Basic code assist support (#910)

13 files changed, 432 insertions, 340 deletions

diff --git a/packages/core/package.json b/packages/core/package.json
index 033fbddc..702fa6f1 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -35,6 +35,7 @@
     "ignore": "^7.0.0",
     "shell-quote": "^1.8.2",
     "strip-ansi": "^7.1.0",
+    "google-auth-library": "^9.11.0",
     "undici": "^7.10.0"
   },
   "devDependencies": {
diff --git a/packages/core/src/code_assist/ccpaServer.ts b/packages/core/src/code_assist/ccpaServer.ts
new file mode 100644
index 00000000..acfec90f
--- /dev/null
+++ b/packages/core/src/code_assist/ccpaServer.ts
@@ -0,0 +1,146 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { OAuth2Client } from 'google-auth-library';
+import {
+  LoadCodeAssistResponse,
+  LoadCodeAssistRequest,
+  OnboardUserRequest,
+  LongrunningOperationResponse,
+} from './types.js';
+import {
+  GenerateContentResponse,
+  GenerateContentParameters,
+  CountTokensParameters,
+  EmbedContentResponse,
+  CountTokensResponse,
+  EmbedContentParameters,
+} from '@google/genai';
+import { Readable } from 'stream';
+import * as readline from 'readline';
+import type { ReadableStream } from 'node:stream/web';
+import { ContentGenerator } from '../core/contentGenerator.js';
+
+// TODO: Use production endpoint once it supports our methods.
+export const CCPA_ENDPOINT =
+  'https://staging-cloudcode-pa.sandbox.googleapis.com';
+export const CCPA_API_VERSION = '/v1internal';
+
+export class CcpaServer implements ContentGenerator {
+  constructor(
+    readonly auth: OAuth2Client,
+    readonly projectId?: string,
+  ) {}
+
+  async generateContentStream(
+    req: GenerateContentParameters,
+  ): Promise<AsyncGenerator<GenerateContentResponse>> {
+    return await this.streamEndpoint<GenerateContentResponse>(
+      'streamGenerateContent',
+      req,
+    );
+  }
+
+  async generateContent(
+    req: GenerateContentParameters,
+  ): Promise<GenerateContentResponse> {
+    return await this.callEndpoint<GenerateContentResponse>(
+      'generateContent',
+      req,
+    );
+  }
+
+  async onboardUser(
+    req: OnboardUserRequest,
+  ): Promise<LongrunningOperationResponse> {
+    return await this.callEndpoint<LongrunningOperationResponse>(
+      'onboardUser',
+      req,
+    );
+  }
+
+  async loadCodeAssist(
+    req: LoadCodeAssistRequest,
+  ): Promise<LoadCodeAssistResponse> {
+    return await this.callEndpoint<LoadCodeAssistResponse>(
+      'loadCodeAssist',
+      req,
+    );
+  }
+
+  async countTokens(_req: CountTokensParameters): Promise<CountTokensResponse> {
+    return { totalTokens: 0 };
+  }
+
+  async embedContent(
+    _req: EmbedContentParameters,
+  ): Promise<EmbedContentResponse> {
+    throw Error();
+  }
+
+  async callEndpoint<T>(method: string, req: object): Promise<T> {
+    const res = await this.auth.request({
+      url: `${CCPA_ENDPOINT}/${CCPA_API_VERSION}:${method}`,
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'X-Goog-User-Project': this.projectId || '',
+      },
+      responseType: 'json',
+      body: JSON.stringify(req),
+    });
+    if (res.status !== 200) {
+      throw new Error(
+        `Failed to fetch from ${method}: ${res.status} ${res.data}`,
+      );
+    }
+    return res.data as T;
+  }
+
+  async streamEndpoint<T>(
+    method: string,
+    req: object,
+  ): Promise<AsyncGenerator<T>> {
+    const res = await this.auth.request({
+      url: `${CCPA_ENDPOINT}/${CCPA_API_VERSION}:${method}`,
+      method: 'POST',
+      params: {
+        alt: 'sse',
+      },
+      headers: { 'Content-Type': 'application/json' },
+      responseType: 'stream',
+      body: JSON.stringify(req),
+    });
+    if (res.status !== 200) {
+      throw new Error(
+        `Failed to fetch from ${method}: ${res.status} ${res.data}`,
+      );
+    }
+
+    return (async function* (): AsyncGenerator<T> {
+      const rl = readline.createInterface({
+        input: Readable.fromWeb(res.data as ReadableStream<Uint8Array>),
+        crlfDelay: Infinity, // Recognizes '\r\n' and '\n' as line breaks
+      });
+
+      let bufferedLines: string[] = [];
+      for await (const line of rl) {
+        // blank lines are used to separate JSON objects in the stream
+        if (line === '') {
+          if (bufferedLines.length === 0) {
+            continue; // no data to yield
+          }
+          yield JSON.parse(bufferedLines.join('\n')) as T;
+          bufferedLines = []; // Reset the buffer after yielding
+        } else if (line.startsWith('data: ')) {
+          bufferedLines.push(line.slice(6).trim());
