# Build Your Own Claude Code — Workshop

A hands-on workshop by [Abhi Aiyer](https://github.com/AbhiAiyer) (Founder/CTO, Mastra) and [Tyler Barnes](https://github.com/TylerBarnes) (Founding Engineer, Mastra) covering the architecture behind [**MastraCode**](https://github.com/mastra-ai/mastra/tree/main/mastracode) — an open-source AI coding agent you can run, extend, and make your own.

## What You'll Learn

The workshop dissects every layer that makes MastraCode work, from the execution harness to cost tracking:

| # | Topic | What It Covers |
|---|-------|----------------|
| 1 | **Intro** | Key components overview |
| 2 | **The Harness** | Stateful, resumable execution architecture |
| 3 | **Prompts & Context** | Dynamic system prompt composition (env, mode, tools, tasks, skills) |
| 4 | **Workspace** | Skills, filesystem sandboxing, purpose-built tools vs bash |
| 5 | **Memory** | Context growth, compaction, observational memory |
| 6 | **Modes** | PLAN, BUILD, FAST, REVIEW, TRIAGE, CUSTOM — rewiring agent behavior |
| 7 | **Steering** | Human-in-the-loop: interrupts, abort, free-form input |
| 8 | **Protocols** | Event system, MCP, SubAgents |
| 9 | **Streaming** | Multi-model streaming, interrupt handling, provider routing |
| 10 | **Policies** | Tool permission matrix, YOLO mode, cost tracking |
| 11 | **Checklist** | Production-readiness criteria |

## Slides

Open `slides/index.html` in a browser. Navigate with arrow keys or the top nav bar.

## Examples

The `examples/` directory contains runnable TypeScript examples that progressively build up from a raw harness to a full TUI:

```bash
cd examples
pnpm install
```

| Example | Run | Description |
|---------|-----|-------------|
| `basic.ts` | `npx tsx basic.ts` | Hand-built Harness with subagents (researcher + poet), memory, and event subscriptions |
| `basic-tui.ts` | `npx tsx basic-tui.ts` | Same hand-built Harness wired into `MastraTUI` for an interactive terminal UI |
| `mc.ts` | `npx tsx mc.ts` | `createMastraCode()` factory — modes, tool grants, MCP manager |
| `tui.ts` | `npx tsx tui.ts` | Full MastraCode TUI in ~14 lines |


## MastraCode

[**MastraCode**](https://github.com/mastra-ai/mastra/tree/main/mastracode) is a coding agent built on the [Mastra Harness](https://github.com/mastra-ai/mastra/tree/main/packages/core/src/harness). It ships with modes, memory, streaming, tool policies, subagents, observational memory, and a terminal UI — everything covered in this workshop. During the live session, MastraCode was used to work on its own codebase as the final demo.

```bash
npm i -g mastracode
mastracode # in the dir you want to work in
```


## Source Code

- [**MastraCode**](https://github.com/mastra-ai/mastra/tree/main/mastracode) — the full CLI agent
- [**Harness**](https://github.com/mastra-ai/mastra/tree/main/packages/core/src/harness) — the core execution engine in `@mastra/core`