feat(cli): add streamlined gemini gemma local model setup

docs/reference/configuration.md

@@ -1706,6 +1706,18 @@ their corresponding top-level category object in your `settings.json` file.
   - **Default:** `false`
   - **Requires restart:** Yes
 
+- **`experimental.gemmaModelRouter.autoStartServer`** (boolean):
+  - **Description:** Automatically start the LiteRT-LM server when Gemini CLI
+    starts and the Gemma router is enabled.
+  - **Default:** `true`
+  - **Requires restart:** Yes
+
+- **`experimental.gemmaModelRouter.binaryPath`** (string):
+  - **Description:** Custom path to the LiteRT-LM binary. Leave empty to use the
+    default location (~/.gemini/bin/litert/).
+  - **Default:** `""`
+  - **Requires restart:** Yes
+
 - **`experimental.gemmaModelRouter.classifier.host`** (string):
   - **Description:** The host of the classifier.
   - **Default:** `"http://localhost:9379"`

packages/cli/src/commands/gemma.ts

@@ -0,0 +1,33 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { CommandModule, Argv } from 'yargs';
+import { initializeOutputListenersAndFlush } from '../gemini.js';
+import { defer } from '../deferred.js';
+import { setupCommand } from './gemma/setup.js';
+import { startCommand } from './gemma/start.js';
+import { stopCommand } from './gemma/stop.js';
+import { statusCommand } from './gemma/status.js';
+import { logsCommand } from './gemma/logs.js';
+
+export const gemmaCommand: CommandModule = {
+  command: 'gemma',
+  describe: 'Manage local Gemma model routing',
+  builder: (yargs: Argv) =>
+    yargs
+      .middleware((argv) => {
+        initializeOutputListenersAndFlush();
+        argv['isCommand'] = true;
+      })
+      .command(defer(setupCommand, 'gemma'))
+      .command(defer(startCommand, 'gemma'))
+      .command(defer(stopCommand, 'gemma'))
+      .command(defer(statusCommand, 'gemma'))
+      .command(defer(logsCommand, 'gemma'))
+      .demandCommand(1, 'You need at least one command before continuing.')
+      .version(false),
+  handler: () => {},
+};

packages/cli/src/commands/gemma/constants.ts

@@ -0,0 +1,34 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import path from 'node:path';
+import { Storage } from '@google/gemini-cli-core';
+
+export const LITERT_RELEASE_VERSION = 'v0.9.0-alpha03';
+export const LITERT_RELEASE_BASE_URL =
+  'https://github.com/google-ai-edge/LiteRT-LM/releases/download';
+export const GEMMA_MODEL_NAME = 'gemma3-1b-gpu-custom';
+export const DEFAULT_PORT = 9379;
+export const HEALTH_CHECK_TIMEOUT_MS = 5000;
+export const SERVER_START_WAIT_MS = 3000;
+
+export const PLATFORM_BINARY_MAP: Record<string, string> = {
+  'darwin-arm64': 'lit.macos_arm64',
+  'linux-x64': 'lit.linux_x86_64',
+  'win32-x64': 'lit.windows_x86_64.exe',
+};
+
+export function getLiteRtBinDir(): string {
+  return path.join(Storage.getGlobalGeminiDir(), 'bin', 'litert');
+}
+
+export function getPidFilePath(): string {
+  return path.join(Storage.getGlobalTempDir(), 'litert-server.pid');
+}
+
+export function getLogFilePath(): string {
+  return path.join(Storage.getGlobalTempDir(), 'litert-server.log');
+}

packages/cli/src/commands/gemma/logs.test.ts

@@ -0,0 +1,51 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import { afterEach, describe, expect, it } from 'vitest';
+import { readLastLines } from './logs.js';
+
+describe('readLastLines', () => {
+  const tempFiles: string[] = [];
+
+  afterEach(async () => {
+    await Promise.all(
+      tempFiles
+        .splice(0)
+        .map((filePath) => fs.promises.rm(filePath, { force: true })),
+    );
+  });
+
+  it('returns only the requested tail lines without reading the whole file eagerly', async () => {
+    const filePath = path.join(
+      os.tmpdir(),
+      `gemma-logs-${Date.now()}-${Math.random().toString(36).slice(2)}.log`,
+    );
+    tempFiles.push(filePath);
+
+    const content = Array.from({ length: 2000 }, (_, i) => `line-${i + 1}`)
+      .join('\n')
+      .concat('\n');
+    await fs.promises.writeFile(filePath, content, 'utf-8');
+
+    await expect(readLastLines(filePath, 3)).resolves.toBe(
+      'line-1998\nline-1999\nline-2000\n',
+    );
+  });
+
+  it('returns an empty string when zero lines are requested', async () => {
+    const filePath = path.join(
+      os.tmpdir(),
+      `gemma-logs-${Date.now()}-${Math.random().toString(36).slice(2)}.log`,
+    );
+    tempFiles.push(filePath);
+    await fs.promises.writeFile(filePath, 'line-1\nline-2\n', 'utf-8');
+
+    await expect(readLastLines(filePath, 0)).resolves.toBe('');
+  });
+});

