fix(worktree): gate sessions on bootstrap readiness (#1762)

Co-authored-by: Leonid Skorobogatyy <bash@opencode.itc.local>
Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/web/server/lib/git/service.js

@@ -3550,6 +3550,19 @@ export async function validateWorktreeCreate(directory, input = {}) {
   }
 }
 
+const assertWorktreeCreatePreflight = async (directory, input = {}) => {
+  const validation = await validateWorktreeCreate(directory, input);
+  if (validation?.ok) {
+    return;
+  }
+
+  const message = validation?.errors
+    ?.map((error) => error?.message)
+    .filter(Boolean)
+    .join('\n') || 'Failed to validate worktree creation';
+  throw new Error(message);
+};
+
 export async function previewWorktreeCreate(directory, input = {}) {
   const mode = input?.mode === 'existing' ? 'existing' : 'new';
   const context = await resolveWorktreeProjectContext(directory);
@@ -3698,6 +3711,11 @@ async function attachGitWorktreeToCandidate(context, candidate, input = {}) {
 export async function createWorktree(directory, input = {}) {
   const mode = input?.mode === 'existing' ? 'existing' : 'new';
   const context = await resolveWorktreeProjectContext(directory);
+
+  if (input?.returnAfterDirectoryCreated === true) {
+    await assertWorktreeCreatePreflight(directory, input);
+  }
+
   await fsp.mkdir(context.worktreeRoot, { recursive: true });
 
   const preferredName = String(input?.worktreeName || input?.name || '').trim();

packages/web/server/lib/git/service.test.js

@@ -8,6 +8,7 @@ import simpleGit from 'simple-git';
 import {
   checkoutCommit,
   cherryPick,
+  createWorktree,
   getStatus,
   removeWorktree,
   resolvePrimaryWorktreeRoot,
@@ -315,6 +316,53 @@ describe('worktree root resolution', () => {
   });
 });
 
+// ---------------------------------------------------------------------------
+// createWorktree
+// ---------------------------------------------------------------------------
+
+describe('createWorktree', () => {
+  it('preflights fast create branch-in-use failures before creating the candidate directory', async () => {
+    if (!canRunGit()) return;
+
+    const previousXdgDataHome = process.env.XDG_DATA_HOME;
+    const dataHome = createTempDir();
+    process.env.XDG_DATA_HOME = dataHome;
+
+    try {
+      const repo = createTempDir();
+      const worktree = createTempDir();
+      runGit(repo, ['init', '-b', 'main']);
+      runGit(repo, ['config', 'user.email', 'test@example.com']);
+      runGit(repo, ['config', 'user.name', 'Test User']);
+      fs.writeFileSync(path.join(repo, 'README.md'), '# Test\n');
+      runGit(repo, ['add', 'README.md']);
+      runGit(repo, ['commit', '-m', 'Initial commit']);
+      const projectID = runGit(repo, ['rev-list', '--max-parents=0', '--all']).trim();
+
+      fs.rmSync(worktree, { recursive: true, force: true });
+      runGit(repo, ['worktree', 'add', '-b', 'feature/in-use', worktree, 'HEAD']);
+      const canonicalWorktree = fs.realpathSync(worktree);
+
+      await expect(createWorktree(repo, {
+        mode: 'existing',
+        existingBranch: 'feature/in-use',
+        branchName: 'feature/in-use',
+        worktreeName: 'feature-in-use',
+        returnAfterDirectoryCreated: true,
+      })).rejects.toThrow(`Branch is already checked out in ${canonicalWorktree}`);
+
+      const candidateDirectory = path.join(dataHome, 'opencode', 'worktree', projectID, 'feature-in-use');
+      expect(fs.existsSync(candidateDirectory)).toBe(false);
+    } finally {
+      if (previousXdgDataHome === undefined) {
+        delete process.env.XDG_DATA_HOME;
+      } else {
+        process.env.XDG_DATA_HOME = previousXdgDataHome;
+      }
+    }
+  });
+});
+
 // ---------------------------------------------------------------------------
 // removeWorktree
 // ---------------------------------------------------------------------------