Merge bitcoin/bitcoin#30272: doc: use TRUC instead of v3 and add release note

926b8e39dcbc0a3a8a75ef0a29bdca2bf738d746 [doc] add release note for TRUC (glozow)
19a9b90617419f68d0f1c90ee115b5220be99a16 use version=3 instead of v3 in debug strings (glozow)
881fac8e609be17eb71bd9a54c0284b304e2e2e2 scripted-diff: change names from V3 to TRUC (glozow)
a573dd261748d2a80560f73db08f7dca788c7fcf [doc] replace mentions of v3 with TRUC (glozow)
089b5757dff39a9a06cdb625aaced9beeb72958d rename mempool_accept_v3.py to mempool_truc.py (glozow)
f543852a89d93441645250c40c3980aeb0c3b664 rename policy/v3_policy.* to policy/truc_policy.* (glozow)

Pull request description:

  Adds a release note for TRUC policy which will be live in v28.0.

  For clarity, replaces mentions of "v3" with "TRUC" in most places. Suggested in
  - https://github.com/bitcoin/bitcoin/pull/29496#discussion_r1629749583
  - https://github.com/bitcoin/bitcoin/pull/29496#discussion_r1624500904

  I changed error strings from "v3-violation" to "TRUC-violation" but left v3 in the debug strings because I think it might be clearer for somebody who is debugging. Similarly, I left some variables unchanged because I think they're more descriptive this way, e.g. `tx_v3_from_v2_and_v3`. I'm happy to debate places that should or shouldn't be documented differently in this PR, whatever is clearest to everyone.

ACKs for top commit:
  instagibbs:
    reACK https://github.com/bitcoin/bitcoin/pull/30272/commits/926b8e39dcbc0a3a8a75ef0a29bdca2bf738d746
  achow101:
    ACK 926b8e39dcbc0a3a8a75ef0a29bdca2bf738d746
  ismaelsadeeq:
    Code review ACK 926b8e39dcbc0a3a8a75ef0a29bdca2bf738d746

Tree-SHA512: 16c88add0a29dc6d1236c4d45f34a17b850f6727b231953cbd52eb9f7268d1d802563eadfc8b7928c94ed3d7a615275dd103e57e81439ebf3ba2b12efa1e42af

