Firelink/TORRENT_FEATURES.md

Firelink Torrent feature matrix

This is the current product-facing comparison for BitTorrent features exposed by Firelink's bundled Aria2 engine. It intentionally excludes Aria2's generic HTTP/FTP/Metalink options, shell hooks, and daemon-admin RPC methods that do not belong in the download UI. The Aria2 reference is the 1.37.0 manual.

Implemented

• Local .torrent files, magnet links, and remote HTTP(S) .torrent metadata. Remote metadata is bounded, SSRF-checked, redirect-checked, parsed, and cached before it enters the normal addTorrent path.
• Bencode validation, canonical info-hash checks, safe output paths, managed metadata retention, selected-file preview, select-file, and index-out.
• Firelink queue admission, per-queue/global permits, pause/resume, cancel, retry/GID replacement, restart recovery, terminal reconciliation, and output ownership for Torrent lifecycles.
• Optional seeding by time and/or ratio, upload progress, upload limits, seeders telemetry, per-Torrent maximum peers, and the Aria2 bt-request-peer-speed-limit threshold.
• Bounded, read-only Torrent peer diagnostics through aria2.getPeers. Firelink discards peer IPs, ports, IDs, and bitfields at the native boundary; the selected-Torrent detail view exposes only operational speeds, seeder, and choking flags, with a bounded display count.
• Global DHT, IPv6 DHT, PEX, and Local Peer Discovery toggles.
• Optional piece-integrity verification, including the explicit policy that disables unverified seeding when verification is requested.
• Optional stall timeout through bt-stop-timeout, persisted with each Torrent and re-applied when it starts or retries. A value of zero disables the policy; Aria2 stops the Torrent after the configured consecutive zero-download-speed interval.
• Additional per-Torrent tracker URLs through bt-tracker, with bounded and credential-free HTTP/HTTPS/UDP validation.
• Per-Torrent tracker exclusion through bt-exclude-tracker, including Aria2's explicit * value for excluding all announce URLs. Exclusions are persisted, normalized, reapplied on retries, and do not change DHT or PEX settings.
• Optional bt-prioritize-piece preview policy for the head, tail, or both ends of every selected file. The constrained policy is validated, persisted, normalized, and reapplied when a Torrent starts or retries.
• Optional bt-remove-unselected-file cleanup after completion when a selected-file subset is configured. Firelink requires explicit confirmation, reserves the unselected paths against competing downloads, keeps those paths separate from removable download ownership, and clears the reservation after observing Aria2's completion cleanup (or on terminal failure, cancellation, or reconfiguration).
• Deterministic local Aria2 smoke coverage for metadata resolution, selected output, piece priority, pause/resume, ownership, cancellation/removal, unavailable trackers, daemon failure, and bt-stop-timeout terminal behavior; RPC-boundary coverage is separate.

Priority tiers for remaining work

Tier 0 — reliability and user-visible control

No remaining Tier 0 items.

Tier 1 — transfer policy and storage behavior

1. File priority beyond selection — Aria2 exposes only the binary selected file state through its Torrent file API and has no supported per-file priority option. Firelink therefore does not pretend that select-file is file priority; this remains pending an engine capability or a safe product-level model.
2. Encryption policy — expose bt-force-encryption, bt-require-crypto, and bt-min-crypto-level as one validated policy so users cannot accidentally select contradictory combinations.
3. Tracker timing controls — expose tracker connect timeout, request timeout, and interval only when their effect on battery/network behavior is explained and persisted.

Tier 2 — advanced networking and daemon tuning

1. Configurable TCP/UDP listen ports, external IP, DHT entry points, IPv6 DHT listen address, and LPD interface, with platform/firewall warnings.
2. Global BitTorrent open-file limits and peer identity/agent controls.
3. Aria2 follow-torrent/in-memory follow behavior for generic downloads only if the resulting child-GID ownership model can be represented safely; the current explicit metadata path intentionally avoids unmapped child jobs.

The first implementation in this task was remote .torrent metadata intake; follow-up implementations add stall-timeout control, bounded peer diagnostics, persisted tracker exclusion, piece-preview priority, and safe unselected-file removal.