fix(server): handle codex spawn errors to prevent daemon crash

Spawning a missing/broken codex binary emits an async "error" event on
the child process. Without a listener, Node.js crashes the daemon with
no log entry. Add child.on("error") in CodexAppServerClient and global
uncaughtException/unhandledRejection handlers that log via pino before
exiting.

packages/server/src/server/agent/providers/codex-app-server-agent.spawn-error.test.ts

@@ -0,0 +1,55 @@
+import { describe, expect, test } from "vitest";
+
+import { CodexAppServerAgentClient } from "./codex-app-server-agent.js";
+import { createTestLogger } from "../../../test-utils/test-logger.js";
+
+describe("CodexAppServerAgentClient spawn error handling", () => {
+  const logger = createTestLogger();
+
+  test("listModels rejects gracefully when the codex binary does not exist", async () => {
+    const client = new CodexAppServerAgentClient(logger, {
+      command: {
+        mode: "replace",
+        argv: ["/nonexistent/codex-binary-that-does-not-exist"],
+      },
+    });
+
+    const uncaughtErrors: unknown[] = [];
+    const onUncaught = (err: unknown) => {
+      uncaughtErrors.push(err);
+    };
+    process.on("uncaughtException", onUncaught);
+
+    try {
+      await expect(client.listModels()).rejects.toThrow();
+      // Drain microtask queue to ensure no deferred uncaught errors
+      await new Promise((resolve) => setTimeout(resolve, 100));
+      expect(uncaughtErrors).toHaveLength(0);
+    } finally {
+      process.off("uncaughtException", onUncaught);
+    }
+  });
+
+  test("listPersistedAgents rejects gracefully when the codex binary does not exist", async () => {
+    const client = new CodexAppServerAgentClient(logger, {
+      command: {
+        mode: "replace",
+        argv: ["/nonexistent/codex-binary-that-does-not-exist"],
+      },
+    });
+
+    const uncaughtErrors: unknown[] = [];
+    const onUncaught = (err: unknown) => {
+      uncaughtErrors.push(err);
+    };
+    process.on("uncaughtException", onUncaught);
+
+    try {
+      await expect(client.listPersistedAgents()).rejects.toThrow();
+      await new Promise((resolve) => setTimeout(resolve, 100));
+      expect(uncaughtErrors).toHaveLength(0);
+    } finally {
+      process.off("uncaughtException", onUncaught);
+    }
+  });
+});

packages/server/src/server/agent/providers/codex-app-server-agent.ts

@@ -511,6 +511,18 @@ class CodexAppServerClient {
       }
     });
 
+    child.on("error", (err) => {
+      this.logger.error({ err }, "Codex app-server child process error");
+      for (const pending of this.pending.values()) {
+        clearTimeout(pending.timer);
+        pending.reject(err);
+      }
+      this.pending.clear();
+      this.disposed = true;
+      this.resolveExitPromise?.();
+      this.resolveExitPromise = null;
+    });
+
     child.on("exit", (code, signal) => {
       const message =
         code === 0 && !signal

packages/server/src/server/index.ts

@@ -158,6 +158,16 @@ async function main() {
 
   process.on("SIGTERM", () => beginShutdown("SIGTERM"));
   process.on("SIGINT", () => beginShutdown("SIGINT"));
+
+  process.on("uncaughtException", (err) => {
+    logger.fatal({ err }, "Uncaught exception — daemon crashing");
+    process.exit(1);
+  });
+
+  process.on("unhandledRejection", (reason) => {
+    logger.fatal({ err: reason }, "Unhandled promise rejection — daemon crashing");
+    process.exit(1);
+  });
 }
 
 main().catch((err) => {