fix(agent-core): hide console window when running hooks on Windows (#1466)

Pass windowsHide:true when spawning the hook process so a visible console
no longer flashes and steals focus on Windows. The Bash-tool path was
already hardened (KAOS buildLocalSpawnOptions); the hook runner missed the
flag even though its own taskkill helper already set it.

Extract the spawn options into a pure builder and add a regression test
asserting windowsHide, mirroring the existing KAOS spawn-options test.

Relates to #1298.

.changeset/fix-hooks-windows-console-popup.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+Fix console windows flashing on Windows each time a hook runs.

packages/agent-core/src/session/hooks/runner.ts

@@ -1,4 +1,4 @@
-import { spawn, type ChildProcessWithoutNullStreams } from 'node:child_process';
+import { spawn, type ChildProcessWithoutNullStreams, type SpawnOptionsWithoutStdio } from 'node:child_process';
 
 import { z } from 'zod';
 
@@ -11,6 +11,24 @@ export interface RunHookOptions {
   readonly signal?: AbortSignal;
 }
 
+export function buildHookSpawnOptions(options: {
+  cwd?: string;
+  env?: Readonly<Record<string, string>>;
+}): SpawnOptionsWithoutStdio {
+  return {
+    shell: true,
+    cwd: options.cwd,
+    stdio: 'pipe',
+    detached: process.platform !== 'win32',
+    // Hide the console Windows would otherwise allocate for the shell child.
+    // Without `windowsHide:true`, each hook flashes a visible console window —
+    // the same regression the Bash tool path already guards against in KAOS
+    // (see `buildLocalSpawnOptions`). Unconditional: it is a no-op on POSIX.
+    windowsHide: true,
+    env: options.env ? { ...process.env, ...options.env } : undefined,
+  };
+}
+
 const DEFAULT_TIMEOUT_SECONDS = 30;
 const KILL_GRACE_MS = 100;
 const OptionalStringSchema = z.preprocess(
@@ -46,13 +64,7 @@ export async function runHook(
 ): Promise<HookResult> {
   let child: ChildProcessWithoutNullStreams;
   try {
-    child = spawn(command, {
-      shell: true,
-      cwd: options.cwd,
-      stdio: 'pipe',
-      detached: process.platform !== 'win32',
-      env: options.env ? { ...process.env, ...options.env } : undefined,
-    });
+    child = spawn(command, buildHookSpawnOptions({ cwd: options.cwd, env: options.env }));
   } catch (error) {
     return allowResult({ stderr: errorMessage(error) });
   }

packages/agent-core/test/hooks/runner.test.ts

@@ -1,5 +1,7 @@
 import { describe, expect, it } from 'vitest';
 
+import { buildHookSpawnOptions } from '../../src/session/hooks/runner';
+
 const RUNNER_MODULE = '../../src/session/hooks/runner' as string;
 
 interface HookResult {
@@ -98,3 +100,27 @@ describe('runHook process runner', () => {
     expect(result.stdout?.trim()).toBe('WriteFile');
   });
 });
+
+// Regression coverage for the "every hook flashes an empty console window on
+// Windows" bug. With `shell:true` and no `windowsHide`, Node allocates a
+// visible console for each hook child process on Windows. The fix is to pass
+// `windowsHide:true` (mirrors KAOS' `buildLocalSpawnOptions` and the runner's
+// own taskkill spawn). The flag is only observable on Windows, so we assert
+// the spawn options builder directly.
+describe('buildHookSpawnOptions (Windows console-window regression)', () => {
+  it('sets windowsHide:true so hooks do not flash a console on Windows', () => {
+    expect(buildHookSpawnOptions({}).windowsHide).toBe(true);
+  });
+
+  it('runs through the shell with stdio piped', () => {
+    const options = buildHookSpawnOptions({});
+    expect(options.shell).toBe(true);
+    expect(options.stdio).toBe('pipe');
+  });
+
+  it('merges hook env onto process.env and forwards cwd', () => {
+    const options = buildHookSpawnOptions({ cwd: '/repo', env: { FOO: 'bar' } });
+    expect(options.cwd).toBe('/repo');
+    expect(options.env).toMatchObject({ FOO: 'bar' });
+  });
+});