Agent Harness

When to use this skill

Use Agent Harness when an AI agent needs a reusable SKILL.md workflow for this job: Guide for AI agents running in the isolated agent-harness environment. Use when you need to discover your agent ID, find your ports, manage your stack with agent-cli.sh, run verification, or understand the multi-agent development setup.

When not to use it

Skip Agent Harness when the task is outside the productivity category, or when a more specific skill in this directory already covers the same workflow with clearer triggers.

How to install

1. Personal install: create ~/.claude/skills/agent-harness/SKILL.md (and any bundled scripts) so Claude Code, Claude Desktop, and compatible agents can load it in every project.
2. Project install: commit the same folder at .claude/skills/agent-harness/ so teammates get the skill with the repo.
3. Restart the agent session after copying files so it re-scans the skills directory, then ask for the task in words that match the skill description.

Full install guide for Claude, Cursor, and Codex

What this skill does

# Agent Harness Quick Start

You are running in an isolated Lightdash development environment managed by the agent-harness. This guide helps you discover your environment and get productive immediately.

## Step 1: Discover Your Agent ID

Your agent ID determines all your ports and resources. Find it by checking for the generated environment file:

```bash ls -la .env.agent.* 2>/dev/null | head -1 ```

This will show something like `.env.agent.1` — the number is your agent ID.

**Alternative**: Check which PM2 processes are running:

```bash pnpm exec pm2 jlist 2>/dev/null | node -e " const data = JSON.parse(require('fs').readFileSync(0, 'utf8')); const agents = [...new Set(data.map(p => p.name.match(/^agent-(\d+)-/)?.[1]).filter(Boolean))]; if (agents.length === 1) console.log('AGENT_ID=' + agents[0]); else if (agents.length > 1) console.log('Multiple agents running: ' + agents.join(', ')); else console.log('No agent processes found'); " ```

## Step 2: Know Your Ports

Once you have your agent ID, your ports are deterministic:

| Service | Formula | Agent 1 | Agent 2 | Agent 3 | |---------|---------|---------|---------|---------| | Frontend (Vite) | 3000 + (ID × 10) | 3010 | 3020 | 3030 | | Backend API | 8000 + (ID × 10) | 8010 | 8020 | 8030 | | Node Debugger | 9200 + (ID × 10) | 9210 | 9220 | 9230 |

**Shared infrastructure** (same for all agents): - PostgreSQL: `localhost:15432` - MinIO S3: `localhost:19000` - Headless Browser: `localhost:13001` - Mailpit SMTP: `localhost:11025` - Mailpit Web UI: `localhost:18025`

Get your URLs with: ```bash ./agent-harness/agent-cli.sh <AGENT_ID> url ```

## Step 3: Use the CLI

All stack management goes through `agent-cli.sh`:

```bash # Replace <ID> with your agent ID (1-5)

# Check process status (uptime, restarts, memory) ./agent-harness/agent-cli.sh <ID> status

# View logs (services: api, frontend, common-watch, warehouses-watch) ./agent-harness/agent-cli.sh <ID> logs api ./agent-harness/agent-cli.sh <ID> logs frontend

# Check API health ./agent-harness/agent-cli.sh <ID> health

# Restart services after code changes ./agent-harness/agent-cli.sh <ID> restart api ./agent-harness/agent-cli.sh <ID> restart frontend

# Run SQL queries against your database ./agent-harness/agent-cli.sh <ID> psql "SELECT * FROM users LIMIT 5;"

# View slow queries (useful for debugging) ./agent-harness/agent-cli.sh <ID> slow-queries

# Run arbitrary command with your agent's environment loaded ./agent-harness/agent-cli.sh <ID> exec pnpm -F backend test:dev:nowatch ```

## Step 4: Verification Workflow

**Run verification after every code change:**

```bash # Quick verification (typecheck + lint + unit tests for changed files) ./agent-harness/verify.sh <ID>

# Full verification (complete test suite + smoke test) ./agent-harness/verify.sh <ID> --full ```

Output is JSON to stdout: ```json { "status": "pass", "stages": [ {"name": "typecheck", "status": "pass", "duration_ms": 3200}, {"name": "lint", "status": "pass", "duration_ms": 1800}, {"name": "test-unit", "status": "pass", "duration_ms": 4500} ], "total_duration_ms": 9500 } ```

