CLAUDE_PROJECT_TOOL
A Claude Code environment variable, read out of the shipped bundle. It was in the build from v2.1.174 and was gone by v2.1.186.
When true (1, true, yes or on), Claude Code loads the Projects tool (search hint read and write the session's attached claude.ai project), which enables itself only when the allow_projects_tool policy permits it and CLAUDE_PROJECT_UUID is set, and fetches a context block for that claude.ai project into the session's user context as attachedProject. The fetch is skipped when the policy disallows it, the API provider is not supported, or Claude Code runs in essential-traffic-only mode. Unset, neither the tool nor the project context is loaded.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.185 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 v2.1.174 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
117One 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.