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@openharness/core

Building blocks for capable, general-purpose AI agents. Part of OpenHarness.

Install

npm install @openharness/core

What's inside

• Agent -- stateless multi-step executor wrapping any AI SDK LanguageModel with tools, subagents, resumable subagent sessions, MCP, and skills
• Session -- batteries-included stateful wrapper with compaction, retry, persistence, and hooks
• Runner & Middleware -- composable FP-style middleware (withRetry, withCompaction, withTurnTracking, withPersistence, withHooks) for pick-and-choose behavior
• Conversation -- lightweight stateful wrapper over a composed Runner, with toResponse() for AI SDK 5 streaming
• Stream combinators -- tap, filter, map, takeUntil for async generator transforms
• Tools -- filesystem tools (readFile, writeFile, editFile, listFiles, grep, deleteFile) and a bash tool
• UI streaming -- sessionEventsToUIStream() maps agent events to AI SDK 5 UIMessageChunk streams

Quick start

Agent (stateless)

import { Agent, fsTools, bash } from "@openharness/core";
import { openai } from "@ai-sdk/openai";

const agent = new Agent({
  name: "dev",
  model: openai("gpt-5.2"),
  tools: { ...fsTools, bash },
});

for await (const event of agent.run([], "Fix the auth bug")) {
  if (event.type === "text.delta") process.stdout.write(event.text);
  if (event.type === "done") console.log(event.result);
}

Middleware + Conversation (composable)

import {
  Agent, Conversation, toRunner, apply,
  withTurnTracking, withCompaction, withRetry,
} from "@openharness/core";

const runner = apply(
  toRunner(agent),
  withTurnTracking(),
  withCompaction({ contextWindow: 200_000, model: agent.model }),
  withRetry(),
);

const chat = new Conversation({ runner });

for await (const event of chat.send("Refactor the config parser")) {
  if (event.type === "text.delta") process.stdout.write(event.text);
}

Session (batteries-included)

import { Session } from "@openharness/core";

const session = new Session({ agent, contextWindow: 200_000 });

for await (const event of session.send("Refactor the config parser")) {
  if (event.type === "text.delta") process.stdout.write(event.text);
}

Next.js route handler

import {
  Agent, Conversation, toRunner, apply,
  withTurnTracking, withCompaction, withRetry,
  extractUserInput,
} from "@openharness/core";

const runner = apply(
  toRunner(agent),
  withTurnTracking(),
  withCompaction({ contextWindow: 128_000, model: agent.model }),
  withRetry(),
);

const chat = new Conversation({ runner });

export async function POST(req: Request) {
  const { messages } = await req.json();
  const input = await extractUserInput(messages);
  return chat.toResponse(input, { signal: req.signal });
}

Documentation

See the full documentation for:

• Agent configuration, events, and lifecycle
• Subagents (foreground, background, resumable sessions, and dynamic catalogs)
• Middleware reference and custom middleware
• Compaction strategies
• MCP server integration
• Skills system
• AI SDK 5 UI integration

License

MIT