+        } else {
+          throw new Error(`Unexpected line format in response: ${line}`);
+        }
+      }
+    })();
+  }
+}
diff --git a/packages/core/src/code_assist/codeAssist.ts b/packages/core/src/code_assist/codeAssist.ts
new file mode 100644
index 00000000..dd5c2ddd
--- /dev/null
+++ b/packages/core/src/code_assist/codeAssist.ts
@@ -0,0 +1,19 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { ContentGenerator } from '../core/contentGenerator.js';
+import { loginWithOauth } from './oauth2.js';
+import { setupUser } from './setup.js';
+import { CcpaServer } from './ccpaServer.js';
+
+export async function createCodeAssistContentGenerator(): Promise<ContentGenerator> {
+  const oauth2Client = await loginWithOauth();
+  const projectId = await setupUser(
+    oauth2Client,
+    process.env.GOOGLE_CLOUD_PROJECT,
+  );
+  return new CcpaServer(oauth2Client, projectId);
+}
diff --git a/packages/core/src/code_assist/constants.ts b/packages/core/src/code_assist/constants.ts
deleted file mode 100644
index 898b6136..00000000
--- a/packages/core/src/code_assist/constants.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-export const DEFAULT_ENDPOINT = 'https://cloudcode-pa.googleapis.com';
diff --git a/packages/core/src/code_assist/login.ts b/packages/core/src/code_assist/login.ts
deleted file mode 100644
index a94b21d4..00000000
--- a/packages/core/src/code_assist/login.ts
+++ /dev/null
@@ -1,119 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-import { OAuth2Client } from 'google-auth-library';
-import * as http from 'http';
-import url from 'url';
-import crypto from 'crypto';
-import * as net from 'net';
-
-//  OAuth Client ID used to initiate OAuth2Client class.
-const OAUTH_CLIENT_ID =
-  '681255809395-oo8ft2oprdrnp9e3aqf6av3hmdib135j.apps.googleusercontent.com';
-
-// OAuth Secret value used to initiate OAuth2Client class.
-const OAUTH_CLIENT_NOT_SO_SECRET = process.env.GCA_OAUTH_SECRET;
-
-// OAuth Scopes for Cloud Code authorization.
-const OAUTH_SCOPE = [
-  'https://www.googleapis.com/auth/cloud-platform',
-  'https://www.googleapis.com/auth/userinfo.email',
-  'https://www.googleapis.com/auth/userinfo.profile',
-];
-
-const HTTP_REDIRECT = 301;
-const SIGN_IN_SUCCESS_URL =
-  'https://developers.google.com/gemini-code-assist/auth_success_gemini';
-const SIGN_IN_FAILURE_URL =
-  'https://developers.google.com/gemini-code-assist/auth_failure_gemini';
-
-export async function doGCALogin(): Promise<OAuth2Client> {
-  const redirectPort: number = await getAvailablePort();
-  const client: OAuth2Client = await createOAuth2Client(redirectPort);
-  await login(client, redirectPort);
-  return client;
-}
-
-function createOAuth2Client(redirectPort: number): OAuth2Client {
-  return new OAuth2Client({
-    clientId: OAUTH_CLIENT_ID,
-    clientSecret: OAUTH_CLIENT_NOT_SO_SECRET,
-    redirectUri: `http://localhost:${redirectPort}/oauth2redirect`,
-  });
-}
-
-/**
- * Returns first available port in user's machine
- * @returns port number
- */
-function getAvailablePort(): Promise<number> {
-  return new Promise((resolve, reject) => {
-    let port = 0;
-    try {
-      const server = net.createServer();
-      server.listen(0, () => {
-        const address = server.address()! as net.AddressInfo;
-        port = address.port;
-      });
-      server.on('listening', () => {
-        server.close();
-        server.unref();
-      });
-      server.on('error', (e) => reject(e));
-      server.on('close', () => resolve(port));
-    } catch (e) {
-      reject(e);
-    }
-  });
-}
-
-function login(oAuth2Client: OAuth2Client, port: number): Promise<boolean> {
-  return new Promise((resolve, reject) => {
-    const state = crypto.randomBytes(32).toString('hex');
-    const authURL: string = oAuth2Client.generateAuthUrl({
-      access_type: 'offline',
-      scope: OAUTH_SCOPE,
-      state,
-    });
-
-    console.log('Login:\n\n', authURL);
-
-    const server = http
-      .createServer(async (req, res) => {
-        try {
-          if (req.url!.indexOf('/oauth2callback') > -1) {
-            // acquire the code from the querystring, and close the web server.
-            const qs = new url.URL(req.url!).searchParams;
-            if (qs.get('error')) {
-              console.error(`Error during authentication: ${qs.get('error')}`);
-
-              res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_FAILURE_URL });
-              res.end();
-              resolve(false);
-            } else if (qs.get('state') !== state) {
-              //check state value
