Gemini

GeminiBuilder presets the Google Generative Language endpoint and auth, and exposes Gemini's native tools and embeddings through the builder. Hand the built client to ChatBuilder::with_model and the rest of chat-rs works the same as any other provider.

Install

Enable the gemini feature (crate chat-gemini):

chat-rs = { version = "0.5.1", features = ["gemini"] }

By default the client reads your key from the GEMINI_API_KEY environment variable. You can also set it explicitly with with_api_key.

Usage

use chat_rs::{ChatBuilder, ChatOutcome, gemini::GeminiBuilder, parts, types::messages};

let client = GeminiBuilder::new()
    .with_model("gemini-2.5-flash")
    .build();

let mut chat = ChatBuilder::new().with_model(client).build();

let mut messages = messages::from_user(parts!["Hey there!"]);

if let ChatOutcome::Complete(res) = chat.complete(&mut messages).await.map_err(|e| e.err)? {
    println!("{:?}", res.content.parts.last());
}

Configuration

The builder methods cover the Gemini-specific surface:

• with_model(impl Into<String>) selects the model and moves the builder into its ready-to-build state.
• with_api_key(String) supplies the key directly instead of reading GEMINI_API_KEY.
• with_thoughts(bool) toggles Gemini's reasoning, surfaced while streaming as StreamEvent::ReasoningChunk.
• with_image_output() requests TEXT and IMAGE response modalities so the model can return generated images. This is experimental and only works on models that support image output.
• with_description(impl Into<String>), with_metadata(key, value), and with_transport(transport) attach metadata or swap in a custom transport.

Native tools (see native tools) are added on the builder:

• with_code_execution() lets the model run code in a sandbox.
• with_google_search() enables grounded search; with_google_search_threshold(f32) does the same with a dynamic retrieval threshold.
• with_google_maps(Option<(f32, f32)>, bool) enables Maps grounding, taking an optional (lat, lng) and whether to emit a map widget.
• with_function_calling_mode(&str, Option<Vec<String>>) sets the calling mode (for example "ANY") and an optional allow-list of function names.

You can combine several native tools on one client:

let client = GeminiBuilder::new()
    .with_model("gemini-2.5-flash")
    .with_google_maps(Some((34.05048, -118.24853)), false)
    .with_google_search()
    .build();

For embeddings, switch the builder into embedding mode:

• with_embeddings(Option<usize>) enables embeddings with an optional output dimension count.
• with_embeddings_task(task) sets the embedding task type.

let client = GeminiBuilder::new()
    .with_model("gemini-embedding-001")
    .with_embeddings(Some(128))
    .build();

let mut chat = ChatBuilder::new().with_model(client).with_embeddings().build();
let response = chat.embed(&mut messages).await.map_err(|e| e.err)?;
println!("{:?}", response.embeddings);

Capabilities

• Completion and streaming are both supported.
• Embeddings and structured output are supported.
• Multimodal input (such as images) works by attaching file parts to a user message.
• Native tools: code execution, Google Search, and Google Maps grounding.