---
title: "VertexAIGeminiChatGenerator"
id: vertexaigeminichatgenerator
slug: "/vertexaigeminichatgenerator"
description: "`VertexAIGeminiChatGenerator` enables chat completion using Google Gemini models."
---

# VertexAIGeminiChatGenerator

`VertexAIGeminiChatGenerator` enables chat completion using Google Gemini models.

:::warning
Deprecation Notice

This integration uses the deprecated google-generativeai SDK, which will lose support after August 2025.

We recommend switching to the new [GoogleGenAIChatGenerator](googlegenaichatgenerator.mdx) integration instead.
:::

|                                        |                                                                                                      |
| :------------------------------------- | :--------------------------------------------------------------------------------------------------- |
| **Most common position in a pipeline** | After a [ChatPromptBuilder](../builders/chatpromptbuilder.mdx)                                                 |
| **Mandatory run variables**            | “messages”: A list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx)  objects representing the chat |
| **Output variables**                   | “replies”: A list of alternative replies of the model to the input chat                              |
| **API reference**                      | [Google Vertex](/reference/integrations-google-vertex)                                                      |
| **GitHub link**                        | https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/google_vertex      |

`VertexAIGeminiGenerator` supports `gemini-1.5-pro` and `gemini-1.5-flash`/  `gemini-2.0-flash` models. Note that [Google recommends upgrading](https://cloud.google.com/vertex-ai/generative-ai/docs/learn/model-versions) from `gemini-1.5-pro` to `gemini-2.0-flash`.

For available models, see https://cloud.google.com/vertex-ai/generative-ai/docs/learn/models.

:::note
To explore the full capabilities of Gemini check out this [article](https://haystack.deepset.ai/blog/gemini-models-with-google-vertex-for-haystack) and the related [🧑‍🍳 Cookbook](https://colab.research.google.com/github/deepset-ai/haystack-cookbook/blob/main/notebooks/vertexai-gemini-examples.ipynb).

:::

### Parameters Overview

`VertexAIGeminiChatGenerator` uses Google Cloud Application Default Credentials (ADCs) for authentication. For more information on how to set up ADCs, see the [official documentation](https://cloud.google.com/docs/authentication/provide-credentials-adc).

Keep in mind that it’s essential to use an account that has access to a project authorized to use Google Vertex AI endpoints.

You can find your project ID in the [GCP resource manager](https://console.cloud.google.com/cloud-resource-manager) or locally by running `gcloud projects list` in your terminal. For more info on the gcloud CLI, see its [official documentation](https://cloud.google.com/cli).

### Streaming

This Generator supports [streaming](guides-to-generators/choosing-the-right-generator.mdx#streaming-support) the tokens from the LLM directly in output. To do so, pass a function to the `streaming_callback` init parameter.

## Usage

You need to install the `google-vertex-haystack` package to use the  `VertexAIGeminiChatGenerator`:

```shell
pip install google-vertex-haystack
```

### On its own

Basic usage:

```python
from haystack.dataclasses import ChatMessage
from haystack_integrations.components.generators.google_vertex import VertexAIGeminiChatGenerator

gemini_chat = VertexAIGeminiChatGenerator()

messages = [ChatMessage.from_user("Tell me the name of a movie")]
res = gemini_chat.run(messages)

print(res["replies"][0].text)

messages += [res["replies"][0], ChatMessage.from_user("Who's the main actor?")]
res = gemini_chat.run(messages)

print(res["replies"][0].text)
```

When chatting with Gemini Pro, you can also easily use function calls. First, define the function locally and convert into a [Tool](../../tools/tool.mdx):

```python
from typing import Annotated
from haystack.tools import create_tool_from_function

## example function to get the current weather
def get_current_weather(
    location: Annotated[str, "The city for which to get the weather, e.g. 'San Francisco'"] = "Munich",
    unit: Annotated[str, "The unit for the temperature, e.g. 'celsius'"] = "celsius",
) -> str:
    return f"The weather in {location} is sunny. The temperature is 20 {unit}."

tool = create_tool_from_function(get_current_weather)
```

Create a new instance of `VertexAIGeminiChatGenerator` to set the tools and a [ToolInvoker](../tools/toolinvoker.mdx) to invoke the tools.:

```python
from haystack_integrations.components.generators.google_vertex import VertexAIGeminiChatGenerator
from haystack.components.tools import ToolInvoker

gemini_chat = VertexAIGeminiChatGenerator(model="gemini-2.0-flash-exp", tools=[tool])

tool_invoker = ToolInvoker(tools=[tool])
```

And then ask our question:

```python
from haystack.dataclasses import ChatMessage

messages = [ChatMessage.from_user("What is the temperature in celsius in Berlin?")]
res = gemini_chat.run(messages=messages)

print(res["replies"][0].tool_calls)

tool_messages = tool_invoker.run(messages=replies)["tool_messages"]
messages = user_message + replies + tool_messages

messages += res["replies"][0] + [ChatMessage.from_function(content=weather, name="get_current_weather")]

final_replies = gemini_chat.run(messages=messages)["replies"]
print(final_replies[0].text)
```

### In a pipeline

```python
from haystack.components.builders import ChatPromptBuilder
from haystack.dataclasses import ChatMessage
from haystack import Pipeline
from haystack_integrations.components.generators.google_vertex import VertexAIGeminiChatGenerator

## no parameter init, we don't use any runtime template variables
prompt_builder = ChatPromptBuilder()
gemini_chat = VertexAIGeminiChatGenerator()

pipe = Pipeline()
pipe.add_component("prompt_builder", prompt_builder)
pipe.add_component("gemini", gemini)
pipe.connect("prompt_builder.prompt", "gemini.messages")

location = "Rome"
messages = [ChatMessage.from_user("Tell me briefly about {{location}} history")]
res = pipe.run(data={"prompt_builder": {"template_variables":{"location": location}, "template": messages}})

print(res)

```

## Additional References

🧑‍🍳 Cookbook: [Function Calling and Multimodal QA with Gemini](https://haystack.deepset.ai/cookbook/vertexai-gemini-examples)
