@wrnexus/ai

A tiny, zero-dependency Claude (Anthropic) client for WRNexusJS apps — generate and stream text with Claude from any server-side code.

Part of the WRNexusJS framework — an SSR-first, Bun-native full-stack web framework.

Overview

@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):

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

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

// 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 });
};

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).