docs: empty-repo hardening notes + verification item

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
(cherry picked from commit d771dbf03575bb60e692ede44110ff17c3043f39)

docs/open.md

@@ -76,6 +76,13 @@ zugleich der erste Test dieser Annahme: schlägt einer davon mit einem Deseriali
 
 ## Offene Verifikation (2026-07-27)
 
+- **Empty-Repo-Hardening (2026-07-30)** — Worker/App neu starten (laufende Instanz hat den
+  Fix noch nicht), dann auf dem Task „HEy this is a Test" (Test List → `C:\Dev\TestRepo`,
+  aktuell 0 Commits) „Open ConPTY session" klicken: muss jetzt starten und in `C:\Dev\TestRepo`
+  genau einen leeren Commit „chore: initialize repository (ClaudeDo)" hinterlassen. Idealerweise
+  auch einmal auf dem Zweit-PC gegentesten (dort zusätzlich: Task-Run auf einem PC ohne
+  `git config user.name/email` — Auto-Commit darf nicht mehr scheitern).
+
 - **List handler (2026-07-27)** — visual pass: the Broom button is gone from the lists footer,
   the context-menu item appears only on lists with a working dir, and the selection dialog has no
   LIST column. (Der real-Claude-Smoke-Run der fünf Phasen ist am 2026-07-29 gelaufen — 6/6 sauber

docs/superpowers/plans/2026-07-30-empty-repo-hardening-plan.md

@@ -0,0 +1,58 @@
+# Empty-repo hardening — implementation plan
+
+Spec: `docs/superpowers/specs/2026-07-30-empty-repo-hardening-design.md`
+
+## Task 1 — GitService: HasHeadCommitAsync + EnsureHeadCommitAsync + friendly unborn error
+
+**Files:** `src/ClaudeDo.Data/Git/GitService.cs`,
+`tests/ClaudeDo.Worker.Tests/Runner/GitServiceBootstrapTests.cs` (new)
+
+1. Tests first (skip when git unavailable, mirroring `WorktreeManagerTests`):
+   - fresh `git init` repo (no commit): `HasHeadCommitAsync` false; after a commit true.
+   - `EnsureHeadCommitAsync` on empty repo → true; `RevParseHeadAsync` then succeeds;
+     `git ls-tree HEAD` empty; second call → false.
+   - staged file in empty repo survives bootstrap: still staged, not in the commit.
+   - corrupt HEAD (write a garbage SHA into `.git/HEAD` as a detached head):
+     `EnsureHeadCommitAsync` throws `InvalidOperationException` mentioning the dir.
+   - `RevParseHeadAsync` on empty repo: message says "has no commits yet" (no raw
+     "ambiguous argument").
+2. Implement: `HasHeadCommitAsync` (`rev-parse --verify --quiet HEAD`),
+   `EnsureHeadCommitAsync` (symbolic-ref guard → hash-object/commit-tree/update-ref
+   plumbing behind a static `SemaphoreSlim` with post-acquire re-check), unborn-HEAD
+   message in `RevParseHeadAsync`.
+3. Build Data + run new tests. Commit `fix(git): bootstrap empty repos with an initial commit`.
+
+## Task 2 — CommitAsync identity fallback
+
+**Files:** same two files.
+
+1. Test: repo with local `user.name`/`user.email` set to empty strings → `CommitAsync`
+   succeeds (retry path), commit exists.
+2. Implement: on identity-signature failure, retry once with
+   `-c user.name=ClaudeDo -c user.email=claudedo@local`.
+3. Commit `fix(git): fall back to a ClaudeDo identity when git has none`.
+
+## Task 3 — call sites
+
+**Files:** `src/ClaudeDo.Worker/Runner/WorktreeManager.cs`,
+`src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs`,
+`tests/ClaudeDo.Worker.Tests/Runner/WorktreeManagerTests.cs`
+
+1. Test: `CreateAsync` on a commit-less repo succeeds; worktree on disk; DB row Active.
+2. Wire `EnsureHeadCommitAsync` into `WorktreeManager.CreateAsync` (log info on
+   bootstrap) and `PlanningSessionManager.StartAsync`.
+3. Full Worker.Tests run. Commit `fix(worktree): auto-bootstrap commit-less repos before creating worktrees`.
+
+## Task 4 — docs
+
+- `src/ClaudeDo.Data/CLAUDE.md`: GitService bullet gains bootstrap/identity-fallback.
+- `docs/open.md`: verification item — open a ConPTY session on a fresh `git init` repo
+  on a second PC.
+- Commit `docs: empty-repo hardening notes`.
+
+## Verification
+
+- `dotnet test tests/ClaudeDo.Worker.Tests -c Release` green.
+- Manual: task 61609f79… in "Test List" (`C:\Dev\TestRepo`, currently commit-less) —
+  opening the ConPTY session must now succeed and leave `C:\Dev\TestRepo` with exactly
+  one empty commit by ClaudeDo.

