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Hearth: Build your own assistant

Today we launched Hearth, an AI home for your family. It’s the first app built on Playground, our library for building collaborative AI coding harnesses for teams that don’t normally code.

Hearth gives you the tools to build your own AI assistant for your family. It’s a shared family notebook with an AI agent that can help keep it all together. But then the agent can build apps on top of all those notes, and you can run the apps right inside of Hearth. It’s like the AI harnesses and sandboxes that cutting-edge software engineers are using, but simpler, easier to lock down1, and built for apps that just serve you and your family.

We think you should see what trouble you can get into with Hearth first. Read on if you want to understand how we think about building AI applications for different verticals.

Custom software for every use case

We don’t think that all software will be completely custom for every application, but we do think the default will go from changing how you work to fit the software to changing the software to fit how you work. Agents will be primarily responsible for the coding required to make that happen.

Agents can write the code, but the people who could use custom software aren’t usually set up to run it. Operating and securing software is difficult, and today’s tools are built for much larger systems.

The future is workspaces where domain knowledge, agents, context, people, and code work together. Hearth is this concept applied to families; one of the simpler use cases.

A Hearth for every domain

We think that the best coding harnesses are designed around the work a group is trying to accomplish. For families, this is relatively simple: the schedules, people, services, and rituals are all fairly well understood even if the specifics change for every family. For difficult, complex work like producing a movie or building a building, we think the best harness for that job will be built for that job while still allowing arbitrary code to work inside of it.

Hearth, Bear (building construction), and movie production architecture

Coding for a particular job

AI-generated apps for Hearth don’t need specialized interfaces; they mostly just call services or read and write markdown. The power of a purpose-built harness is realized when we give the app framework abstractions for doing a particular kind of work.

All harnesses provide basic filesystem and network access. Then each harness can inject the library or data models needed for a particular kind of work. Hearth mostly relies on Markdown, which is enough for most families. For construction, we provide APIs for modeling buildings and querying the model’s graph.

import q from "bear/query";
import type BearGraph from "bear/graph";
import type Playground from "playground";

/**
 * Analyzes the structural steel connections in a building
 *
 * @param playground - Filesystem access, app capabilities, etc.
 * @param graph - The compiled graph of building nodes to inspect.
 * @returns The backend response containing the connection analysis result.
 */
async function analyzeSteelConnections(
  playground: Playground,
  graph: BearGraph,
): Promise<Response> {
  const connectedNodes = q(graph)
    .system("structural")
    .where(node => node.material === "steel")
    .and(node => node.connections > 0);

  // "mySteelService" has credentials configured outside the app and injected
  return playground.capabilities.mySteelService.fetch("/api/connection-analyzer", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(connectedNodes),
  });
}

The same idea can be used to provide interfaces for agents to write apps for all sorts of complexity (e.g. movie editing, airfoil analysis, manufacturing system engineering, ERPs, etc), all running in isolated, per-project environments that are purpose-built for the task at hand.

Coming soon

In the upcoming weeks and months we’re going to have a lot more to say and a lot more to show.

  • Open sourcing Playground as a library and Hearth as a demo app
  • Making it easy for Hearth users to share skills and apps amongst each other
  • Opening up access to Bear, our Playground-based app for building construction

We can’t wait to see what you build!

Further reading

We have been inspired and validated by a lot of other great work.

Footnotes

  1. Hearth is beta software and while the design is secure by default, we have not thoroughly audited the codebase. Please use caution. ↩