pydantic_ai.models.vertexai

Custom interface to the *-aiplatform.googleapis.com API for Gemini models.

This model uses GeminiAgentModel with just the URL and auth method changed from the default GeminiModel, it relies on the VertexAI generateContent function endpoint and streamGenerateContent function endpoints having the same schemas as the equivalent Gemini endpoints.

There are four advantages of using this API over the generativelanguage.googleapis.com API which GeminiModel uses, and one big disadvantage.

Advantages:

1. The VertexAI API seems to be less flakey, less likely to occasionally return a 503 response.
2. You can purchase provisioned throughput with VertexAI.
3. If you're running PydanticAI inside GCP, you don't need to set up authentication, it should "just work".
4. You can decide which region to use, which might be important from a regulatory perspective, and might improve latency.

Disadvantage:

1. When authorization doesn't just work, it's much more painful to set up than an API key.

Example Usage

With the default google project already configured in your environment:

vertex_example_env.py

from pydantic_ai import Agent
from pydantic_ai.models.vertexai import VertexAIModel

model = VertexAIModel('gemini-1.5-flash')
agent = Agent(model)
result = agent.run_sync('Tell me a joke.')
print(result.data)
#> Did you hear about the toothpaste scandal? They called it Colgate.

Or using a service account JSON file:

vertex_example_service_account.py

from pydantic_ai import Agent
from pydantic_ai.models.vertexai import VertexAIModel

model = VertexAIModel(
    'gemini-1.5-flash',
    service_account_file='path/to/service-account.json',
)
agent = Agent(model)
result = agent.run_sync('Tell me a joke.')
print(result.data)
#> Did you hear about the toothpaste scandal? They called it Colgate.

VERTEX_AI_URL_TEMPLATE module-attribute

VERTEX_AI_URL_TEMPLATE = "https://{region}-aiplatform.googleapis.com/v1/projects/{project_id}/locations/{region}/publishers/{model_publisher}/models/{model}:"

URL template for Vertex AI.

See generateContent docs and streamGenerateContent docs for more information.

The template is used thus:

• region is substituted with the region argument, see available regions
• model_publisher is substituted with the model_publisher argument
• model is substituted with the model_name argument
• project_id is substituted with the project_id from auth/credentials
• function (generateContent or streamGenerateContent) is added to the end of the URL

VertexAIModel dataclass

Bases: Model

A model that uses Gemini via the *-aiplatform.googleapis.com VertexAI API.

Source code in pydantic_ai_slim/pydantic_ai/models/vertexai.py

@dataclass(init=False)
class VertexAIModel(Model):
    """A model that uses Gemini via the `*-aiplatform.googleapis.com` VertexAI API."""

    model_name: GeminiModelName
    service_account_file: Path | str | None
    project_id: str | None
    region: VertexAiRegion
    model_publisher: Literal['google']
    http_client: AsyncHTTPClient
    url_template: str

    auth: BearerTokenAuth | None
    url: str | None

    # TODO __init__ can be removed once we drop 3.9 and we can set kw_only correctly on the dataclass
    def __init__(
        self,
        model_name: GeminiModelName,
        *,
        service_account_file: Path | str | None = None,
        project_id: str | None = None,
        region: VertexAiRegion = 'us-central1',
        model_publisher: Literal['google'] = 'google',
        http_client: AsyncHTTPClient | None = None,
        url_template: str = VERTEX_AI_URL_TEMPLATE,
    ):
        """Initialize a Vertex AI Gemini model.

        Args:
            model_name: The name of the model to use. I couldn't find a list of supported Google models, in VertexAI
                so for now this uses the same models as the [Gemini model][pydantic_ai.models.gemini.GeminiModel].
            service_account_file: Path to a service account file.
                If not provided, the default environment credentials will be used.
            project_id: The project ID to use, if not provided it will be taken from the credentials.
            region: The region to make requests to.
            model_publisher: The model publisher to use, I couldn't find a good list of available publishers,
                and from trial and error it seems non-google models don't work with the `generateContent` and
                `streamGenerateContent` functions, hence only `google` is currently supported.
                Please create an issue or PR if you know how to use other publishers.
            http_client: An existing `httpx.AsyncClient` to use for making HTTP requests.
            url_template: URL template for Vertex AI, see
                [`VERTEX_AI_URL_TEMPLATE` docs][pydantic_ai.models.vertexai.VERTEX_AI_URL_TEMPLATE]
                for more information.
        """
        self.model_name = model_name
        self.service_account_file = service_account_file
        self.project_id = project_id
        self.region = region
        self.model_publisher = model_publisher
        self.http_client = http_client or cached_async_http_client()
        self.url_template = url_template

        self.auth = None
        self.url = None

    async def agent_model(
        self,
        function_tools: Mapping[str, AbstractToolDefinition],
        allow_text_result: bool,
        result_tools: Sequence[AbstractToolDefinition] | None,
    ) -> GeminiAgentModel:
        url, auth = await self._ainit()
        return GeminiAgentModel(
            http_client=self.http_client,
            model_name=self.model_name,
            auth=auth,
            url=url,
            function_tools=function_tools,
            allow_text_result=allow_text_result,
            result_tools=result_tools,
        )

    async def _ainit(self) -> tuple[str, BearerTokenAuth]:
        if self.url is not None and self.auth is not None:
            return self.url, self.auth

