fix(nodejs): handle stdio stdin errors

nodejs/src/client.ts

@@ -490,6 +490,13 @@ export class CopilotClient {
         }
     }
 
+    private logDebug(message: string): void {
+        const level = this.options.logLevel?.toLowerCase();
+        if (level === "debug" || level === "all") {
+            process.stderr.write(`[copilot-sdk] ${message}\n`);
+        }
+    }
+
     /**
      * Creates a new CopilotClient instance.
      *
@@ -2304,10 +2311,19 @@ export class CopilotClient {
             throw new Error("CLI process not started");
         }
 
-        // Add error handler to stdin to prevent unhandled rejections during forceStop
+        // Keep stdin pipe errors inside the normal JSON-RPC teardown path.
+        // Preserve the failure reason via the gated debug log rather than discarding it.
         this.cliProcess.stdin?.on("error", (err) => {
-            if (!this.forceStopping) {
-                throw err;
+            if (this.forceStopping) {
+                return;
+            }
+            this.state = "error";
+            const reason = err instanceof Error ? (err.stack ?? err.message) : String(err);
+            this.logDebug(`stdin pipe error: ${reason}`);
+            try {
+                this.connection?.dispose();
+            } catch {
+                // The connection may already be closing after the child process exited.
             }
         });
 

nodejs/test/client.test.ts

@@ -1,6 +1,7 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { EventEmitter } from "node:events";
 import { describe, expect, it, onTestFinished, vi } from "vitest";
+import { PassThrough } from "stream";
 import {
     approveAll,
     CopilotClient,
@@ -14,6 +15,22 @@ import { defaultJoinSessionPermissionHandler } from "../src/types.js";
 // This file is for unit tests. Where relevant, prefer to add e2e tests in e2e/*.test.ts instead
 
 describe("CopilotClient", () => {
+    it("disposes the stdio connection when child stdin emits an error", async () => {
+        const client = new CopilotClient();
+        onTestFinished(() => client.forceStop());
+
+        const stdin = new PassThrough();
+        const stdout = new PassThrough();
+        (client as any).cliProcess = { stdin, stdout };
+        await (client as any).connectToChildProcessViaStdio();
+
+        const dispose = vi.spyOn((client as any).connection, "dispose");
+
+        const boom = new Error("broken pipe");
+        expect(() => stdin.emit("error", boom)).not.toThrow();
+        expect(dispose).toHaveBeenCalledOnce();
+    });
+
     it("does not respond to v3 permission requests when handler returns no-result", async () => {
         const session = new CopilotSession("session-1", {} as any);
         session.registerPermissionHandler(() => ({ kind: "no-result" }));