v26.04rc1 is paying fees via bolt12 if the destination is a direct peer

[daywalker90]

When using bolt12 and paying direct peers as destination, both pay and xpay seem to suddenly pay fees.

Fetching an invoice for 10000msat and pay it and i get:

l1-cli pay "<removed>"
{
   "destination": "035ed467e11a1990fd4fc7d98dafbc3c49abcf8d2a48fb24f914e909e95a6737cb",
   "payment_hash": "b461b5fae962473ad0d198c0a69e458cbd6a9ef959918ea5cd6c434e75422ff4",
   "created_at": 1774304621.999080537,
   "parts": 1,
   "amount_msat": 10001,
   "amount_sent_msat": 10001,
   "payment_preimage": "a70a45a55d5121b9ba54daeb62a8cb0bb31fcaeda643974ef3ed8952c0c83f55",
   "status": "complete"
}

Similar with xpay, but with xpay only amount_sent_msat is increased.

I would expect pay/xpay to not pay fees when the destination of the payment is a direct peer.

[Lagrang3]

I don't think this is an issue.
Bolt12 comes with blinded paths.

Two examples come to my mind:

1. "ABC"

Consider the graph:
A --> B --> C

A wants to pay an offer created by B, but B sends A a bolt12 invoice for which C is the entry point to the blinded path.
In this case A will have to route the payment through hops ["A->B", "B->C", "C->B"] being the last hop a blinded hop.
A will pay for fees.

2. "AB"

Same as before but B sends A a bolt12 invoice for which A is the entry point to the blinded path.
In this case A will have to route the payment through hops ["A->B"] being again the last hop a blinded hop.
It is not clear to me if C-lightning will make A pay fees to himself in this case.

[daywalker90]

I don't see anything in the CHANGELOG to explain why this behaviour is not present in v25.12.

Btw for "AB" it happens as well, fresh regtest setup with 2 nodes:

l2-cli offer any ifjeoij
{
   "offer_id": "f27d457e47af54f92b384b29b124e7ea76ce6618c336203b0566dfcc73fc6b13",
   "active": true,
   "single_use": false,
   "bolt12": "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",
   "used": false,
   "created": true
}


l1-cli xpay "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" 100000
# ->020000000000000000000000000000000000000000000000000000000000000001: Success: preimage=3dfdcda540ac6910d756c518317d20d99953598f60eae32be0643cba7068f371
{
   "payment_preimage": "3dfdcda540ac6910d756c518317d20d99953598f60eae32be0643cba7068f371",
   "amount_msat": 100000,
   "amount_sent_msat": 100002,
   "failed_parts": 0,
   "successful_parts": 1
}

and we are not paying to ourselves:

