fix(server): Windows worktrees with long paths no longer fail or strand

[That1Drifter]

Problem

Git for Windows refuses to create or delete any path longer than MAX_PATH (260 characters) unless core.longpaths is set. The OS-level LongPathsEnabled registry value does not cover it, and git leaves the setting off by default. Worktrees live under <T3 home>/worktrees/<repo>/<branch>, deeper than the repository itself, so a repository that works fine in place can fail as a worktree:

• git worktree add fails with Filename too long / fatal: Could not reset index file to revision 'HEAD' (Worktree creation fails when path's are too long #635).
• git worktree remove --force fails partway, after git has already dropped its record of the worktree. The directory stays on disk and git worktree list no longer shows it, so nothing cleans it up.

Reproduced today on current main, git 2.52.0.windows.1, LongPathsEnabled=1, core.longpaths unset at every scope, with a tracked file whose relative path is 205 characters:

$ git worktree add -b a <97-char worktree path> main
fatal: cannot create directory at 'node_modules/.pnpm/...': Filename too long     (exit 128)
$ git -c core.longpaths=true worktree add -b b <same path> main                    (exit 0)
$ git worktree remove --force <same path>
error: failed to delete '<same path>': Filename too long                           (exit 255)
# afterwards: not in `git worktree list`, directory still on disk

The test suite never sees this because apps/server/src/testUtils/gitConfig.setup.ts turns core.longpaths on for every git child it spawns.

Change

On Windows, GitVcsDriverCore now appends core.longpaths=true to every git process it spawns. It goes in through the GIT_CONFIG_COUNT / GIT_CONFIG_KEY_n / GIT_CONFIG_VALUE_n env vars, added after any entries already present.

• Env instead of -c: tests in GitVcsDriverCore.test.ts match on spawned argv (command.args[0] === "push" and similar), and HostProcessPlatform defaults to the real host, so an argv prefix would break them on Windows only. Env leaves argv identical on every platform and writes nothing to the user's config.
• Inherited count: it is read the way git's own parser reads it (leading whitespace, optional +, -0). It is looked up case-insensitively, because Windows env names are case-insensitive and two spellings collapse to one on spawn. A count git would reject is left alone, so git still reports the error instead of getting a quietly different config.
• Precedence: env config sits above config files and below -c. A user's explicit core.longpaths=false is overridden for T3's own git calls. That's intentional: without the override, T3 can't create or clean up its own worktrees.

Every worktree add, remove and prune goes through executeRaw, as does storageCleanup's removeWorktree call, so they are all covered.

Scope and approval

This rebuilds #6327 on the V2 base, as asked when it was closed after #2829. It fixes #635.

It covers only GitVcsDriverCore. #13538 separately adds -c core.longpaths=true to the checkpoint commands in GitVcsDriver.ts and leaves GitVcsDriverCore out on purpose, so the two PRs don't overlap. If both land they compose cleanly: a -c true on top of an env true.

Verification

All on Windows 11, git 2.52.0.windows.1:

• vp test run src/vcs/GitVcsDriverCore.test.ts -t "Windows long path": 5 passed. The win32 integration test runs real git config --get through driver.execute, with the suite's core.longpaths=true overridden to false. It asserts true comes back and that inherited entries still resolve. A linux run asserts nothing changes.
• Negative control: with the helper unwired from the spawn, the win32 test fails (expected 'false' to equal 'true'). It passes again once restored.
• Ran every count edge case ("", 0, -0, 1, +1, 01, nope, 1x, -1, 1.5, whitespace-only, trailing space) through real git. The accept/reject table matches git exactly.
• A separate review pass also confirmed that a 264-character worktree is removed cleanly with the env in place, where it was stranded without it.
• Full GitVcsDriverCore.test.ts on Windows: everything else passes except keeps untracked filenames with pathspec magic in the review, which also fails on unmodified main (it writes a file named :(exclude)after.ts, which Windows doesn't allow).
• vp lint and vp fmt --check are clean on both files.

Not checked: macOS and Linux beyond the platform-gated test. The change does nothing off Windows.

