jellyfin-client/AGENTS.md

AI Agent & Contributor Guidelines: Rust Dependency & Feature Minimization

Core Principle: Minimal Features & Fast Compilation

To ensure fast compilation times and prevent binary and dependency bloat on development and embedded/kiosk hardware:

1. Always use default-features = false by default on all external crates unless explicitly proven unnecessary.
2. Never enable meta-features or "all" feature flags:
   • ❌ Never use tokio = { features = ["full"] }.
   • ❌ Never use egui_extras = { features = ["all_loaders"] }.
   • ❌ Never enable default formats in the image crate (pulls in rayon, exr, tiff, dds, hdr, etc.).
3. Avoid heavy rasterization / rendering stacks:
   • Do NOT enable svg or resvg in egui_extras. The resvg/usvg/tiny-skia dependency tree adds dozens of crates and heavily impacts compilation time.
   • Do NOT enable wgpu in eframe. Use glow (OpenGL) only.
4. Iterate with cargo check:
   • Always run cargo check instead of cargo build during development cycles to test type checking and borrow checking in seconds.

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Approved Dependency Feature Matrix

When editing or updating jellyfin-kiosk-rs/Cargo.toml, adhere strictly to the following configurations:

Crate	Approved Configuration	Rationale / Prohibited Features
eframe	default-features = false, features = ["default_fonts", "glow", "wayland", "x11"]	Keep wgpu disabled. Only build necessary windowing and OpenGL backends.
egui_extras	default-features = false, features = ["http", "image"]	Only needed for fetching/rendering HTTP posters & backdrops. Never enable all_loaders or svg.
image	default-features = false, features = ["jpeg", "png"]	Jellyfin images are JPEGs/PNGs. Disabling default features avoids rayon and heavy decoders.
tokio	default-features = false, features = ["rt-multi-thread", "macros", "net", "io-util", "sync", "time"]	Never use "full". fs, process, and signal from Tokio are not used (standard library equivalents are used).
axum	default-features = false, features = ["http1", "json", "tokio"]	The REST API only handles JSON POST/GET requests and Tokio serving. No form or query parsers needed.
reqwest	default-features = false, features = ["json", "default-tls", "http2"]	Minimal HTTP client features required for communication with the Jellyfin server.
tracing-subscriber	features = ["env-filter"]	Standard lightweight log filtering and formatting.
rumqttc	default-features = false	MQTT client for Home Assistant discovery and state reporting. Avoids rustls/aws-lc-rs crypto bloat.

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Verification Before Committing

Whenever dependencies or features are changed:

1. Run cargo check in jellyfin-kiosk-rs to ensure compilation without warnings/errors.
2. Check dependency count in Cargo.lock (grep "name = " Cargo.lock | wc -l) to confirm no unexpected transitive bloat was introduced.
3. Verify that cargo build links successfully.