server turns them on nothing changes.
Evidence

proactiveLevelActive: P

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 v2.1.248 →