fix: ensure story branch exists before cloning at task start

Add ensureStoryBranch() that runs git ls-remote to check, then clones
into a temp dir to create and push the branch if missing. Called before
the task's own clone so checkout is guaranteed to succeed.

Removes the post-checkout fallback hack added in the previous commit.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 53 insertions, 9 deletions

diff --git a/internal/executor/container.go b/internal/executor/container.go
index d90a273..61ac29c 100644
--- a/internal/executor/container.go
+++ b/internal/executor/container.go
@@ -58,6 +58,48 @@ func (r *ContainerRunner) ExecLogDir(execID string) string {
 	return filepath.Join(r.LogDir, execID)
 }
 
+// ensureStoryBranch checks whether branchName exists in remoteURL and creates
+// it from main if not. Uses localPath as a reference clone for speed if set.
+func (r *ContainerRunner) ensureStoryBranch(ctx context.Context, remoteURL, branchName, localPath string) error {
+	// Check if branch already exists.
+	out, err := r.command(ctx, "git", "ls-remote", "--heads", remoteURL, branchName).CombinedOutput()
+	if err == nil && len(strings.TrimSpace(string(out))) > 0 {
+		return nil // already exists
+	}
+
+	r.Logger.Info("story branch missing, creating from main", "branch", branchName, "remote", remoteURL)
+
+	// Clone into a temp dir so we can create the branch.
+	tmp, err := os.MkdirTemp("", "claudomator-branchsetup-*")
+	if err != nil {
+		return fmt.Errorf("mktemp for branch setup: %w", err)
+	}
+	defer os.RemoveAll(tmp)
+
+	// Remove the dir git clone expects to create.
+	if err := os.Remove(tmp); err != nil {
+		return fmt.Errorf("removing tmp dir before clone: %w", err)
+	}
+
+	var cloneArgs []string
+	if localPath != "" {
+		cloneArgs = []string{"clone", "--reference", localPath, remoteURL, tmp}
+	} else {
+		cloneArgs = []string{"clone", remoteURL, tmp}
+	}
+	if out, err := r.command(ctx, "git", cloneArgs...).CombinedOutput(); err != nil {
+		return fmt.Errorf("git clone for branch setup: %w\n%s", err, string(out))
+	}
+	if out, err := r.command(ctx, "git", "-C", tmp, "checkout", "-b", branchName).CombinedOutput(); err != nil {
+		return fmt.Errorf("git checkout -b %q: %w\n%s", branchName, err, string(out))
+	}
+	if out, err := r.command(ctx, "git", "-C", tmp, "push", "origin", branchName).CombinedOutput(); err != nil {
+		return fmt.Errorf("git push %q: %w\n%s", branchName, err, string(out))
+	}
+	r.Logger.Info("story branch created and pushed", "branch", branchName)
+	return nil
+}
+
 func (r *ContainerRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
 	var err error
 	repoURL := t.RepositoryURL
@@ -114,7 +156,16 @@ func (r *ContainerRunner) Run(ctx context.Context, t *task.Task, e *storage.Exec
 		storyBranch = t.BranchName
 	}
 
-	// 2. Clone repo into workspace if not resuming.
+	// 2. Ensure story branch exists in the remote before cloning.
+	// If the branch is missing (e.g. story approved before fix, or branch push failed),
+	// create it from main using the project local path as a reference repo.
+	if storyBranch != "" && !isResume {
+		if err := r.ensureStoryBranch(ctx, repoURL, storyBranch, storyLocalPath); err != nil {
+			r.Logger.Warn("ensureStoryBranch failed (will attempt checkout anyway)", "branch", storyBranch, "error", err)
+		}
+	}
+
+	// 3. Clone repo into workspace if not resuming.
 	// git clone requires the target directory to not exist; remove the MkdirTemp-created dir first.
 	if !isResume {
 		if err := os.Remove(workspace); err != nil {
@@ -133,14 +184,7 @@ func (r *ContainerRunner) Run(ctx context.Context, t *task.Task, e *storage.Exec
 		if storyBranch != "" {
 			r.Logger.Info("checking out story branch", "branch", storyBranch)
 			if out, err := r.command(ctx, "git", "-C", workspace, "checkout", storyBranch).CombinedOutput(); err != nil {
-				// Branch doesn't exist in the remote yet — create it from HEAD and push.
-				r.Logger.Warn("story branch not found, creating from HEAD", "branch", storyBranch)
-				if out2, err2 := r.command(ctx, "git", "-C", workspace, "checkout", "-b", storyBranch).CombinedOutput(); err2 != nil {
-					return fmt.Errorf("git checkout story branch %q failed: %w\n%s\ncreate attempt: %s", storyBranch, err, string(out), string(out2))
-				}
-				if out2, err2 := r.command(ctx, "git", "-C", workspace, "push", "origin", storyBranch).CombinedOutput(); err2 != nil {
-					r.Logger.Warn("push of auto-created story branch failed", "branch", storyBranch, "error", err2, "output", string(out2))
-				}
+				return fmt.Errorf("git checkout story branch %q failed: %w\n%s", storyBranch, err, string(out))
 			}
 		}
 		if err = os.Chmod(workspace, 0755); err != nil {