docs/superpowers/specs/2026-07-30-empty-repo-hardening-design.md

@@ -0,0 +1,98 @@
+# Empty-repo hardening (unborn HEAD) — design
+
+**Date:** 2026-07-30
+**Status:** approved (option "Auto-Bootstrap" chosen by Mika)
+
+## Problem
+
+`GetInteractiveLaunchSpec` (embedded ConPTY session) fails with a raw git error when the
+task's list points at a git repository that has **no commits yet** (fresh `git init`,
+unborn HEAD):
+
+```
+HubException: git rev-parse HEAD failed (exit 128): fatal: ambiguous argument 'HEAD': unknown revision ...
+```
+
+Root cause chain: `InteractiveLaunchSpecService.BuildForTaskAsync` → `WorktreeManager.CreateAsync`
+→ `IsGitRepoAsync` (passes — `rev-parse --git-dir` works on an empty repo) →
+`ResolveBaseCommitAsync` → `RevParseHeadAsync` (fatals — HEAD is unborn). The same gap
+exists in `PlanningSessionManager.StartAsync` and hits autonomous runs (`TaskRunner` →
+`CreateAsync` → task `Failed` with the same cryptic message).
+
+This is a "works on my laptop" class of bug: on a fresh PC the first thing a user tries is
+a freshly init-ed test repo, which breaks instantly. A second member of the same class:
+a PC without `git config user.name/email` breaks every auto-commit
+("Please tell me who you are").
+
+## Decision
+
+**Auto-bootstrap:** when a worktree (task run / ConPTY / planning) needs a base commit and
+the repo has zero commits, ClaudeDo creates an empty initial commit automatically and
+proceeds. Nothing can be lost — the repo is empty. Genuinely broken states (HEAD not a
+symbolic ref and not resolvable) still produce a clear, actionable error instead of raw
+git stderr.
+
+## Design
+
+### 1. `GitService.HasHeadCommitAsync(dir)`
+
+`git rev-parse --verify --quiet HEAD` → exit 0 means HEAD resolves to a commit.
+
+### 2. `GitService.EnsureHeadCommitAsync(dir)` → `bool` (true = bootstrapped)
+
+- HEAD resolves → return `false` (no-op).
+- `git symbolic-ref -q HEAD` fails → repo is corrupt (detached HEAD onto a missing
+  commit, mangled `.git/HEAD`) → throw `InvalidOperationException` with a clear message
+  naming the directory. Auto-fixing a corrupt repo is out of scope by design.
+- Otherwise HEAD is an unborn branch → bootstrap **via plumbing only** (never touches the
+  user's index or working tree — staged/untracked files stay exactly as they were):
+  1. `git hash-object -w -t tree --stdin` with empty stdin → empty tree object.
+  2. `git -c user.name=ClaudeDo -c user.email=claudedo@local commit-tree <tree> -m
+     "chore: initialize repository (ClaudeDo)"` — inline identity so this works on a PC
+     with no git identity configured.
+  3. `git update-ref <unborn-branch-ref> <commit>`.
+- Serialized behind a process-wide gate with a re-check after acquiring, so two parallel
+  task starts on the same empty repo bootstrap exactly once.
+
+### 3. Defense-in-depth: friendly `RevParseHeadAsync` error
+
+When `rev-parse HEAD` fails with the unborn-HEAD signature ("ambiguous argument 'HEAD'"),
+throw "The repository at {dir} has no commits yet" instead of raw stderr — covers any
+future call site that forgets the preflight.
+
+### 4. Call sites
+
+- `WorktreeManager.CreateAsync` — after the `IsGitRepoAsync` guard, call
+  `EnsureHeadCommitAsync`; log when a bootstrap happened. Covers autonomous runs,
+  interactive ConPTY sessions, improvement/planning children.
+- `PlanningSessionManager.StartAsync` — same, before its own `RevParseHeadAsync`.
+
+### 5. Git identity fallback for auto-commits
+
+`GitService.CommitAsync`: if the commit fails with the missing/empty-identity signature,
+retry once with inline `-c user.name="ClaudeDo" -c user.email="claudedo@local"`.
+Happy path costs nothing (no preflight call); a fresh PC without git identity no longer
+fails every task auto-commit.
+
+## Out of scope
+
+- UI validation when configuring a list's WorkingDir (nice-to-have; the worktree paths now
+  either self-heal or produce clear errors).
+- Repairing corrupt repos.
+
+## Test plan (real git, Worker.Tests)
+
+- `HasHeadCommitAsync`: false on fresh `git init`, true after a commit.
+- `EnsureHeadCommitAsync` on an empty repo: returns true, `rev-parse HEAD` then works,
+  tree of the bootstrap commit is empty, second call returns false.
+- Staged-file preservation: file staged in empty repo → after bootstrap it is still
+  staged and NOT part of the bootstrap commit.
+- Corrupt HEAD (point `.git/HEAD` at a bogus ref? no — detach onto a garbage SHA by
+  writing `.git/HEAD` directly): clear error, no bootstrap.
+- `CommitAsync` identity fallback: local `user.name`/`user.email` set to empty strings
+  (forces the identity failure deterministically regardless of global config) → commit
+  succeeds via fallback, author is ClaudeDo.
+- `WorktreeManager.CreateAsync` on an empty repo: succeeds; worktree exists; base commit
+  = bootstrap commit.
+- `PlanningSessionManager.StartAsync` on an empty repo: succeeds (if existing test infra
+  makes this cheap; otherwise covered by the shared code path).

