The full lean prompt system that compresses all tool descriptions and system prompt content for reduced token usage.
Feature-flagged behind tengu_vellum_lantern (default false), overridable with CLAUDE_CODE_LEAN_PROMPT=1.
- Currently restricted to Opus 4.6+ and Opus 4.7 models
- The
tengu_ochre_finchflag controls lean memory prompts independently - When fully enabled, tool descriptions are 60-80% shorter while preserving essential usage information
- Users can preview it now via the environment variable
tengu_vellum_lantern Off in both readingsThe 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 v2.1.120: no gate table built for this version
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 v2.1.120. It isn't a statement about your account. What a flag value here can and cannot tell you
A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.