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Cortex · Prompt and context

Context producers (context)

context is a list of producers: a string, an array of strings, a Message[], or a function (sync or async) of deps, input and the agent that returns one of those. Each string becomes a system message, in the list’s order, after the finish protocol; a function runs once, when the run starts.

Agent
type Deps = { programme: { night: string; title: string }[] };

const desk = defineAgent<undefined, Deps>({
  id: 'desk',
  instructions: 'Answer the member in one sentence.',
  context: [
    'Doors open thirty minutes before the show.',
    ({ deps }) => deps.programme.map((show) => `${show.night}: ${show.title}`),
  ],
});

const preview = await desk.preview('What plays on Sunday?', { llm, deps: { programme } });
Messages after the finish protocol
system    Doors open thirty minutes before the show.
system    2026-10-23: The Tempest
system    2026-10-24: The Tempest
system    2026-10-25: Twelfth Night
user      What plays on Sunday?
Order
[
  'system Doors open thirty minutes before the show.',
  'system 2026-10-23: The Tempest',
  'system 2026-10-24: The Tempest',
  'system 2026-10-25: Twelfth Night',
  'user What plays on Sunday?',
]
Output matches the expected value

Runs in this page on the installed package. The input and the expected output are defined by the example.