1 files changed, 647 insertions, 0 deletions

diff --git a/test/functional/mempool_truc.py b/test/functional/mempool_truc.py
new file mode 100755
index 0000000000..e1f3d77201
--- /dev/null
+++ b/test/functional/mempool_truc.py
@@ -0,0 +1,647 @@
+#!/usr/bin/env python3
+# Copyright (c) 2024 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+from decimal import Decimal
+
+from test_framework.messages import (
+    MAX_BIP125_RBF_SEQUENCE,
+    WITNESS_SCALE_FACTOR,
+)
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal,
+    assert_greater_than,
+    assert_greater_than_or_equal,
+    assert_raises_rpc_error,
+)
+from test_framework.wallet import (
+    COIN,
+    DEFAULT_FEE,
+    MiniWallet,
+)
+
+MAX_REPLACEMENT_CANDIDATES = 100
+TRUC_MAX_VSIZE = 10000
+
+def cleanup(extra_args=None):
+    def decorator(func):
+        def wrapper(self):
+            try:
+                if extra_args is not None:
+                    self.restart_node(0, extra_args=extra_args)
+                func(self)
+            finally:
+                # Clear mempool again after test
+                self.generate(self.nodes[0], 1)
+                if extra_args is not None:
+                    self.restart_node(0)
+        return wrapper
+    return decorator
+
+class MempoolTRUC(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+        self.extra_args = [[]]
+        self.setup_clean_chain = True
+
+    def check_mempool(self, txids):
+        """Assert exact contents of the node's mempool (by txid)."""
+        mempool_contents = self.nodes[0].getrawmempool()
+        assert_equal(len(txids), len(mempool_contents))
+        assert all([txid in txids for txid in mempool_contents])
+
+    @cleanup(extra_args=["-datacarriersize=20000"])
+    def test_truc_max_vsize(self):
+        node = self.nodes[0]
+        self.log.info("Test TRUC-specific maximum transaction vsize")
+        tx_v3_heavy = self.wallet.create_self_transfer(target_weight=(TRUC_MAX_VSIZE + 1) * WITNESS_SCALE_FACTOR, version=3)
+        assert_greater_than_or_equal(tx_v3_heavy["tx"].get_vsize(), TRUC_MAX_VSIZE)
+        expected_error_heavy = f"TRUC-violation, version=3 tx {tx_v3_heavy['txid']} (wtxid={tx_v3_heavy['wtxid']}) is too big"
+        assert_raises_rpc_error(-26, expected_error_heavy, node.sendrawtransaction, tx_v3_heavy["hex"])
+        self.check_mempool([])
+
+        # Ensure we are hitting the TRUC-specific limit and not something else
+        tx_v2_heavy = self.wallet.send_self_transfer(from_node=node, target_weight=(TRUC_MAX_VSIZE + 1) * WITNESS_SCALE_FACTOR, version=2)
+        self.check_mempool([tx_v2_heavy["txid"]])
+
+    @cleanup(extra_args=["-datacarriersize=1000"])
+    def test_truc_acceptance(self):
+        node = self.nodes[0]
+        self.log.info("Test a child of a TRUC transaction cannot be more than 1000vB")
+        tx_v3_parent_normal = self.wallet.send_self_transfer(from_node=node, version=3)
+        self.check_mempool([tx_v3_parent_normal["txid"]])
+        tx_v3_child_heavy = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_v3_parent_normal["new_utxo"],
+            target_weight=4004,
+            version=3
+        )
+        assert_greater_than_or_equal(tx_v3_child_heavy["tx"].get_vsize(), 1000)
+        expected_error_child_heavy = f"TRUC-violation, version=3 child tx {tx_v3_child_heavy['txid']} (wtxid={tx_v3_child_heavy['wtxid']}) is too big"
+        assert_raises_rpc_error(-26, expected_error_child_heavy, node.sendrawtransaction, tx_v3_child_heavy["hex"])
+        self.check_mempool([tx_v3_parent_normal["txid"]])
+        # tx has no descendants
+        assert_equal(node.getmempoolentry(tx_v3_parent_normal["txid"])["descendantcount"], 1)
+
+        self.log.info("Test that, during replacements, only the new transaction counts for TRUC descendant limit")
+        tx_v3_child_almost_heavy = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE,
+            utxo_to_spend=tx_v3_parent_normal["new_utxo"],
+            target_weight=3987,
+            version=3
+        )
+        assert_greater_than_or_equal(1000, tx_v3_child_almost_heavy["tx"].get_vsize())
+        self.check_mempool([tx_v3_parent_normal["txid"], tx_v3_child_almost_heavy["txid"]])
+        assert_equal(node.getmempoolentry(tx_v3_parent_normal["txid"])["descendantcount"], 2)
+        tx_v3_child_almost_heavy_rbf = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE * 2,
+            utxo_to_spend=tx_v3_parent_normal["new_utxo"],
