Agent Harness

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:

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:

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:

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:

./agent-harness/agent-cli.sh <AGENT_ID> url

Step 3: Use the CLI

All stack management goes through agent-cli.sh:

# 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:

# 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:

{
  "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:    demo@lightdash.com
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:

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

4. Run verification:

   ./agent-harness/verify.sh <ID>
   

Debugging API issues

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

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

# Check for errors in Maple (local tracing)
maple errors --since 5m

# Get trace details (full 32-char trace ID from the logs)
maple trace <trace-id>

Debugging frontend issues

# 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

# 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:

# 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

# 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