Made with Claude Opus 5.5 (1M context) in Claude Code (via T3 Code), with an adversarial review pass by Claude Fable 5.1.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The PR is a localized Windows Git bug fix with focused tests, but it changes the effective default for every Windows Git command and overrides an explicit user setting. That product-default change requires human review.

Notes:

• Diff unchanged. Approvability was decided on eligibility alone.

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

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🧰 Additional context used

📚 Code guidelines (1)

docs/internals/effect-services.md — configured

📝 Walkthrough

Walkthrough

On Windows, Git subprocesses now receive core.longpaths=true through Git’s environment configuration. The change preserves inherited configuration entries and leaves non-Windows environments and invalid counts unchanged.

Changes

Windows Git long-path configuration

Layer / File(s)	Summary
Build the Windows long-path override apps/server/src/vcs/GitVcsDriverCore.ts, apps/server/src/vcs/GitVcsDriverCore.test.ts	The exported helper appends core.longpaths=true on Windows when the inherited count is valid or absent. Tests cover inherited entries, count parsing, invalid counts, and non-Windows behavior.
Apply the override to Git subprocesses apps/server/src/vcs/GitVcsDriverCore.ts	makeGitVcsDriverCore merges the Windows configuration after inherited, request-specific, and Trace2 environment values.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: juliusmarminge

Merge Risk: 🟡 Moderate · up to d0c0d

Some Windows worktree operations may still fail on long paths when Git configuration keys differ in casing. Normalize those keys before merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to d0c0d

The override is process-local and does not directly change credentials or operating-system permissions. Downgrading can restore the old cleanup failure for newly supported long-path worktrees. This is a bounded rollback risk, not a demonstrated privilege-escalation vulnerability.

Retained concerns

• Low · reliability · inferred: Downgrading to a binary without the override can strand long-path worktrees created while it was enabled. The setting is not persisted, and the documented older Git invocation can remove registration before failing to delete the directory. This is expanded rollback exposure to a pre-existing cleanup weakness, not an observed security vulnerability.

Security review details

Security Blast Radius

• inferred — The behavioral scope is Windows Git commands routed through this driver, not only worktree commands. Repository path depth can now reach longer filesystem paths under the existing process identity and filesystem permissions; the setting itself grants no additional operating-system permissions.

Trust Boundaries and Controls

• observed — The inspected spawn path retains the existing executable, arguments, working directory, and inherited/request environment flow. The new helper replaces no credential or identity variable. Authentication of callers and downstream Git helper authority are not established by this evidence.

Resilience and Maintainability Implications

• observed — The existing removal path treats an already-missing directory as a no-op and prunes registration. Other failures remain errors; this path supplies no fallback directory deletion when Git leaves files behind. That recovery limitation predates the environment change.

Hardening Proposals

• proposed — For downgrade compatibility, keep a long-path-capable cleanup route available or remove affected worktrees before reverting to a binary without the override. This is a rollback safeguard, not evidence of an existing deployment control.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise, specific, and accurately describes the primary change: preventing Windows worktree failures caused by long paths.
Description check	✅ Passed	The description includes complete Problem, Change, Scope and approval, and Verification sections. It explains the failure mode, implementation, scope, linked issues, test coverage, known platform-spec…
Linked Issues check	✅ Passed	The PR addresses the Windows long-path requirement in [#635]. GitVcsDriverCore appends core.longpaths=true through Git GIT_CONFIG_* environment variables for Windows Git processes. The change pr…
Out of Scope Changes check	✅ Passed	The changes remain within the scope of [#635]. The environment change is limited to GitVcsDriverCore, which executes the affected Git worktree commands. The removal and pruning coverage addresses th…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…

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Actionable comments posted: 1

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Inline comments:
Review comments at @apps/server/src/vcs/GitVcsDriverCore.ts:
- Around line 846-848: Update windowsLongPathConfigEnv to normalize merged Git
configuration keys case-insensitively while preserving input.env precedence,
then increment the resolved GIT_CONFIG_COUNT and append the long-path entry
without leaving conflicting mixed-case keys. Add a Windows integration test
covering lowercase process.env and uppercase input.env count keys.

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• apps/server/src/vcs/GitVcsDriverCore.test.ts
• apps/server/src/vcs/GitVcsDriverCore.ts

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