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
     "version": "8.0.418",
-    "rollForward": "latestFeature"
+    "rollForward": "latestMajor"
   }
 }

src/ClaudeDo.Data/CLAUDE.md

@@ -80,10 +80,15 @@ dir(s) via an optional `AttachmentStore` ctor param (defaults to the production
 - Merge: ff-only, no-ff, abort, mid-merge detection (`MERGE_HEAD`), conflicted files
 - Revert: `RevertMergeCommitAsync` (`git revert --no-edit -m 1 <sha>`), `RevertAbortAsync`, `IsMidRevertAsync` (`REVERT_HEAD`, mirrors `IsMidMergeAsync`)
 - `PreviewMergeAsync` (non-destructive check via `git merge-tree --write-tree`), `CountChangedFilesAsync`, rev-parse, is-git-repo
+- Empty repos: `HasHeadCommitAsync` (HEAD resolves to a real commit) and `EnsureHeadCommitAsync` — a fresh `git init` repo (unborn HEAD) gets an empty bootstrap commit via plumbing only (mktree/commit-tree/update-ref), so the user's index and working tree stay untouched; identity is passed inline, so it also works with no git config, and a broken HEAD throws instead of guessing
+- Identity fallback: `CommitAsync` retries once as the ClaudeDo identity when the machine has none configured
 
 ⚠️ **Revert never resets or rewrites** — it always produces a new commit, because the working
 directory it operates on is shared with other concurrent sessions.
 
