diff --git a/test/e2e/runTest.ts b/test/e2e/runTest.ts
index 543c383..383f9af 100644
--- a/test/e2e/runTest.ts
+++ b/test/e2e/runTest.ts
@@ -13,11 +13,20 @@ async function main(): Promise<void> {
   const workspace = fs.mkdtempSync(path.join(os.tmpdir(), "cowriting-e2e-"));
   fs.cpSync(fixture, workspace, { recursive: true });
 
+  // VS Code derives its IPC socket path from --user-data-dir. The default
+  // (`<projectRoot>/.vscode-test/user-data`) plus `/<version>-main.sock` can blow
+  // past macOS's ~103-char UNIX-socket limit (`listen EINVAL`) when the project
+  // lives at a long path (e.g. a git worktree). Pin the user-data dir to a SHORT
+  // root under /tmp so the socket path stays well under the limit. (os.tmpdir() on
+  // macOS is itself a long /var/folders/… path, so we use /tmp directly.)
+  const userDataRoot = process.platform === "win32" ? os.tmpdir() : "/tmp";
+  const userDataDir = fs.mkdtempSync(path.join(userDataRoot, "cwud-"));
+
   try {
     await runTests({
       extensionDevelopmentPath,
       extensionTestsPath,
-      launchArgs: [workspace, "--disable-extensions"],
+      launchArgs: [workspace, "--disable-extensions", "--user-data-dir", userDataDir],
       extensionTestsEnv: { E2E_WORKSPACE: workspace },
     });
 
@@ -26,10 +35,11 @@ async function main(): Promise<void> {
     await runTests({
       extensionDevelopmentPath,
       extensionTestsPath: path.resolve(__dirname, "./suite-no-workspace/index"),
-      launchArgs: ["--disable-extensions"],
+      launchArgs: ["--disable-extensions", "--user-data-dir", userDataDir],
     });
   } finally {
     fs.rmSync(workspace, { recursive: true, force: true });
+    fs.rmSync(userDataDir, { recursive: true, force: true });
   }
 }