[BUG] --worktree (-w) flag silently ignored due to server-side feature flag not rolled out

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?

claude -w (or claude --worktree <name>) silently does nothing — no worktree is created, no error is shown, and the session starts in the main repo as if -w was never passed.

This occurs on every repository I've tested (two completely unrelated repos, one with submodules and one without). Manual git worktree add works fine in both.

What Should Happen?

claude -w test should create a worktree and start the session inside it, as documented. If worktree creation fails or is unsupported for some reason, an error message should be shown.

Error Messages/Logs

No error messages — that's the problem. The flag is silently ignored with no output.

Steps to Reproduce

1. Run claude -w test in any git repository
2. Inside the session, run pwd and git worktree list
3. Observe: no worktree created, session is in the main repo, no error shown

What I've investigated so far:

Running strings on the compiled binary (v2.1.50) revealed what appears to be the --worktree option gated behind an internal flag called tengu_worktree_mode. The startup code appears to check this flag and, if it evaluates to false, set the worktree option to undefined — silently ignoring -w.

This flag was not present in my cachedGrowthBookFeatures in .claude.json. When I manually added "tengu_worktree_mode": true to that object, claude -w started working correctly.

Note: This analysis is based on examining strings in a compiled/minified binary, so the exact mechanism may differ from what I've described. The observable facts are:

• -w silently does nothing out of the box
• Adding "tengu_worktree_mode": true to cachedGrowthBookFeatures in .claude.json fixes it

Claude Model

Opus

Is this a regression?

No, this never worked

Claude Code Version

2.1.50 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Xterm

Additional Information

• Tested on Ubuntu 24.04, zsh
• Two unrelated repos tested — same result
• Manual git worktree add works fine
• Related silent worktree failures (different root causes): #27150, #27466

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This issue was investigated using Claude Code, which performed the binary analysis via strings and identified the workaround.