fix(v2): detect MSYS2 bash from native toolchain git exec paths

.changeset/v2-msys2-bash-detection.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+Fix bash auto-detection on Windows in the experimental v2 engine when git comes from a native MSYS2 toolchain (ucrt64/clang64/clangarm64).

packages/agent-core-v2/src/_base/execEnv/environmentProbe.ts

@@ -7,10 +7,10 @@
  * same suite runs identically on any host OS. `probeHostEnvironmentFromNode()`
  * bundles the Node defaults for production callers and memoises the promise.
  *
- * On Windows the probe expects Git Bash (the canonical POSIX shell that ships
- * with Git for Windows). If it cannot be located the function throws a plain
- * `Error` with the checked paths in the message; the App-scope host-environment
- * service catches that at first resolution. Set `KIMI_SHELL_PATH` to override.
+ * On Windows the probe expects bash from Git for Windows or MSYS2. If it
+ * cannot be located the function throws a plain `Error` with the checked paths
+ * in the message; the App-scope host-environment service catches that at first
+ * resolution. Set `KIMI_SHELL_PATH` to override.
  *
  * Vendored from `@moonshot-ai/kaos` `environment.ts` — kept as a pure helper
  * with no DI dependencies.
@@ -57,6 +57,14 @@ export interface HostEnvironmentProbeDeps {
 
 const GIT_EXEC_PATH_TIMEOUT_MS = 5_000;
 
+const MINGW_PREFIX_SET: ReadonlySet<string> = new Set([
+  'mingw32',
+  'mingw64',
+  'ucrt64',
+  'clang64',
+  'clangarm64',
+]);
+
 function resolveOsKind(platform: string): OsKind {
   switch (platform) {
     case 'darwin':
@@ -222,7 +230,7 @@ function gitBashCandidatesFromGitExecPath(execPath: string): readonly string[] {
   const parts = normalized.split('\\');
   for (let i = parts.length - 1; i >= 0; i -= 1) {
     const segment = parts[i]?.toLowerCase();
-    if (segment === 'mingw32' || segment === 'mingw64') {
+    if (segment !== undefined && MINGW_PREFIX_SET.has(segment)) {
       const root = parts.slice(0, i).join('\\');
       if (root.length > 0) {
         return gitBashCandidatesFromGitRoot(root);

packages/agent-core-v2/test/_base/execEnv/environmentProbe.test.ts

@@ -0,0 +1,100 @@
+/**
+ * Host environment probe — MSYS2 bash detection.
+ *
+ * Pins the Windows shell probe against native MSYS2 toolchains: a git whose
+ * `git --exec-path` reports an `ucrt64` / `clang64` / `clangarm64` prefix
+ * (e.g. `C:/msys64/ucrt64/libexec/git-core`) must walk back to the MSYS2 root
+ * and resolve the shared bash at `usr\bin\bash.exe`, instead of failing to
+ * detect any shell.
+ *
+ * All tests expect `probeHostEnvironment()` to be a pure function of injected
+ * platform probes (no ambient state) so the same suite runs identically on
+ * macOS/Linux/Windows CI runners.
+ *
+ * Ported from `packages/kaos/test/environment.test.ts` (the MSYS2 cases added
+ * by the bash-detection fix); the v1 file carries the full POSIX / Git for
+ * Windows / Scoop shim matrix, which the vendored probe shares verbatim.
+ */
+
+import { describe, expect, it } from 'vitest';
+
+import {
+  probeHostEnvironment,
+  type HostEnvironmentProbeDeps,
+} from '#/_base/execEnv/environmentProbe';
+
+interface StubOpts {
+  readonly platform: string;
+  readonly env?: Record<string, string | undefined>;
+  readonly existingPaths?: readonly string[];
+  readonly execFileResults?: Readonly<Record<string, string>>;
+}
+
+/** Build a stub deps bag mimicking Node's `os` + `process` surface. */
+function stubDeps(opts: StubOpts): HostEnvironmentProbeDeps {
+  const existing = new Set(opts.existingPaths ?? []);
+  return {
+    platform: opts.platform,
+    arch: 'x86_64',
+    release: '1.2.3',
+    homeDir: 'C:\\Users\\me',
+    env: opts.env ?? {},
+    isFile: async (path: string) => existing.has(path),
+    execFileText: async (file: string, args: readonly string[]) =>
+      opts.execFileResults?.[execFileKey(file, args)],
+  };
+}
+
+function execFileKey(file: string, args: readonly string[]): string {
+  return [file, ...args].join('\0');
+}
+
+describe('probeHostEnvironment', () => {
+  it('resolves MSYS2 ucrt64 native git through git --exec-path', async () => {
+    const gitExe = 'C:\\msys64\\ucrt64\\bin\\git.exe';
+    const env = await probeHostEnvironment(
+      stubDeps({
+        platform: 'win32',
+        env: { PATH: 'C:\\msys64\\ucrt64\\bin' },
+        execFileResults: {
+          [execFileKey(gitExe, ['--exec-path'])]: 'C:/msys64/ucrt64/libexec/git-core\n',
+        },
+        existingPaths: [gitExe, 'C:\\msys64\\usr\\bin\\bash.exe'],
+      }),
+    );
+    expect(env.shellName).toBe('bash');
+    expect(env.shellPath).toBe('C:\\msys64\\usr\\bin\\bash.exe');
+  });
+
+  it('resolves MSYS2 clang64 native git through git --exec-path', async () => {
+    const gitExe = 'C:\\msys64\\clang64\\bin\\git.exe';
+    const env = await probeHostEnvironment(
+      stubDeps({
+        platform: 'win32',
+        env: { PATH: 'C:\\msys64\\clang64\\bin' },
+        execFileResults: {
+          [execFileKey(gitExe, ['--exec-path'])]: 'C:/msys64/clang64/libexec/git-core\n',
+        },
+        existingPaths: [gitExe, 'C:\\msys64\\usr\\bin\\bash.exe'],
+      }),
+    );
+    expect(env.shellName).toBe('bash');
+    expect(env.shellPath).toBe('C:\\msys64\\usr\\bin\\bash.exe');
+  });
+
+  it('resolves MSYS2 clangarm64 native git through git --exec-path', async () => {
+    const gitExe = 'C:\\msys64\\clangarm64\\bin\\git.exe';
+    const env = await probeHostEnvironment(
+      stubDeps({
+        platform: 'win32',
+        env: { PATH: 'C:\\msys64\\clangarm64\\bin' },
+        execFileResults: {
+          [execFileKey(gitExe, ['--exec-path'])]: 'C:/msys64/clangarm64/libexec/git-core\n',
+        },
+        existingPaths: [gitExe, 'C:\\msys64\\usr\\bin\\bash.exe'],
+      }),
+    );
+    expect(env.shellName).toBe('bash');
+    expect(env.shellPath).toBe('C:\\msys64\\usr\\bin\\bash.exe');
+  });
+});