fix: deny stale team hook paths safely

Catch project hook resolution and load failures in the cross-shell Node launcher, returning a sanitized structured denial instead of a module-loader error.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

README.md

@@ -58,7 +58,7 @@ From inside your repo, paste this. Switches you to team mode, bootstraps the rep
 (cd ~/.claude/skills/gstack && ./setup --team) && ~/.claude/skills/gstack/bin/gstack-team-init required && git add .claude/ CLAUDE.md && git commit -m "require gstack for AI-assisted work"
 ```
 
-No vendored gstack install in your repo, no version drift, no manual upgrades. Required mode commits one Node 18+ CommonJS enforcement hook, so the same project hook works from POSIX and Windows hook runners without duplicate shell-specific handlers. If the hook runner omits its project directory, enforcement fails closed with an intentional denial instead of a hook error. Every Claude Code session starts with a fast auto-update check (throttled to once/hour, network-failure-safe, completely silent).
+No vendored gstack install in your repo, no version drift, no manual upgrades. Required mode commits one Node 18+ CommonJS enforcement hook, so the same project hook works from POSIX and Windows hook runners without duplicate shell-specific handlers. If the hook runner omits its project directory or provides a stale path, enforcement fails closed with an intentional denial instead of a hook error. Every Claude Code session starts with a fast auto-update check (throttled to once/hour, network-failure-safe, completely silent).
 
 Swap `required` for `optional` if you'd rather nudge teammates than block them.
 

bin/gstack-team-init

@@ -179,7 +179,7 @@ HOOK_EOF
       if (!settings.hooks) settings.hooks = {};
       if (!settings.hooks.PreToolUse) settings.hooks.PreToolUse = [];
 
-      const hookCommand = \"node -e \\\"const projectDir=process.env.CLAUDE_PROJECT_DIR;if(!projectDir){const reason='BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.';console.error(reason);console.log(JSON.stringify({hookSpecificOutput:{hookEventName:'PreToolUse',permissionDecision:'deny',permissionDecisionReason:reason}}))}else{require(require('node:path').join(projectDir, '.claude', 'hooks', 'check-gstack.cjs'))}\\\"\";
+      const hookCommand = \"node -e \\\"const deny=reason=>{console.error(reason);console.log(JSON.stringify({hookSpecificOutput:{hookEventName:'PreToolUse',permissionDecision:'deny',permissionDecisionReason:reason}}))};const projectDir=process.env.CLAUDE_PROJECT_DIR;if(!projectDir){deny('BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.')}else{try{require(require('node:path').join(projectDir, '.claude', 'hooks', 'check-gstack.cjs'))}catch{deny('BLOCKED: the required gstack hook could not be loaded. Verify project hook setup and retry.')}}\\\"\";
       let found = false;
       settings.hooks.PreToolUse = settings.hooks.PreToolUse.filter(entry => {
         if (entry.matcher !== 'Skill' || !entry.hooks) return true;

implementation-notes.html

@@ -14,6 +14,7 @@
       <li>Required mode generates <code>.claude/hooks/check-gstack.cjs</code>. The explicit CommonJS extension is unaffected by a consumer repository's <code>package.json</code> module type.</li>
       <li>The one registered command launches Node 18+ and resolves <code>CLAUDE_PROJECT_DIR</code> inside JavaScript through <code>process.env</code>. It contains no Bash, PowerShell, or cmd environment expansion.</li>
       <li>The launcher validates <code>CLAUDE_PROJECT_DIR</code> before calling <code>path.join</code>. Missing or empty project context emits a structured <code>PreToolUse</code> denial, writes a clear reason to stderr, and exits zero instead of surfacing a hook execution error.</li>
+      <li>Path resolution and module loading run inside the same <code>try/catch</code>. A nonexistent project, an existing project without the generated hook, or any other load failure returns the same concise denial without exposing a stack trace or the full project path.</li>
       <li>The generated hook resolves the user home in <code>HOME</code>, <code>USERPROFILE</code>, then <code>os.homedir()</code> order so POSIX, Git Bash, PowerShell, and cmd runners use the expected global install root.</li>
       <li>The hook contract follows <code>docs/spikes/claude-code-hook-mutation.md</code>: pass-through writes <code>{}</code>; denial writes a <code>hookSpecificOutput</code> object for <code>PreToolUse</code> with <code>permissionDecision: "deny"</code>.</li>
       <li>Missing or unreadable gstack is an intentional denial with exit code zero. Install instructions are present in stderr and <code>permissionDecisionReason</code>, so the runner does not report a hook execution error.</li>

test/team-mode.test.ts

@@ -13,6 +13,10 @@ function bashCommand(filePath: string): string {
 const SETTINGS_HOOK = bashCommand(path.join(ROOT, 'bin', 'gstack-settings-hook'));
 const SESSION_UPDATE = bashCommand(path.join(ROOT, 'bin', 'gstack-session-update'));
 const TEAM_INIT = bashCommand(path.join(ROOT, 'bin', 'gstack-team-init'));
+const MISSING_PROJECT_REASON =
+  'BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.';
