feat(git): let users choose the worktree branch prefix

[t3dotgg]

Generated worktree branches always start with t3code/, which conflicts with personal and team branch conventions.

Add a server-owned Worktree branch prefix setting under Settings > General. It defaults to t3code, accepts validated custom prefixes, and can be cleared to create branches without a prefix. Temporary branches stay unchanged, and the server applies the prefix when it generates the final branch name for web, desktop, mobile, and remote clients.

Inspired by and with thanks to:

• @yasinkavakli for #7887
• @filipgutica for #6037
• @jssblck for #3954
• @MrSimmmons for #6428

Verified with 116 focused tests, targeted lint, and scoped typechecks for contracts, shared, client runtime, server, web, and mobile.

Model: GPT-5.6 Sol
Harness: Codex in T3 Code

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Note

Medium Risk
Touches git branch naming and persisted server settings. Invalid prefixes are schema-validated, but misconfigured prefixes still change how worktrees are renamed for all clients.

Overview
Users can now set a Worktree branch prefix in Settings > General. Generated worktree names still default to t3code/…, but a custom prefix (including nested paths like teams/platform) is applied server-side, and clearing the field creates unprefixed branches.

buildGeneratedWorktreeBranchName strips a leftover t3code/ from the model output when it is not the configured prefix, then sanitizes the remainder. Temporary worktree branches are unchanged.

The new worktreeBranchPrefix setting is validated (lowercase, max 64, no // or leading/trailing separators) and wired through dirty/reset/search plus user docs.

^{Reviewed by Cursor Bugbot for commit 5e5ed3f. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add configurable worktreeBranchPrefix setting defaulting to t3code

• Adds a worktreeBranchPrefix field to ServerSettings, defaulting to t3code and validated by the new WorktreeBranchPrefix schema (max 64 chars, lowercase alphanumerics, no adjacent slashes).
• Updates buildGeneratedWorktreeBranchName in ProviderCommandReactor.ts to accept a prefix argument and sanitize it via sanitizeBranchFragment.
• Adds a UI control in the General Settings panel to edit the prefix, with settings search indexing and restore-defaults support.
• Behavioral Change: buildGeneratedWorktreeBranchName now requires a prefix parameter; existing callers must be updated.

^{Macroscope summarized 5e5ed3f.}

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.4 KiB	13.4 KiB	+6 B (+0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.9 KiB	6.9 KiB	+2 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+4 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	55.0 KiB	55.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	16	16	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.4 KiB	−29 B (−0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.9 KiB	6.9 KiB	−1 B (−0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.5 KiB	−28 B (−0.4%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	55.8 KiB	55.8 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	16	16	0 (0.0%)	21	✅

Baseline: e6a109b · PR result: 5e5ed3f · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 109.4 KiB
• Claude decoded thread snapshot: 110.1 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a new settings workflow and changes how generated worktree branches are renamed, including persisted server configuration and custom Git prefixes. The scope is focused and backwards-compatible, but the user-visible Git behavior warrants human review.

^{You can add or adjust custom eligibility rules. Learn more.}

[MrSimmmons]

For my example of #6428, do you have thoughts on allowing full branch name customization at worktree creation rather than just the prefix instead?
The way that my teams works is we use the prefix of the branch to indicate the type of branch (so bug/..., feat/... etc) and just allowing the customization of it wouldn't really work for that use case.
Otherwise I don't really see the a use for the prefix of a branch?

Where as if you gave people the option to just fully customize the branch name on worktree creation, they can then have whatever they want and everyone wins