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BRC-133: SSM addressing note for coinbase #172

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sirdeggen merged 1 commit into from
Jul 30, 2026
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BRC-133: SSM addressing note for coinbase #172

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8 changes: 8 additions & 0 deletions transactions/0133.md
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,13 @@ The group index `0xFFFE` is in the reserved control-plane range and never
overlaps with data-plane shard groups (maximum shard group index is `0x0FFF` for
`shard_bits=12`).

The address is shown in ASM form (`FF0E::B:FFFE`), intra-domain only under RFC
8815; inter-domain delivery uses the SSM address `FF3E::B:FFFE` (see
[BRC-129](./0129.md)). The frame format and NACK path are unchanged. Coinbase
and block-announce frames are separate flows but share the same egress source
(the emitting proxy, `senderIPv6`), so SSM receivers `(S,G)`-join `0xFFFE` once;
block-broadcast sources are distributed per BRC-129.

### Wire Format

Coinbase transactions are carried as BRC-131 frames (FrameVer `0x04`) with
Expand Down Expand Up @@ -112,5 +119,6 @@ same `FF0E::B:FFFE` multicast destination.

- [BRC-124: Multicast Transaction Frame Format](./0124.md) — base header layout
reused by BRC-131
- [BRC-129: Multicast Group Address Assignments](./0129.md) — SSM/ASM addressing, scopes, and `(S,G)` source discovery
- [BRC-134: Chained Anchor Transaction Frames](./0134.md) — another
control-group transaction type