diff --git a/src/cli/browser-cli-extension.test.ts b/src/cli/browser-cli-extension.test.ts
index 89f905d469a..19b994d56c9 100644
--- a/src/cli/browser-cli-extension.test.ts
+++ b/src/cli/browser-cli-extension.test.ts
@@ -65,11 +65,16 @@ describe("browser extension install", () => {
 
     try {
       const { installChromeExtension } = await import("./browser-cli-extension.js");
-      const sourceDir = path.resolve(process.cwd(), "assets/chrome-extension");
+      // Keep this test hermetic + fast: use a tiny fixture instead of copying the
+      // full repo assets tree.
+      const sourceDir = path.join(tmp, "source-ext");
+      writeManifest(sourceDir);
+      fs.writeFileSync(path.join(sourceDir, "test.txt"), "ok");
       const result = await installChromeExtension({ stateDir: tmp, sourceDir });
 
       expect(result.path).toBe(path.join(tmp, "browser", "chrome-extension"));
       expect(fs.existsSync(path.join(result.path, "manifest.json"))).toBe(true);
+      expect(fs.existsSync(path.join(result.path, "test.txt"))).toBe(true);
       expect(result.path.includes("node_modules")).toBe(false);
     } finally {
       fs.rmSync(tmp, { recursive: true, force: true });