diff --git a/browse/src/security.ts b/browse/src/security.ts
index a5d27ff2ad..2770096e6a 100644
--- a/browse/src/security.ts
+++ b/browse/src/security.ts
@@ -330,6 +330,33 @@ function findTelemetryBinary(): string | null {
   return null;
 }
 
+/**
+ * Build the [cmd, args] tuple for invoking a bash-script telemetry binary
+ * in a way that works on both POSIX and Windows.
+ *
+ * POSIX: returns [bin, args] unchanged — shebang gets honored by execve.
+ * Win32: wraps in bash explicitly. `gstack-telemetry-log` is a shell script
+ * (`#!/usr/bin/env bash`) and Windows `CreateProcess` can't dispatch on a
+ * shebang — it tries to load the file as a PE image, fails with ENOEXEC,
+ * and our 'error' handler silently swallows it. Most Windows dev boxes
+ * running gstack ship Git Bash, which puts bash.exe on PATH; if bash is
+ * missing, spawn() will still fire 'error' and the same swallow path kicks
+ * in. Either way, the local `attempts.jsonl` write in logAttempt() keeps
+ * the audit trail intact.
+ *
+ * Exported for testability — resolution is a pure function of (platform,
+ * bin, args) so we can assert on it without actually spawning.
+ */
+export function buildTelemetrySpawnCommand(
+  bin: string,
+  args: string[],
+): { cmd: string; cmdArgs: string[] } {
+  if (process.platform === 'win32') {
+    return { cmd: 'bash', cmdArgs: [bin, ...args] };
+  }
+  return { cmd: bin, cmdArgs: args };
+}
+
 /**
  * Fire-and-forget subprocess invocation of gstack-telemetry-log with the
  * attack_attempt event type. The binary handles tier gating internally
@@ -343,14 +370,15 @@ function reportAttemptTelemetry(record: AttemptRecord): void {
   const bin = findTelemetryBinary();
   if (!bin) return;
   try {
-    const child = spawn(bin, [
+    const { cmd, cmdArgs } = buildTelemetrySpawnCommand(bin, [
       '--event-type', 'attack_attempt',
       '--url-domain', record.urlDomain || '',
       '--payload-hash', record.payloadHash,
       '--confidence', String(record.confidence),
       '--layer', record.layer,
       '--verdict', record.verdict,
-    ], {
+    ]);
+    const child = spawn(cmd, cmdArgs, {
       stdio: 'ignore',
       detached: true,
     });
diff --git a/browse/test/security.test.ts b/browse/test/security.test.ts
index bf8064c039..d524147ee9 100644
--- a/browse/test/security.test.ts
+++ b/browse/test/security.test.ts
@@ -20,6 +20,7 @@ import {
   readSessionState,
   getStatus,
   extractDomain,
+  buildTelemetrySpawnCommand,
   type LayerSignal,
 } from '../src/security';
 
@@ -320,3 +321,32 @@ describe('extractDomain', () => {
     expect(extractDomain('')).toBe('');
   });
 });
+
+// ─── Telemetry spawn command (Windows bash wrapper) ──────────
+
+describe('buildTelemetrySpawnCommand', () => {
+  const bin = '/home/user/.claude/skills/gstack/bin/gstack-telemetry-log';
+  const args = ['--event-type', 'attack_attempt', '--confidence', '0.95'];
+
+  test('on POSIX, returns the binary path and args unchanged', () => {
+    if (process.platform === 'win32') return;
+    const out = buildTelemetrySpawnCommand(bin, args);
+    expect(out.cmd).toBe(bin);
+    expect(out.cmdArgs).toEqual(args);
+  });
+
+  test('on win32, wraps the call in bash with the script as first arg', () => {
+    if (process.platform !== 'win32') return;
+    const out = buildTelemetrySpawnCommand(bin, args);
+    expect(out.cmd).toBe('bash');
+    // Script path must come first so bash treats it as the file to execute,
+    // followed by the original telemetry flags as bash's positional args.
+    expect(out.cmdArgs).toEqual([bin, ...args]);
+  });
+
+  test('does not mutate the caller-supplied args array', () => {
+    const originalArgs = [...args];
+    buildTelemetrySpawnCommand(bin, args);
+    expect(args).toEqual(originalArgs);
+  });
+});