What probably matters to youSection of the release
What
A fork is a subagent, a helper agent, that starts with a copy of the current conversation. Fork mode lets Claude start forks itself. Changes:
The Agent tool description now explains subagent_type: "fork" and has a ## When to fork section. Forks inherit the conversation and run on the same model, and Claude is told not to peek at them or race them. The section is only included when fork mode is available.
That section has two wordings. One says "The tool result includes an output_file path". The other says "A background fork's tool result includes an output_file path" and talks about what to do "After launching a background fork". Which one appears depends on how fork mode was turned on and another condition.
Fork mode is off when CLAUDE_CODE_FORK_SUBAGENT is set to false, or when the new forkSubagentDisabled setting is set. It is also off on certain accounts when the tengu_federated_ullman flag is true and the variable is not set to true. Otherwise it counts as available. Nothing has been read about tengu_federated_ullman for this release.
Separately, a new bundled plugin, cc-plugin-easel, is registered when Claude Code is not running as a local agent, and cc-plugin-responsive-mode now also loads in remote sessions.
Why
Claude may now start forks for research when fork mode is available. If you do not want that, set forkSubagentDisabled in your settings or set CLAUDE_CODE_FORK_SUBAGENT to 0.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeChanged fork subagents (subagent_type: "fork") to be on by default in claude -p, the Agent SDK, the desktop app and VS Code, as they already…
