Documentation
Everything here is generated from the docs in the repository, so the site and the source never drift apart.
Get started
Quickstart
Download the app, describe a game in one sentence, and playtest what the agent builds. About ten minutes.
Desktop App
Installing and updating Hearth on macOS, Windows, and Linux, including what to expect the first time an unsigned build launches.
Projects & Chats
Where the work lives on your disk: the project folder a chat creates, the .hearth directory inside it, and how to move, back up, or open an existing folder.
Playtesting
The Private Tester
A model that plays your game the way a person would, keeps memory across sessions, and reports what it actually experienced: the honesty rules, how it presses keys, and what it cannot know.
Bot Sweeps
The headless half of playtesting: policies and seeds, what a sweep detects, the verdicts and screenshots it leaves behind, and how to read a report back into the conversation.
Probe Shim
The optional window.__hearthProbe contract a game can implement for deeper senses: capability tiers, the version 1 shape, and what stays true without it.
Connect Your Engine
What a connector has to do to let the bots drive a runtime that is not a web game, and what is and is not connected today.
Agents
Bring Your Own Agent
The three doors into a conversation: the Claude Code you are signed into, ChatGPT through the open-source Codex CLI, or any CLI you already use in the built-in terminal. Plus the model selector, permission modes, approvals, and where keys are stored.
Dev Team Mode
One conversation that runs a whole build: the lead, the spec you approve, the plan, the engineers working in parallel, the run controls, and the files it all lives in.
Probe over MCP
Give an agent working outside the app the same playtests the app runs: the probe as an MCP server, its tools, and how to register it.
Probe CLI
The headless probe on the command line: running a sweep, the flags that shape it, and the report it writes.