-              console.log('State mismatch. Possible CSRF attack');
-
-              res.end('State mismatch. Possible CSRF attack');
-              resolve(false);
-            } else if (!qs.get('code')) {
-              const { tokens } = await oAuth2Client.getToken(qs.get('code')!);
-              console.log('Logged in! Tokens:\n\n', tokens);
-
-              oAuth2Client.setCredentials(tokens);
-              res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_SUCCESS_URL });
-              res.end();
-              resolve(true);
-            }
-          }
-        } catch (e) {
-          reject(e);
-        }
-        server.close();
-      })
-      .listen(port);
-  });
-}
diff --git a/packages/core/src/code_assist/metadata.ts b/packages/core/src/code_assist/metadata.ts
deleted file mode 100644
index 7f74f962..00000000
--- a/packages/core/src/code_assist/metadata.ts
+++ /dev/null
@@ -1,37 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-export interface ClientMetadata {
-  ideType?: ClientMetadataIdeType | null;
-  ideVersion?: string | null;
-  pluginVersion?: string | null;
-  platform?: ClientMetadataPlatform | null;
-  updateChannel?: string | null;
-  duetProject?: string | null;
-  pluginType?: ClientMetadataPluginType | null;
-  ideName?: string | null;
-}
-
-export type ClientMetadataIdeType =
-  | 'IDE_UNSPECIFIED'
-  | 'VSCODE'
-  | 'INTELLIJ'
-  | 'VSCODE_CLOUD_WORKSTATION'
-  | 'INTELLIJ_CLOUD_WORKSTATION'
-  | 'CLOUD_SHELL';
-export type ClientMetadataPlatform =
-  | 'PLATFORM_UNSPECIFIED'
-  | 'DARWIN_AMD64'
-  | 'DARWIN_ARM64'
-  | 'LINUX_AMD64'
-  | 'LINUX_ARM64'
-  | 'WINDOWS_AMD64';
-export type ClientMetadataPluginType =
-  | 'PLUGIN_UNSPECIFIED'
-  | 'CLOUD_CODE'
-  | 'GEMINI'
-  | 'AIPLUGIN_INTELLIJ'
-  | 'AIPLUGIN_STUDIO';
diff --git a/packages/core/src/code_assist/oauth2.ts b/packages/core/src/code_assist/oauth2.ts
new file mode 100644
index 00000000..af87caea
--- /dev/null
+++ b/packages/core/src/code_assist/oauth2.ts
@@ -0,0 +1,116 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { OAuth2Client } from 'google-auth-library';
+import * as http from 'http';
+import url from 'url';
+import crypto from 'crypto';
+import * as net from 'net';
+import open from 'open';
+
+//  OAuth Client ID used to initiate OAuth2Client class.
+const OAUTH_CLIENT_ID =
+  '681255809395-oo8ft2oprdrnp9e3aqf6av3hmdib135j.apps.googleusercontent.com';
+
+// OAuth Secret value used to initiate OAuth2Client class.
+// Note: It's ok to save this in git because this is an installed application
+// as described here: https://developers.google.com/identity/protocols/oauth2#installed
+// "The process results in a client ID and, in some cases, a client secret,
+// which you embed in the source code of your application. (In this context,
+// the client secret is obviously not treated as a secret.)"
+const OAUTH_CLIENT_SECRET = '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';
+
+// OAuth Scopes for Cloud Code authorization.
+const OAUTH_SCOPE = [
+  'https://www.googleapis.com/auth/cloud-platform',
+  'https://www.googleapis.com/auth/userinfo.email',
+  'https://www.googleapis.com/auth/userinfo.profile',
+];
+
+const HTTP_REDIRECT = 301;
+const SIGN_IN_SUCCESS_URL =
+  'https://developers.google.com/gemini-code-assist/auth_success_gemini';
+const SIGN_IN_FAILURE_URL =
+  'https://developers.google.com/gemini-code-assist/auth_failure_gemini';
+
+export async function loginWithOauth(): Promise<OAuth2Client> {
+  const port = await getAvailablePort();
+  const oAuth2Client = new OAuth2Client({
+    clientId: OAUTH_CLIENT_ID,
+    clientSecret: OAUTH_CLIENT_SECRET,
+    redirectUri: `http://localhost:${port}/oauth2callback`,
+  });
+
+  return new Promise((resolve, reject) => {
+    const state = crypto.randomBytes(32).toString('hex');
+    const authURL: string = oAuth2Client.generateAuthUrl({
+      access_type: 'offline',
+      scope: OAUTH_SCOPE,
+      state,
+    });
+    open(authURL);
+
+    const server = http.createServer(async (req, res) => {
+      try {
+        if (req.url!.indexOf('/oauth2callback') === -1) {
+          console.log('Unexpected request:', req.url);
+          res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_FAILURE_URL });
+          res.end();
+          reject(new Error('Unexpected request: ' + req.url));
+        }
+        // acquire the code from the querystring, and close the web server.
+        const qs = new url.URL(req.url!, 'http://localhost:3000').searchParams;
+        console.log('Processing request:', qs);
+        if (qs.get('error')) {
