How it works

OpenComputer runs agents defined as TypeScript functions. You describe the agent for the current step; OpenComputer supplies the managed harness that calls the model, executes tools, streams output, and records the durable session.

The runtime model

Your agent function describes the next step

The default export is a synchronous function. It reads the current input, selects resources with hooks, and returns instructions:

import { useInput, useModel, useTool } from "@opencomputer/agent";
import { inspectRepository } from "./tools/inspect-repository";

export default function Agent() {
  const input = useInput();

  useModel("anthropic/claude-sonnet-4.6");
  useTool(inspectRepository);

  return `
    You are a release-readiness agent.
    Inspect the repository before giving a RELEASE or DO NOT RELEASE verdict.

    Current request: ${input.text ?? "Review the configured repository."}
  `;
}

The function does not call the model or execute the tool. Each hook contributes to the effective configuration for the next model step.

The harness performs the loop

OpenComputer owns the agent harness. For each step it:

renders the agent function;
builds a model request from the returned instructions and selected resources;
streams the model response;
validates and executes requested tools;
records the resulting events; and
renders again when another model step is required.

Because a function can render more than once during a turn, keep it synchronous and free of external side effects. Network calls and mutations belong in tools or remote MCP servers.

A session makes execution durable

A session stores the conversation and runtime events across turns. Clients can disconnect, reconnect, and continue without reconstructing the agent’s history themselves. Every session remains pinned to the immutable deployment it started with. A new development sync or production deployment affects new sessions, not code already running inside an existing session.

Capabilities are selected, not executed, during render

Use the narrowest capability that fits the work:

Capability	What the harness receives
`useTool(tool)`	One typed operation implemented by your project
`useMcpServer(server)`	A collection of tools advertised by a remote MCP server
`useSubagent(agent)`	Another project agent available for delegation
A skill under `skills/`	Reusable instructions and supporting resources

The model decides whether to request an available tool. The harness remains responsible for validating the request, executing it, and recording the result. See Agent capabilities for the full comparison.

Deployment registers; rendering selects

A deployment packages the agents and resources that are allowed to exist. A render selects which of those resources are available for one model step. Development and Production point to different deployments and keep operational configuration—such as secrets, schedule state, webhook tokens, and channel bindings—separate. Read Deployments and environments for that lifecycle.

Remember this

The agent function decides what the agent is for this step.
The harness decides how to run that step.
The session remembers what happened.

Explore each concept

Reactive agents

Define instructions and select resources with ordinary TypeScript.

Sessions and turns

Understand durable conversations and runtime events.

Capabilities

Choose between tools, MCP servers, skills, and subagents.

Schedules

Start recurring sessions from code-defined cron schedules.

Webhooks

Start sessions from authenticated external services.

Channels and outboxes

Receive conversational events and publish durable notifications.

Getting started

Concepts

Agent API

Test and operate

Examples

The runtime model

Your agent function describes the next step

The harness performs the loop

A session makes execution durable

Capabilities are selected, not executed, during render

Deployment registers; rendering selects

Remember this

Explore each concept

Reactive agents

Sessions and turns

Capabilities

Schedules

Webhooks

Channels and outboxes

​The runtime model

​Your agent function describes the next step

​The harness performs the loop

​A session makes execution durable

​Capabilities are selected, not executed, during render

​Deployment registers; rendering selects

​Remember this

​Explore each concept

Reactive agents

Sessions and turns

Capabilities

Schedules

Webhooks

Channels and outboxes

The runtime model

Your agent function describes the next step

The harness performs the loop

A session makes execution durable

Capabilities are selected, not executed, during render

Deployment registers; rendering selects

Remember this

Explore each concept