sync_controller

Aggregate a set of subscription filters into one covering filter.

Direct port of client/stream/index.ts:#computeUnionFilter.

• Channels are unioned.
• Namespaces: if any subscription omits namespaces (wildcard), the union is unscoped (omits the key). Otherwise, deduplicated union.
• Depth: if any subscription omits depth (unbounded), the union is unbounded (omits the key). Otherwise, take the max. depth=0 is a valid bounded value — never omit when all subscriptions provide it.

Whether coverer is a superset of target.

Direct port of client/stream/index.ts:filterCovers. Depth coverage accounts for namespace-prefix offset: a scoped coverer needs enough depth to absorb the extra levels of any deeper target namespace prefix.

Handle for one sync filtered event stream.

Protocol implemented by sync SSE and WebSocket transports.

Owns the sync shared SSE handle, subscription registry, and fan-out thread.