diff --git a/src/main/nodecg/process-manager.ts b/src/main/nodecg/process-manager.ts
index b463fbe..6c9db98 100644
--- a/src/main/nodecg/process-manager.ts
+++ b/src/main/nodecg/process-manager.ts
@@ -49,6 +49,8 @@ export function createNodecgProcessManager({
 
   let nodecgProcess: ChildProcess | null = null;
   let stopNodecgPromise: Promise<void> | null = null;
+  let lastExit: { code: number | null; signal: NodeJS.Signals | null } | null = null;
+  let lastStderrLine: string | null = null;
 
   const startNodecgProcess = async (): Promise<ChildProcess> => {
     validateNodecgInstall(
@@ -85,16 +87,21 @@ export function createNodecgProcessManager({
     });
 
     child.stderr?.on("data", (chunk) => {
-      resolvedDeps.stderrWrite(String(chunk));
+      const line = String(chunk);
+      lastStderrLine = line.trim().length > 0 ? line.trim() : lastStderrLine;
+      resolvedDeps.stderrWrite(line);
     });
 
     log(`NodeCG started with pid=${child.pid} using ${NODE_RUNTIME_NAME}`);
 
     child.on("exit", (code, signal) => {
       log(`NodeCG exited code=${code} signal=${signal ?? "none"}`);
+      lastExit = { code, signal };
       nodecgProcess = null;
     });
 
+    lastExit = null;
+    lastStderrLine = null;
     nodecgProcess = child;
     return child;
   };
@@ -102,7 +109,19 @@ export function createNodecgProcessManager({
   const waitForNodecgReady = async (startTime: number): Promise<void> => {
     while (Date.now() - startTime < appConfig.startupTimeoutMs) {
       if (!nodecgProcess) {
-        throw new Error("NodeCG terminó antes de estar listo.");
+        const exitDetails = lastExit
+          ? `Última salida registrada: code=${lastExit.code ?? "null"}, signal=${lastExit.signal ?? "none"}.`
+          : "No se registró código de salida del proceso NodeCG.";
+        const stderrDetails = lastStderrLine ? `Último stderr: ${lastStderrLine}` : "Sin salida stderr capturada.";
+        throw new Error(
+          [
+            "NodeCG terminó antes de estar listo.",
+            exitDetails,
+            stderrDetails,
+            `Ruta NodeCG: ${nodecgRootPath}`,
+            "Revisa que lib/nodecg tenga dependencias instaladas y que el bundle exista.",
+          ].join("\n"),
+        );
       }
 
       try {
diff --git a/src/tests/process-manager.test.ts b/src/tests/process-manager.test.ts
index 013d802..579b5fb 100644
--- a/src/tests/process-manager.test.ts
+++ b/src/tests/process-manager.test.ts
@@ -236,3 +236,46 @@ test("startNodeCG falla si el puerto ya está ocupado", async () => {
     await manager.startNodecgProcess();
   }, /ya está en uso/);
 });
+
+test("waitForNodeCGReady expone diagnóstico cuando NodeCG sale antes de readiness", async () => {
+  const child = new MockChildProcess(4242);
+  const manager = createNodecgProcessManager({
+    isDev: true,
+    nodecgRootPath: "/fake/nodecg",
+    nodecgBaseUrl: "http://127.0.0.1:9090",
+    appConfig: getBaseConfig(),
+    log: () => undefined,
+    deps: {
+      pathExists: () => true,
+      platform: "linux",
+      spawnProcess: () => child as unknown as import("node:child_process").ChildProcess,
+      fetchUrl: async () => {
+        child.emit("exit", 1, null);
+        throw new Error("still starting");
+      },
+      setTimer: (handler) => {
+        handler();
+        return 0;
+      },
+      stdoutWrite: () => undefined,
+      stderrWrite: () => undefined,
+      probePortAvailable: async () => true,
+      hasReadWriteAccess: () => true,
+    },
+  });
+
+  await manager.startNodecgProcess();
+
+  await assert.rejects(
+    async () => {
+      await manager.waitForNodecgReady(Date.now());
+    },
+    (error: unknown) => {
+      assert.ok(error instanceof Error);
+      assert.match(error.message, /NodeCG terminó antes de estar listo/);
+      assert.match(error.message, /Última salida registrada/);
+      assert.match(error.message, /Ruta NodeCG: \/fake\/nodecg/);
+      return true;
+    },
+  );
+});