Google Gemini (React)

First, install the Google adapter package:

npm install @hashbrownai/google

Streaming Text Responses

Hashbrown’s Google Gemini adapter lets you stream chat completions from Google Gemini models, handling function calls, response schemas, and request transforms.

API Reference

HashbrownGoogle.stream.text(options)

Streams a Gemini chat completion as a series of encoded frames. Handles content, tool calls, and errors, and yields each frame as a Uint8Array.

Options:

Name	Type	Description
apiKey	string	Your Google Gemini API Key.
request	Chat.Api.CompletionCreateParams	The chat request: model, messages, tools, system, responseFormat, etc.
transformRequestOptions	(params) => params | Promise	(Optional) Transform or override the final Gemini request before it is sent.

Supported Features:

• Roles: user, assistant, tool, error
• Tools: Supports tool calling with OpenAPI schemas automatically converted to Gemini format.
• Response Format: Optionally specify a JSON schema for model output validation.
• System Prompt: Included as Gemini’s systemInstruction.
• Tool Calling: Handles Gemini’s tool calling modes and emits tool call frames.
• Streaming: Each chunk/frame is encoded using @hashbrownai/core’s encodeFrame.

How It Works

• Messages are mapped to Gemini's Content objects, including tool calls and tool responses.
• Tools/Functions: Tools are converted to Gemini FunctionDeclaration format, including parameter schema conversion via OpenAPI.
• Response Schema: If you specify responseFormat, it's converted and set as responseSchema for Gemini.
• Streaming: All data is sent as a stream of encoded frames (Uint8Array). Chunks may contain text, tool calls, errors, or finish signals.
• Error Handling: Any thrown errors are sent as error frames before the stream ends.

Example: Using with Express

import { HashbrownGoogle } from '@hashbrownai/google';
import { decodeFrame } from '@hashbrownai/core';

app.post('/chat', async (req, res) => {
  const stream = HashbrownGoogle.stream.text({
    apiKey: process.env.GOOGLE_API_KEY!,
    request: req.body, // must be Chat.Api.CompletionCreateParams
  });

  res.header('Content-Type', 'application/octet-stream');
  for await (const chunk of stream) {
    res.write(chunk); // Pipe each encoded frame as it arrives
  }
  res.end();
});

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Transform Request Options

The transformRequestOptions parameter allows you to intercept and modify the request before it's sent to Google Gemini. This is useful for server-side prompts, message filtering, logging, and dynamic configuration.

app.post('/chat', async (req, res) => {
  const stream = HashbrownGoogle.stream.text({
    apiKey: process.env.GOOGLE_API_KEY!,
    request: req.body,
    transformRequestOptions: (options) => {
      return {
        ...options,
        // Add system instructions for Gemini
        systemInstruction: {
          parts: [{ text: 'You are a helpful AI assistant specialized in technical topics.' }]
        },
        // Adjust generation config based on content type
        generationConfig: {
          ...options.generationConfig,
          temperature: req.body.contentType === 'creative' ? 0.8 : 0.2,
        },
      };
    },
  });

  // ... rest of the code
});

Learn more about transformRequestOptions

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Advanced: Tools and Response Schema

• Tools: Add tools using OpenAI-style function specs. They will be auto-converted for Gemini.
• Tool Calling: Supported via Gemini's tool configuration, with control over auto, required, or none modes.
• Response Format: Pass a JSON schema in responseFormat for structured output.