diff --git a/electron/ipc/git-worktree.test.ts b/electron/ipc/git-worktree.test.ts
index 697af82d..37bf3ccb 100644
--- a/electron/ipc/git-worktree.test.ts
+++ b/electron/ipc/git-worktree.test.ts
@@ -7,6 +7,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import {
   createWorktree,
+  ensureClaudeSandboxFiles,
   ensureSymlinkExcludes,
   getSymlinkCandidates,
   refreshWorktreeNodeModules,
@@ -491,3 +492,49 @@ describe('ensureSymlinkExcludes', () => {
     expect(status).toContain('starZZfile');
   });
 });
+
+describe('ensureClaudeSandboxFiles', () => {
+  function makeWorktreeDir(): string {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'parallel-code-claude-worktree-'));
+    tempDirs.push(dir);
+    return dir;
+  }
+
+  it('does not seed .claude/worktrees/ into a new worktree', () => {
+    const root = initRepository();
+    const sourceWorktrees = path.join(root, '.claude', 'worktrees', 'some-agent-id');
+    fs.mkdirSync(sourceWorktrees, { recursive: true });
+    fs.writeFileSync(path.join(sourceWorktrees, 'marker.txt'), 'a nested worktree checkout\n');
+
+    const worktreePath = makeWorktreeDir();
+    ensureClaudeSandboxFiles(worktreePath, root);
+
+    expect(fs.existsSync(path.join(worktreePath, '.claude', 'worktrees'))).toBe(false);
+  });
+
+  it('still excludes plans/ and steps.json (pre-existing behavior)', () => {
+    const root = initRepository();
+    fs.mkdirSync(path.join(root, '.claude', 'plans'), { recursive: true });
+    fs.writeFileSync(path.join(root, '.claude', 'steps.json'), '{}\n');
+
+    const worktreePath = makeWorktreeDir();
+    ensureClaudeSandboxFiles(worktreePath, root);
+
+    expect(fs.existsSync(path.join(worktreePath, '.claude', 'plans'))).toBe(false);
+    expect(fs.existsSync(path.join(worktreePath, '.claude', 'steps.json'))).toBe(false);
+  });
+
+  it('still seeds ordinary .claude/ entries (e.g. skills/) from the source', () => {
+    const root = initRepository();
+    const sourceSkills = path.join(root, '.claude', 'skills');
+    fs.mkdirSync(sourceSkills, { recursive: true });
+    fs.writeFileSync(path.join(sourceSkills, 'example.md'), '# example skill\n');
+
+    const worktreePath = makeWorktreeDir();
+    ensureClaudeSandboxFiles(worktreePath, root);
+
+    expect(
+      fs.readFileSync(path.join(worktreePath, '.claude', 'skills', 'example.md'), 'utf8'),
+    ).toBe('# example skill\n');
+  });
+});
diff --git a/electron/ipc/git.ts b/electron/ipc/git.ts
index f8508ec3..63a35458 100644
--- a/electron/ipc/git.ts
+++ b/electron/ipc/git.ts
@@ -149,7 +149,17 @@ const DEFAULT_SYMLINK_CANDIDATES = new Set(SYMLINK_CANDIDATES);
  * Entries inside `.claude/` that must NOT be seeded from the main repo's
  * `.claude/` into new worktrees (per-worktree-local state).
  */
-const CLAUDE_DIR_EXCLUDE = new Set(['plans', 'steps.json']);
+const CLAUDE_DIR_EXCLUDE = new Set([
+  'plans',
+  'steps.json',
+  // Claude Code's own runtime worktree registry. Never seed this into a new
+  // worktree: the main repo's .claude/worktrees/ can itself contain other
+  // active worktrees' full checkouts (each an independent copy of the
+  // repository), so copying it duplicates every one of them into every new
+  // task. Confirmed via `git worktree list` that entries seeded this way are
+  // never real registered worktrees -- always orphaned duplicate content.
+  'worktrees',
+]);
 
 /**
  * Files Claude Code's sandbox (bwrap) read-only-binds on startup. They must