+⚠️ **Git stdin is BOM-less UTF-8** — `Encoding.UTF8` writes a BOM preamble, which git rejects
+as input (`mktree` fails with "input format error", and commit messages would carry it).
+
 ## Schema
 
 Tables (one per line so parallel migrations don't collide on the same line):

src/ClaudeDo.Data/Git/GitService.cs

@@ -25,7 +25,16 @@ public sealed class GitService
     {
         var (exitCode, stdout, stderr) = await RunGitAsync(dir, ["rev-parse", "HEAD"], ct);
         if (exitCode != 0)
+        {
+            // Unborn HEAD (fresh `git init`, no commits) — the raw git stderr ("ambiguous
+            // argument 'HEAD'") is useless to a user; call sites should have run
+            // EnsureHeadCommitAsync, this message is the safety net for any that didn't.
+            if (stderr.Contains("ambiguous argument 'HEAD'", StringComparison.Ordinal) ||
+                stderr.Contains("unknown revision", StringComparison.Ordinal))
+                throw new InvalidOperationException(
+                    $"The repository at {dir} has no commits yet (unborn or broken HEAD) — ClaudeDo needs at least one commit to work in it.");
             throw new InvalidOperationException($"git rev-parse HEAD failed (exit {exitCode}): {stderr}");
+        }
         return stdout.Trim();
     }
 
@@ -55,6 +64,67 @@ public sealed class GitService
         return exitCode == 0 ? stdout.Trim() : null;
     }
 
+    /// <summary>HEAD resolves to a commit (false for a fresh `git init` repo or a broken HEAD).</summary>
+    public async Task<bool> HasHeadCommitAsync(string dir, CancellationToken ct = default)
+    {
+        // ^{commit} forces the object to actually exist and be a commit — a bare
+        // `--verify HEAD` happily accepts a detached HEAD pointing at a missing object.
+        var (exitCode, _, _) = await RunGitAsync(dir, ["rev-parse", "--verify", "--quiet", "HEAD^{commit}"], ct);
+        return exitCode == 0;
+    }
+
+    private const string FallbackUserName = "ClaudeDo";
+    private const string FallbackUserEmail = "claudedo@local";
+
+    // Two parallel task starts on the same empty repo must create exactly one initial commit.
+    private static readonly SemaphoreSlim BootstrapGate = new(1, 1);
+
+    /// <summary>
+    /// Guarantees HEAD resolves to a commit so worktrees can be created. A repo with an
+    /// unborn HEAD (fresh `git init`) gets an empty initial commit built from plumbing only
+    /// (hash-object/commit-tree/update-ref) — the user's index and working tree are never
+    /// touched, so staged and untracked files stay exactly as they were. Identity is passed
+    /// inline, so this also works on machines with no git identity configured. A repo whose
+    /// HEAD is broken (not a symbolic ref and not resolvable) throws instead of guessing.
+    /// </summary>
+    /// <returns>true if a bootstrap commit was created; false if HEAD already resolved.</returns>
+    public async Task<bool> EnsureHeadCommitAsync(string dir, CancellationToken ct = default)
+    {
+        if (await HasHeadCommitAsync(dir, ct)) return false;
+
+        var (symExit, symRef, _) = await RunGitAsync(dir, ["symbolic-ref", "--quiet", "HEAD"], ct);
+        if (symExit != 0)
+            throw new InvalidOperationException(
+                $"The repository at {dir} has a broken HEAD (detached onto a missing commit, or a corrupt .git/HEAD). Repair the repository manually.");
+
+        await BootstrapGate.WaitAsync(ct);
+        try
+        {
+            if (await HasHeadCommitAsync(dir, ct)) return false;
+
+            var (treeExit, treeSha, treeErr) = await RunGitAsync(dir, ["mktree"], ct, stdinData: "");
+            if (treeExit != 0)
+                throw new InvalidOperationException($"git mktree failed (exit {treeExit}): {treeErr}");
+
+            var (commitExit, commitSha, commitErr) = await RunGitAsync(dir,
+                ["-c", $"user.name={FallbackUserName}", "-c", $"user.email={FallbackUserEmail}",
+                 "commit-tree", treeSha.Trim(), "-m", "chore: initialize repository (ClaudeDo)"], ct);
+            if (commitExit != 0)
+                throw new InvalidOperationException($"git commit-tree failed (exit {commitExit}): {commitErr}");
+
+            var (refExit, _, refErr) = await RunGitAsync(dir,
+                ["update-ref", symRef.Trim(), commitSha.Trim()], ct);
+            if (refExit != 0)
+                throw new InvalidOperationException($"git update-ref failed (exit {refExit}): {refErr}");
+
+            return true;
+        }
+        finally
+        {
+            BootstrapGate.Release();
+        }
+    }
+
     public async Task WorktreeAddAsync(string repoDir, string branchName, string worktreePath, string baseCommit, CancellationToken ct = default)
     {
         await WorktreeAddGate.WaitAsync(ct);
@@ -135,10 +205,24 @@ public sealed class GitService
     {
         // Use -F - (read message from stdin) to handle multi-line messages safely.
         var (exitCode, _, stderr) = await RunGitAsync(worktreePath, ["commit", "-F", "-"], ct, stdinData: message);
+        if (exitCode != 0 && IsMissingIdentityError(stderr))
+        {
+            // A machine without git identity configured must not fail every auto-commit —
+            // retry once as ClaudeDo. The happy path pays no preflight cost.
+            (exitCode, _, stderr) = await RunGitAsync(worktreePath,
+                ["-c", $"user.name={FallbackUserName}", "-c", $"user.email={FallbackUserEmail}",
+                 "commit", "-F", "-"], ct, stdinData: message);
+        }
         if (exitCode != 0)
             throw new InvalidOperationException($"git commit failed (exit {exitCode}): {stderr}");
     }
 
