@wrnexus/ai is a thin, dependency-free wrapper over the Anthropic Messages API, built on fetch (Bun-native, no SDK). Use it in API routes, jobs, or middleware to call Claude. It defaults to the most capable model, claude-opus-4-8, reads your key from ANTHROPIC_API_KEY, and supports both one-shot generation and streaming.

Installation

bun add @wrnexus/ai

Private package — the machine must be authenticated to the wrnexus npm org (a read token in ~/.npmrc). Requires Bun (Node is not supported).

Set your key in the environment (e.g. .env):

ANTHROPIC_API_KEY=sk-ant-...

API

`createAI(config?)`

Creates a client. The key is read at call time, so it's safe to create at import.

import { createAI } from "@wrnexus/ai";
const ai = createAI(); // or createAI({ apiKey, model, maxTokens, baseURL, version })

AIConfig fields (all optional):

Field	Default	Description
`apiKey`	`ANTHROPIC_API_KEY`	Anthropic API key
`model`	`"claude-opus-4-8"`	Model id
`maxTokens`	`4096`	Default max output tokens
`baseURL`	`https://api.anthropic.com`	API base URL
`version`	`"2023-06-01"`	`anthropic-version` header

`ai.generate(prompt, opts?): Promise<string>`

One-shot text generation. prompt is a string or a Message[] history.

const text = await ai.generate("Write a haiku about Bun.");

const reply = await ai.generate(
  [
    { role: "user", content: "My name is Ada." },
    { role: "assistant", content: "Hi Ada!" },
    { role: "user", content: "What's my name?" },
  ],
  { system: "You are concise." },
);

`ai.stream(prompt, opts?): AsyncGenerator<string>`

Yields text deltas as they arrive.

for await (const chunk of ai.stream("Tell me a story.")) {
  process.stdout.write(chunk);
}

`ai.streamResponse(prompt, opts?): Response`

Returns a streaming text/plain Response — drop it straight into an API route.

// app/api/chat.ts
import { createAI } from "@wrnexus/ai";
const ai = createAI();

export const POST = async (ctx) => {
  const { prompt } = await ctx.req.json();
  return ai.streamResponse(prompt);
};

`GenerateOptions`

Option	Type	Description
`system`	`string`	System prompt
`model`	`string`	Override the model for this call
`maxTokens`	`number`	Override max output tokens
`thinking`	`boolean`	Enable adaptive extended thinking (deeper reasoning)
`effort`	`"low" \| "medium" \| "high" \| "xhigh" \| "max"`	Reasoning effort / token spend
`messages`	`Message[]`	Full history — supersedes `prompt`
`signal`	`AbortSignal`	Cancel the request

temperature / top_p are intentionally not exposed — the current Claude models reject them (400). Steer output with prompting instead.

`AIError`

Thrown on non-2xx responses or a model refusal. Carries .status and .type (e.g. "authentication_error", "rate_limit_error", "refusal").

import { AIError } from "@wrnexus/ai";
try {
  await ai.generate("...");
} catch (e) {
  if (e instanceof AIError && e.type === "rate_limit_error") {
    /* back off */
  }
}

Usage

Return generated JSON from an API route

// app/api/summarize.ts — summarize posted text
import { createAI } from "@wrnexus/ai";
const ai = createAI();

export const POST = async (ctx) => {
  const { text } = await ctx.req.json().catch(() => ({}));
  if (!text) return Response.json({ error: "Provide 'text'." }, { status: 400 });
  const summary = await ai.generate(`Summarize in one sentence:\n\n${text}`, {
    system: "You are a precise summarizer.",
  });
  return Response.json({ summary });
};

Stream a chat response to the browser

// app/api/chat.ts
import { createAI } from "@wrnexus/ai";

const ai = createAI({ model: "claude-sonnet-5" });

export const POST = async (ctx) => {
  const { messages } = await ctx.req.json();
  return ai.streamResponse(messages, {
    system: "Answer using concise Markdown.",
    maxTokens: 1_500,
  });
};

Requirements / Notes

Bun-only. Uses fetch, ReadableStream, TextDecoder/TextEncoder, and reads ANTHROPIC_API_KEY from Bun.env (falls back to process.env).
Zero dependencies — no @anthropic-ai/sdk; talks to the Messages API directly.
Defaults to claude-opus-4-8. Pass { model } for a different model (e.g. "claude-sonnet-5" for speed/cost, "claude-haiku-4-5" for the fastest).