l1-cli listpeerchannels
{
   "channels": [
      {
         "peer_id": "0302028b4a3399d1f193788251c061f3116fb570f0fdd1d47e4b6ba3714c8d5f64",
         "peer_connected": true,
         "reestablished": true,
         "channel_type": {
            "bits": [
               12,
               22
            ],
            "names": [
               "static_remotekey/even",
               "anchors/even"
            ]
         },
         "ignore_fee_limits": true,
         "updates": {
            "local": {
               "htlc_minimum_msat": 0,
               "htlc_maximum_msat": 1089000000,
               "cltv_expiry_delta": 6,
               "fee_base_msat": 1,
               "fee_proportional_millionths": 10
            },
            "remote": {
               "htlc_minimum_msat": 0,
               "htlc_maximum_msat": 1089000000,
               "cltv_expiry_delta": 6,
               "fee_base_msat": 1,
               "fee_proportional_millionths": 10
            }
         },
         "last_stable_connection": 1774880918,
         "state": "CHANNELD_NORMAL",
         "scratch_txid": "b86c504c9f68da990f6211efb50ef4b71fbff3f3f69d5504e92591a04d2ed5fc",
         "last_tx_fee_msat": 1411000,
         "lost_state": false,
         "feerate": {
            "perkw": 1255,
            "perkb": 5020
         },
         "owner": "channeld",
         "short_channel_id": "1291x1x2",
         "direction": 1,
         "channel_id": "42362ec232151fb98444ad812f03f220cc883f33637904f44fbb73ad0ee85d29",
         "funding_txid": "e4b29b70fad0d09253d7e9796ed8e26100d86fb7815ee59fa710bf316e741185",
         "funding_outnum": 2,
         "close_to_addr": "bcrt1pnjzg2whav9j06uvt3f4auend43dy3quq56s4qes46eun8hv3fqfq2585e9",
         "close_to": "51209c84853afd6164fd718b8a6bde666dac5a488380a6a1506615d67933dd914812",
         "private": false,
         "opener": "local",
         "alias": {
            "local": "3950597x11902622x35970",
            "remote": "7530681x14847217x23018"
         },
         "features": [
            "option_static_remotekey",
            "option_anchors"
         ],
         "funding": {
            "local_funds_msat": 1000000000,
            "remote_funds_msat": 100000000,
            "pushed_msat": 0,
            "psbt": "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",
            "withheld": false
         },
         "to_us_msat": 999899998,
         "min_to_us_msat": 999899998,
         "max_to_us_msat": 1000000000,
         "total_msat": 1100000000,
         "fee_base_msat": 1,
         "fee_proportional_millionths": 10,
         "dust_limit_msat": 546000,
         "their_max_htlc_value_in_flight_msat": 18446744073709551615,
         "our_max_htlc_value_in_flight_msat": 18446744073709551615,
         "their_reserve_msat": 11000000,
         "our_reserve_msat": 11000000,
         "spendable_msat": 984593998,
         "receivable_msat": 89100002,
         "minimum_htlc_in_msat": 0,
         "minimum_htlc_out_msat": 0,
         "maximum_htlc_out_msat": 1089000000,
         "their_to_self_delay": 6,
         "our_to_self_delay": 6,
         "max_accepted_htlcs": 483,
         "state_changes": [
            {
               "timestamp": "2026-03-30T14:27:33.772Z",
               "old_state": "DUALOPEND_OPEN_COMMITTED",
               "new_state": "DUALOPEND_AWAITING_LOCKIN",
               "cause": "user",
               "message": "Sigs exchanged, waiting for lock-in"
            },
            {
               "timestamp": "2026-03-30T14:27:38.147Z",
               "old_state": "DUALOPEND_AWAITING_LOCKIN",
               "new_state": "CHANNELD_NORMAL",
               "cause": "user",
               "message": "Lockin complete"
            }
         ],
         "status": [
            "CHANNELD_NORMAL:Channel ready for use."
         ],
         "in_payments_offered": 0,
         "in_offered_msat": 0,
         "in_payments_fulfilled": 0,
         "in_fulfilled_msat": 0,
         "out_payments_offered": 1,
         "out_offered_msat": 100002,
         "out_payments_fulfilled": 1,
         "out_fulfilled_msat": 100002,
         "htlcs": []
      }
   ]
}

[Lagrang3]

You're right. There is something off. If we pay fees to ourselves then the HTLC should be equal to the payment amount, we are instead paying the fees to the recipient of the payment:

def test_bolt12_fees(node_factory):
    AMT_MSAT = 10000
    FEES_MSAT = 5000
    l1, l2 = node_factory.get_nodes(
        2, opts={"may_reconnect": True, "fee-base": FEES_MSAT, "fee-per-satoshi": 0}
    )
    node_factory.join_nodes([l1, l2], wait_for_announce=True)

    # BOLT 12, direct peer
    offer = l2.rpc.offer("any")["bolt12"]
    b12 = l1.rpc.fetchinvoice(offer, AMT_MSAT)["invoice"]

    b12_decode = l1.rpc.decode(b12)
    assert b12_decode["invoice_amount_msat"] == AMT_MSAT
    assert len(b12_decode["invoice_paths"]) == 1
    assert b12_decode["invoice_paths"][0]["first_node_id"] == l1.info["id"]
    assert b12_decode["invoice_paths"][0]["payinfo"]["fee_base_msat"] == FEES_MSAT
    assert b12_decode["invoice_paths"][0]["payinfo"]["fee_proportional_millionths"] == 0

    ret = l1.rpc.xpay(invstring=b12)
    assert ret["failed_parts"] == 0
    assert ret["successful_parts"] == 1
    assert ret["amount_msat"] == AMT_MSAT
    assert ret["amount_sent_msat"] == AMT_MSAT + FEES_MSAT

    # we pay fees to ourselves
    htlcs = l1.rpc.listhtlcs()["htlcs"]
    assert len(htlcs) == 1
    assert htlcs[0]["payment_hash"] == b12_decode["invoice_payment_hash"]
    assert htlcs[0]["amount_msat"] == AMT_MSAT

Fails the last assertion with 15000 == 10000