lnwallet: expose negotiated configs in aux chan state

### funding/manager.go
@@ -2363,19 +2363,9 @@ func (f *Manager) waitForPsbt(intent *chanfunding.PsbtIntent,
 		// At this point, we'll see if there's an AuxFundingDesc we
 		// need to deliver so the funding process can continue
 		// properly.
-		auxFundingDesc, err := fn.MapOptionZ(
-			f.cfg.AuxFundingController,
-			func(c AuxFundingController) AuxFundingDescResult {
-				return c.DescFromPendingChanID(
-					cid.tempChanID,
-					lnwallet.NewAuxChanState(
-						resCtx.reservation.ChanState(),
-					),
-					resCtx.reservation.CommitmentKeyRings(),
-					true,
-				)
-			},
-		).Unpack()
+		auxFundingDesc, err := f.auxFundingDesc(
+			cid.tempChanID, resCtx.reservation,
+		)
 		if err != nil {
 			failFlow("error continuing PSBT flow", err)
 			return
@@ -2407,6 +2397,22 @@ func (f *Manager) waitForPsbt(intent *chanfunding.PsbtIntent,
 	}
 }
 
+// auxFundingDesc returns any aux funding descriptor for the pending channel.
+func (f *Manager) auxFundingDesc(pid PendingChanID,
+	reservation *lnwallet.ChannelReservation) (
+	fn.Option[lnwallet.AuxFundingDesc], error) {
+
+	return fn.MapOptionZ(
+		f.cfg.AuxFundingController,
+		func(c AuxFundingController) AuxFundingDescResult {
+			return c.DescFromPendingChanID(
+				pid, reservation.AuxChanState(),
+				reservation.CommitmentKeyRings(), true,
+			)
+		},
+	).Unpack()
+}
+
 // continueFundingAccept continues the channel funding flow once our
 // contribution is finalized, the channel output is known and the funding
 // transaction is signed.
@@ -2552,17 +2558,9 @@ func (f *Manager) fundeeProcessFundingCreated(peer lnpeer.Peer,
 
 	// At this point, we'll see if there's an AuxFundingDesc we need to
 	// deliver so the funding process can continue properly.
-	auxFundingDesc, err := fn.MapOptionZ(
-		f.cfg.AuxFundingController,
-		func(c AuxFundingController) AuxFundingDescResult {
-			return c.DescFromPendingChanID(
-				cid.tempChanID, lnwallet.NewAuxChanState(
-					resCtx.reservation.ChanState(),
-				), resCtx.reservation.CommitmentKeyRings(),
-				true,
-			)
-		},
-	).Unpack()
+	auxFundingDesc, err := f.auxFundingDesc(
+		cid.tempChanID, resCtx.reservation,
+	)
 	if err != nil {
 		log.Errorf("error continuing PSBT flow: %v", err)
 		f.failFundingFlow(peer, cid, err)

### funding/manager_test.go
@@ -22,6 +22,7 @@ import (
 	"github.com/btcsuite/btcd/btcutil/v2"
 	"github.com/btcsuite/btcd/chaincfg/v2"
 	"github.com/btcsuite/btcd/chainhash/v2"
+	"github.com/btcsuite/btcd/psbt/v2"
 	"github.com/btcsuite/btcd/wire/v2"
 	"github.com/btcsuite/btcwallet/wallet"
 	"github.com/lightningnetwork/lnd/actor"
@@ -43,11 +44,13 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lntest/mock"
 	"github.com/lightningnetwork/lnd/lntest/wait"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnutils"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwallet/chanfunding"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/msgmux"
 	"github.com/stretchr/testify/require"
 )
 
