RUSTUP_HOME
A Claude Code environment variable, read out of the shipped bundle. It was in the build from v2.1.242 and was gone by v2.1.265.
Protects rustup's directory from plugin writes: when a plugin's function hooks call $.fs.writeFile, a target at or under the path in RUSTUP_HOME is refused as a startup file or folder that rustup reads on its next start. An unset or empty value protects nothing.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.263 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 v2.1.242 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
2Build by build
57One 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.