+            target_weight=3500,
+            version=3
+        )
+        assert_greater_than_or_equal(tx_v3_child_almost_heavy["tx"].get_vsize() + tx_v3_child_almost_heavy_rbf["tx"].get_vsize(), 1000)
+        self.check_mempool([tx_v3_parent_normal["txid"], tx_v3_child_almost_heavy_rbf["txid"]])
+        assert_equal(node.getmempoolentry(tx_v3_parent_normal["txid"])["descendantcount"], 2)
+
+    @cleanup(extra_args=None)
+    def test_truc_replacement(self):
+        node = self.nodes[0]
+        self.log.info("Test TRUC transactions may be replaced by TRUC transactions")
+        utxo_v3_bip125 = self.wallet.get_utxo()
+        tx_v3_bip125 = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE,
+            utxo_to_spend=utxo_v3_bip125,
+            sequence=MAX_BIP125_RBF_SEQUENCE,
+            version=3
+        )
+        self.check_mempool([tx_v3_bip125["txid"]])
+
+        tx_v3_bip125_rbf = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE * 2,
+            utxo_to_spend=utxo_v3_bip125,
+            version=3
+        )
+        self.check_mempool([tx_v3_bip125_rbf["txid"]])
+
+        self.log.info("Test TRUC transactions may be replaced by non-TRUC (BIP125) transactions")
+        tx_v3_bip125_rbf_v2 = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE * 3,
+            utxo_to_spend=utxo_v3_bip125,
+            version=2
+        )
+        self.check_mempool([tx_v3_bip125_rbf_v2["txid"]])
+
+        self.log.info("Test that replacements cannot cause violation of inherited TRUC")
+        utxo_v3_parent = self.wallet.get_utxo()
+        tx_v3_parent = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE,
+            utxo_to_spend=utxo_v3_parent,
+            version=3
+        )
+        tx_v3_child = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE,
+            utxo_to_spend=tx_v3_parent["new_utxo"],
+            version=3
+        )
+        self.check_mempool([tx_v3_bip125_rbf_v2["txid"], tx_v3_parent["txid"], tx_v3_child["txid"]])
+
+        tx_v3_child_rbf_v2 = self.wallet.create_self_transfer(
+            fee_rate=DEFAULT_FEE * 2,
+            utxo_to_spend=tx_v3_parent["new_utxo"],
+            version=2
+        )
+        expected_error_v2_v3 = f"TRUC-violation, non-version=3 tx {tx_v3_child_rbf_v2['txid']} (wtxid={tx_v3_child_rbf_v2['wtxid']}) cannot spend from version=3 tx {tx_v3_parent['txid']} (wtxid={tx_v3_parent['wtxid']})"
+        assert_raises_rpc_error(-26, expected_error_v2_v3, node.sendrawtransaction, tx_v3_child_rbf_v2["hex"])
+        self.check_mempool([tx_v3_bip125_rbf_v2["txid"], tx_v3_parent["txid"], tx_v3_child["txid"]])
+
+
+    @cleanup(extra_args=None)
+    def test_truc_bip125(self):
+        node = self.nodes[0]
+        self.log.info("Test TRUC transactions that don't signal BIP125 are replaceable")
+        assert_equal(node.getmempoolinfo()["fullrbf"], False)
+        utxo_v3_no_bip125 = self.wallet.get_utxo()
+        tx_v3_no_bip125 = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE,
+            utxo_to_spend=utxo_v3_no_bip125,
+            sequence=MAX_BIP125_RBF_SEQUENCE + 1,
+            version=3
+        )
+
+        self.check_mempool([tx_v3_no_bip125["txid"]])
+        assert not node.getmempoolentry(tx_v3_no_bip125["txid"])["bip125-replaceable"]
+        tx_v3_no_bip125_rbf = self.wallet.send_self_transfer(
+            from_node=node,
+            fee_rate=DEFAULT_FEE * 2,
+            utxo_to_spend=utxo_v3_no_bip125,
+            version=3
+        )
+        self.check_mempool([tx_v3_no_bip125_rbf["txid"]])
+
+    @cleanup(extra_args=["-datacarriersize=40000"])
+    def test_truc_reorg(self):
+        node = self.nodes[0]
+        self.log.info("Test that, during a reorg, TRUC rules are not enforced")
+        tx_v2_block = self.wallet.send_self_transfer(from_node=node, version=2)
+        tx_v3_block = self.wallet.send_self_transfer(from_node=node, version=3)
+        tx_v3_block2 = self.wallet.send_self_transfer(from_node=node, version=3)
+        self.check_mempool([tx_v3_block["txid"], tx_v2_block["txid"], tx_v3_block2["txid"]])
+
+        block = self.generate(node, 1)
+        self.check_mempool([])
+        tx_v2_from_v3 = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v3_block["new_utxo"], version=2)
+        tx_v3_from_v2 = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v2_block["new_utxo"], version=3)
+        tx_v3_child_large = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v3_block2["new_utxo"], target_weight=5000, version=3)
