From b2207e88d39657359111e881aeb38cf165fb0026 Mon Sep 17 00:00:00 2001
From: enaples <enaples@users.noreply.github.com>
Date: Mon, 26 Jan 2026 16:36:23 +0100
Subject: [PATCH 1/2] tests: test reproduce #8863

---
 tests/test_opening.py | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tests/test_opening.py b/tests/test_opening.py
index a8090f9ac697..76b72555034d 100644
--- a/tests/test_opening.py
+++ b/tests/test_opening.py
@@ -17,6 +17,44 @@ def find_next_feerate(node, peer):
     chan = only_one(node.rpc.listpeerchannels(peer.info['id'])['channels'])
     return chan['next_feerate']
 
+@pytest.mark.openchannel('v2')
+@unittest.skipIf(TEST_NETWORK != 'regtest', "requires regtest")
+def test_opening_dualfund_with_unknown_feerates(node_factory, bitcoind):
+    """
+    Test dualfund openchannel when feerates are unknown (like on signet/testnet with empty mempool).
+    """
+    opts = {
+        'ignore-fee-limits': True,
+        'feerates': None,
+        'dev-no-fake-fees': True,
+    }
+
+    l1, l2= node_factory.get_nodes(2, opts=[opts, opts])
+
+    l1.fundwallet(FUNDAMOUNT)
+
+    # Connect peers
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+
+    # Verify fee estimation is failing
+    l1.daemon.wait_for_log('Unable to estimate any fees')
+    l2.daemon.wait_for_log('Unable to estimate any fees')
+
+    # Open channel l1 <-> l2
+    fund_tx = l1.rpc.fundchannel(l2.info['id'], 100000, feerate='253perkw', minconf=0)['txid']
+
+    # Verify mempool is not empty
+    mempool = bitcoind.rpc.getrawmempool()
+    assert fund_tx in mempool and len(mempool) == 1
+
+    # Verify fee estimation is still failing
+    l1.daemon.wait_for_log('Unable to estimate any fees')
+    l2.daemon.wait_for_log('Unable to estimate any fees')
+
+    # Mine blocks to confirm channels
+    bitcoind.generate_block(1, wait_for_mempool=1)
+
+    l2.rpc.listpeerchannels(l1.info['id'])['channels']
 
 @unittest.skipIf(TEST_NETWORK != 'regtest', 'elementsd doesnt yet support PSBT features we need')
 @pytest.mark.openchannel('v2')

From b52903491ff2c7789fb5ec7c89c45b893ec5a613 Mon Sep 17 00:00:00 2001
From: enaples <enaples@users.noreply.github.com>
Date: Mon, 26 Jan 2026 17:07:48 +0100
Subject: [PATCH 2/2] tests: test cause crash only with
 `experimental-dual-fund`

---
 tests/test_opening.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/test_opening.py b/tests/test_opening.py
index 76b72555034d..4571fb0260b3 100644
--- a/tests/test_opening.py
+++ b/tests/test_opening.py
@@ -27,6 +27,7 @@ def test_opening_dualfund_with_unknown_feerates(node_factory, bitcoind):
         'ignore-fee-limits': True,
         'feerates': None,
         'dev-no-fake-fees': True,
+        'experimental-dual-fund': None
     }
 
     l1, l2= node_factory.get_nodes(2, opts=[opts, opts])