+    private static bool IsMissingIdentityError(string stderr) =>
+        stderr.Contains("tell me who you are", StringComparison.OrdinalIgnoreCase) ||
+        stderr.Contains("empty ident", StringComparison.OrdinalIgnoreCase) ||
+        stderr.Contains("no email was given", StringComparison.OrdinalIgnoreCase) ||
+        stderr.Contains("unable to auto-detect email address", StringComparison.OrdinalIgnoreCase);
+
     public async Task<string> GetDiffAsync(
         string worktreePath, IReadOnlyList<string>? paths = null, CancellationToken ct = default)
     {
@@ -584,7 +668,9 @@ public sealed class GitService
             CreateNoWindow = true,
             StandardOutputEncoding = Encoding.UTF8,
             StandardErrorEncoding = Encoding.UTF8,
-            StandardInputEncoding = stdinData is not null ? Encoding.UTF8 : null,
+            // BOM-less: Encoding.UTF8 writes a BOM preamble, which git rejects as input
+            // (mktree "input format error") and would prepend to stdin commit messages.
+            StandardInputEncoding = stdinData is not null ? new UTF8Encoding(false) : null,
         };
         psi.ArgumentList.Add("-C");
         psi.ArgumentList.Add(workDir);

src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs

@@ -98,6 +98,9 @@ public sealed class PlanningSessionManager
         if (!await _git.IsGitRepoAsync(listWorkingDir, ct))
             throw new InvalidOperationException($"Working directory is not a git repository: {listWorkingDir}");
 
+        // A fresh `git init` repo has no HEAD commit to base the planning worktree on.
+        await _git.EnsureHeadCommitAsync(listWorkingDir, ct);
+
         var appSettings = await settings.GetAsync(ct);
         var worktreePath = WorktreePathFor(taskId, appSettings.WorktreeStrategy, appSettings.CentralWorktreeRoot, listWorkingDir);
         var branchName = BranchNameFor(taskId);

src/ClaudeDo.Worker/Runner/WorktreeManager.cs

@@ -46,6 +46,10 @@ public sealed class WorktreeManager
         if (!await _git.IsGitRepoAsync(workingDir, ct))
             throw new InvalidOperationException($"working_dir is not a git repository: {workingDir}");
 
