# CLAUDE.md

## Project Overview

**Sandlot** is a CLI tool for branch-based development using git worktrees and [Apple Container](https://github.com/apple/container). Each branch gets its own isolated worktree and container. The primary workflow is: create a session (`sandlot new <branch>`), do work with Claude Code inside the container, then merge and clean up.

**Platform requirement**: macOS on Apple Silicon only.

## Tech Stack

- **Runtime**: [Bun](https://bun.sh) (not Node.js — use `bun` for everything)
- **Language**: TypeScript (strict, ESNext, bundler module resolution)
- **CLI parsing**: [Commander.js](https://github.com/tj/commander.js) 13.x
- **Containers**: Apple Container (`brew install container`)
- **Entry point**: `src/cli.ts` (shebang: `#!/usr/bin/env bun`, runs directly without compilation)

## Commands

```bash
bun install          # install dependencies
bun link             # make `sandlot` available globally
sandlot --help       # list all commands
```

No build step. TypeScript runs directly via Bun. There are no tests.

## Source Structure

```
src/
  cli.ts      # CLI entry point, all command handlers (Commander.js)
  git.ts      # Git operations: worktrees, branches, merge
  vm.ts       # Container lifecycle: create, provision, exec, shell, claude
  state.ts    # Per-repo session persistence (.sandlot/state.json)
  config.ts   # Load optional sandlot.json config from repo root
  spinner.ts  # CLI progress spinner (braille frames)
```

## Architecture

Each module has a single responsibility. No classes — only exported async functions.

**Session flow for `sandlot new <branch>`:**
1. `git.createWorktree()` → creates worktree at `~/.sandlot/<repo>/<branch>`
2. Creates symlink `<repo-root>/.sandlot/<branch>` → worktree path
3. `vm.ensure()` → start/create/provision the container
4. `state.setSession()` → write to `.sandlot/state.json`
5. `vm.claude()` → launch Claude Code in container at worktree path

**Worktree location**: `~/.sandlot/<repo-name>/<branch>/` (outside the repo)
**Symlink in repo**: `<repo-root>/.sandlot/<branch>` → worktree
**State file**: `<repo-root>/.sandlot/state.json`
**Container name**: always `"sandlot"` (single shared container per machine)

## Container Details

- Image: `ubuntu:24.04`
- User: `ubuntu`
- Mounts: `~/dev` and `~/.sandlot` from host
- Provisioned once on first use: installs `curl git neofetch fish`, Claude Code, git identity, API key helper
- API key: read from `~/.env` on host (`ANTHROPIC_API_KEY=...`), written as `~/.claude/api-key-helper.sh` in the container (never passed as a process argument)
- Claude settings: `skipDangerousModePermissionPrompt: true` in container

## Shell Command Pattern

Uses Bun's `$` template literal for shell execution:

```typescript
import { $ } from "bun"

// Capture output
const text = await $`git rev-parse --show-toplevel`.cwd(dir).nothrow().quiet().text()

// Suppress output, ignore failures
await $`git worktree prune`.cwd(cwd).nothrow().quiet()

// Check exit code
const result = await $`git diff --staged --quiet`.nothrow().quiet()
if (result.exitCode === 0) { ... }
```

Always use `.nothrow()` for commands that may fail non-fatally. Use `.quiet()` to suppress stdout/stderr.

## Configuration

Optional `sandlot.json` at repo root (loaded by `config.ts`):

```json
{
  "vm": {
    "cpus": 4,
    "memory": "8GB",
    "image": "ubuntu:24.04",
    "mounts": { "/host/path": "/container/path" }
  }
}
```

Note: `config.ts` loads this but `vm.ts` does not yet use it — the container is hardcoded with `-m 4G` and `ubuntu:24.04`.

## State Schema

`.sandlot/state.json` (per repo, gitignored):

```json
{
  "sessions": {
    "branch-name": {
      "branch": "branch-name",
      "worktree": "/Users/you/.sandlot/repo/branch-name",
      "created_at": "2026-02-16T10:30:00Z"
    }
  }
}
```

## Error Handling Conventions

- Throw `Error` with descriptive messages from git/vm modules
- CLI commands catch and display errors, then `process.exit(1)`
- On `new` failure, roll back: remove worktree, delete branch, unlink symlink
- Non-fatal cleanup steps use `.catch(() => {})` to continue past failures

## Key Implementation Notes

- `vm.exec()` prepends `export PATH=$HOME/.local/bin:$PATH` so `claude` binary is found
- `vm.claude()` uses `Bun.spawn` with `stdin/stdout/stderr: "inherit"` for interactive TTY
- Branch creation in `createWorktree()` handles three cases: local branch, remote branch (tracks origin), new branch from HEAD
- `sandlot save` uses Claude (`claude -p "..."`) inside the container to generate commit messages
- `.sandlot/` should be in the repo's `.gitignore`