+          res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_FAILURE_URL });
+          res.end();
+          reject(new Error(`Error during authentication: ${qs.get('error')}`));
+        } else if (qs.get('state') !== state) {
+          res.end('State mismatch. Possible CSRF attack');
+          reject(new Error('State mismatch. Possible CSRF attack'));
+        } else if (qs.get('code')) {
+          const code: string = qs.get('code')!;
+          console.log();
+          const { tokens } = await oAuth2Client.getToken(code);
+          console.log('Logged in! Tokens:\n\n', tokens);
+
+          oAuth2Client.setCredentials(tokens);
+          res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_SUCCESS_URL });
+          res.end();
+          resolve(oAuth2Client);
+        } else {
+          reject(new Error('No code found in request'));
+        }
+      } catch (e) {
+        reject(e);
+      } finally {
+        server.close();
+      }
+    });
+    server.listen(port);
+  });
+}
+
+function getAvailablePort(): Promise<number> {
+  return new Promise((resolve, reject) => {
+    let port = 0;
+    try {
+      const server = net.createServer();
+      server.listen(0, () => {
+        const address = server.address()! as net.AddressInfo;
+        port = address.port;
+      });
+      server.on('listening', () => {
+        server.close();
+        server.unref();
+      });
+      server.on('error', (e) => reject(e));
+      server.on('close', () => resolve(port));
+    } catch (e) {
+      reject(e);
+    }
+  });
+}
diff --git a/packages/core/src/code_assist/onboard.ts b/packages/core/src/code_assist/onboard.ts
deleted file mode 100644
index fc04fe35..00000000
--- a/packages/core/src/code_assist/onboard.ts
+++ /dev/null
@@ -1,90 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-import { OAuth2Client } from 'google-auth-library';
-
-import { ClientMetadata } from './metadata.js';
-import { DEFAULT_ENDPOINT } from './constants.js';
-
-const ONBOARD_USER_ENDPOINT = '/v1internal:onboardUser';
-
-export async function doOnboardUser(
-  req: OnboardUserRequest,
-  oauth2Client: OAuth2Client,
-): Promise<LongrunningOperationResponse> {
-  console.log('OnboardUser req: ', JSON.stringify(req));
-  const authHeaders = await oauth2Client.getRequestHeaders();
-  const headers = { 'Content-Type': 'application/json', ...authHeaders };
-  const res: Response = await fetch(
-    new URL(ONBOARD_USER_ENDPOINT, DEFAULT_ENDPOINT),
-    {
-      method: 'POST',
-      headers,
-      body: JSON.stringify(req),
-    },
-  );
-  const data: LongrunningOperationResponse =
-    (await res.json()) as LongrunningOperationResponse;
-  console.log('OnboardUser res: ', JSON.stringify(data));
-  return data;
-}
-
-/**
- * Proto signature of OnboardUserRequest as payload to OnboardUser call
- */
-export interface OnboardUserRequest {
-  tierId: string | undefined;
-  cloudaicompanionProject: string | undefined;
-  metadata: ClientMetadata | undefined;
-}
-
-/**
- * Represents LongrunningOperation proto
- * http://google3/google/longrunning/operations.proto;rcl=698857719;l=107
- */
-export interface LongrunningOperationResponse {
-  name: string;
-  done?: boolean;
-  response?: OnboardUserResponse;
-}
-
-/**
- * Represents OnboardUserResponse proto
- * http://google3/google/internal/cloud/code/v1internal/cloudcode.proto;l=215
- */
-export interface OnboardUserResponse {
-  // tslint:disable-next-line:enforce-name-casing This is the name of the field in the proto.
-  cloudaicompanionProject?: {
-    id: string;
-    name: string;
-  };
-}
-
-/**
- * Status code of user license status
- * it does not stricly correspond to the proto
- * Error value is an additional value assigned to error responses from OnboardUser
- */
-export enum OnboardUserStatusCode {
-  Default = 'DEFAULT',
-  Notice = 'NOTICE',
-  Warning = 'WARNING',
-  Error = 'ERROR',
-}
-
-/**
- * Status of user onboarded to gemini
- */
-export interface OnboardUserStatus {
-  statusCode: OnboardUserStatusCode;
-  displayMessage: string;
-  helpLink: HelpLinkUrl | undefined;
-}
-
-export interface HelpLinkUrl {
-  description: string;
-  url: string;
-}
diff --git a/packages/core/src/code_assist/setup.ts b/packages/core/src/code_assist/setup.ts
index d8a6dd45..a3162c81 100644
--- a/packages/core/src/code_assist/setup.ts
+++ b/packages/core/src/code_assist/setup.ts
@@ -4,52 +4,46 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import { ClientMetadata, OnboardUserRequest } from './types.js';
+import { CcpaServer } from './ccpaServer.js';
 import { OAuth2Client } from 'google-auth-library';
 
