Skip to content

Quick Start

1. Create a config

Create a file called my_experiment.yaml:

model: "claude-sonnet-4-20250514"
provider: anthropic
work_dir: "./repos/my_project"
session_mode: isolated

system_prompt: |
  You are exploring a Python codebase. Use MEMORY.md to keep notes.

sessions:
  - session_index: 1
    prompt: "Explore the project structure. Take notes in MEMORY.md."
  - session_index: 2
    prompt: "Read the main module in detail. Update your notes."

2. Run it

harness run my_experiment.yaml

The harness will:

  1. Initialize a shadow git repo to track all file changes
  2. Seed MEMORY.md in the working directory
  3. Run each session sequentially
  4. Save ATIF trajectories, diffs, and metadata to runs/<run-name>/

3. Inspect results

# CLI summary
harness inspect runs/<run-name>

# Or browse in the web UI
cd ui && npm run dev
# Open http://localhost:5173

4. Resample for variance

# Resample a specific API turn
harness resample runs/<run-name> --session 1 --request 5 --count 10

# Or re-run a full session
harness resample-session runs/<run-name> --session 2 --count 5

Example output

$ harness run tests/smoke.yaml

[session 1] starting (mode=isolated)...
[session 1] done -- 15 steps, 5 tool calls, $0.0596

Run complete: runs/2026-03-15T10-30-00_claude-sonnet-4-20250514

Next steps