fix(kaos): hide console window for spawned commands on Windows (#957)

- add windowsHide:true to spawn options so commands do not flash a console on Windows
- extract buildLocalSpawnOptions helper shared by exec and execWithEnv
- add regression coverage for the Windows console-window behavior

.changeset/fix-windows-console-flash.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+Fix commands flashing an empty console window on Windows.

packages/kaos/src/local.ts

@@ -1,4 +1,4 @@
-import type { ChildProcess } from 'node:child_process';
+import type { ChildProcess, SpawnOptions } from 'node:child_process';
 import { spawn } from 'node:child_process';
 import {
   appendFile,
@@ -37,6 +37,20 @@ function cycleKey(s: { dev: number; ino: number }): string | null {
   return `${String(s.dev)}:${String(s.ino)}`;
 }
 
+export function buildLocalSpawnOptions(
+  isWindows: boolean,
+  cwd: string,
+  env: Record<string, string> | undefined,
+): SpawnOptions {
+  return {
+    cwd,
+    env,
+    stdio: ['pipe', 'pipe', 'pipe'],
+    detached: !isWindows,
+    windowsHide: true,
+  };
+}
+
 class LocalProcess implements KaosProcess {
   readonly stdin: Writable;
   readonly stdout: Readable;
@@ -544,16 +558,11 @@ export class LocalKaos implements Kaos {
       throw new Error('LocalKaos.exec(): at least one argument (the command to run) is required.');
     }
     const restArgs = args.slice(1);
-    const child = spawn(command, restArgs, {
-      cwd: this._cwd,
-      stdio: ['pipe', 'pipe', 'pipe'],
-      // POSIX `detached:true` makes the child a process-group leader so
-      // `LocalProcess.kill()` can signal the entire tree. No-op on Windows
-      // (`taskkill /T` handles the tree there). We do not call `child.unref()`
-      // because the parent still waits on the child's exit through `wait()`.
-      detached: !isWindows,
-      env: this._buildExecEnv(),
-    });
+    const child = spawn(
+      command,
+      restArgs,
+      buildLocalSpawnOptions(isWindows, this._cwd, this._buildExecEnv()),
+    );
     await waitForSpawn(child);
     return new LocalProcess(child);
   }
@@ -566,12 +575,11 @@ export class LocalKaos implements Kaos {
       );
     }
     const restArgs = args.slice(1);
-    const child = spawn(command, restArgs, {
-      cwd: this._cwd,
-      stdio: ['pipe', 'pipe', 'pipe'],
-      detached: !isWindows,
-      env: this._buildExecEnv(env),
-    });
+    const child = spawn(
+      command,
+      restArgs,
+      buildLocalSpawnOptions(isWindows, this._cwd, this._buildExecEnv(env)),
+    );
     await waitForSpawn(child);
     return new LocalProcess(child);
   }

packages/kaos/test/spawn-options.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest';
+
+import { buildLocalSpawnOptions } from '#/local';
+
+// Regression coverage for the "every command pops an empty console window on
+// Windows" bug. `child_process.spawn` defaults `windowsHide` to `false`; on
+// Windows that makes Node allocate a *visible* console for each child process
+// the agent spawns through `BashTool` → `LocalKaos.exec`/`execWithEnv`. The
+// fix is to pass `windowsHide: true`. The flag is only observable on Windows,
+// so we assert the spawn options builder directly.
+
+describe('buildLocalSpawnOptions (Windows console-window regression)', () => {
+  it('sets windowsHide:true on Windows so commands do not flash a console', () => {
+    const options = buildLocalSpawnOptions(true, 'C:\\repo', undefined);
+    expect(options.windowsHide).toBe(true);
+  });
+
+  it('sets windowsHide:true on POSIX too (it is ignored there, kept unconditional)', () => {
+    const options = buildLocalSpawnOptions(false, '/repo', undefined);
+    expect(options.windowsHide).toBe(true);
+  });
+
+  it('keeps detached platform-conditional (POSIX tree-kill vs Windows taskkill /T)', () => {
+    expect(buildLocalSpawnOptions(true, 'C:\\repo', undefined).detached).toBe(false);
+    expect(buildLocalSpawnOptions(false, '/repo', undefined).detached).toBe(true);
+  });
+
+  it('pipes stdin/stdout/stderr and forwards cwd + env', () => {
+    const env = { FOO: 'bar' };
+    const options = buildLocalSpawnOptions(false, '/repo', env);
+    expect(options.stdio).toEqual(['pipe', 'pipe', 'pipe']);
+    expect(options.cwd).toBe('/repo');
+    expect(options.env).toBe(env);
+  });
+});