-import { ClientMetadata } from './metadata.js';
-import { doLoadCodeAssist, LoadCodeAssistResponse } from './load.js';
-import { doGCALogin } from './login.js';
-import {
-  doOnboardUser,
-  LongrunningOperationResponse,
-  OnboardUserRequest,
-} from './onboard.js';
-
-export async function doSetup(): Promise<string> {
-  const oauth2Client: OAuth2Client = await doGCALogin();
+/**
+ *
+ * @param projectId the user's project id, if any
+ * @returns the user's actual project id
+ */
+export async function setupUser(
+  oAuth2Client: OAuth2Client,
+  projectId?: string,
+): Promise<string> {
+  const ccpaServer: CcpaServer = new CcpaServer(oAuth2Client, projectId);
   const clientMetadata: ClientMetadata = {
     ideType: 'IDE_UNSPECIFIED',
-    ideVersion: null,
-    pluginVersion: null,
     platform: 'PLATFORM_UNSPECIFIED',
-    updateChannel: null,
-    duetProject: 'aipp-internal-testing',
     pluginType: 'GEMINI',
-    ideName: null,
   };
+  if (process.env.GOOGLE_CLOUD_PROJECT) {
+    clientMetadata.duetProject = process.env.GOOGLE_CLOUD_PROJECT;
+  }
 
