fix(core): the runtime failure is recorded even when the thrown value cannot be printed

Author: miguel-heygen

packages/core/src/runtime/diagnostics.ts

@@ -31,9 +31,15 @@ import { getDebugSurface } from "./globals.js";
 
 /** The named error readiness waits fail with once start-up or a timeline post throws; it stays set. */
 export function recordStartupError(error: unknown): void {
-  const detail = error instanceof Error ? `${error.name}: ${error.message}` : String(error);
+  let detail = "unknown error";
+  try {
+    detail = error instanceof Error ? `${error.name}: ${error.message}` : String(error);
+  } catch (err) {
+    swallow("runtime.startupError", err);
+  }
   (window as Window & { __hfStartupError?: string }).__hfStartupError =
-    `HyperFrames runtime failed: ${detail}. Fix the composition script or window.__timelines entry that threw.`;
+    `HyperFrames runtime failed: ${detail}. Check the composition's scripts and window.__timelines ` +
+    `entries; if they look right, report this as a HyperFrames bug.`;
 }
 
 export function swallow(label: string, error?: unknown): void {

packages/core/src/runtime/entry.startupFailure.test.ts

@@ -42,7 +42,20 @@ describe("runtime start-up failure", () => {
 
     await expect(evaluateRuntime()).rejects.toThrow("boom");
     expect(window.__hfStartupError).toContain("HyperFrames runtime failed: TypeError: boom");
-    expect(window.__hfStartupError).toContain("Fix the composition script or window.__timelines entry");
+    expect(window.__hfStartupError).toContain("Check the composition's scripts and window.__timelines");
+  });
+
+  it("still records the failure when the thrown value cannot be printed", async () => {
+    const thrown: unknown = Object.create(null);
+    vi.doMock("./init", async (importOriginal) => ({
+      ...(await importOriginal<typeof import("./init")>()),
+      initSandboxRuntimeModular: () => {
+        throw thrown;
+      },
+    }));
+
+    await expect(evaluateRuntime()).rejects.toBe(thrown);
+    expect(window.__hfStartupError).toContain("HyperFrames runtime failed: unknown error.");
   });
 
   it("is not marked render-ready when posting the timeline throws", async () => {