fix(conpty): use absolute cmd.exe path and normalize CWD slashes on Windows

When the daemon launches via a Windows Scheduled Task or Startup shortcut,
the restricted environment cannot resolve 'cmd.exe' through PATH, causing
CreateProcess to fail with 'File not found' and all sessions to enter the
error state with a runaway restart loop.

Fix: resolve cmd.exe via COMSPEC env var (always set by Windows), falling
back to %SystemRoot%\system32\cmd.exe. Also convert CWD backslashes to
forward slashes to avoid node-pty's internal path.resolve error 267 on
some versions.

Tests: 3 new cases for COMSPEC resolution, fallback path, and CWD slash
normalization.

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

Author: IM.codes

src/agent/conpty.ts

@@ -138,9 +138,18 @@ export async function conptyNewSession(
 
   const cols = opts?.cols ?? 200;
   const rows = opts?.rows ?? 50;
-  // Normalize cwd: forward slashes → backslashes on Windows (node-pty's CreateProcess requires native paths)
+  // Normalize cwd: backslashes → forward slashes. node-pty on some versions calls
+  // path.resolve() internally which can fail with error 267 (ERROR_DIRECTORY) when
+  // passed Windows-style backslash paths.
   const rawCwd = opts?.cwd ?? process.cwd();
-  const cwd = process.platform === 'win32' ? rawCwd.replace(/\//g, '\\') : rawCwd;
+  const cwd = process.platform === 'win32' ? rawCwd.replace(/\\/g, '/') : rawCwd;
+
+  // Use absolute path to cmd.exe — when the daemon is launched via a Windows
+  // Scheduled Task or Startup shortcut the environment may be restricted and
+  // CreateProcess cannot resolve a bare 'cmd.exe' through PATH.
+  const cmdExe = process.platform === 'win32'
+    ? (process.env.COMSPEC ?? `${process.env.SystemRoot ?? 'C:\\Windows'}\\system32\\cmd.exe`)
+    : 'cmd.exe';
 
   // Strip redundant cwdPrefix from the command string.
   // Drivers prepend `cd /d "C:\path" && ` or `cd "path" && ` for tmux/wezterm,
@@ -151,7 +160,7 @@ export async function conptyNewSession(
     cleanCmd = cleanCmd.slice(cdMatch[0].length);
   }
 
-  const pty = spawn('cmd.exe', ['/c', cleanCmd], {
+  const pty = spawn(cmdExe, ['/c', cleanCmd], {
     cwd,
     env: process.platform === 'win32'
       ? buildWindowsEnv(opts?.env)

test/agent/conpty.test.ts

@@ -171,6 +171,67 @@ describe('conpty backend', () => {
         cwd: expect.any(String),
       }));
     });
+
+    // ── Windows cmd.exe path resolution (regression for "File not found" on restricted launch) ──
+
+    it('uses COMSPEC absolute path on Windows instead of bare cmd.exe', async () => {
+      const origPlatform = process.platform;
+      const origComspec = process.env.COMSPEC;
+      Object.defineProperty(process, 'platform', { value: 'win32' });
+      process.env.COMSPEC = 'C:\\Windows\\system32\\cmd.exe';
+
+      try {
+        await conpty.conptyNewSession('comspec-test', 'claude --help', { cwd: 'C:/Users/admin' });
+        const spawnedExe = spawnMock.mock.calls.at(-1)?.[0] as string;
+        expect(spawnedExe).toBe('C:\\Windows\\system32\\cmd.exe');
+        // Must NOT use the bare name that fails in restricted environments
+        expect(spawnedExe).not.toBe('cmd.exe');
+      } finally {
+        Object.defineProperty(process, 'platform', { value: origPlatform });
+        if (origComspec === undefined) delete process.env.COMSPEC;
+        else process.env.COMSPEC = origComspec;
+      }
+    });
+
+    it('falls back to SystemRoot\\system32\\cmd.exe when COMSPEC is unset on Windows', async () => {
+      const origPlatform = process.platform;
+      const origComspec = process.env.COMSPEC;
+      const origSystemRoot = process.env.SystemRoot;
+      Object.defineProperty(process, 'platform', { value: 'win32' });
+      delete process.env.COMSPEC;
+      process.env.SystemRoot = 'C:\\Windows';
+
+      try {
+        await conpty.conptyNewSession('fallback-cmd', 'echo hi', { cwd: 'C:/tmp' });
+        const spawnedExe = spawnMock.mock.calls.at(-1)?.[0] as string;
+        expect(spawnedExe).toBe('C:\\Windows\\system32\\cmd.exe');
+      } finally {
+        Object.defineProperty(process, 'platform', { value: origPlatform });
+        if (origComspec === undefined) delete process.env.COMSPEC;
+        else process.env.COMSPEC = origComspec;
+        if (origSystemRoot === undefined) delete process.env.SystemRoot;
+        else process.env.SystemRoot = origSystemRoot;
+      }
+    });
+
+    it('normalizes backslash CWD to forward slashes on Windows (avoids node-pty error 267)', async () => {
+      const origPlatform = process.platform;
+      const origComspec = process.env.COMSPEC;
+      Object.defineProperty(process, 'platform', { value: 'win32' });
+      process.env.COMSPEC = 'C:\\Windows\\system32\\cmd.exe';
+
+      try {
+        await conpty.conptyNewSession('cwd-slash', 'claude', { cwd: 'C:\\Users\\admin\\project' });
+        const spawnedCwd = spawnMock.mock.calls.at(-1)?.[2]?.cwd as string;
+        // Backslashes must be converted to forward slashes
+        expect(spawnedCwd).toBe('C:/Users/admin/project');
+        expect(spawnedCwd).not.toContain('\\');
+      } finally {
+        Object.defineProperty(process, 'platform', { value: origPlatform });
+        if (origComspec === undefined) delete process.env.COMSPEC;
+        else process.env.COMSPEC = origComspec;
+      }
+    });
   });
 
   describe('conptySessionExists / conptyListSessions', () => {