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AGENTS.md

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+# Agent Guidelines
+
+## README.md size constraint
+
+The README.md is synced to Docker Hub, which has a **25,000 character limit**.
+Any change to README.md **must** keep the file under 25,000 characters (`wc -c README.md`).
+If an addition would exceed the limit, trim existing prose elsewhere — prefer tightening verbose descriptions over removing sections.
+
+## Tech stack
+
+- **Backend:** Python 3.13+, aiohttp, python-socketio 5.x, yt-dlp
+- **Frontend:** Angular 21, TypeScript, Bootstrap 5, SASS, ngx-socket-io
+- **Package managers:** uv (Python), pnpm (frontend)
+- **Container:** Multi-stage Docker (Node builder + Python runtime), multi-arch (amd64/arm64)
+
+## Build & test commands
+
+```bash
+# Frontend (run from ui/)
+pnpm install --frozen-lockfile
+pnpm run lint
+pnpm run build
+pnpm exec ng test --watch=false
+
+# Backend (run from repo root)
+uv sync --frozen --group dev
+python -m compileall app
+uv run pytest app/tests/
+```
+
+All of these run in CI (`.github/workflows/main.yml`) on every push to master and must pass.
+
+## Code style
+
+Follow `.editorconfig`:
+- Python: 4-space indent
+- Everything else (TypeScript, YAML, JSON, HTML): 2-space indent
+- UTF-8, LF line endings, trim trailing whitespace, final newline
+
+Frontend additionally uses ESLint (`ui/eslint.config.js`) and Prettier (config in `ui/package.json`: `printWidth=100`, `singleQuote=true`).
+
+## Project structure
+
+```
+app/main.py          — HTTP server, Socket.IO events, REST API routes, Config class
+app/ytdl.py          — Download queue logic, yt-dlp integration
+app/subscriptions.py — Channel/playlist subscription manager
+app/state_store.py   — JSON-based persistent storage with atomic writes
+app/dl_formats.py    — Video/audio codec/quality mapping
+app/tests/           — pytest tests (asyncio_mode=auto)
+ui/src/app/          — Angular standalone components (no NgModules)
+```
+
+## Key conventions
+
+- Backend configuration lives in the `Config` class in `app/main.py` with env-var defaults in `_DEFAULTS`. New env vars go there.
+- Real-time communication uses Socket.IO events, not REST polling.
+- Frontend uses standalone Angular components with `inject()` for DI, RxJS Subjects for state, and `takeUntilDestroyed()` for cleanup.
+- State is persisted as JSON files via `AtomicJsonStore` in `app/state_store.py`.
+- No pre-commit hooks — linting and tests are enforced in CI only.