[BUG] Agent tool schema exposes isolation as required field with only "worktree" accepted, breaking subagents in non-git directories

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The Agent tool's runtime schema exposes isolation as a required field with "worktree" as the only accepted value. This contradicts the documentation, which states isolation is optional and only activates worktree behavior when explicitly set.

As a result, any subagent invocation from a non-git directory fails unconditionally — even for agents that have no need for git worktree isolation (e.g. browser automation via Playwright MCP). More importantly, this breaks all multi-repo workflows, where I want to spawn subagent at a directory dir with multiple repos in dir/repo1, dir/repo2, dir/repo3.

What Should Happen?

Per the docs and common-workflows, isolation is optional. Omitting it (or setting it to a non-worktree value) should allow the subagent to run in the current working directory without attempting to create a git worktree.

Error Messages/Logs

Error: Cannot create agent worktree: not in a git repository and no WorktreeCreate hooks are configured. Configure WorktreeCreate/WorktreeRemove hooks in settings.json to use worktree isolation with other VCS systems.

Steps to Reproduce

1. Create or navigate to a directory that is not a git repository:

``
mkdir ~/test-workspace && cd ~/test-workspace
``

1. Launch Claude Code from that directory:

``
claude
``

1. Ask Claude to spawn any subagent — e.g.:

``
Use the general-purpose agent to say hello.
``

1. Observe the error:

``
Error: Cannot create agent worktree: not in a git repository and no
WorktreeCreate hooks are configured.
``

1. To confirm the schema constraint, ask Claude directly in the session:

``
Can you show me the isolation field options available to you in the Agent tool schema?
`
Claude will report that isolation is required and "worktree"` is the only accepted value.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.87

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_