mkdir my-agent && cd my-agent
bun init -y
bun add @open-harness/core

import { createWorkflow, ClaudeHarness } from "@open-harness/core";

// 1. Define your state type
type State = {
  topic: string;
  summary: string | null;
};

// 2. Create a typed workflow factory
const { agent, runReactive } = createWorkflow<State>();

// 3. Define a reactive agent
const summarizer = agent({
  prompt: `Summarize this topic in 2-3 sentences: {{ state.topic }}`,
  activateOn: ["workflow:start"],
  emits: ["summary:complete"],
  updates: "summary",
});

// 4. Run the workflow
async function main() {
  const harness = new ClaudeHarness({
    model: "claude-sonnet-4-20250514",
  });

  const result = await runReactive({
    agents: { summarizer },
    state: {
      topic: "The history of artificial intelligence",
      summary: null,
    },
    harness,
    endWhen: (s) => s.summary !== null,
  });

  console.log("Summary:", result.state.summary);
  console.log("Duration:", result.metrics.durationMs, "ms");
}

main();

bun run index.ts

Summary: Artificial intelligence research began in the 1950s with pioneers like Alan Turing...
Duration: 1234 ms

activateOn: ["workflow:start"]  // React to workflow lifecycle
activateOn: ["analysis:done"]   // React to custom signals

updates: "summary"  // output → state.summary

endWhen: (state) => state.summary !== null