diff --git a/bin/agent-browser.js b/bin/agent-browser.js
index ee97cf3..4933947 100755
--- a/bin/agent-browser.js
+++ b/bin/agent-browser.js
@@ -9,7 +9,7 @@
  */
 
 import { spawn } from 'child_process';
-import { existsSync } from 'fs';
+import { existsSync, accessSync, chmodSync, constants } from 'fs';
 import { dirname, join } from 'path';
 import { fileURLToPath } from 'url';
 import { platform, arch } from 'os';
@@ -73,6 +73,23 @@ function main() {
     process.exit(1);
   }
 
+  // Ensure binary is executable (fixes EACCES on macOS/Linux when postinstall didn't run,
+  // e.g., when using bun which blocks lifecycle scripts by default)
+  if (platform() !== 'win32') {
+    try {
+      accessSync(binaryPath, constants.X_OK);
+    } catch {
+      // Binary exists but isn't executable - fix it
+      try {
+        chmodSync(binaryPath, 0o755);
+      } catch (chmodErr) {
+        console.error(`Error: Cannot make binary executable: ${chmodErr.message}`);
+        console.error('Try running: chmod +x ' + binaryPath);
+        process.exit(1);
+      }
+    }
+  }
+
   // Spawn the native binary with inherited stdio
   const child = spawn(binaryPath, process.argv.slice(2), {
     stdio: 'inherit',