diff --git a/plugin/scripts/bun-runner.js b/plugin/scripts/bun-runner.js
index 80e8f44f..414fc332 100644
--- a/plugin/scripts/bun-runner.js
+++ b/plugin/scripts/bun-runner.js
@@ -70,16 +70,56 @@ if (!bunPath) {
   process.exit(1);
 }
 
+// Fix #646: Buffer stdin in Node.js before passing to Bun.
+// On Linux, Bun's libuv calls fstat() on inherited pipe fds and crashes with
+// EINVAL when the pipe comes from Claude Code's hook system. By reading stdin
+// in Node.js first and writing it to a fresh pipe, Bun receives a normal pipe
+// that it can fstat() without errors.
+function collectStdin() {
+  return new Promise((resolve) => {
+    // If stdin is a TTY (interactive), there's no piped data to collect
+    if (process.stdin.isTTY) {
+      resolve(null);
+      return;
+    }
+
+    const chunks = [];
+    process.stdin.on('data', (chunk) => chunks.push(chunk));
+    process.stdin.on('end', () => {
+      resolve(chunks.length > 0 ? Buffer.concat(chunks) : null);
+    });
+    process.stdin.on('error', () => {
+      // stdin may not be readable (e.g. already closed), treat as no data
+      resolve(null);
+    });
+
+    // Safety: if no data arrives within 5s, proceed without stdin
+    setTimeout(() => {
+      process.stdin.removeAllListeners();
+      process.stdin.pause();
+      resolve(chunks.length > 0 ? Buffer.concat(chunks) : null);
+    }, 5000);
+  });
+}
+
+const stdinData = await collectStdin();
+
 // Spawn Bun with the provided script and args
 // Use spawn (not spawnSync) to properly handle stdio
 // Note: Don't use shell mode on Windows - it breaks paths with spaces in usernames
 // Use windowsHide to prevent a visible console window from spawning on Windows
 const child = spawn(bunPath, args, {
-  stdio: 'inherit',
+  stdio: [stdinData ? 'pipe' : 'ignore', 'inherit', 'inherit'],
   windowsHide: true,
   env: process.env
 });
 
+// Write buffered stdin to child's pipe, then close it so the child sees EOF
+if (stdinData && child.stdin) {
+  child.stdin.write(stdinData);
+  child.stdin.end();
+}
+
 child.on('error', (err) => {
   console.error(`Failed to start Bun: ${err.message}`);
   process.exit(1);