+        assert_greater_than(node.getmempoolentry(tx_v3_child_large["txid"])["vsize"], 1000)
+        self.check_mempool([tx_v2_from_v3["txid"], tx_v3_from_v2["txid"], tx_v3_child_large["txid"]])
+        node.invalidateblock(block[0])
+        self.check_mempool([tx_v3_block["txid"], tx_v2_block["txid"], tx_v3_block2["txid"], tx_v2_from_v3["txid"], tx_v3_from_v2["txid"], tx_v3_child_large["txid"]])
+        # This is needed because generate() will create the exact same block again.
+        node.reconsiderblock(block[0])
+
+
+    @cleanup(extra_args=["-limitdescendantsize=10", "-datacarriersize=40000"])
+    def test_nondefault_package_limits(self):
+        """
+        Max standard tx size + TRUC rules imply the ancestor/descendant rules (at their default
+        values), but those checks must not be skipped. Ensure both sets of checks are done by
+        changing the ancestor/descendant limit configurations.
+        """
+        node = self.nodes[0]
+        self.log.info("Test that a decreased limitdescendantsize also applies to TRUC child")
+        parent_target_weight = 9990 * WITNESS_SCALE_FACTOR
+        child_target_weight = 500 * WITNESS_SCALE_FACTOR
+        tx_v3_parent_large1 = self.wallet.send_self_transfer(
+            from_node=node,
+            target_weight=parent_target_weight,
+            version=3
+        )
+        tx_v3_child_large1 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_v3_parent_large1["new_utxo"],
+            target_weight=child_target_weight,
+            version=3
+        )
+
+        # Parent and child are within v3 limits, but parent's 10kvB descendant limit is exceeded
+        assert_greater_than_or_equal(TRUC_MAX_VSIZE, tx_v3_parent_large1["tx"].get_vsize())
+        assert_greater_than_or_equal(1000, tx_v3_child_large1["tx"].get_vsize())
+        assert_greater_than(tx_v3_parent_large1["tx"].get_vsize() + tx_v3_child_large1["tx"].get_vsize(), 10000)
+
+        assert_raises_rpc_error(-26, f"too-long-mempool-chain, exceeds descendant size limit for tx {tx_v3_parent_large1['txid']}", node.sendrawtransaction, tx_v3_child_large1["hex"])
+        self.check_mempool([tx_v3_parent_large1["txid"]])
+        assert_equal(node.getmempoolentry(tx_v3_parent_large1["txid"])["descendantcount"], 1)
+        self.generate(node, 1)
+
+        self.log.info("Test that a decreased limitancestorsize also applies to v3 parent")
+        self.restart_node(0, extra_args=["-limitancestorsize=10", "-datacarriersize=40000"])
+        tx_v3_parent_large2 = self.wallet.send_self_transfer(
+            from_node=node,
+            target_weight=parent_target_weight,
+            version=3
+        )
+        tx_v3_child_large2 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_v3_parent_large2["new_utxo"],
+            target_weight=child_target_weight,
+            version=3
+        )
+
+        # Parent and child are within TRUC limits
+        assert_greater_than_or_equal(TRUC_MAX_VSIZE, tx_v3_parent_large2["tx"].get_vsize())
+        assert_greater_than_or_equal(1000, tx_v3_child_large2["tx"].get_vsize())
+        assert_greater_than(tx_v3_parent_large2["tx"].get_vsize() + tx_v3_child_large2["tx"].get_vsize(), 10000)
+
+        assert_raises_rpc_error(-26, f"too-long-mempool-chain, exceeds ancestor size limit", node.sendrawtransaction, tx_v3_child_large2["hex"])
+        self.check_mempool([tx_v3_parent_large2["txid"]])
+
+    @cleanup(extra_args=["-datacarriersize=1000"])
+    def test_truc_ancestors_package(self):
+        self.log.info("Test that TRUC ancestor limits are checked within the package")
+        node = self.nodes[0]
+        tx_v3_parent_normal = self.wallet.create_self_transfer(
+            fee_rate=0,
+            target_weight=4004,
+            version=3
+        )
+        tx_v3_parent_2_normal = self.wallet.create_self_transfer(
+            fee_rate=0,
+            target_weight=4004,
+            version=3
+        )
+        tx_v3_child_multiparent = self.wallet.create_self_transfer_multi(
+            utxos_to_spend=[tx_v3_parent_normal["new_utxo"], tx_v3_parent_2_normal["new_utxo"]],
+            fee_per_output=10000,
+            version=3
+        )
+        tx_v3_child_heavy = self.wallet.create_self_transfer_multi(
+            utxos_to_spend=[tx_v3_parent_normal["new_utxo"]],
+            target_weight=4004,
+            fee_per_output=10000,
+            version=3
+        )
+
+        self.check_mempool([])
