## Yao Sandbox Environment

### Environment Variables

These environment variables are set by the Yao sandbox. **Always use these variables — never hardcode paths.**

| Variable | Purpose | Example |
|----------|---------|---------|
| `$WORKDIR` | Sandbox working directory (project root) | `/workspace` |
| `$HOME` | Same as `$WORKDIR` (redirected by sandbox) | `/workspace` |
| `$CTX_SKILLS_DIR` | Skills directory for this assistant | `$WORKDIR/.yao/assistants/<id>/skills` |
| `$CTX_ASSISTANT_ID` | Current assistant ID | `yao.agent-smith` |
| `$CTX_WORKSPACE_ID` | Current workspace ID | `ws-abc123` |

### Path Rules

- **Use `$WORKDIR`** for all file paths — never hardcode `/workspace`
- **Use `$CTX_SKILLS_DIR`** for assistant-specific skills (custom skills provided by the assistant)
- System tool skills are in `$HOME/.claude/skills/` and are **auto-discovered** — you do not need to read them manually
- The `Read` and `Write` tools do **NOT** expand shell variables.
  Resolve first: `echo "$WORKDIR"`, then use the printed value.
- On Windows, use `$env:WORKDIR` / `$env:CTX_SKILLS_DIR` syntax instead.

### Attachments

User-uploaded files are placed in `$WORKDIR/.attachments/{chatID}/`.
When the user references an attached file, read it from this directory.

## Yao System Tools

You have access to Yao system tools via the `tai` command in bash.

**Calling convention**: `tai tool <name> '<json_args>'`

| Tool | Skill (auto-loaded) | Description |
|------|---------------------|-------------|
| `web_search` | yao-web | Search the web for real-time information |
| `web_fetch` | yao-web | Fetch and read a web page by URL |
| `process_call` | yao-process | Execute a Yao Process (server-side function) |
| `process_allowed` | yao-process | Check which processes are allowed |
| `doc_list` | yao-doc | Search/list available process documentation |
| `doc_inspect` | yao-doc | Get detailed docs for a specific process |
| `doc_validate` | yao-doc | Validate a process name and get suggestions |

The three system skills (`yao-web`, `yao-process`, `yao-doc`) in `$HOME/.claude/skills/` are **auto-discovered** — they contain detailed parameter docs and workflow guidance. You do not need to manually read them; they are loaded automatically when your task matches their description.