diff --git a/packages/cli/src/commands/preview.test.ts b/packages/cli/src/commands/preview.test.ts
index 4d6c7528fd..e90dade70f 100644
--- a/packages/cli/src/commands/preview.test.ts
+++ b/packages/cli/src/commands/preview.test.ts
@@ -9,6 +9,7 @@ import {
   foregroundPreviewReadyPayload,
   handlePreviewKillAll,
   handlePreviewList,
+  openStudioBrowser,
   previewLaunchMode,
   previewLaunchModeError,
   previewPortError,
@@ -21,12 +22,19 @@ import {
   studioSummaryUrls,
   waitForStudioChildClose,
 } from "./preview.js";
+import { openBrowser } from "../utils/openBrowser.js";
+
+vi.mock("../utils/openBrowser.js", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("../utils/openBrowser.js")>()),
+  openBrowser: vi.fn(),
+}));
 
 const tempDirs: string[] = [];
 
 afterEach(() => {
   for (const dir of tempDirs.splice(0)) rmSync(dir, { recursive: true, force: true });
   vi.restoreAllMocks();
+  vi.unstubAllGlobals();
   process.exitCode = undefined;
 });
 
@@ -493,3 +501,30 @@ describe("waitForStudioChildClose", () => {
     expect(signalTarget.off).toHaveBeenCalledTimes(2);
   });
 });
+
+describe("openStudioBrowser", () => {
+  it("warms the preview route before the browser launch, and also under --no-open", () => {
+    const order: string[] = [];
+    vi.stubGlobal(
+      "fetch",
+      vi.fn((url: string) => {
+        order.push(`fetch ${url}`);
+        return Promise.resolve({ body: null } as Response);
+      }),
+    );
+    vi.mocked(openBrowser)
+      .mockReset()
+      .mockImplementation(() => {
+        order.push("openBrowser");
+      });
+
+    openStudioBrowser("http://127.0.0.1:4567", "Launch #1", "/tmp/launch");
+    openStudioBrowser("http://127.0.0.1:4567", "demo", "/tmp/demo", { noOpen: true });
+
+    expect(order).toEqual([
+      "fetch http://127.0.0.1:4567/api/projects/Launch%20%231/preview",
+      "openBrowser",
+      "fetch http://127.0.0.1:4567/api/projects/demo/preview",
+    ]);
+  });
+});
diff --git a/packages/cli/src/commands/preview.ts b/packages/cli/src/commands/preview.ts
index 5203d7eead..ddd092786e 100644
--- a/packages/cli/src/commands/preview.ts
+++ b/packages/cli/src/commands/preview.ts
@@ -1258,12 +1258,20 @@ function previewLifecycleSession(options: {
   };
 }
 
-function openStudioBrowser(
+export function openStudioBrowser(
   url: string,
   projectName: string,
   projectDir: string,
   options?: BrowserLaunchOptions,
 ): void {
+  // Pay the route's cold compiler import here so the browser's first request
+  // doesn't. The shader query params the player appends aren't in the route's
+  // ETag; the timeout stops an unsettled fetch holding the CLI's event loop.
+  void fetch(`${url}/api/projects/${encodeURIComponent(projectName)}/preview`, {
+    signal: AbortSignal.timeout(10_000),
+  })
+    .then((res) => res.body?.cancel())
+    .catch(() => {});
   if (options?.noOpen) return;
   openBrowser(studioDeepLink(url, projectName, projectDir), {
     browserPath: options?.browserPath,