-  // Call LoadCodeAssist.
-  const loadCodeAssistRes: LoadCodeAssistResponse = await doLoadCodeAssist(
-    {
-      cloudaicompanionProject: 'aipp-internal-testing',
-      metadata: clientMetadata,
-    },
-    oauth2Client,
-  );
+  // TODO: Support Free Tier user without projectId.
+  const loadRes = await ccpaServer.loadCodeAssist({
+    cloudaicompanionProject: process.env.GOOGLE_CLOUD_PROJECT,
+    metadata: clientMetadata,
+  });
 
-  // Call OnboardUser until long running operation is complete.
-  const onboardUserReq: OnboardUserRequest = {
+  const onboardReq: OnboardUserRequest = {
     tierId: 'legacy-tier',
-    cloudaicompanionProject: loadCodeAssistRes.cloudaicompanionProject || '',
+    cloudaicompanionProject: loadRes.cloudaicompanionProject || '',
     metadata: clientMetadata,
   };
-  let lroRes: LongrunningOperationResponse = await doOnboardUser(
-    onboardUserReq,
-    oauth2Client,
-  );
+
+  // Poll onboardUser until long running operation is complete.
+  let lroRes = await ccpaServer.onboardUser(onboardReq);
   while (!lroRes.done) {
     await new Promise((f) => setTimeout(f, 5000));
-    lroRes = await doOnboardUser(onboardUserReq, oauth2Client);
+    lroRes = await ccpaServer.onboardUser(onboardReq);
   }
 
   return lroRes.response?.cloudaicompanionProject?.id || '';
diff --git a/packages/core/src/code_assist/load.ts b/packages/core/src/code_assist/types.ts
index 507268a6..733780e9 100644
--- a/packages/core/src/code_assist/load.ts
+++ b/packages/core/src/code_assist/types.ts
@@ -4,34 +4,38 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { OAuth2Client } from 'google-auth-library';
-
-import { ClientMetadata } from './metadata.js';
-import { DEFAULT_ENDPOINT } from './constants.js';
-
-const LOAD_CODE_ASSIST_ENDPOINT = '/v1internal:loadCodeAssist';
-
-export async function doLoadCodeAssist(
-  req: LoadCodeAssistRequest,
-  oauth2Client: OAuth2Client,
-): Promise<LoadCodeAssistResponse> {
-  console.log('LoadCodeAssist req: ', JSON.stringify(req));
-  const authHeaders = await oauth2Client.getRequestHeaders();
-  const headers = { 'Content-Type': 'application/json', ...authHeaders };
-  const res: Response = await fetch(
-    new URL(LOAD_CODE_ASSIST_ENDPOINT, DEFAULT_ENDPOINT),
-    {
-      method: 'POST',
-      headers,
-      body: JSON.stringify(req),
-    },
-  );
-  const data: LoadCodeAssistResponse =
-    (await res.json()) as LoadCodeAssistResponse;
-  console.log('LoadCodeAssist res: ', JSON.stringify(data));
-  return data;
+export interface ClientMetadata {
+  ideType?: ClientMetadataIdeType;
+  ideVersion?: string;
+  pluginVersion?: string;
+  platform?: ClientMetadataPlatform;
+  updateChannel?: string;
+  duetProject?: string;
+  pluginType?: ClientMetadataPluginType;
+  ideName?: string;
 }
 
+export type ClientMetadataIdeType =
+  | 'IDE_UNSPECIFIED'
+  | 'VSCODE'
+  | 'INTELLIJ'
+  | 'VSCODE_CLOUD_WORKSTATION'
+  | 'INTELLIJ_CLOUD_WORKSTATION'
+  | 'CLOUD_SHELL';
+export type ClientMetadataPlatform =
+  | 'PLATFORM_UNSPECIFIED'
+  | 'DARWIN_AMD64'
+  | 'DARWIN_ARM64'
+  | 'LINUX_AMD64'
+  | 'LINUX_ARM64'
+  | 'WINDOWS_AMD64';
+export type ClientMetadataPluginType =
+  | 'PLUGIN_UNSPECIFIED'
+  | 'CLOUD_CODE'
+  | 'GEMINI'
+  | 'AIPLUGIN_INTELLIJ'
+  | 'AIPLUGIN_STUDIO';
+
 export interface LoadCodeAssistRequest {
   cloudaicompanionProject?: string;
   metadata: ClientMetadata;
@@ -64,6 +68,20 @@ export interface GeminiUserTier {
 }
 
