gemini-api-models

name	gemini-api-models
description	Use when selecting a Gemini model, checking rate limits or quotas, configuring the gemini-rust crate, or debugging model name mismatches.

Gemini API Model Compatibility

Overview

rs-summarizer uses the gemini-rust crate to interact with Google's Gemini API for text generation and embeddings. Model names must exactly match the API identifiers.

Model Name Format

Models are referenced via Model::Custom(format!("models/{}", name)). The name field in ModelOption is the part after models/.

let gemini_model = Model::Custom(format!("models/{}", model.name));
let client = Gemini::with_model(&self.api_key, gemini_model)?;

Available Text Generation Models (as of June 2026)

Config Name	API ID	RPM	RPD	Notes
gemini-3.5-flash	models/gemini-3.5-flash	5	20	Default selection
gemma-4-31b-it	models/gemma-4-31b-it	15	1500	Free, no system prompt
gemma-4-26b-a4b-it	models/gemma-4-26b-a4b-it	15	1500	Free, no system prompt
gemini-3.1-flash-lite	models/gemini-3.1-flash-lite	15	500	Stable version, high quota
gemini-2.5-flash	models/gemini-2.5-flash	5	20	Solid all-rounder
gemini-2.5-flash-lite	models/gemini-2.5-flash-lite	10	20	Lightweight
gemini-3-flash-preview	models/gemini-3-flash-preview	5	20	Preview version

Embedding Model

Config Name	API ID	RPM	RPD
gemini-embedding-001	models/gemini-embedding-001	100	1000

Important: Do NOT use Model::TextEmbedding004 — that maps to models/text-embedding-004 which doesn't exist. Use Model::Custom instead.

System Prompt Compatibility

Gemini models support system prompts via .with_system_prompt().

Gemma models do NOT support system prompts ("Developer instruction is not enabled"). The code conditionally skips the system prompt:

let mut builder = client.generate_content();
if !model.name.starts_with("gemma") {
    builder = builder.with_system_prompt("...");
}
let mut stream = builder.with_user_message(&prompt).execute_stream().await?;

Streaming

Text generation uses .execute_stream() which returns an async stream of chunks. Each chunk may contain:

• response.text() — the generated text fragment
• response.usage_metadata — token counts (typically only in the last chunk)

Rate Limit Detection

fn is_rate_limit_error(err_str: &str) -> bool {
    err_str.contains("ResourceExhausted")
        || err_str.contains("429")
        || err_str.contains("RESOURCE_EXHAUSTED")
}

Listing Available Models

To discover correct model IDs:

curl -s "https://generativelanguage.googleapis.com/v1beta/models?key=$GEMINI_API_KEY" | \
  python3 -c "import sys,json; [print(m['name']) for m in json.load(sys.stdin)['models'] if 'generateContent' in m.get('supportedGenerationMethods',[])]"

Relevant Files

• src/services/summary.rs — Text generation with streaming
• src/services/embedding.rs — Embedding computation
• src/main.rs — Model option configuration
• src/state.rs — ModelOption struct definition