The agentic framework
for TypeScript.

import { createFevex, defineAgent } from '@fevex/core';
import { fakeModel } from '@fevex/core/testing';

const app = createFevex({
  models: { default: fakeModel({ output: 'Hello from FEVEX.' }) },
  agents: [defineAgent({
    name: 'assistant',
    instructions: 'Be clear. Be helpful.',
  })],
});

const result = await app.runAgent('assistant', { input: 'Hello!' });
console.log(result.output); // Hello from FEVEX.

Runs locally. No API key required.

import { defineTool } from '@fevex/core';
import { z } from 'zod';

export const getAccount = defineTool({
  name: 'accounts_get',
  description: 'Get an account by ID.',
  inputSchema: z.object({ accountId: z.number() }),
  outputSchema: z.object({
    accountId: z.number(), status: z.literal('active'),
  }),
  execute({ accountId }) {
    return { accountId, status: 'active' };
  },
});

This example also uses Zod: npm install zod.

import { createOpenAI } from '@fevex/openai';
import { createDeepSeek } from '@fevex/deepseek';

const openai = createOpenAI({
  apiKey: process.env.OPENAI_API_KEY!,
});
const deepseek = createDeepSeek({
  apiKey: process.env.DEEPSEEK_API_KEY!,
});

// Choose a model ID supported by your provider.
export const models = {
  default: openai(process.env.OPENAI_MODEL!),
  alternative: deepseek(process.env.DEEPSEEK_MODEL!),
};

Add the provider package and your server-side API key.

import { createFevex, defineAgent } from '@fevex/core';
import { fakeModel } from '@fevex/core/testing';

const app = createFevex({
  models: { default: fakeModel({ output: 'Hello from FEVEX.' }) },
  agents: [defineAgent({ name: 'assistant', instructions: 'Be helpful.' })],
  onEvent(event) {
    console.log(event.type);
  },
});

await app.runAgent('assistant', { input: 'Hello!' });
// run.started → model.started → … → run.completed

A local example with observable lifecycle events.