+const HOOK_LOAD_REASON =
+  'BLOCKED: the required gstack hook could not be loaded. Verify project hook setup and retry.';
 
 function mkTmpDir(): string {
   return fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-team-test-'));
@@ -77,6 +81,22 @@ function runHookInPowerShell(
   };
 }
 
+function expectStructuredDeny(
+  result: { stdout: string; stderr: string; exitCode: number },
+  reason: string,
+): void {
+  expect(result.exitCode).toBe(0);
+  expect(result.stderr.trim()).toBe(reason);
+  expect(result.stderr).not.toContain('MODULE_NOT_FOUND');
+  expect(JSON.parse(result.stdout)).toEqual({
+    hookSpecificOutput: {
+      hookEventName: 'PreToolUse',
+      permissionDecision: 'deny',
+      permissionDecisionReason: reason,
+    },
+  });
+}
+
 describe('gstack-settings-hook', () => {
   let tmpDir: string;
   let settingsFile: string;
@@ -312,7 +332,7 @@ describe('gstack-team-init', () => {
     expect(entry.hooks).toHaveLength(1);
     expect(entry.hooks[0]).not.toHaveProperty('shell');
     expect(entry.hooks[0].command).toBe(
-      `node -e "const projectDir=process.env.CLAUDE_PROJECT_DIR;if(!projectDir){const reason='BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.';console.error(reason);console.log(JSON.stringify({hookSpecificOutput:{hookEventName:'PreToolUse',permissionDecision:'deny',permissionDecisionReason:reason}}))}else{require(require('node:path').join(projectDir, '.claude', 'hooks', 'check-gstack.cjs'))}"`,
+      `node -e "const deny=reason=>{console.error(reason);console.log(JSON.stringify({hookSpecificOutput:{hookEventName:'PreToolUse',permissionDecision:'deny',permissionDecisionReason:reason}}))};const projectDir=process.env.CLAUDE_PROJECT_DIR;if(!projectDir){deny('BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.')}else{try{require(require('node:path').join(projectDir, '.claude', 'hooks', 'check-gstack.cjs'))}catch{deny('BLOCKED: the required gstack hook could not be loaded. Verify project hook setup and retry.')}}"`,
     );
     expect(entry.hooks[0].command).not.toMatch(
       /\$CLAUDE_PROJECT_DIR|\$env:CLAUDE_PROJECT_DIR|%CLAUDE_PROJECT_DIR%/,
@@ -359,16 +379,7 @@ describe('gstack-team-init', () => {
       env: { CLAUDE_PROJECT_DIR: '' },
     });
 
-    expect(result.exitCode).toBe(0);
+    expectStructuredDeny(result, MISSING_PROJECT_REASON);
-    expect(result.stderr).toContain('BLOCKED: CLAUDE_PROJECT_DIR is unavailable');
-    expect(JSON.parse(result.stdout)).toEqual({
-      hookSpecificOutput: {
-        hookEventName: 'PreToolUse',
-        permissionDecision: 'deny',
-        permissionDecisionReason:
-          'BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.',
-      },
-    });
   });
 
   test('required: missing project env denies through PowerShell', () => {
@@ -385,16 +396,55 @@ describe('gstack-team-init', () => {
       env: { CLAUDE_PROJECT_DIR: '' },
     });
 
-    expect(result.exitCode).toBe(0);
+    expectStructuredDeny(result, MISSING_PROJECT_REASON);
-    expect(result.stderr).toContain('BLOCKED: CLAUDE_PROJECT_DIR is unavailable');
+  });
-    expect(JSON.parse(result.stdout)).toEqual({
+
-      hookSpecificOutput: {
+  test('required: stale project paths deny through the platform default shell', () => {
-        hookEventName: 'PreToolUse',
+    run(`${TEAM_INIT} required`, { cwd: tmpDir });
-        permissionDecision: 'deny',
+    const settings = JSON.parse(
-        permissionDecisionReason:
+      fs.readFileSync(path.join(tmpDir, '.claude', 'settings.json'), 'utf-8'),
-          'BLOCKED: CLAUDE_PROJECT_DIR is unavailable, so the required gstack hook cannot be loaded.',
+    );
-      },
+    const command = settings.hooks.PreToolUse[0].hooks[0].command;
-    });
+    const existingWithoutHook = path.join(tmpDir, 'existing-without-hook');
+    fs.mkdirSync(existingWithoutHook);
+
+    for (const projectDir of [
+      path.join(tmpDir, 'nonexistent-project'),
+      existingWithoutHook,
+    ]) {
+      const result = runHook(command, {
+        cwd: tmpDir,
+        env: { CLAUDE_PROJECT_DIR: projectDir },
+      });
+
+      expectStructuredDeny(result, HOOK_LOAD_REASON);
+      expect(result.stderr).not.toContain(projectDir);
+    }
+  });
+
+  test('required: stale project paths deny through PowerShell', () => {
+    if (process.platform !== 'win32') return;
+
+    run(`${TEAM_INIT} required`, { cwd: tmpDir });
+    const settings = JSON.parse(
+      fs.readFileSync(path.join(tmpDir, '.claude', 'settings.json'), 'utf-8'),
+    );
+    const command = settings.hooks.PreToolUse[0].hooks[0].command;
+    const existingWithoutHook = path.join(tmpDir, 'powershell-without-hook');
+    fs.mkdirSync(existingWithoutHook);
+
+    for (const projectDir of [
+      path.join(tmpDir, 'powershell-nonexistent'),
+      existingWithoutHook,
+    ]) {
+      const result = runHookInPowerShell(command, {
+        cwd: tmpDir,
+        env: { CLAUDE_PROJECT_DIR: projectDir },
+      });
+
+      expectStructuredDeny(result, HOOK_LOAD_REASON);
+      expect(result.stderr).not.toContain(projectDir);
+    }
   });
 
   test('required: hook runs in PowerShell with USERPROFILE home fallback', () => {