@@ -277,6 +280,60 @@ func (m *mockZeroConfAcceptor) Accept(
 	}
 }
 
+// mockAuxFundingController records the aux channel state passed by the funding
+// manager.
+type mockAuxFundingController struct {
+	auxChanStates chan lnwallet.AuxChanState
+}
+
+// Name returns the name of the mock endpoint.
+func (m *mockAuxFundingController) Name() msgmux.EndpointName {
+	return "mock-aux-funding"
+}
+
+// CanHandle returns false as the mock does not handle any peer messages.
+func (m *mockAuxFundingController) CanHandle(msg msgmux.PeerMsg) bool {
+	return false
+}
+
+// SendMessage is a no-op that reports the message as not handled.
+func (m *mockAuxFundingController) SendMessage(_ context.Context,
+	msg msgmux.PeerMsg) bool {
+
+	return false
+}
+
+// DescFromPendingChanID records the aux channel state it was called with
+// and returns an empty funding descriptor.
+func (m *mockAuxFundingController) DescFromPendingChanID(pid PendingChanID,
+	openChan lnwallet.AuxChanState,
+	keyRing lntypes.Dual[lnwallet.CommitmentKeyRing],
+	initiator bool) AuxFundingDescResult {
+
+	m.auxChanStates <- openChan
+
+	return fn.Ok(fn.None[lnwallet.AuxFundingDesc]())
+}
+
+// DeriveTapscriptRoot returns no tapscript root.
+func (m *mockAuxFundingController) DeriveTapscriptRoot(
+	PendingChanID) AuxTapscriptResult {
+
+	return fn.Ok(fn.None[chainhash.Hash]())
+}
+
+// ChannelReady is a no-op.
+func (m *mockAuxFundingController) ChannelReady(
+	lnwallet.AuxChanState) error {
+
+	return nil
+}
+
+// ChannelFinalized is a no-op.
+func (m *mockAuxFundingController) ChannelFinalized(PendingChanID) error {
+	return nil
+}
+
 type newChannelMsg struct {
 	channel *lnpeer.NewChannel
 	err     chan error
@@ -3148,12 +3205,122 @@ func TestFundingManagerPrivateRestart(t *testing.T) {
 	assertNoFwdingPolicy(t, alice, bob, channelReadyAlice.ChanID)
 }
 