+        // A fresh `git init` repo has no HEAD commit to base a worktree on — bootstrap one.
+        if (await _git.EnsureHeadCommitAsync(workingDir, ct))
+            _logger.LogInformation("Repository at {Dir} had no commits; created an empty bootstrap commit", workingDir);
+
         var baseCommit = await ResolveBaseCommitAsync(task, workingDir, ct);
         // Use the full task id (dashes stripped) in the branch name so
         // two GUIDs sharing an 8-char prefix cannot collide on the same branch.

tests/ClaudeDo.Worker.Tests/Runner/GitServiceBootstrapTests.cs

@@ -0,0 +1,139 @@
+using ClaudeDo.Data.Git;
+using ClaudeDo.Worker.Tests.Infrastructure;
+
+namespace ClaudeDo.Worker.Tests.Runner;
+
+// Covers the empty-repo (unborn HEAD) hardening: HasHeadCommitAsync, EnsureHeadCommitAsync
+// (plumbing-only bootstrap commit), the friendly RevParseHeadAsync unborn message, and the
+// CommitAsync git-identity fallback. All tests run real git against throwaway repos.
+public class GitServiceBootstrapTests : IDisposable
+{
+    private readonly List<string> _tempDirs = new();
+    private readonly GitService _git = new();
+
+    private static bool GitAvailable => GitRepoFixture.IsGitAvailable();
+
+    // A repo straight out of `git init` — no commits, and deliberately NO identity
+    // configured: the bootstrap must not depend on machine-level git config.
+    private string InitEmptyRepo()
+    {
+        var dir = Path.Combine(Path.GetTempPath(), $"claudedo_emptyrepo_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(dir);
+        GitRepoFixture.RunGit(dir, "init", "-b", "main");
+        _tempDirs.Add(dir);
+        return dir;
+    }
+
+    [Fact]
+    public async Task HasHeadCommit_FalseOnEmptyRepo_TrueAfterCommit()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var dir = InitEmptyRepo();
+        Assert.False(await _git.HasHeadCommitAsync(dir));
+
+        GitRepoFixture.RunGit(dir, "-c", "user.name=t", "-c", "user.email=t@t", "commit", "--allow-empty", "-m", "x");
+        Assert.True(await _git.HasHeadCommitAsync(dir));
+    }
+
+    [Fact]
+    public async Task EnsureHeadCommit_BootstrapsEmptyRepo_Once()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var dir = InitEmptyRepo();
+
+        Assert.True(await _git.EnsureHeadCommitAsync(dir));
+
+        // HEAD now resolves and RevParseHeadAsync works — the original failure mode is gone.
+        var head = await _git.RevParseHeadAsync(dir);
+        Assert.Matches("^[0-9a-f]{40,64}$", head);
+
+        // The bootstrap commit is empty: nothing of the user's ends up in it.
+        var tree = GitRepoFixture.RunGit(dir, "ls-tree", "HEAD").Trim();
+        Assert.Equal(string.Empty, tree);
+
+        // Idempotent: a repo with a HEAD commit is left alone.
+        Assert.False(await _git.EnsureHeadCommitAsync(dir));
+        Assert.Equal(head, await _git.RevParseHeadAsync(dir));
+    }
+
+    [Fact]
+    public async Task EnsureHeadCommit_LeavesStagedFilesStaged()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var dir = InitEmptyRepo();
+        File.WriteAllText(Path.Combine(dir, "mine.txt"), "user work\n");
+        GitRepoFixture.RunGit(dir, "add", "mine.txt");
+
+        Assert.True(await _git.EnsureHeadCommitAsync(dir));
+
+        // Still staged (index vs HEAD shows it as pending), NOT committed.
+        var staged = GitRepoFixture.RunGit(dir, "diff", "--cached", "--name-only").Trim();
+        Assert.Equal("mine.txt", staged);
+        var tree = GitRepoFixture.RunGit(dir, "ls-tree", "HEAD").Trim();
+        Assert.Equal(string.Empty, tree);
+    }
+
+    [Fact]
+    public async Task EnsureHeadCommit_CorruptHead_ThrowsClearError()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var dir = InitEmptyRepo();
+        // Detach HEAD onto a commit that doesn't exist — not an unborn branch, a broken repo.
+        File.WriteAllText(Path.Combine(dir, ".git", "HEAD"), new string('f', 40) + "\n");
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => _git.EnsureHeadCommitAsync(dir));
+        Assert.Contains(dir, ex.Message);
+    }
+
+    [Fact]
+    public async Task RevParseHead_EmptyRepo_ReportsNoCommitsInsteadOfRawGitError()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var dir = InitEmptyRepo();
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => _git.RevParseHeadAsync(dir));
+        Assert.Contains("no commits yet", ex.Message);
+        Assert.Contains(dir, ex.Message);
+        Assert.DoesNotContain("ambiguous argument", ex.Message);
+    }
+
+    [Fact]
+    public async Task CommitAsync_MissingIdentity_FallsBackToClaudeDoIdentity()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var dir = InitEmptyRepo();
+        GitRepoFixture.RunGit(dir, "-c", "user.name=t", "-c", "user.email=t@t", "commit", "--allow-empty", "-m", "seed");
+        // Empty local identity overrides any machine-level config, so the first commit
+        // attempt fails with git's identity error no matter where this test runs.
+        GitRepoFixture.RunGit(dir, "config", "user.name", "");
+        GitRepoFixture.RunGit(dir, "config", "user.email", "");
+
+        File.WriteAllText(Path.Combine(dir, "work.txt"), "content\n");
+        await _git.AddAllAsync(dir);
+
+        await _git.CommitAsync(dir, "feat(test): identity fallback");
+
+        var author = GitRepoFixture.RunGit(dir, "log", "-1", "--format=%an <%ae>").Trim();
+        Assert.Equal("ClaudeDo <claudedo@local>", author);
+    }
+
+    public void Dispose()
+    {
+        foreach (var dir in _tempDirs)
+        {
+            try
+            {
+                if (!Directory.Exists(dir)) continue;
+                foreach (var file in Directory.EnumerateFiles(dir, "*", SearchOption.AllDirectories))
+                    File.SetAttributes(file, FileAttributes.Normal);
+                Directory.Delete(dir, true);
+            }
+            catch { /* best effort */ }
+        }
+    }
+}

