diff --git a/lib/parallel-execution.js b/lib/parallel-execution.js
index f4bc0fc..69c443c 100644
--- a/lib/parallel-execution.js
+++ b/lib/parallel-execution.js
@@ -18,19 +18,39 @@ import { fileURLToPath } from 'url';
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 
+/**
+ * Check if file is a native binary (Mach-O, ELF, etc.) vs JavaScript
+ * @param {string} filePath - Path to file
+ * @returns {boolean} true if native binary
+ */
+function isNativeBinary(filePath) {
+  try {
+    const magic = Buffer.alloc(4);
+    const fd = fs.openSync(filePath, 'r');
+    fs.readSync(fd, magic, 0, 4, 0);
+    fs.closeSync(fd);
+    const hex = magic.toString('hex');
+    return hex === 'cffaedfe' || hex === 'cafebabe' || hex === '7f454c46';
+  } catch {
+    return false;
+  }
+}
+
 /**
  * Detect if TeammateTool is available in current Claude Code installation
  * Auto-enables if possible
  */
 export function detectTeammateTool() {
   try {
-    // Find Claude Code installation
     const claudePath = findClaudeCodeBinary();
     if (!claudePath) {
       return { available: false, reason: 'Claude Code binary not found' };
     }
 
-    // Read CLI content
+    if (isNativeBinary(claudePath)) {
+      return { available: false, reason: 'Native binary detected - patching not supported', isNative: true };
+    }
+
     const cliContent = fs.readFileSync(claudePath, 'utf8');
 
     // Check for TeammateTool presence
@@ -130,6 +150,10 @@ export function enableTeammateTool() {
       throw new Error('Claude Code binary not found');
     }
 
+    if (isNativeBinary(claudePath)) {
+      return { success: false, error: 'Native binary detected - patching not supported. TeammateTool patching only works with npm-installed Claude Code.' };
+    }
+
     // Backup original
     const backupPath = `${claudePath}.backup-${Date.now()}`;
     fs.copyFileSync(claudePath, backupPath);
diff --git a/test/unit/parallel-execution.test.js b/test/unit/parallel-execution.test.js
index 667e696..7838779 100644
--- a/test/unit/parallel-execution.test.js
+++ b/test/unit/parallel-execution.test.js
@@ -39,6 +39,36 @@ describe('Parallel Execution', () => {
       expect(result.reason).toContain('binary not found');
     });
 
+    it('should detect native Mach-O binary and skip patching', () => {
+      execSync.mockImplementation((cmd) => {
+        if (cmd.includes('npm root -g')) {
+          return '/usr/local/lib/node_modules\n';
+        }
+        if (cmd.includes('which') || cmd.includes('where')) {
+          return '/usr/local/bin/claude\n';
+        }
+        throw new Error('Unexpected command');
+      });
+
+      fs.existsSync.mockReturnValue(true);
+      fs.realpathSync.mockImplementation((p) => p);
+      fs.openSync.mockReturnValue(42);
+      fs.readSync.mockImplementation((fd, buffer) => {
+        buffer[0] = 0xcf;
+        buffer[1] = 0xfa;
+        buffer[2] = 0xed;
+        buffer[3] = 0xfe;
+        return 4;
+      });
+      fs.closeSync.mockReturnValue(undefined);
+
+      const result = detectTeammateTool();
+
+      expect(result.available).toBe(false);
+      expect(result.reason).toContain('Native binary');
+      expect(result.isNative).toBe(true);
+    });
+
     it('should detect when TeammateTool code is not present (old version)', () => {
       // Mock execSync completely - no real calls
       execSync.mockImplementation((cmd) => {
@@ -127,6 +157,35 @@ describe('Parallel Execution', () => {
   });
 
   describe('enableTeammateTool', () => {
+    it('should reject native Mach-O binary', () => {
+      execSync.mockImplementation((cmd) => {
+        if (cmd.includes('npm root -g')) {
+          return '/usr/local/lib/node_modules\n';
+        }
+        if (cmd.includes('which') || cmd.includes('where')) {
+          return '/usr/local/bin/claude\n';
+        }
+        throw new Error('Unexpected command');
+      });
+
+      fs.existsSync.mockReturnValue(true);
+      fs.realpathSync.mockImplementation((p) => p);
+      fs.openSync.mockReturnValue(42);
+      fs.readSync.mockImplementation((fd, buffer) => {
+        buffer[0] = 0xcf;
+        buffer[1] = 0xfa;
+        buffer[2] = 0xed;
+        buffer[3] = 0xfe;
+        return 4;
+      });
+      fs.closeSync.mockReturnValue(undefined);
+
+      const result = enableTeammateTool();
+
+      expect(result.success).toBe(false);
+      expect(result.error).toContain('Native binary');
+    });
+
     it('should create backup before patching', () => {
       execSync.mockReturnValue('/usr/local/lib/node_modules');
       fs.existsSync.mockReturnValue(true);