Unit 11 · Ship AI systems you can operate

Fall back without changing your app contract

You route across models by capability, health, latency, price, or application policy. A fallback preserves the typed contract and remains observable.

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Worked example

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const llm = ai({ name: router, config: { model: preferredModel } });

Run itIn your own project

npm install @ax-llm/ax

import { ai, ax } from '@ax-llm/ax';

const llm = ai({ name: 'openai', apiKey: process.env.OPENAI_APIKEY! });
const classify = ax('review:string -> sentiment:class "positive, negative, neutral"');

const result = await classify.forward(llm, {
  review: 'Useful and boring in the best way.',
});

Set OPENAI_APIKEY in your environment before running provider-backed code.

In the ax repo

From a clone of the ax repo:

npm run example -- typescript src/examples/typescript/long-agents/smart-defaults-agent.ts

Active practice

Show that you can use it

Answer 2 in a row to learn this · attempt 1

Keep exploring

See the idea in context

Show that you can use it

Source-backed follow-up