diff --git a/src/lib/agent-sdk-assets.spec.ts b/src/lib/agent-sdk-assets.spec.ts
index beb2c8be..e6004462 100644
--- a/src/lib/agent-sdk-assets.spec.ts
+++ b/src/lib/agent-sdk-assets.spec.ts
@@ -2,7 +2,7 @@ import { existsSync } from 'node:fs';
 import { gzipSync } from 'node:zlib';
 import { afterEach, describe, expect, it, vi } from 'vitest';
 import { AGENT_SDK_TARGET, AGENT_SDK_VERSION } from '../generated/agent-sdk-manifest.js';
-import { downloadTarball, ensureClaudeCodeExecutable, extractTarEntry } from './agent-sdk-assets.js';
+import { downloadTarball, ensureClaudeCodeExecutable, extractTarEntry, isBunVirtualFsUrl } from './agent-sdk-assets.js';
 
 function tarHeader(name: string, size: number): Buffer {
   const header = Buffer.alloc(512);
@@ -27,6 +27,25 @@ function makeTarball(entries: Array<[string, Buffer]>): Buffer {
   return gzipSync(Buffer.concat(parts));
 }
 
+describe('isBunVirtualFsUrl', () => {
+  it('detects the POSIX compiled-binary virtual filesystem', () => {
+    expect(isBunVirtualFsUrl('file:///$bunfs/root/workos')).toBe(true);
+  });
+
+  it('detects the Windows virtual filesystem with the tilde percent-encoded', () => {
+    expect(isBunVirtualFsUrl('file:///B:/%7EBUN/root/workos-windows-x64.exe')).toBe(true);
+  });
+
+  it('detects a raw Windows virtual path', () => {
+    expect(isBunVirtualFsUrl('B:\\~BUN\\root\\workos-windows-x64.exe')).toBe(true);
+  });
+
+  it('rejects source-mode module URLs', () => {
+    expect(isBunVirtualFsUrl(import.meta.url)).toBe(false);
+    expect(isBunVirtualFsUrl('file:///home/dev/cli/src/lib/agent-sdk-assets.ts')).toBe(false);
+  });
+});
+
 describe('ensureClaudeCodeExecutable', () => {
   it('resolves the current platform executable from node_modules in source mode', async () => {
     expect(AGENT_SDK_TARGET).toBe(`${process.platform}-${process.arch}`);
diff --git a/src/lib/agent-sdk-assets.ts b/src/lib/agent-sdk-assets.ts
index 465f0e27..29a5eccf 100644
--- a/src/lib/agent-sdk-assets.ts
+++ b/src/lib/agent-sdk-assets.ts
@@ -54,9 +54,19 @@ function runtimeTarget(): string {
   return `${process.platform}-${process.arch}${isMuslRuntime() ? '-musl' : ''}`;
 }
 
+/**
+ * Whether a module URL points into a Bun compiled binary's virtual filesystem:
+ * `/$bunfs/` on POSIX, `B:\~BUN\` on Windows — which import.meta.url surfaces
+ * with the tilde percent-encoded (`file:///B:/%7EBUN/root/…`). Exported for
+ * tests.
+ */
+export function isBunVirtualFsUrl(url: string): boolean {
+  return url.includes('$bunfs') || url.includes('~BUN') || url.includes('%7EBUN');
+}
+
 /** Running from a compiled binary: the module graph lives in Bun's virtual filesystem. */
 function isCompiledBinary(): boolean {
-  return import.meta.url.includes('$bunfs') || import.meta.url.includes('~BUN');
+  return isBunVirtualFsUrl(import.meta.url);
 }
 
 function agentSdkCacheRoot(): string {