fix(cli): normalize instrumentation boot errors

Co-authored-by: diegosouzapw <8016841+diegosouzapw@users.noreply.github.com>

src/instrumentation.ts

@@ -34,9 +34,10 @@ export async function register(registerNodejsFn?: () => Promise<void>) {
       // up while every DB-touching route 500s forever with a permanently
       // empty app.log. This guarantees stdout/app.log is never silently
       // empty on a failed boot, regardless of platform or which step threw.
-      const message = err instanceof Error ? err.message : String(err);
+      const normalizedError = err instanceof Error ? err : new Error(String(err));
+      const message = normalizedError.message;
       console.error("[STARTUP] Fatal: instrumentation hook failed during boot:", message);
-      throw err;
+      throw normalizedError;
     }
   }
 }

tests/unit/instrumentation-hook-boot-fatal-log-10171.test.ts

@@ -78,7 +78,15 @@ test("#10171: a non-Error throw during instrumentation-hook boot is still logged
   };
 
   try {
-    await assert.rejects(() => register(fakeRegisterNodejs));
+    await assert.rejects(
+      () => register(fakeRegisterNodejs),
+      (err: unknown) => {
+        assert.ok(err instanceof Error, "register() must rethrow a real Error instance");
+        err.message += " (augmented by Next)";
+        assert.equal(err.message, "raw string boot failure (augmented by Next)");
+        return true;
+      }
+    );
 
     const fatalLine = captured.find(
       (line) => line.includes("[STARTUP] Fatal:") && line.includes("raw string boot failure")