tests/ClaudeDo.Worker.Tests/Runner/WorktreeManagerTests.cs

@@ -191,6 +191,34 @@ public class WorktreeManagerTests : IDisposable
         Assert.Contains("hello.txt", row.DiffStat);
     }
 
+    [Fact]
+    public async Task CreateAsync_EmptyRepo_BootstrapsInitialCommit()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        // Fresh `git init`, zero commits, no identity configured — the cross-PC failure
+        // that surfaced as "git rev-parse HEAD failed: ambiguous argument 'HEAD'".
+        var repoDir = Path.Combine(Path.GetTempPath(), $"claudedo_emptyrepo_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(repoDir);
+        GitRepoFixture.RunGit(repoDir, "init", "-b", "main");
+        _tempDirs.Add(repoDir);
+
+        var (task, list) = MakeEntities(repoDir);
+        var (mgr, db) = await CreateManagerAsync(task, list);
+
+        var ctx = await mgr.CreateAsync(task, list, CancellationToken.None);
+        _worktreeCleanups.Add((repoDir, ctx.WorktreePath));
+
+        Assert.True(Directory.Exists(ctx.WorktreePath));
+        // The base commit is the auto-created bootstrap commit.
+        var head = GitRepoFixture.RunGit(repoDir, "rev-parse", "HEAD").Trim();
+        Assert.Equal(head, ctx.BaseCommit);
+
+        using var readCtx = db.CreateContext();
+        var row = await new WorktreeRepository(readCtx).GetByTaskIdAsync(task.Id);
+        Assert.Equal(WorktreeState.Active, row!.State);
+    }
+
     [Fact]
     public async Task CreateAsync_NonGitDir_Throws_NoRow()
     {