Writer (React)

First, install the Writer adapter package:

npm install @hashbrownai/writer

Streaming Text Responses

Hashbrown’s Writer adapter lets you stream chat completions from Writer models, including support for tool calling, response schemas, and request transforms.

API Reference

HashbrownWriter.stream.text(options)

Streams a Writer 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 Writer 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 Writer request before it is sent.

Supported Features:

• Roles: user, assistant, tool
• Tools: Supports Writer tool calling, including toolCalls and strict function schemas.
• Response Format: Optionally specify a JSON schema for structured output (Writer’s response_format parameter).
• System Prompt: Included as the first message if provided.
• Tool Calling: Handles Writer tool calling modes and emits tool call frames.
• Streaming: Each chunk/frame is encoded into a resilient streaming format.

How It Works

• Messages: Translated to Writer’s message format, supporting all roles and tool calls.
• Tools/Functions: Tools are passed as function definitions, using your JSON schemas as parameters.
• Response Format: Pass a JSON schema in responseFormat for Writer to validate the model output.
• 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 { HashbrownWriter } from '@hashbrownai/writer';
import { decodeFrame } from '@hashbrownai/core';

app.post('/chat', async (req, res) => {
  const stream = HashbrownWriter.stream.text({
    apiKey: process.env.WRITER_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 Writer. This is useful for server-side prompts, message filtering, logging, and dynamic configuration.

app.post('/chat', async (req, res) => {
  const stream = HashbrownWriter.stream.text({
    apiKey: process.env.WRITER_API_KEY!,
    request: req.body,
    transformRequestOptions: (options) => {
      return {
        ...options,
        // Add server-side system prompt
        messages: [
          { role: 'system', content: 'You are a helpful AI writing assistant.' },
          ...options.messages,
        ],
        // Adjust parameters based on writing task
        temperature: req.body.taskType === 'creative' ? 0.8 : 0.3,
      };
    },
  });

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

Learn more about transformRequestOptions

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Advanced: Tools and Response Schema

• Tools: Add tools using function specs (name, description, parameters) compatible with Writer.
• Tool Calling: Supported via toolChoice (auto, required, none, etc.).
• Response Format: Pass a JSON schema in responseFormat for Writer to return validated structured output.