 /**
+ * Includes information specifying the reasons for a user's ineligibility for a specific tier.
+ * @param reasonCode mnemonic code representing the reason for in-eligibility.
+ * @param reasonMessage message to display to the user.
+ * @param tierId id of the tier.
+ * @param tierName name of the tier.
+ */
+export interface IneligibleTier {
+  reasonCode: IneligibleTierReasonCode;
+  reasonMessage: string;
+  tierId: UserTierId;
+  tierName: string;
+}
+
+/**
  * List of predefined reason codes when a tier is blocked from a specific tier.
  * https://source.corp.google.com/piper///depot/google3/google/internal/cloud/code/v1internal/cloudcode.proto;l=378
  */
@@ -79,21 +97,6 @@ export enum IneligibleTierReasonCode {
   UNSUPPORTED_LOCATION = 'UNSUPPORTED_LOCATION',
   // go/keep-sorted end
 }
-
-/**
- * Includes information specifying the reasons for a user's ineligibility for a specific tier.
- * @param reasonCode mnemonic code representing the reason for in-eligibility.
- * @param reasonMessage message to display to the user.
- * @param tierId id of the tier.
- * @param tierName name of the tier.
- */
-export interface IneligibleTier {
-  reasonCode: IneligibleTierReasonCode;
-  reasonMessage: string;
-  tierId: UserTierId;
-  tierName: string;
-}
-
 /**
  * UserTierId represents IDs returned from the Cloud Code Private API representing a user's tier
  *
@@ -113,3 +116,60 @@ export interface PrivacyNotice {
   showNotice: boolean;
   noticeText?: string;
 }
+
+/**
+ * Proto signature of OnboardUserRequest as payload to OnboardUser call
+ */
+export interface OnboardUserRequest {
+  tierId: string | undefined;
+  cloudaicompanionProject: string | undefined;
+  metadata: ClientMetadata | undefined;
+}
+
+/**
+ * Represents LongrunningOperation proto
+ * http://google3/google/longrunning/operations.proto;rcl=698857719;l=107
+ */
+export interface LongrunningOperationResponse {
+  name: string;
+  done?: boolean;
+  response?: OnboardUserResponse;
+}
+
+/**
+ * Represents OnboardUserResponse proto
+ * http://google3/google/internal/cloud/code/v1internal/cloudcode.proto;l=215
+ */
+export interface OnboardUserResponse {
+  // tslint:disable-next-line:enforce-name-casing This is the name of the field in the proto.
+  cloudaicompanionProject?: {
+    id: string;
+    name: string;
+  };
+}
+
+/**
+ * Status code of user license status
+ * it does not stricly correspond to the proto
+ * Error value is an additional value assigned to error responses from OnboardUser
+ */
+export enum OnboardUserStatusCode {
+  Default = 'DEFAULT',
+  Notice = 'NOTICE',
+  Warning = 'WARNING',
+  Error = 'ERROR',
+}
+
+/**
+ * Status of user onboarded to gemini
+ */
+export interface OnboardUserStatus {
+  statusCode: OnboardUserStatusCode;
+  displayMessage: string;
+  helpLink: HelpLinkUrl | undefined;
+}
+
+export interface HelpLinkUrl {
+  description: string;
+  url: string;
+}
diff --git a/packages/core/src/core/client.test.ts b/packages/core/src/core/client.test.ts
index 58ad5dbd..024544ed 100644
--- a/packages/core/src/core/client.test.ts
+++ b/packages/core/src/core/client.test.ts
@@ -273,7 +273,9 @@ describe('Gemini Client (client.ts)', () => {
       const mockGenerator: Partial<ContentGenerator> = {
         countTokens: vi.fn().mockResolvedValue({ totalTokens: 0 }),
       };
-      client['contentGenerator'] = mockGenerator as ContentGenerator;
+      client['contentGenerator'] = Promise.resolve(
+        mockGenerator as ContentGenerator,
+      );
 
