lnworker: use channel_id instead of scid in ReceivedMPPHtlc

diff --git a/electrum/lnpeer.py b/electrum/lnpeer.py
index eaaddac..ec13629 100644
--- a/electrum/lnpeer.py
+++ b/electrum/lnpeer.py
@@ -2150,7 +2150,7 @@ class Peer(Logger, EventListener):
         Does additional checks on the incoming htlc and return the payment key if the tests pass,
         otherwise raises OnionRoutingError which will get the htlc failed.
         """
-        _log_fail_reason = self._log_htlc_fail_reason_cb(chan.short_channel_id, htlc, processed_onion.hop_data.payload)
+        _log_fail_reason = self._log_htlc_fail_reason_cb(chan.channel_id, htlc, processed_onion.hop_data.payload)
 
         # Check that our blockchain tip is sufficiently recent so that we have an approx idea of the height.
         # We should not release the preimage for an HTLC that its sender could already time out as
@@ -2269,7 +2269,7 @@ class Peer(Logger, EventListener):
         self.lnworker.dont_expire_htlcs.pop(payment_hash.hex(), None)  # htlcs wont get expired anymore
         for mpp_htlc in list(htlc_set.htlcs):
             htlc_id = mpp_htlc.htlc.htlc_id
-            chan = self.lnworker.get_channel_by_short_id(mpp_htlc.scid)
+            chan = self.lnworker.channels[mpp_htlc.channel_id]
             if chan.channel_id not in self.channels:
                 # this htlc belongs to another peer and has to be settled in their htlc_switch
                 continue
@@ -2311,7 +2311,7 @@ class Peer(Logger, EventListener):
         self.lnworker.dont_expire_htlcs.pop(payment_hash.hex(), None)
         self.lnworker.dont_settle_htlcs.pop(payment_hash.hex(), None)  # already failed
         for mpp_htlc in list(htlc_set.htlcs):
-            chan = self.lnworker.get_channel_by_short_id(mpp_htlc.scid)
+            chan = self.lnworker.channels[mpp_htlc.channel_id]
             htlc_id = mpp_htlc.htlc.htlc_id
             if chan.channel_id not in self.channels:
                 # this htlc belongs to another peer and has to be settled in their htlc_switch
@@ -2854,7 +2854,7 @@ class Peer(Logger, EventListener):
                     )
                     self.lnworker.update_or_create_mpp_with_received_htlc(
                         payment_key=payment_key,
-                        scid=chan.short_channel_id,
+                        channel_id=chan.channel_id,
                         htlc=htlc,
                         unprocessed_onion_packet=onion_packet_hex,  # outer onion if trampoline
                     )
@@ -2938,11 +2938,12 @@ class Peer(Logger, EventListener):
 
     def _log_htlc_fail_reason_cb(
         self,
-        scid: ShortChannelID,
+        channel_id: bytes,
         htlc: UpdateAddHtlc,
         onion_payload: dict
     ) -> Callable[[str], None]:
         def _log_fail_reason(reason: str) -> None:
+            scid = self.lnworker.channels[channel_id].short_channel_id
             self.logger.info(f"will FAIL HTLC: {str(scid)=}. {reason=}. {str(htlc)=}. {onion_payload=}")
         return _log_fail_reason
 
@@ -2960,7 +2961,7 @@ class Peer(Logger, EventListener):
                     onion_payload = {}
 
                 self._log_htlc_fail_reason_cb(
-                    mpp_htlc.scid,
+                    mpp_htlc.channel_id,
                     mpp_htlc.htlc,
                     onion_payload,
                 )(f"mpp set {id(mpp_set)} failed: {reason}")
@@ -3074,7 +3075,7 @@ class Peer(Logger, EventListener):
 
         if mpp_set.resolution == RecvMPPResolution.WAITING:
             # calculate the sum of just in time channel opening fees
-            htlc_channels = [self.lnworker.get_channel_by_short_id(scid) for scid in set(h.scid for h in mpp_set.htlcs)]
+            htlc_channels = [self.lnworker.channels[channel_id] for channel_id in set(h.channel_id for h in mpp_set.htlcs)]
             jit_opening_fees_msat = sum((c.jit_opening_fee or 0) for c in htlc_channels)
 
             # check if set is first stage multi-trampoline payment to us
diff --git a/electrum/lnutil.py b/electrum/lnutil.py
index 70256a7..f670b4b 100644
--- a/electrum/lnutil.py
+++ b/electrum/lnutil.py
@@ -1965,18 +1965,18 @@ del r
 
 
 class ReceivedMPPHtlc(NamedTuple):
-    scid: ShortChannelID
+    channel_id: bytes
     htlc: UpdateAddHtlc
     unprocessed_onion: str
 
     def __repr__(self):
-        return f"{self.scid}, {self.htlc=}, {self.unprocessed_onion[:15]=}..."
+        return f"chan_id={self.channel_id.hex()}, {self.htlc=}, {self.unprocessed_onion[:15]=}..."
 
