network.bsky.jetstream.getZstdDictionary

Download the zstd dictionary used by the network.bsky.jetstream.subscribeEvents stream's optional compression scheme. The dictionary is requested by its zstd dictionary ID (the same ID embedded in every compressed frame's header); a client that wants compressed frames first fetches the server's current dictionary, then opts in on the websocket with zstdDictionary=<id>. The response is a raw zstd structured dictionary (RFC 8878 section 5), immutable for a given ID and CDN-cacheable. Servers may retire old dictionaries after retraining; a client holding a retired ID re-fetches without an id parameter to obtain the current one.