Tracearr/Media-Server-SSE v0.6.0 on GitHub

library.item.downloaded event on Jellyfin and Emby when a user downloads an item, from the server's activity log. Payload carries userId, itemId (absent on Emby, whose entry has none), itemName (the activity entry's name), and app and device parsed from the entry's overview.
On Emby, the activity entry names the user by numeric internal id, so library.item.downloaded looks the user up and sends the same 32-character GUID that playback events carry. userId is omitted when no user matches.
download.transcoded event on Jellyfin for clients that download at reduced quality through the stream endpoint, which logs no activity. A device session that transcodes without reporting playback for 20 seconds emits phase: "started", and phase: "ended" when the transcode goes away. Payload carries userId, deviceId, itemId, bitrate, width, height, videoCodec, audioCodec, container, bytesTranscoded, and completionPercentage. itemId and bytesTranscoded are read from Jellyfin's internal transcoding job list and are omitted if that read fails.