+// TestFundingManagerAuxChanStatePsbt checks that the PSBT initiator path passes
+// the fully negotiated channel configs to the aux funding controller.
+func TestFundingManagerAuxChanStatePsbt(t *testing.T) {
+	t.Parallel()
+
+	auxController := &mockAuxFundingController{
+		auxChanStates: make(chan lnwallet.AuxChanState, 1),
+	}
+	alice, bob := setupFundingManagers(t, func(cfg *Config) {
+		cfg.AuxFundingController = fn.Some[AuxFundingController](
+			auxController,
+		)
+	})
+	t.Cleanup(func() {
+		tearDownFundingManagers(t, alice, bob)
+	})
+
+	const fundingAmt = btcutil.Amount(5_000_000)
+	updateChan := make(chan *lnrpc.OpenStatusUpdate, 1)
+	errChan := make(chan error, 1)
+	assembler := chanfunding.NewPsbtAssembler(
+		fundingAmt, nil, fundingNetParams.Params, false,
+	)
+	initReq := &InitFundingMsg{
+		Peer:            bob,
+		TargetPubkey:    bob.privKey.PubKey(),
+		ChainHash:       *fundingNetParams.GenesisHash,
+		LocalFundingAmt: fundingAmt,
+		ChanFunder:      assembler,
+		Updates:         updateChan,
+		Err:             errChan,
+	}
+
+	alice.fundingMgr.InitFundingWorkflow(initReq)
+	openChannel, ok := assertFundingMsgSent(
+		t, alice.msgChan, "OpenChannel",
+	).(*lnwire.OpenChannel)
+	require.True(t, ok)
+	bob.fundingMgr.ProcessFundingMsg(openChannel, alice)
+	acceptChannel, ok := assertFundingMsgSent(
+		t, bob.msgChan, "AcceptChannel",
+	).(*lnwire.AcceptChannel)
+	require.True(t, ok)
+	alice.fundingMgr.ProcessFundingMsg(acceptChannel, bob)
+
+	var psbtUpdate *lnrpc.ReadyForPsbtFunding
+	select {
+	case update := <-updateChan:
+		psbtFund, ok := update.Update.(*lnrpc.OpenStatusUpdate_PsbtFund)
+		require.True(t, ok)
+		psbtUpdate = psbtFund.PsbtFund
+
+	case err := <-errChan:
+		require.NoError(t, err)
+
+	case <-time.After(5 * time.Second):
+		t.Fatal("PSBT funding update not received")
+	}
+
+	packet, err := psbt.NewFromRawBytes(
+		bytes.NewReader(psbtUpdate.Psbt), false,
+	)
+	require.NoError(t, err)
+	packet.UnsignedTx.TxIn = []*wire.TxIn{{
+		PreviousOutPoint: wire.OutPoint{Index: 0},
+	}}
+	packet.Inputs = []psbt.PInput{{
+		WitnessUtxo: &wire.TxOut{
+			Value:    int64(fundingAmt + 1),
+			PkScript: append([]byte{0, 20}, make([]byte, 20)...),
+		},
+	}}
+
+	resCtx, err := alice.fundingMgr.getReservationCtx(
+		bobPubKey, openChannel.PendingChannelID,
+	)
+	require.NoError(t, err)
+	localCfg := *resCtx.reservation.OurContribution().ChannelConfig
+	remoteCfg := *resCtx.reservation.TheirContribution().ChannelConfig
+
+	err = alice.fundingMgr.cfg.Wallet.PsbtFundingVerify(
+		openChannel.PendingChannelID, packet, false,
+	)
+	require.NoError(t, err)
+
+	// Finalizing separately ensures verification, including the reserved
+	// value check, completes before the funding manager resumes.
+	packet.UnsignedTx.TxIn[0].Witness = wire.TxWitness{[]byte{1}}
+	err = alice.fundingMgr.cfg.Wallet.PsbtFundingFinalize(
+		openChannel.PendingChannelID, nil, packet.UnsignedTx,
+	)
+	require.NoError(t, err)
+
+	select {
+	case auxState := <-auxController.auxChanStates:
+		require.Equal(t, localCfg, auxState.LocalChanCfg)
+		require.Equal(t, remoteCfg, auxState.RemoteChanCfg)
+
+	case <-time.After(5 * time.Second):
+		t.Fatal("aux funding controller was not called")
+	}
+}
+
 // TestFundingManagerCustomChannelParameters checks that custom requirements we
 // specify during the channel funding flow is preserved correctly on both sides.
 func TestFundingManagerCustomChannelParameters(t *testing.T) {
 	t.Parallel()
 
-	alice, bob := setupFundingManagers(t)
+	auxController := &mockAuxFundingController{
+		auxChanStates: make(chan lnwallet.AuxChanState, 2),
+	}
+	alice, bob := setupFundingManagers(t, func(cfg *Config) {
+		cfg.AuxFundingController = fn.Some[AuxFundingController](
+			auxController,
+		)
+	})
 	t.Cleanup(func() {
 		tearDownFundingManagers(t, alice, bob)
 	})
@@ -3288,6 +3455,23 @@ func TestFundingManagerCustomChannelParameters(t *testing.T) {
 		t, alice.msgChan, "FundingCreated",
 	).(*lnwire.FundingCreated)
 
+	// Helper method for checking that the aux funding controller received
+	// the negotiated channel configs of both parties.
+	assertAuxChanState := func(localCfg,
+		remoteCfg channeldb.ChannelConfig) {
+
+		t.Helper()
+
+		select {
+		case auxState := <-auxController.auxChanStates:
+			require.Equal(t, localCfg, auxState.LocalChanCfg)
+			require.Equal(t, remoteCfg, auxState.RemoteChanCfg)
+
+		case <-time.After(time.Second * 5):
+			t.Fatalf("aux funding controller was not called")
+		}
+	}
+
 	// Helper method for checking the CSV delay stored for a reservation.
 	assertDelay := func(resCtx *reservationWithCtx,
 		ourDelay, theirDelay uint16) error {
@@ -3417,9 +3601,19 @@ func TestFundingManagerCustomChannelParameters(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	// Snapshot the negotiated configs before resuming the funding flow.
+	// The aux controller must receive exactly these values even though
+	// they have not yet been copied into the pending channel state.
+	localCfg := *resCtx.reservation.OurContribution().ChannelConfig
+	remoteCfg := *resCtx.reservation.TheirContribution().ChannelConfig
+
 	// Give the message to Bob.
 	bob.fundingMgr.ProcessFundingMsg(fundingCreated, alice)
 