     @staticmethod
-    def from_tuple(scid, htlc, unprocessed_onion) -> 'ReceivedMPPHtlc':
-        assert is_hex_str(unprocessed_onion) and is_hex_str(scid)
+    def from_tuple(channel_id, htlc, unprocessed_onion) -> 'ReceivedMPPHtlc':
+        assert is_hex_str(unprocessed_onion) and is_hex_str(channel_id)
         return ReceivedMPPHtlc(
-            scid=ShortChannelID(bytes.fromhex(scid)),
+            channel_id=bytes.fromhex(channel_id),
             htlc=UpdateAddHtlc.from_tuple(*htlc),
             unprocessed_onion=unprocessed_onion,
         )
diff --git a/electrum/lnworker.py b/electrum/lnworker.py
index f28c99a..1db9d0d 100644
--- a/electrum/lnworker.py
+++ b/electrum/lnworker.py
@@ -2583,7 +2583,7 @@ class LNWallet(LNWorker):
         self,
         *,
         payment_key: str,
-        scid: ShortChannelID,
+        channel_id: bytes,
         htlc: UpdateAddHtlc,
         unprocessed_onion_packet: str,
     ):
@@ -2610,7 +2610,7 @@ class LNWallet(LNWorker):
 
         if mpp_status.resolution > RecvMPPResolution.WAITING:
             # we are getting a htlc for a set that is not in WAITING state, it cannot be safely added
-            self.logger.info(f"htlc set cannot accept htlc, failing htlc: {scid=} {htlc.htlc_id=}")
+            self.logger.info(f"htlc set cannot accept htlc, failing htlc: {channel_id=} {htlc.htlc_id=}")
             if mpp_status == RecvMPPResolution.EXPIRED:
                 raise OnionRoutingFailure(code=OnionFailureCode.MPP_TIMEOUT, data=b'')
             raise OnionRoutingFailure(
@@ -2619,7 +2619,7 @@ class LNWallet(LNWorker):
             )
 
         new_htlc = ReceivedMPPHtlc(
-            scid=scid,
+            channel_id=channel_id,
             htlc=htlc,
             unprocessed_onion=unprocessed_onion_packet,
         )
@@ -2707,7 +2707,7 @@ class LNWallet(LNWorker):
         # only cleanup when channel is REDEEMED as mpp set is still required for lnsweep
         assert chan._state == ChannelState.REDEEMED
         for payment_key_hex, mpp_status in list(self.received_mpp_htlcs.items()):
-            htlcs_to_remove = [htlc for htlc in mpp_status.htlcs if htlc.scid == chan.short_channel_id]
+            htlcs_to_remove = [htlc for htlc in mpp_status.htlcs if htlc.channel_id == chan.channel_id]
             for stale_mpp_htlc in htlcs_to_remove:
                 assert mpp_status.resolution != RecvMPPResolution.WAITING
                 self.logger.info(f'maybe_cleanup_mpp: removing htlc of MPP {payment_key_hex}')
@@ -3547,7 +3547,7 @@ class LNWallet(LNWorker):
                 assert not any_outer_onion.are_we_final
                 assert len(processed_htlc_set) == 1, processed_htlc_set
                 forward_htlc = any_mpp_htlc.htlc
-                incoming_chan = self.get_channel_by_short_id(any_mpp_htlc.scid)
+                incoming_chan = self.channels[any_mpp_htlc.channel_id]
                 next_htlc = await self._maybe_forward_htlc(
                     incoming_chan=incoming_chan,
                     htlc=forward_htlc,
diff --git a/electrum/wallet_db.py b/electrum/wallet_db.py
index 325eb36..068499c 100644
--- a/electrum/wallet_db.py
+++ b/electrum/wallet_db.py
@@ -69,7 +69,7 @@ class WalletUnfinished(WalletFileException):
 # seed_version is now used for the version of the wallet file
 OLD_SEED_VERSION = 4        # electrum versions < 2.0
 NEW_SEED_VERSION = 11       # electrum versions >= 2.0
-FINAL_SEED_VERSION = 64     # electrum >= 2.7 will set this to prevent
+FINAL_SEED_VERSION = 65     # electrum >= 2.7 will set this to prevent
                             # old versions from overwriting new format
 
 
@@ -236,6 +236,7 @@ class WalletDBUpgrader(Logger):
         self._convert_version_62()
         self._convert_version_63()
         self._convert_version_64()
+        self._convert_version_65()
         self.put('seed_version', FINAL_SEED_VERSION)  # just to be sure
 
     def _convert_wallet_type(self):
@@ -1288,6 +1289,32 @@ class WalletDBUpgrader(Logger):
         self.data['lightning_payments'] = new_payment_infos
         self.data['seed_version'] = 64
 
+    def _convert_version_65(self):
+        """Store channel_id instead of short_channel_id in ReceivedMPPHtlc"""
+        if not self._is_upgrade_method_needed(64, 64):
+            return
+
+        channels = self.data.get('channels', {})
+        def scid_to_channel_id(scid):
+            for channel_id, channel_data in channels.items():
+                if scid == channel_data.get('short_channel_id'):
+                    return channel_id
+            raise KeyError(f"missing {scid=} in channels")
+
+        mpp_sets = self.data.get('received_mpp_htlcs', {})
+        new_mpp_sets = {}
+        for payment_key, mpp_set in mpp_sets.items():
+            resolution, htlc_list, parent_set_key = mpp_set
+            new_htlc_list = []
+            for htlc_data_tuple in htlc_list:
+                scid, update_add_htlc, onion = htlc_data_tuple
+                channel_id = scid_to_channel_id(scid)
+                new_htlc_list.append((channel_id, update_add_htlc, onion))
+            new_mpp_sets[payment_key] = (resolution, new_htlc_list, parent_set_key)
+
+        self.data['received_mpp_htlcs'] = new_mpp_sets
+        self.data['seed_version'] = 65
+
     def _convert_imported(self):
         if not self._is_upgrade_method_needed(0, 13):
             return