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Add fulfillment_payload to attribution data #1344

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Merged
t-bast merged 3 commits into from
Jul 27, 2026
Merged

Add fulfillment_payload to attribution data #1344

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134585b
BOLT 2/4: Add fulfillment_payload to update_fulfill_htlc
joostjager Jun 16, 2026
1927f3a
f: Exclude fulfillment tag from padding size
joostjager Jun 18, 2026
8ed85ba
f: Exclude fulfillment from final attribution
joostjager Jun 23, 2026
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11 changes: 11 additions & 0 deletions 02-peer-protocol.md
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Expand Up @@ -2929,6 +2929,15 @@ To supply the preimage:
2. data:
* [`20*u32`:`htlc_hold_times`]
* [`210*sha256[..4]`:`truncated_hmacs`]
1. type: 3 (`fulfillment_payload`)
2. data:
* [`...*byte`:`fulfillment_payload`]

The `fulfillment_payload` field is an opaque encrypted blob for the benefit of
the original HTLC initiator, as defined in
[BOLT #4](04-onion-routing.md#successful-payments). It mirrors the `reason`
field of `update_fail_htlc`: the final node originates it, and intermediate
nodes obfuscate and relay it.

For a timed out or route-failed HTLC:

Expand Down Expand Up @@ -2985,6 +2994,8 @@ A node:
- When supporting `option_attribution_data`:
- if `path_key` is not set in the incoming `update_add_htlc`:
- MUST initialize `attribution_data` and include it in `update_fail_htlc` and `update_fulfill_htlc`. See [BOLT04](04-onion-routing.md).
- if a `fulfillment_payload` is present in the `update_fulfill_htlc` received from the downstream node:
- MUST obfuscate and relay it in the outgoing `update_fulfill_htlc`, including in a blinded path. See [BOLT04](04-onion-routing.md).

A receiving node:
- if the `id` does not correspond to an HTLC in its current commitment transaction:
Expand Down
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