Horton agent

The built-in assistant registered by the DARIX dev server. Horton can chat conversationally, search the web, read and edit files, run shell commands, and dispatch subagents (workers) for isolated subtasks.

Source: packages/ts-darix-server/src/darix-agents/agents/horton.ts

Try it

With the dev server running (pnpm start:darix):

pnpm darix spawn /horton/my-horton
pnpm darix send /horton/my-horton 'What's in this directory?'
pnpm darix observe /horton/my-horton

Tools

Horton is configured with ctx.darixTools plus the seven Horton tools:

Tool	Purpose
bash	Run shell commands in the working directory.
read	Read a file. Tracked in a per-wake readSet.
write	Create or overwrite a file.
edit	Targeted string replacement (file must be read first).
brave_search	Web search via the Brave Search API.
fetch_url	Fetch a URL and return it as markdown.
spawn_worker	Dispatch a subagent for an isolated subtask.

brave_search requires BRAVE_SEARCH_API_KEY in the environment; without it the tool errors at call time.

Title generation

On the first wake, Horton calls generateTitle() (Haiku) to summarise the user's first message into a 3-5 word session title and stores it via ctx.setTag('title', title). Failures are logged and ignored — the entity continues without a title.

Details

Property	Value
Type name	horton
Model	HORTON_MODEL (claude-sonnet-4-5-20250929)
Title model	claude-haiku-4-5-20251001
Tools	ctx.darixTools + Horton tool set (7 tools)
Working directory	Passed at bootstrap (defaults to process.cwd())
Title generation	Yes, on first wake

Extending Horton

The system prompt and tool factory are exported so you can build your own variants:

import {
  HORTON_MODEL,
  buildHortonSystemPrompt,
  createHortonTools,
} from "@durable-streams/ts-darix-server"

registry.define("my-assistant", {
  description: "Horton with an extra custom tool",
  async handler(ctx) {
    const readSet = new Set<string>()
    ctx.useAgent({
      systemPrompt: buildHortonSystemPrompt(process.cwd()),
      model: HORTON_MODEL,
      tools: [
        ...ctx.darixTools,
        ...createHortonTools(process.cwd(), ctx, readSet),
        myCustomTool,
      ],
    })
    await ctx.agent.run()
  },
})

Related

• Worker — the subagent type Horton dispatches via spawn_worker.