Stages run in order, stopping on first failure: 1. **typecheck** — TypeScript for common, backend, frontend (parallel) 2. **lint** — ESLint for common, backend, frontend (parallel) 3. **test-unit** — Unit tests for changed files 4. **test-full** (--full only) — Complete test suite 5. **smoke** (--full only) — API health check

## Step 5: Test Login Credentials

``` Email: [email protected] Password: demo_password! ```

## Common Workflows

### Making code changes

1. Edit files as needed 2. If you changed `packages/common/`, the TypeScript watcher auto-rebuilds 3. If you changed `packages/backend/`, restart the API: ```bash ./agent-harness/agent-cli.sh <ID> restart api ``` 4. Run verification: ```bash ./agent-harness/verify.sh <ID> ```

### Debugging API issues

```bash # Check health ./agent-harness/agent-cli.sh <ID> health

# View recent API logs ./agent-harness/agent-cli.sh <ID> logs api

# Check for errors using Spotlight MCP mcp__spotlight__search_errors with filters: {"timeWindow": 300}

# Get trace details mcp__spotlight__get_traces with traceId: "<8-char-prefix-from-logs>" ```

### Debugging frontend issues

```bash # View Vite server logs ./agent-harness/agent-cli.sh <ID> logs frontend

# Use Chrome DevTools MCP for browser automation # (Your frontend URL is http://localhost:<3000 + ID*10>) ```

### Database queries

```bash # View schema ./agent-harness/agent-cli.sh <ID> psql "\d tablename"

# Run queries ./agent-harness/agent-cli.sh <ID> psql "SELECT * FROM projects LIMIT 5;"

# Check slow queries ./agent-harness/agent-cli.sh <ID> slow-queries ```

## Definition of Done

Your task is complete when ALL are true: - `./agent-harness/verify.sh <ID> --full` returns `"status": "pass"` - Feature/fix works in browser at your frontend URL - Tests cover the change - No TypeScript errors or lint warnings - Changes are committed

## What NOT to Do

- **Do NOT** modify shared infrastructure (PostgreSQL, MinIO containers) - **Do NOT** hardcode ports — always derive from your agent ID - **Do NOT** run `docker compose` commands — use `agent-cli.sh` - **Do NOT** touch other agents' databases or processes - **Do NOT** manually edit `.env.agent.<ID>` or `ecosystem.agent.<ID>.config.cjs` - **Do NOT** disable tests to make verification pass

## Tmux Session Management

If you were launched with `--claude`, you're running inside a named tmux session `agent-<ID>`.

**For human supervisors** to attach to your session: ```bash # Attach to a specific agent's tmux session ./agent-harness/attach.sh <ID>

# Or directly with tmux tmux attach -t agent-<ID>

# List all agent sessions tmux list-sessions | grep "^agent-" ```

**Useful tmux commands** (prefix is `Ctrl-a` on cloud servers, `Ctrl-b` locally): - `prefix + d` — Detach from session (leaves Claude running) - `prefix + [` — Enter scroll mode (q to exit) - `prefix + c` — Create new window - `prefix + n/p` — Next/previous window

## Quick Reference Card

```bash # Status & Health ./agent-harness/agent-cli.sh <ID> status ./agent-harness/agent-cli.sh <ID> health ./agent-harness/agent-cli.sh <ID> url

# Logs ./agent-harness/agent-cli.sh <ID> logs api ./agent-harness/agent-cli.sh <ID> logs frontend

# Restart ./agent-harness/agent-cli.sh <ID> restart api ./agent-harness/agent-cli.sh <ID> restart frontend

# Database ./agent-harness/agent-cli.sh <ID> psql "<SQL>" ./agent-harness/agent-cli.sh <ID> slow-queries

# Verification ./agent-harness/verify.sh <ID> # Quick ./agent-harness/verify.sh <ID> --full # Complete

# Package commands (use your agent's env) pnpm -F common typecheck pnpm -F backend typecheck pnpm -F frontend typecheck pnpm -F backend lint pnpm -F common test pnpm generate-api # After TSOA controller changes ```

Intended uses

• Use Agent Harness when this documented workflow matches the task.