fix(agents): keep WorktreeCreate hooks authoritative

Revert silent git fallback after hook failure. Treat WorktreeCreate hook
errors as recoverable in AgentTool so multi-repo cwd overrides still work
without bypassing configured hooks at the worktree layer.

src/tools/AgentTool/AgentTool.schema.test.ts

@@ -179,12 +179,17 @@ describe('AgentTool input schema isolation contract', () => {
     ).toThrow('cwd must be an existing directory.')
   })
 
-  test('detects missing-git worktree errors for fallback', () => {
+  test('detects missing-git and WorktreeCreate hook worktree errors for fallback', () => {
     expect(
       isMissingGitAgentWorktreeError(
         'Cannot create agent worktree: not in a git repository and no WorktreeCreate hooks are configured.',
       ),
     ).toBe(true)
+    expect(
+      isMissingGitAgentWorktreeError(
+        'WorktreeCreate hook failed: no successful output',
+      ),
+    ).toBe(true)
     expect(isMissingGitAgentWorktreeError('some other failure')).toBe(false)
   })
 

src/tools/AgentTool/AgentTool.tsx

@@ -198,9 +198,14 @@ export function resolveAgentToolCwdOverride(
   return worktreeInfo?.worktreePath ?? cwd;
 }
 
-/** True when worktree creation failed only because no git root was available. */
+/** True when worktree creation failed in a way AgentTool can recover from by
+ * falling back to a cwd override (missing git root, or WorktreeCreate hook
+ * failure in a non-git / multi-repo parent session). */
 export function isMissingGitAgentWorktreeError(message: string): boolean {
-  return message.includes('Cannot create agent worktree: not in a git repository');
+  return (
+    message.includes('Cannot create agent worktree: not in a git repository') ||
+    message.includes('WorktreeCreate hook failed:')
+  );
 }
 
 // Output schema - multi-agent spawned schema added dynamically at runtime when enabled

src/utils/worktree.ts

@@ -1066,26 +1066,17 @@ export async function createAgentWorktree(
 
   // Try hook-based worktree creation first (allows user-configured VCS).
   // Forward sessionCwd so hooks operating from a multi-repo parent can target
-  // the selected child repository (#2052). If the hook fails but the cwd is a
-  // git repo, fall through to the git worktree path instead of hard-failing.
+  // the selected child repository (#2052). Hook failure remains terminal here —
+  // AgentTool decides whether to fall back to a cwd override.
   if (hasWorktreeCreateHook()) {
-    try {
-      const hookResult = await executeWorktreeCreateHook(slug, {
-        cwd: sessionCwd,
-      })
-      logForDebugging(
-        `Created hook-based agent worktree at: ${hookResult.worktreePath}`,
-      )
+    const hookResult = await executeWorktreeCreateHook(slug, {
+      cwd: sessionCwd,
+    })
+    logForDebugging(
+      `Created hook-based agent worktree at: ${hookResult.worktreePath}`,
+    )
 
-      return { worktreePath: hookResult.worktreePath, hookBased: true }
-    } catch (error) {
-      if (!findCanonicalGitRoot(sessionCwd)) {
-        throw error
-      }
-      logForDebugging(
-        `WorktreeCreate hook failed; falling back to git worktree at ${sessionCwd}: ${error instanceof Error ? error.message : String(error)}`,
-      )
-    }
+    return { worktreePath: hookResult.worktreePath, hookBased: true }
   }
 
   // Fall back to git worktree