       // Act
       const stream = client.sendMessageStream(
diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index 3046116e..8de8e503 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -5,7 +5,6 @@
  */
 
 import {
-  EmbedContentResponse,
   EmbedContentParameters,
   GenerateContentConfig,
   Part,
@@ -37,7 +36,6 @@ import {
   ContentGenerator,
   createContentGenerator,
 } from './contentGenerator.js';
-
 import { ProxyAgent, setGlobalDispatcher } from 'undici';
 
 const proxy =
@@ -52,7 +50,7 @@ if (proxy) {
 
 export class GeminiClient {
   private chat: Promise<GeminiChat>;
-  private contentGenerator: ContentGenerator;
+  private contentGenerator: Promise<ContentGenerator>;
   private model: string;
   private embeddingModel: string;
   private generateContentConfig: GenerateContentConfig = {
@@ -162,7 +160,7 @@ export class GeminiClient {
       const systemInstruction = getCoreSystemPrompt(userMemory);
 
       return new GeminiChat(
-        this.contentGenerator,
+        await this.contentGenerator,
         this.model,
         {
           systemInstruction,
@@ -289,6 +287,7 @@ export class GeminiClient {
     model: string = 'gemini-2.0-flash',
     config: GenerateContentConfig = {},
   ): Promise<Record<string, unknown>> {
+    const cg = await this.contentGenerator;
     const attempt = 1;
     const startTime = Date.now();
     try {
@@ -302,7 +301,7 @@ export class GeminiClient {
 
       let inputTokenCount = 0;
       try {
-        const { totalTokens } = await this.contentGenerator.countTokens({
+        const { totalTokens } = await cg.countTokens({
           model,
           contents,
         });
@@ -317,7 +316,7 @@ export class GeminiClient {
       this._logApiRequest(model, inputTokenCount);
 
       const apiCall = () =>
-        this.contentGenerator.generateContent({
+        cg.generateContent({
           model,
           config: {
             ...requestConfig,
@@ -397,6 +396,7 @@ export class GeminiClient {
     generationConfig: GenerateContentConfig,
     abortSignal: AbortSignal,
   ): Promise<GenerateContentResponse> {
+    const cg = await this.contentGenerator;
     const modelToUse = this.model;
     const configToUse: GenerateContentConfig = {
       ...this.generateContentConfig,
@@ -417,7 +417,7 @@ export class GeminiClient {
 
       let inputTokenCount = 0;
       try {
-        const { totalTokens } = await this.contentGenerator.countTokens({
+        const { totalTokens } = await cg.countTokens({
           model: modelToUse,
           contents,
         });
@@ -432,7 +432,7 @@ export class GeminiClient {
       this._logApiRequest(modelToUse, inputTokenCount);
 
       const apiCall = () =>
-        this.contentGenerator.generateContent({
+        cg.generateContent({
           model: modelToUse,
           config: requestConfig,
           contents,
@@ -478,8 +478,9 @@ export class GeminiClient {
       model: this.embeddingModel,
       contents: texts,
     };
-    const embedContentResponse: EmbedContentResponse =
-      await this.contentGenerator.embedContent(embedModelParams);
+
+    const cg = await this.contentGenerator;
+    const embedContentResponse = await cg.embedContent(embedModelParams);
     if (
       !embedContentResponse.embeddings ||
       embedContentResponse.embeddings.length === 0
@@ -508,7 +509,8 @@ export class GeminiClient {
     const chat = await this.chat;
     const history = chat.getHistory(true); // Get curated history
 
-    const { totalTokens } = await this.contentGenerator.countTokens({
+    const cg = await this.contentGenerator;
+    const { totalTokens } = await cg.countTokens({
       model: this.model,
       contents: history,
     });
diff --git a/packages/core/src/core/contentGenerator.ts b/packages/core/src/core/contentGenerator.ts
index 736ab7e1..c8d1866a 100644
--- a/packages/core/src/core/contentGenerator.ts
+++ b/packages/core/src/core/contentGenerator.ts
@@ -13,6 +13,7 @@ import {
   EmbedContentParameters,
   GoogleGenAI,
 } from '@google/genai';
+import { createCodeAssistContentGenerator } from '../code_assist/codeAssist.js';
 
 /**
  * Interface abstracting the core functionalities for generating content and counting tokens.
@@ -35,11 +36,15 @@ export type ContentGeneratorConfig = {
   model: string;
   apiKey?: string;
   vertexai?: boolean;
+  codeAssist?: boolean;
 };
 
-export function createContentGenerator(
+export async function createContentGenerator(
   config: ContentGeneratorConfig,
-): ContentGenerator {
+): Promise<ContentGenerator> {
+  if (config.codeAssist) {
+    return createCodeAssistContentGenerator();
+  }
   const version = process.env.CLI_VERSION || process.version;
   const googleGenAI = new GoogleGenAI({
     apiKey: config.apiKey === '' ? undefined : config.apiKey,