Providers

Anthropic and OpenAI adapters — zero vendor SDK dependencies.

kenpachi talks to LLMs over raw fetch. Both built-in providers support streaming (streamTurn) automatically — no extra config for agent.stream() or onText.

---

Anthropic Provider

import { createAnthropicProvider } from "kenpachi";

const provider = createAnthropicProvider({
  apiKey: process.env.ANTHROPIC_API_KEY!,
  model: "claude-sonnet-4-6", // Required
});

Options

apiKey · string · required

Anthropic API key string.

model · string · required

Model name — must be explicitly specified (e.g. "claude-sonnet-4-6", "claude-3-5-haiku-20241022").

---

OpenAI Provider

import { createOpenAIProvider } from "kenpachi";

const provider = createOpenAIProvider({
  apiKey: process.env.OPENAI_API_KEY!,
  model: "gpt-4o", // Required
});

Options

apiKey · string · required

OpenAI API key string.

model · string · required

Model name — must be explicitly specified (e.g. "gpt-4o", "gpt-4o-mini", "gpt-4-turbo").

---

Custom providers

Implement the ModelProvider interface to plug in any backend:

interface ModelProvider {
  name: string;
  createTurn(input: ModelTurnInput): Promise<ModelTurnResult>;
  streamTurn?(input: ModelTurnInput): AsyncIterable<StreamChunk>; // optional — enables token streaming
}

If you only implement createTurn, streaming still works — text is emitted as a single chunk.

---

Tool Serialization Across Providers

kenpachi automatically converts Zod tool schemas into standard JSON Schemas (serializeZodSchema) and maps them to provider-specific function declaration shapes:

Anthropic Provider

Maps tools to Anthropic’s expected input_schema shape:

{
  name: tool.name,
  description: tool.description,
  input_schema: {
    type: "object",
    properties: serializedProperties,
    required: serializedRequired
  }
}

OpenAI Provider

Maps tools to OpenAI’s function declaration shape:

{
  type: "function",
  function: {
    name: tool.name,
    description: tool.description,
    parameters: {
      type: "object",
      properties: serializedProperties,
      required: serializedRequired
    }
  }
}