Add SWIP-87: BPS explicit multi-publisher — roster and end of stream over BPS-lite

[zelig]

SWIP-87: BPS explicit multi-publisher — the admin's roster and end of stream over BPS-lite.

Stacked on SWIP-74 BPS-lite (#111): this PR's base is swip-bps-lite, so the diff is SWIPs/swip-87.md alone.

The admin of a BPS-lite channel names who else may publish by publishing a roster on a feed of its own, and can end the channel with an EOS. It is the roster slice of SWIP-60 (#104), with nothing else of it: two more Kind values (EOS = 3, ROSTER = 4) and one payload message (Roster). No new frame, and no change to Join, Ack or the cohort spec. A cohort is multi-publisher iff its admin ever publishes a roster.

What the SWIP specifies:

• the roster and EOS feeds: owned by the admin alone, verified end to end, full state rather than deltas;
• pending streams for rostered addresses, with the roster as the grantee's cue;
• roles that change only by rejoining;
• a cursor per publisher and per service kind;
• publisher streams that receive what the others publish;
• revocation by roster: the revoked streams are written the roster and closed, and what they send meanwhile is dropped, never punished;
• the EOS as the one signed, final end;
• bounds, outcomes, replay rows, the WebSocket bridge, and conformance.

Three rules are to be carried back to SWIP-60: roles change only by rejoining; revocation closes the revoked streams with no grace period and no punishment; and the cursor table is bounded by the roster.

Implementation: ethersphere/bee#5661 (draft, stacked on bee #5626).

Open points are marked (?) in the text.

🤖 Generated with Claude Code

[Copilot]

🔵 Needs a closer look

It introduces a large, intricate protocol specification with multiple deliberate open design points and cross-SWIP dependencies that warrant final human editorial and technical review.

0 open findings

What changed in this PR

This PR adds SWIP-87, the second step of the Broadcast Pub/Sub (BPS) family, specified as a strict extension of SWIP-74 (BPS-lite). It gives a BPS-lite channel's admin a signed control plane: a roster feed naming additional publishers and an end-of-stream (EOS) feed to close the channel attributably. It is the "roster slice" of SWIP-60, lifted out so it can be implemented and conformance-tested independently. The change is purely a new specification document — no code.

Changes:

• Adds two Kind values (EOS = 3, ROSTER = 4) and one payload message (Roster) on the existing Broadcast frame, with no change to Join, Ack, or CohortSpec.
• Defines broker/subscriber rules: pending streams for rostered addresses, per-publisher and per-service-kind cursors, delivery to publisher streams, roster-based revocation (no grace period, dropped-not-punished), and channel end via signed EOS.
• States three rules to be carried back to SWIP-60 (roles change only by rejoining; revocation closes streams without punishment; cursor table bounded by the roster).

File	Description
SWIPs/​swip-87.md	New Draft Standards Track SWIP specifying the admin roster and EOS control plane over BPS-lite, including wire format, validation, revocation, bounds, outcomes, WebSocket bridge, and conformance.

🧠 Review effort: Balanced

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