packages/cli/src/commands/gemma/logs.ts

@@ -0,0 +1,158 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { CommandModule } from 'yargs';
+import fs from 'node:fs';
+import { spawn } from 'node:child_process';
+import { debugLogger } from '@google/gemini-cli-core';
+import { exitCli } from '../utils.js';
+import { getLogFilePath } from './constants.js';
+
+export async function readLastLines(
+  filePath: string,
+  count: number,
+): Promise<string> {
+  if (count <= 0) {
+    return '';
+  }
+
+  const CHUNK_SIZE = 64 * 1024;
+  const fileHandle = await fs.promises.open(filePath, fs.constants.O_RDONLY);
+
+  try {
+    const stats = await fileHandle.stat();
+    if (stats.size === 0) {
+      return '';
+    }
+
+    const chunks: Buffer[] = [];
+    let totalBytes = 0;
+    let newlineCount = 0;
+    let position = stats.size;
+
+    while (position > 0 && newlineCount <= count) {
+      const readSize = Math.min(CHUNK_SIZE, position);
+      position -= readSize;
+
+      const buffer = Buffer.allocUnsafe(readSize);
+      const { bytesRead } = await fileHandle.read(
+        buffer,
+        0,
+        readSize,
+        position,
+      );
+
+      if (bytesRead === 0) {
+        break;
+      }
+
+      const chunk =
+        bytesRead === readSize ? buffer : buffer.subarray(0, bytesRead);
+      chunks.unshift(chunk);
+      totalBytes += chunk.length;
+
+      for (const byte of chunk) {
+        if (byte === 0x0a) {
+          newlineCount += 1;
+        }
+      }
+    }
+
+    const content = Buffer.concat(chunks, totalBytes).toString('utf-8');
+    const lines = content.split('\n');
+
+    if (position > 0 && lines.length > 0) {
+      const boundary = Buffer.allocUnsafe(1);
+      const { bytesRead } = await fileHandle.read(boundary, 0, 1, position - 1);
+      if (bytesRead === 1 && boundary[0] !== 0x0a) {
+        lines.shift();
+      }
+    }
+
+    if (lines.length > 0 && lines[lines.length - 1] === '') {
+      lines.pop();
+    }
+
+    if (lines.length === 0) {
+      return '';
+    }
+
+    return lines.slice(-count).join('\n') + '\n';
+  } finally {
+    await fileHandle.close();
+  }
+}
+
+const isWindows = process.platform === 'win32';
+
+export const logsCommand: CommandModule = {
+  command: 'logs',
+  describe: 'View LiteRT-LM server logs',
+  builder: (yargs) =>
+    yargs
+      .option('lines', {
+        alias: 'n',
+        type: 'number',
+        description: 'Show the last N lines and exit (omit to follow live)',
+      })
+      .option('follow', {
+        alias: 'f',
+        type: 'boolean',
+        default: true,
+        description: 'Follow log output (default when --lines is not set)',
+      }),
+  handler: async (argv) => {
+    const logPath = getLogFilePath();
+
+    try {
+      await fs.promises.access(logPath, fs.constants.F_OK);
+    } catch {
+      debugLogger.log(`No log file found at ${logPath}`);
+      debugLogger.log(
+        'Is the LiteRT server running? Start it with: gemini gemma start',
+      );
+      await exitCli(1);
+      return;
+    }
+
+    const rawLines = argv['lines'];
+    const lines = Number.isFinite(rawLines) ? Number(rawLines) : undefined;
+
+    if (lines !== undefined) {
+      if (isWindows) {
+        process.stdout.write(await readLastLines(logPath, lines));
+        await exitCli(0);
+        return;
+      }
+      const tailArgs = ['-n', String(lines), logPath];
+      const child = spawn('tail', tailArgs, { stdio: 'inherit' });
+      child.on('close', async (code) => {
+        await exitCli(code ?? 0);
+      });
+      return;
+    }
+
+    if (isWindows) {
+      debugLogger.log(
+        'Live log following is not supported on Windows. Use --lines N to view recent logs.',
+      );
+      await exitCli(1);
+      return;
+    }
+
+    debugLogger.log(`Tailing ${logPath} (Ctrl+C to stop)\n`);
+    const tailArgs = ['-f', '-n', '20', logPath];
+    const child = spawn('tail', tailArgs, { stdio: 'inherit' });
+
+    process.on('SIGINT', () => {
+      child.kill('SIGTERM');
+    });
+
+    child.on('close', async (code) => {
+      await exitCli(code ?? 0);
+    });
+  },
+};