spelunkai/labeling/backend

Labeling Tool — Backend

API + data model for the bounding-box labeling tool. See CLAUDE.md §3.2 for the full requirements this is built against.

Status: core data model + CRUD API implemented (sets, hierarchical classes, frames, labels, per-frame/per-set status), frame image serving, and bulk frame ingest from a recording session (see labeling/frontend/ for the UI). Not yet implemented: dataset versioning/promotion (enemy-v1, enemy-v2, ...) — deferred since it needs its own design pass (snapshot semantics: labels are editable at any time, but a promoted dataset version must stay reproducible). Also not yet implemented: auth/login (see below) or the active-learning auto-label workflow.

Stack

• FastAPI + SQLAlchemy (2.0), SQLite by default (./labeling.db), swappable via the DATABASE_URL env var (e.g. to Postgres later without code changes — one Postgres-compatible ORM).
• Multi-user, no auth yet: labels/status changes take a plain created_by / updated_by username string, resolved via get-or-create (users.py). There's no login flow — attribution only, since there's no UI yet that would need real auth.

Data model

• LabelSet — a label set (Enemy, Items, Traps, ...), one per detector model.
• MainClass / SubClass — the per-set Main → Sub class hierarchy (e.g. Enemy → Bat, Snake), created ad hoc via the API, no migration needed to add classes.
• Frame — one labelable image, identified by (session_name, frame_index) — matches the recording tool's frame-extraction output 1:1.
• Label — one bounding box (x, y, width, height in pixel space), scoped to a frame + set + sub-class.
• FrameSetStatus — per-frame, per-set label state (unlabeled / auto_labeled / reviewed).

Frame images are served from FRAMES_ROOT (env var, default ./frames) at /images/<image_path>; Frame.image_path is always relative to that root.

Setup

python -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

Run

spelunkai-labeling-backend
# or: uvicorn spelunkai_labeling_backend.main:create_app --factory --reload

Interactive API docs at http://127.0.0.1:8000/docs once running.

Bulk-ingesting a recording session

After a session's extracted frames (recording/'s extract-frames output) have been copied/rsynced onto this machine under FRAMES_ROOT, register them all in one shot (writes directly to the database, no server needs to be running):

spelunkai-labeling-backend ingest-session \
  --frames-dir /path/under/FRAMES_ROOT/run01_frames \
  --session-name run01

--image-path-prefix defaults to the frames directory's own name (here run01_frames) — override it if the directory was copied under a different name. Safe to re-run: frames already registered for that session (by frame index) are skipped. --width/--height default to 1280x720 (Spelunky Classic HD's fixed capture resolution).

Testing

pytest

Each test gets a fully isolated app + SQLite file via create_app(database_url=...) (see tests/conftest.py) — no shared state between tests, no real server needed.