+	// Bob's aux funding controller must have been handed the negotiated
+	// configs as part of the aux channel state.
+	assertAuxChanState(localCfg, remoteCfg)
+
 	// Finally, Bob should send the FundingSigned message.
 	fundingSigned := assertFundingMsgSent(
 		t, bob.msgChan, "FundingSigned",

### lnwallet/reservation.go
@@ -911,6 +911,20 @@ func (r *ChannelReservation) ChanState() *chanstate.OpenChannel {
 	return r.partialState
 }
 
+// AuxChanState returns a view of the current open channel state for aux
+// funding callers, populated with the negotiated contribution configs. It
+// must only be called after both channel contributions have been processed.
+func (r *ChannelReservation) AuxChanState() AuxChanState {
+	r.RLock()
+	defer r.RUnlock()
+
+	auxState := NewAuxChanState(r.partialState)
+	auxState.LocalChanCfg = r.ourContribution.toChanConfig()
+	auxState.RemoteChanCfg = r.theirContribution.toChanConfig()
+
+	return auxState
+}
+
 // CommitmentKeyRings returns the local+remote key ring used for the very first
 // commitment transaction both parties.
 //

### lnwallet/reservation_test.go
@@ -0,0 +1,60 @@
+package lnwallet
+
+import (
+	"testing"
+
+	"github.com/btcsuite/btcd/btcec/v2"
+	"github.com/btcsuite/btcd/btcutil/v2"
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/stretchr/testify/require"
+)
+
+// TestReservationAuxChanStatePopulatesNegotiatedConfigs asserts that the aux
+// channel state view of a reservation carries the negotiated local and remote
+// channel configs rather than the still empty configs of the partial state.
+func TestReservationAuxChanStatePopulatesNegotiatedConfigs(t *testing.T) {
+	t.Parallel()
+
+	localCfg := &channeldb.ChannelConfig{
+		ChannelStateBounds: channeldb.ChannelStateBounds{
+			ChanReserve:      btcutil.Amount(1200),
+			MaxPendingAmount: lnwire.MilliSatoshi(100_000),
+			MinHTLC:          lnwire.MilliSatoshi(1000),
+			MaxAcceptedHtlcs: 30,
+		},
+		CommitmentParams: channeldb.CommitmentParams{
+			DustLimit: btcutil.Amount(600),
+			CsvDelay:  144,
+		},
+	}
+	remoteCfg := &channeldb.ChannelConfig{
+		ChannelStateBounds: channeldb.ChannelStateBounds{
+			ChanReserve:      btcutil.Amount(2200),
+			MaxPendingAmount: lnwire.MilliSatoshi(200_000),
+			MinHTLC:          lnwire.MilliSatoshi(2000),
+			MaxAcceptedHtlcs: 40,
+		},
+		CommitmentParams: channeldb.CommitmentParams{
+			DustLimit: btcutil.Amount(700),
+			CsvDelay:  288,
+		},
+	}
+
+	_, peerPub := btcec.PrivKeyFromBytes([]byte{1})
+	reservation := &ChannelReservation{
+		ourContribution: &ChannelContribution{
+			ChannelConfig: localCfg,
+		},
+		theirContribution: &ChannelContribution{
+			ChannelConfig: remoteCfg,
+		},
+		partialState: &channeldb.OpenChannel{
+			IdentityPub: peerPub,
+		},
+	}
+
+	auxState := reservation.AuxChanState()
+	require.Equal(t, *localCfg, auxState.LocalChanCfg)
+	require.Equal(t, *remoteCfg, auxState.RemoteChanCfg)
+}