# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Repository purpose

LeLab is a FastAPI + React web interface wrapping the [LeRobot](https://github.com/huggingface/lerobot) framework for the SO-101 leader/follower arm. It exposes teleoperation, dataset recording, calibration, replay, and training as HTTP/WebSocket endpoints, replacing LeRobot's CLI + keyboard-driven flows.

The frontend (React + Vite) lives in [`frontend/`](frontend/). The bundle in `frontend/dist/` is not committed: [setup.py](setup.py) builds it while building the wheel, with Node from the `nodejs-wheel-binaries` build requirement, and ships it as package data (`frontend.__init__.py` makes setuptools treat it as a package); [`lelab/server.py`](lelab/server.py) mounts it as `StaticFiles` at `/` so a single `lelab` process serves both API and UI on `:8000`. The `frontend/` directory is also force-pushed to the [LeLab HF Space](https://huggingface.co/spaces/lerobot/LeLab) by [`.github/workflows/sync_space.yml`](.github/workflows/sync_space.yml) — that's a separate runtime; the Space builds the [Dockerfile](frontend/Dockerfile) (which runs `npm run build` itself).

## Common commands

Install (editable, requires Python ≥3.10):

```bash
pip install -e .
```

`lerobot` is pinned to a release tag on `huggingface/lerobot` (currently `v0.6.0`, see [pyproject.toml](pyproject.toml)) — installed from git rather than PyPI because the published wheels don't expose the `lerobot-rollout` script that [lelab/rollout.py](lelab/rollout.py) shells out to. Bump the tag when you want a newer upstream release; expect import-path drift (e.g. `lerobot.configs.dataset`, `lerobot.utils.feature_utils`, `lerobot.common.control_utils`) and adjust call sites accordingly.

Run servers (entry point defined in [pyproject.toml](pyproject.toml)):

```bash
lelab          # uvicorn on :8000, serves built frontend at /, opens browser
lelab --dev    # spawns Vite dev (:8080) + uvicorn --reload (:8000), opens browser to :8080
```

Editable installs skip the frontend build: `lelab --dev` serves directly from Vite, and `lelab --rebuild` builds `frontend/dist/` with your local Node.js 22 when you want to try the production bundle. The SO-101 meshes in `frontend/public/` are kept out of LFS because installing from git does not fetch LFS files.

Run the Python tests with `pytest` (config in [pyproject.toml](pyproject.toml); install dev deps via `pip install -e ".[test]"`). Tests live in [tests/](tests/) and cover request schemas, pure helpers, and idle/mutex branches of the feature handlers — subprocess/thread happy paths and HF Jobs integration are deliberately not unit-tested. Lint with `ruff check` / `ruff format` (config in [pyproject.toml](pyproject.toml)). There is no Python build step; for end-to-end validation, run `lelab` and exercise endpoints (curl or via the frontend).

## Architecture

### Backend module layout (`lelab/`)

[server.py](lelab/server.py) is a thin FastAPI router. Each feature lives in its own module that owns its global state and exposes `handle_*` functions plus a Pydantic request model:

- [record.py](lelab/record.py) — dataset recording (wraps `lerobot.record.record`); patches `lerobot.common.utils.control_utils` keyboard listener so frontend buttons replace arrow-key controls. The worker is a daemon thread, so the server's shutdown hook calls `stop_recording_and_wait()` to let an active session finalize on Ctrl+C.
- [teleoperate.py](lelab/teleoperate.py) — leader→follower teleoperation (wraps `lerobot.teleoperate`).
- [calibrate.py](lelab/calibrate.py) — step-by-step web calibration with a `CalibrationManager` singleton and `_step_complete` threading.Event.
- [train.py](lelab/train.py) — wraps the LeRobot training CLI as a subprocess (psutil for lifecycle, queue for log streaming).
- [datasets.py](lelab/datasets.py) — dataset listing (local cache + Hub, merged under a `source` field) plus the episode-browsing handlers behind `/dataset-episodes`, `/dataset-episode`, `/dataset-frame`, `/dataset-thumbnails`, `/dataset-motion` and `/dataset-video`.
- [episode_media.py](lelab/episode_media.py) — reads the LeRobot v3.0 on-disk layout (`meta/episodes/*.parquet` + `videos/`) and decodes frames with PyAV. Deliberately does **not** go through `LeRobotDataset`, so browsing a dataset never builds a robot config or imports torch. Several episodes share one mp4, so locating an episode resolves both the file and the `from_/to_timestamp` window inside it — which is why `/dataset-video` is addressed by chunk/file rather than by episode. Call `ensure_episode_index(repo_id)` before opening a local dataset with `LeRobotDataset`: LeRobot writes the index only in `finalize()`, and without it reads the dataset as "not downloaded yet" and fetches it from the Hub, which 404s for a dataset that was never pushed.
- [utils/config.py](lelab/utils/config.py) — shared paths and persistence: calibration JSON, saved ports, saved config selections. **Import shared constants from here, do not hardcode paths in feature modules.**

### State model

Each feature module owns module-level globals (e.g. `recording_active`, `teleoperation_active`, `current_robot`) protected by threads/locks where needed. There's no shared session object — features are mutually exclusive in practice (you can't teleoperate and record simultaneously) but this is **not** enforced in code.

### WebSocket broadcast

[server.py](lelab/server.py#L104-L206) defines a single `ConnectionManager` with a background `_broadcast_worker` thread that drains a `queue.Queue` and forwards joint data to all `/ws/joint-data` clients via a thread-local asyncio loop. Feature modules get the manager passed in (e.g. `handle_start_teleoperation(request, manager)`) and call `manager.broadcast_joint_data_sync(data)` from their worker threads. Don't `await` from these threads — use the sync queue method.

### Persistent state on disk

All under `~/.cache/huggingface/lerobot/` (managed in [utils/config.py](lelab/utils/config.py)):

- `calibration/teleoperators/so101_leader/*.json` — leader calibration files (also called "teleop")
- `calibration/robots/so101_follower/*.json` — follower calibration files (also called "robot")
- `ports/{leader,follower}_port.txt` — last-used serial ports
- `saved_configs/{leader,follower}_config.txt` — last-selected config name

`device_type` in API requests is `"teleop"` or `"robot"` (mapped to leader/follower paths). `robot_type` in port endpoints is `"leader"` or `"follower"`. Don't conflate the two vocabularies.

### Calibration files: dual-location pattern

[setup_calibration_files](lelab/utils/config.py#L30-L74) copies user-selected configs from `LEADER_CONFIG_PATH` / `FOLLOWER_CONFIG_PATH` into LeRobot's expected locations under `~/.cache/huggingface/lerobot/calibration/`. Recording, teleoperation, and replay all call this before starting. New features that drive a robot must do the same.

## Hardware target

Hardcoded for **SO-101 leader/follower arms** (`so101_leader`, `so101_follower`). Adding another robot type requires touching every feature module's config construction (search for `SO101LeaderConfig` / `SO101FollowerConfig`).

## Phone camera / HTTPS

Phone-as-camera streaming requires HTTPS. See [PHONE_CAMERA_SETUP.md](PHONE_CAMERA_SETUP.md) and [HTTPS_SETUP.md](HTTPS_SETUP.md). Self-signed certs go in `certs/`. The default `lelab-fullstack` does **not** start with HTTPS — for phone cameras run uvicorn manually with `--ssl-keyfile certs/key.pem --ssl-certfile certs/cert.pem`.