        if self.service_account_file is not None:
            creds: BaseCredentials | ServiceAccountCredentials = _creds_from_file(self.service_account_file)
            assert creds.project_id is None or isinstance(creds.project_id, str)
            creds_project_id: str | None = creds.project_id
            creds_source = 'service account file'
        else:
            creds, creds_project_id = await _async_google_auth()
            creds_source = '`google.auth.default()`'

        if self.project_id is None:
            if creds_project_id is None:
                raise UserError(f'No project_id provided and none found in {creds_source}')
            project_id = creds_project_id
        else:
            if creds_project_id is not None and self.project_id != creds_project_id:
                raise UserError(
                    f'The project_id you provided does not match the one from {creds_source}: '
                    f'{self.project_id!r} != {creds_project_id!r}'
                )
            project_id = self.project_id

        self.url = url = self.url_template.format(
            region=self.region,
            project_id=project_id,
            model_publisher=self.model_publisher,
            model=self.model_name,
        )
        self.auth = auth = BearerTokenAuth(creds)
        return url, auth

    def name(self) -> str:
        return f'vertexai:{self.model_name}'

__init__

__init__(
    model_name: GeminiModelName,
    *,
    service_account_file: Path | str | None = None,
    project_id: str | None = None,
    region: VertexAiRegion = "us-central1",
    model_publisher: Literal["google"] = "google",
    http_client: AsyncClient | None = None,
    url_template: str = VERTEX_AI_URL_TEMPLATE
)

Initialize a Vertex AI Gemini model.

Parameters:

Name	Type	Description	Default
model_name	GeminiModelName	The name of the model to use. I couldn't find a list of supported Google models, in VertexAI so for now this uses the same models as the Gemini model.	required
service_account_file	Path | str | None	Path to a service account file. If not provided, the default environment credentials will be used.	None
project_id	str | None	The project ID to use, if not provided it will be taken from the credentials.	None
region	VertexAiRegion	The region to make requests to.	'us-central1'
model_publisher	Literal['google']	The model publisher to use, I couldn't find a good list of available publishers, and from trial and error it seems non-google models don't work with the generateContent and streamGenerateContent functions, hence only google is currently supported. Please create an issue or PR if you know how to use other publishers.	'google'
http_client	AsyncClient | None	An existing httpx.AsyncClient to use for making HTTP requests.	None
url_template	str	URL template for Vertex AI, see VERTEX_AI_URL_TEMPLATE docs for more information.	VERTEX_AI_URL_TEMPLATE

Source code in pydantic_ai_slim/pydantic_ai/models/vertexai.py

def __init__(
    self,
    model_name: GeminiModelName,
    *,
    service_account_file: Path | str | None = None,
    project_id: str | None = None,
    region: VertexAiRegion = 'us-central1',
    model_publisher: Literal['google'] = 'google',
    http_client: AsyncHTTPClient | None = None,
    url_template: str = VERTEX_AI_URL_TEMPLATE,
):
    """Initialize a Vertex AI Gemini model.

    Args:
        model_name: The name of the model to use. I couldn't find a list of supported Google models, in VertexAI
            so for now this uses the same models as the [Gemini model][pydantic_ai.models.gemini.GeminiModel].
        service_account_file: Path to a service account file.
            If not provided, the default environment credentials will be used.
        project_id: The project ID to use, if not provided it will be taken from the credentials.
        region: The region to make requests to.
        model_publisher: The model publisher to use, I couldn't find a good list of available publishers,
            and from trial and error it seems non-google models don't work with the `generateContent` and
            `streamGenerateContent` functions, hence only `google` is currently supported.
            Please create an issue or PR if you know how to use other publishers.
        http_client: An existing `httpx.AsyncClient` to use for making HTTP requests.
        url_template: URL template for Vertex AI, see
            [`VERTEX_AI_URL_TEMPLATE` docs][pydantic_ai.models.vertexai.VERTEX_AI_URL_TEMPLATE]
            for more information.
    """
    self.model_name = model_name
    self.service_account_file = service_account_file
    self.project_id = project_id
    self.region = region
    self.model_publisher = model_publisher
    self.http_client = http_client or cached_async_http_client()
    self.url_template = url_template

    self.auth = None
    self.url = None

VertexAiRegion module-attribute

VertexAiRegion = Literal[
    "us-central1",
    "us-east1",
    "us-east4",
    "us-south1",
    "us-west1",
    "us-west2",
    "us-west3",
    "us-west4",
    "us-east5",
    "europe-central2",
    "europe-north1",
    "europe-southwest1",
    "europe-west1",
    "europe-west2",
    "europe-west3",
    "europe-west4",
    "europe-west6",
    "europe-west8",
    "europe-west9",
    "europe-west12",
    "africa-south1",
    "asia-east1",
    "asia-east2",
    "asia-northeast1",
    "asia-northeast2",
    "asia-northeast3",
    "asia-south1",
    "asia-southeast1",
    "asia-southeast2",
    "australia-southeast1",
    "australia-southeast2",
    "me-central1",
    "me-central2",
    "me-west1",
    "northamerica-northeast1",
    "northamerica-northeast2",
    "southamerica-east1",
    "southamerica-west1",
]

Regions available for Vertex AI.

More details here.