Chat with a Google Gemini or Vertex AI model

Google's AI offering is broken up into two parts: Gemini and Vertex AI. Most enterprises are likely to use Vertex AI, and individuals are likely to use Gemini.

Use google_upload() to upload files (PDFs, images, video, audio, etc.)

Authentication

These functions try a number of authentication strategies, in this order:

• An API key set in the GOOGLE_API_KEY env var, or, for chat_google_gemini() only, GEMINI_API_KEY.

• Google's default application credentials, if the gargle package is installed.

• Viewer-based credentials on Posit Connect, if the connectcreds package.

• . An browser-based OAuth flow, if you're in an interactive session. This currently uses an unverified OAuth app (so you will get a scary warning); we plan to verify in the near future.

Usage

chat_google_gemini(
  system_prompt = NULL,
  base_url = "https://generativelanguage.googleapis.com/v1beta/",
  api_key = NULL,
  credentials = NULL,
  model = NULL,
  params = NULL,
  api_args = list(),
  api_headers = character(),
  echo = NULL
)

chat_google_vertex(
  location,
  project_id,
  system_prompt = NULL,
  model = NULL,
  params = NULL,
  api_args = list(),
  api_headers = character(),
  echo = NULL
)

models_google_gemini(
  base_url = "https://generativelanguage.googleapis.com/v1beta/",
  api_key = NULL,
  credentials = NULL
)

models_google_vertex(location, project_id, credentials = NULL)

Arguments

system_prompt

A system prompt to set the behavior of the assistant.

base_url

The base URL to the endpoint; the default is OpenAI's public API.

api_key

Use credentials instead.

credentials

A function that returns a list of authentication headers or NULL, the default, to use ambient credentials. See above for details.

model

The model to use for the chat (defaults to "gemini-2.5-flash"). We regularly update the default, so we strongly recommend explicitly specifying a model for anything other than casual use. Use models_google_gemini() to see all options.

params

Common model parameters, usually created by params().

api_args

Named list of arbitrary extra arguments appended to the body of every chat API call. Combined with the body object generated by ellmer with modifyList().

api_headers

Named character vector of arbitrary extra headers appended to every chat API call.

echo

One of the following options:

• none: don't emit any output (default when running in a function).

• output: echo text and tool-calling output as it streams in (default when running at the console).

• all: echo all input and output.

Note this only affects the chat() method.

location

Location, e.g. us-east1, me-central1, africa-south1 or global.

project_id

Project ID.

Value

A Chat object.

See also

Other chatbots: chat_anthropic(), chat_aws_bedrock(), chat_azure_openai(), chat_cloudflare(), chat_databricks(), chat_deepseek(), chat_github(), chat_groq(), chat_huggingface(), chat_mistral(), chat_ollama(), chat_openai(), chat_openai_compatible(), chat_openrouter(), chat_perplexity(), chat_portkey()

Examples

if (FALSE) { # \dontrun{
chat <- chat_google_gemini()
chat$chat("Tell me three jokes about statisticians")
} # }