CLAUDE_CODE_UPFRONT_TOOLS
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.314, including the newest one read.
Setting CLAUDE_CODE_UPFRONT_TOOLS to a list of tool names makes those tools load at the start instead of being held back until needed
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.314.
In the changelogs
1Releases whose published page names CLAUDE_CODE_UPFRONT_TOOLS.
-
v2.1.314
New
CLAUDE_CODE_UPFRONT_TOOLSvariable picks tools to load at the startSetting
CLAUDE_CODE_UPFRONT_TOOLSto a list of tool names makes those tools load at the start instead of being held back until neededfound in this entry's text, named in this entry
First cited
1The earliest release whose published evidence quoted CLAUDE_CODE_UPFRONT_TOOLS was v2.1.314, 30 Oct 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
1Build by build
1One 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.