[BUG] teammateMode: "tmux" in settings.json ignored — requires CLI flag --teammate-mode tmux

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?

Setting "teammateMode": "tmux" in settings.json (any scope: user, project, or local) has no effect. Teammates spawn in-process regardless. The only way to get tmux split-pane behavior is via the CLI flag:

claude --teammate-mode tmux

The setting appears to be read but not applied to actual teammate spawning behavior.

What Should Happen?

Per the settings docs, teammateMode is a valid settings.json key with values "auto", "in-process", and "tmux". Setting "teammateMode": "tmux" should produce the same tmux split-pane teammate behavior as --teammate-mode tmux on the CLI.

Error Messages/Logs

No error — the setting is silently ignored. Teammates just spawn in-process.

Steps to Reproduce

1. Ensure tmux is running and CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 is set
2. Add "teammateMode": "tmux" to ~/.claude/settings.json (or project/local scope)
3. Start claude with no CLI flags
4. Trigger a team workflow that spawns teammates (e.g. TeamCreate + Task with team_name)
5. Observe: teammates run in-process, no tmux split panes created
6. Now restart with claude --teammate-mode tmux — teammates correctly spawn in tmux panes

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.34

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

tmux

Additional Information

The CLI flag works perfectly — this is specifically about the settings.json path not being wired through to teammate spawning logic.