diff --git a/plugins/draw/package.json b/plugins/draw/package.json
index 7fe9079..67ebcfe 100644
--- a/plugins/draw/package.json
+++ b/plugins/draw/package.json
@@ -11,7 +11,8 @@
     "build": "tsc && cd ui && npm install && npm run build",
     "build:server": "tsc",
     "build:ui": "cd ui && npm install && npm run build",
-    "dev": "tsc --watch"
+    "dev": "tsc --watch",
+    "test": "npm run build:server && node --test test/**/*.test.mjs"
   },
   "dependencies": {
     "nanoid": "^5.0.0",
diff --git a/plugins/draw/src/server/tunnel.ts b/plugins/draw/src/server/tunnel.ts
index f5f964a..8290905 100644
--- a/plugins/draw/src/server/tunnel.ts
+++ b/plugins/draw/src/server/tunnel.ts
@@ -1,4 +1,6 @@
-import { spawn, execSync, type ChildProcess } from 'node:child_process';
+import { spawn, type ChildProcess } from 'node:child_process';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
 
 export interface TunnelResult {
   url: string;
@@ -9,8 +11,30 @@ export interface TunnelResult {
 type TunnelBackend = 'cloudflared' | 'ngrok' | 'bore';
 
 function commandExists(cmd: string): boolean {
+  if (!cmd) {
+    return false;
+  }
+
+  if (cmd.includes(path.sep)) {
+    return isExecutable(cmd);
+  }
+
+  for (const entry of (process.env.PATH || '').split(path.delimiter)) {
+    if (!entry) {
+      continue;
+    }
+
+    if (isExecutable(path.join(entry, cmd))) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+function isExecutable(filePath: string): boolean {
   try {
-    execSync(`command -v ${cmd}`, { stdio: 'ignore' });
+    fs.accessSync(filePath, fs.constants.X_OK);
     return true;
   } catch {
     return false;
diff --git a/plugins/draw/test/tunnel.test.mjs b/plugins/draw/test/tunnel.test.mjs
new file mode 100644
index 0000000..dc559bd
--- /dev/null
+++ b/plugins/draw/test/tunnel.test.mjs
@@ -0,0 +1,25 @@
+import assert from 'node:assert/strict';
+import * as fs from 'node:fs';
+import * as os from 'node:os';
+import * as path from 'node:path';
+import test from 'node:test';
+
+import { detectTunnel } from '../dist/server/tunnel.js';
+
+test('detectTunnel checks PATH without invoking a shell', () => {
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'crabcode-draw-'));
+  const originalPath = process.env.PATH;
+  const ngrokPath = path.join(tempDir, 'ngrok');
+
+  try {
+    fs.writeFileSync(ngrokPath, '#!/bin/sh\nexit 0\n', { mode: 0o755 });
+    process.env.PATH = tempDir;
+
+    assert.equal(detectTunnel('ngrok'), 'ngrok');
+    assert.equal(detectTunnel('cloudflared'), null);
+    assert.equal(detectTunnel('ngrok; echo nope'), null);
+  } finally {
+    process.env.PATH = originalPath;
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  }
+});