CLAUDE_CODE_RUSTLING_PIXEL
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.280, including the newest one read.
Overrides the tengu_rustling_pixel flag (default all) that picks when Claude Code keeps thinking from a different model across a model change: all turns on api_keep_thinking_on_model_change, upgrade turns on api_keep_thinking_on_upgrade, none turns on neither. Any other value logs a warning and uses upgrade. The mode is none regardless when an earlier gate or the first-party API base URL check fails; _CLAUDE_CODE_ASSUME_FIRST_PARTY_BASE_URL skips the base URL check.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.286 bundle, and it can be wrong.
In the changelogs
0No changelog entry here has ever named it. That is a statement about what has been written, not about the name: it has been in the build since v2.1.280 without anybody writing a line about it.
First cited
0No release's published evidence quotes this name. The ledger indexes the Evidence lines of every changelog on this site, so this says nobody here has ever quoted it; it says nothing about how old the name is.
Presence across releases
1Build by build
27One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the environment variable does. All environment variables.