---
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.
:::

<div className="key-value-table">

|  |  |
| --- | --- |
| **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      |

</div>

`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.

:::info
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)
>>> The Shawshank Redemption

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

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

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)
>>> [ToolCall(tool_name='get_current_weather',
>>>           arguments={'unit': 'celsius', 'location': 'Berlin'}, id=None)]

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)
>>> The temperature in Berlin is 20 degrees Celsius.
```

### 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)

>>> - **753 B.C.:** Traditional date of the founding of Rome by Romulus and Remus.
>>> - **509 B.C.:** Establishment of the Roman Republic, replacing the Etruscan monarchy.
>>> - **492-264 B.C.:** Series of wars against neighboring tribes, resulting in the expansion of the Roman Republic's territory.
>>> - **264-146 B.C.:** Three Punic Wars against Carthage, resulting in the destruction of Carthage and the Roman Republic becoming the dominant power in the Mediterranean.
>>> - **133-73 B.C.:** Series of civil wars and slave revolts, leading to the rise of Julius Caesar.
>>> - **49 B.C.:** Julius Caesar crosses the Rubicon River, starting the Roman Civil War.
>>> - **44 B.C.:** Julius Caesar is assassinated, leading to the Second Triumvirate of Octavian, Mark Antony, and Lepidus.
>>> - **31 B.C.:** Battle of Actium, where Octavian defeats Mark Antony and Cleopatra, becoming the sole ruler of Rome.
>>> - **27 B.C.:** The Roman Republic is transformed into the Roman Empire, with Octavian becoming the first Roman emperor, known as Augustus.
>>> - **1st century A.D.:** The Roman Empire reaches its greatest extent, stretching from Britain to Egypt.
>>> - **3rd century A.D.:** The Roman Empire begins to decline, facing internal instability, invasions by Germanic tribes, and the rise of Christianity.
>>> - **476 A.D.:** The last Western Roman emperor, Romulus Augustulus, is overthrown by the Germanic leader Odoacer, marking the end of the Roman Empire in the West.
```

## Additional References

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