CLAUDE_CODE_FORK_SUBAGENT

A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.138, including the newest one read.

Releases whose published page names CLAUDE_CODE_FORK_SUBAGENT.

1. v2.1.302 16 Oct 2026
   New forkSubagentDisabled setting turns off fork mode

   Fork mode can now be turned off with the forkSubagentDisabled setting, and a server-controlled switch can also turn it off

   found in this entry's text

2. v2.1.302 16 Oct 2026
   Attribution block can name a project, and one fork subagent check no longer reads its variable

   The attribution block can now carry a project tag, and one fork subagent check now depends on remote sessions instead of CLAUDE_CODE_FORK_SUBAGENT

   found in this entry's text

3. v2.1.302 16 Oct 2026
   Background subagent wording now names the terminal, desktop app and VS Code

   Claude Code's text now says the run-in-background option is withheld when subagents are forced into the background, including with CLAUDE_CODE_FORK_SUBAGENT=1

   found in this entry's text

4. v2.1.302 16 Oct 2026
   Claude is told when to fork the conversation into a subagent

   The Agent tool's instructions include a 'When to fork' section on forked subagents, which you can turn off with an environment variable or setting

   found in this entry's text

5. v2.1.232 13 Aug 2026
   Three more variables can be set from settings.json

   You can now set OTEL_SERVICE_NAME, OTEL_TRACES_EXPORT_INTERVAL and CLAUDE_CODE_FORK_SUBAGENT in settings.json.

   named in this entry, found in this entry's text

6. v2.1.232 13 Aug 2026
   Fork-subagent setting is resolved once per session, with the environment checked first

   Setting CLAUDE_CODE_FORK_SUBAGENT decides fork subagents up front, and the answer is cached per session.

   named in this entry, found in this entry's text

7. v2.1.232 13 Aug 2026
   Forked subagents are on by default

   Forked subagents are on by default in interactive sessions; set CLAUDE_CODE_FORK_SUBAGENT to false to opt out.

   named in this entry, found in this entry's text

8. v2.1.117 21 Apr 2026
   /fork Command

   found in this entry's text

9. v2.1.117 21 Apr 2026
   Fork Subagent Feature Gate [Gradual Rollout]

   found in this entry's text

The earliest release whose published evidence quoted CLAUDE_CODE_FORK_SUBAGENT was v2.1.232, 13 Aug 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.

One 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.