Limits on fine‑grained cancellation in Waku v2 Filter Protocol

Current cancellation behavior

The Waku v2 Filter Protocol (v2.0.0) defines a subscription message that includes a filter identifier and a set of topics. The protocol does not expose a dedicated cancellation message for individual filters; only a session close signal terminates all active subscriptions.

Missing timeout support

Clients are required to implement their own timeout logic. The subscription request lacks any deadline or timeout field, and the specification does not mandate how a peer should communicate a cancellation request.

Unresolved decision

There is an open question whether the protocol should introduce a separate unsubscribe message containing the filter_id or add a deadline parameter to the subscription request to enable fine‑grained cancellation and timeout handling.

Specific questions

• Should the specification add an explicit unsubscribe message with a filter_id field?
• Would incorporating a deadline or timeout field in the subscription message be more appropriate?
• What are the implications for multi‑subscription sessions if a coarse session‑level close remains the only supported termination method?