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 v2.1.251 Home All releases olderv2.1.250
Claude Code v2.1.251

Two dispatch implementations selected by the same switches

Not switched on
Useful2 Signal4
API Routing Notable not in their notes

Two alternate internal dispatch implementations are selectable by environment variables, both off by default.

Second dispatch paths sit behind env vars and remote flags that default off.

Feature flag
tengu_dreamy_frost Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.251: on

tengu_cedar_lattice Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.251: on

Read once, for one account on one subscription tier, against v2.1.251. It isn't a statement about your account. What a flag value here can and cannot tell you

CLAUDE_CODE_DISPATCH_V2DCLAUDE_CODE_DISPATCH_V2S
What

Alongside the request header, the code picks between two internal dispatch implementations using the same controls: CLAUDE_CODE_DISPATCH_V2D and CLAUDE_CODE_DISPATCH_V2S, falling back to the remote flags tengu_dreamy_frost and tengu_cedar_lattice, both defaulting to off.

Details
  • With nothing set, the existing implementation runs.
Evidence

CLAUDE_CODE_DISPATCH_V2D

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 →