Legacy SDK Migration

If you have @google/generative-ai code, port it

The legacy @google/generative-ai reached EOL in August 2025. The migration is mechanical and the new package fits the same problem with cleaner shape.

Six things change

Aspect	Legacy	New
Class	`GoogleGenerativeAI`	`GoogleGenAI`
Import	`@google/generative-ai`	`@google/genai`
Model	`genAI.getGenerativeModel({model})`	(none — pass `model` per call)
Generate	`model.generateContent(text)`	`ai.models.generateContent({model, contents})`
Response text	`result.response.text()` (method)	`response.text` (property)
Chat	`model.startChat()`	`ai.chats.create({model})`
Files	Separate `FileManager`	`ai.files.upload(...)`
Vertex	Separate `@google-cloud/vertexai`	`GoogleGenAI({vertexai: true})`

The .text() vs .text bug

The single biggest porting gotcha: legacy used result.response.text() (method call). The new SDK uses response.text (property access). Forgetting to drop the parentheses gives you TypeError: response.text is not a function. Grep your codebase for .text() when porting and fix all of them at once.

Code

Side-by-side migration·typescript

// ❌ BEFORE — legacy, EOL Aug 2025
import { GoogleGenerativeAI } from '@google/generative-ai';

const genAI = new GoogleGenerativeAI(process.env.GEMINI_API_KEY!);
const model = genAI.getGenerativeModel({ model: 'gemini-pro' });
const result = await model.generateContent('Tell me a story.');
console.log(result.response.text());  // METHOD CALL

// ✅ AFTER — new SDK
import { GoogleGenAI } from '@google/genai';

const ai = new GoogleGenAI({ apiKey: process.env.GOOGLE_API_KEY! });
const response = await ai.models.generateContent({
  model: 'gemini-2.5-flash',
  contents: 'Tell me a story.',
});
console.log(response.text);  // PROPERTY

Chat migration·typescript

// ❌ BEFORE
const chat = model.startChat({ history: [...] });
const r = await chat.sendMessage('Hi');
console.log(r.response.text());

// ✅ AFTER
const chat = ai.chats.create({
  model: 'gemini-2.5-flash',
  history: [...],  // optional, same shape
});
const r = await chat.sendMessage({ message: 'Hi' });
console.log(r.text);

Streaming migration·typescript

// ❌ BEFORE
const result = await model.generateContentStream('Story');
for await (const chunk of result.stream) {
  console.log(chunk.text());
}

// ✅ AFTER
const stream = await ai.models.generateContentStream({
  model: 'gemini-2.5-flash',
  contents: 'Story',
});
for await (const chunk of stream) {
  if (chunk.text) process.stdout.write(chunk.text);
}

If you have @google/generative-ai code, port it

Six things change

The .text() vs .text bug

Code

External links

Exercise

Progress

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