diff --git a/.changeset/fix-ripgrep-cross-device-install.md b/.changeset/fix-ripgrep-cross-device-install.md
new file mode 100644
index 0000000000..2095138af3
--- /dev/null
+++ b/.changeset/fix-ripgrep-cross-device-install.md
@@ -0,0 +1,6 @@
+---
+"@moonshot-ai/agent-core": patch
+"@moonshot-ai/kimi-code": patch
+---
+
+Fix automatic ripgrep installation when the temporary directory is on a different filesystem.
diff --git a/packages/agent-core/src/tools/support/rg-locator.ts b/packages/agent-core/src/tools/support/rg-locator.ts
index f8b0ec002f..a5e3c178fb 100644
--- a/packages/agent-core/src/tools/support/rg-locator.ts
+++ b/packages/agent-core/src/tools/support/rg-locator.ts
@@ -14,9 +14,9 @@
 
 import { createHash } from 'node:crypto';
 import { createWriteStream, existsSync } from 'node:fs';
-import { chmod, mkdir, mkdtemp, readFile, rename, rm, stat } from 'node:fs/promises';
+import { chmod, copyFile, mkdir, mkdtemp, readFile, rename, rm, stat } from 'node:fs/promises';
 import { homedir, tmpdir } from 'node:os';
-import { basename, join } from 'pathe';
+import { basename, dirname, join } from 'pathe';
 import { Readable } from 'node:stream';
 import { pipeline } from 'node:stream/promises';
 
@@ -243,8 +243,7 @@ async function downloadAndInstallRg(shareDir: string): Promise<string> {
             'CDN content may have changed.',
         );
       }
-      await rename(extracted, destination);
-      await chmod(destination, 0o755);
+      await installExtractedRg(extracted, destination);
     }
     return destination;
   } finally {
@@ -252,6 +251,36 @@ async function downloadAndInstallRg(shareDir: string): Promise<string> {
   }
 }
 
+/** @internal for tests — install an extracted rg binary into the persistent bin dir. */
+export async function installExtractedRg(extracted: string, destination: string): Promise<void> {
+  try {
+    await rename(extracted, destination);
+    await chmod(destination, 0o755);
+    return;
+  } catch (error) {
+    if (!isCrossDeviceRenameError(error)) throw error;
+  }
+
+  const stagingDir = await mkdtemp(join(dirname(destination), '.rg-install-'));
+  const staged = join(stagingDir, basename(destination));
+  try {
+    await copyFile(extracted, staged);
+    await chmod(staged, 0o755);
+    await rename(staged, destination);
+  } finally {
+    await rm(stagingDir, { recursive: true, force: true });
+  }
+}
+
+function isCrossDeviceRenameError(error: unknown): boolean {
+  return (
+    typeof error === 'object' &&
+    error !== null &&
+    'code' in error &&
+    (error as { readonly code?: unknown }).code === 'EXDEV'
+  );
+}
+
 /** @internal for tests — fail closed before extracting downloaded bytes. */
 export async function verifyArchiveChecksum(
   archivePath: string,
diff --git a/packages/agent-core/test/tools/rg-locator.test.ts b/packages/agent-core/test/tools/rg-locator.test.ts
index badd679439..105f906163 100644
--- a/packages/agent-core/test/tools/rg-locator.test.ts
+++ b/packages/agent-core/test/tools/rg-locator.test.ts
@@ -9,7 +9,15 @@
  */
 
 import { createHash } from 'node:crypto';
-import { existsSync, mkdirSync, readFileSync, rmSync, writeFileSync, chmodSync } from 'node:fs';
+import {
+  chmodSync,
+  existsSync,
+  mkdirSync,
+  readFileSync,
+  rmSync,
+  statSync,
+  writeFileSync,
+} from 'node:fs';
 import type * as FsPromises from 'node:fs/promises';
 import { tmpdir } from 'node:os';
 import { join } from 'pathe';
@@ -169,6 +177,91 @@ describe('verifyArchiveChecksum', () => {
   });
 });
 
+describe('installExtractedRg', () => {
+  let fakeDir: string;
+  beforeEach(() => {
+    fakeDir = join(
+      tmpdir(),
+      `kimi-rg-install-${String(Date.now())}-${String(Math.random()).slice(2)}`,
+    );
+    mkdirSync(fakeDir, { recursive: true });
+  });
+  afterEach(() => {
+    rmSync(fakeDir, { recursive: true, force: true });
+    vi.doUnmock('node:fs/promises');
+    vi.resetModules();
+    vi.restoreAllMocks();
+  });
+
+  it('falls back to a target-side staged copy when rename crosses devices', async () => {
+    const extractDir = join(fakeDir, 'extract');
+    const binDir = join(fakeDir, 'bin');
+    const extracted = join(extractDir, 'rg');
+    const destination = join(binDir, 'rg');
+    const payload = '#!/bin/sh\necho ripgrep\n';
+    mkdirSync(extractDir, { recursive: true });
+    mkdirSync(binDir, { recursive: true });
+    writeFileSync(extracted, payload);
+    const renameCalls: Array<[string, string]> = [];
+
+    vi.resetModules();
+    vi.doMock('node:fs/promises', async () => {
+      const actual = await vi.importActual<typeof FsPromises>('node:fs/promises');
+      return {
+        ...actual,
+        rename: async (from: string, to: string) => {
+          renameCalls.push([from, to]);
+          if (from === extracted && to === destination) {
+            throw Object.assign(new Error('cross-device rename'), { code: 'EXDEV' });
+          }
+          return actual.rename(from, to);
+        },
+      };
+    });
+
+    const { installExtractedRg } = await import('../../src/tools/support/rg-locator');
+
+    await installExtractedRg(extracted, destination);
+
+    expect(readFileSync(destination, 'utf8')).toBe(payload);
+    expect(renameCalls).toHaveLength(2);
+    expect(renameCalls[0]).toEqual([extracted, destination]);
+    expect(renameCalls[1]?.[0]).toContain(join(binDir, '.rg-install-'));
+    expect(renameCalls[1]?.[1]).toBe(destination);
+    if (process.platform !== 'win32') {
+      expect(statSync(destination).mode & 0o777).toBe(0o755);
+    }
+  });
+
+  it('does not mask non-EXDEV rename failures', async () => {
+    const extractDir = join(fakeDir, 'extract');
+    const binDir = join(fakeDir, 'bin');
+    const extracted = join(extractDir, 'rg');
+    const destination = join(binDir, 'rg');
+    mkdirSync(extractDir, { recursive: true });
+    mkdirSync(binDir, { recursive: true });
+    writeFileSync(extracted, 'rg bytes');
+
+    vi.resetModules();
+    vi.doMock('node:fs/promises', async () => {
+      const actual = await vi.importActual<typeof FsPromises>('node:fs/promises');
+      return {
+        ...actual,
+        rename: async () => {
+          throw Object.assign(new Error('permission denied'), { code: 'EACCES' });
+        },
+      };
+    });
+
+    const { installExtractedRg } = await import('../../src/tools/support/rg-locator');
+
+    await expect(installExtractedRg(extracted, destination)).rejects.toMatchObject({
+      code: 'EACCES',
+    });
+    expect(existsSync(destination)).toBe(false);
+  });
+});
+
 describe('ensureRgPath download branch', () => {
   let fakeShare: string;
   let savedPath: string | undefined;