+        result = node.submitpackage([tx_v3_parent_normal["hex"], tx_v3_parent_2_normal["hex"], tx_v3_child_multiparent["hex"]])
+        assert_equal(result['package_msg'], f"TRUC-violation, tx {tx_v3_child_multiparent['txid']} (wtxid={tx_v3_child_multiparent['wtxid']}) would have too many ancestors")
+        self.check_mempool([])
+
+        self.check_mempool([])
+        result = node.submitpackage([tx_v3_parent_normal["hex"], tx_v3_child_heavy["hex"]])
+        # tx_v3_child_heavy is heavy based on weight, not sigops.
+        assert_equal(result['package_msg'], f"TRUC-violation, version=3 child tx {tx_v3_child_heavy['txid']} (wtxid={tx_v3_child_heavy['wtxid']}) is too big: {tx_v3_child_heavy['tx'].get_vsize()} > 1000 virtual bytes")
+        self.check_mempool([])
+
+        tx_v3_parent = self.wallet.create_self_transfer(version=3)
+        tx_v3_child = self.wallet.create_self_transfer(utxo_to_spend=tx_v3_parent["new_utxo"], version=3)
+        tx_v3_grandchild = self.wallet.create_self_transfer(utxo_to_spend=tx_v3_child["new_utxo"], version=3)
+        result = node.testmempoolaccept([tx_v3_parent["hex"], tx_v3_child["hex"], tx_v3_grandchild["hex"]])
+        assert all([txresult["package-error"] == f"TRUC-violation, tx {tx_v3_grandchild['txid']} (wtxid={tx_v3_grandchild['wtxid']}) would have too many ancestors" for txresult in result])
+
+    @cleanup(extra_args=None)
+    def test_truc_ancestors_package_and_mempool(self):
+        """
+        A TRUC transaction in a package cannot have 2 TRUC parents.
+        Test that if we have a transaction graph A -> B -> C, where A, B, C are
+        all TRUC transactions, that we cannot use submitpackage to get the
+        transactions all into the mempool.
+
+        Verify, in particular, that if A is already in the mempool, then
+        submitpackage(B, C) will fail.
+        """
+        node = self.nodes[0]
+        self.log.info("Test that TRUC ancestor limits include transactions within the package and all in-mempool ancestors")
+        # This is our transaction "A":
+        tx_in_mempool = self.wallet.send_self_transfer(from_node=node, version=3)
+
+        # Verify that A is in the mempool
+        self.check_mempool([tx_in_mempool["txid"]])
+
+        # tx_0fee_parent is our transaction "B"; just create it.
+        tx_0fee_parent = self.wallet.create_self_transfer(utxo_to_spend=tx_in_mempool["new_utxo"], fee=0, fee_rate=0, version=3)
+
+        # tx_child_violator is our transaction "C"; create it:
+        tx_child_violator = self.wallet.create_self_transfer_multi(utxos_to_spend=[tx_0fee_parent["new_utxo"]], version=3)
+
+        # submitpackage(B, C) should fail
+        result = node.submitpackage([tx_0fee_parent["hex"], tx_child_violator["hex"]])
+        assert_equal(result['package_msg'], f"TRUC-violation, tx {tx_child_violator['txid']} (wtxid={tx_child_violator['wtxid']}) would have too many ancestors")
+        self.check_mempool([tx_in_mempool["txid"]])
+
+    @cleanup(extra_args=None)
+    def test_sibling_eviction_package(self):
+        """
+        When a transaction has a mempool sibling, it may be eligible for sibling eviction.
+        However, this option is only available in single transaction acceptance. It doesn't work in
+        a multi-testmempoolaccept (where RBF is disabled) or when doing package CPFP.
+        """
+        self.log.info("Test TRUC sibling eviction in submitpackage and multi-testmempoolaccept")
+        node = self.nodes[0]
+        # Add a parent + child to mempool
+        tx_mempool_parent = self.wallet.send_self_transfer_multi(
+            from_node=node,
+            utxos_to_spend=[self.wallet.get_utxo()],
+            num_outputs=2,
+            version=3
+        )
+        tx_mempool_sibling = self.wallet.send_self_transfer(
+            from_node=node,
+            utxo_to_spend=tx_mempool_parent["new_utxos"][0],
+            version=3
+        )
+        self.check_mempool([tx_mempool_parent["txid"], tx_mempool_sibling["txid"]])
+
+        tx_sibling_1 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_mempool_parent["new_utxos"][1],
+            version=3,
+            fee_rate=DEFAULT_FEE*100,
+        )
+        tx_has_mempool_uncle = self.wallet.create_self_transfer(utxo_to_spend=tx_sibling_1["new_utxo"], version=3)
+
+        tx_sibling_2 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_mempool_parent["new_utxos"][0],
+            version=3,
+            fee_rate=DEFAULT_FEE*200,
+        )
+
+        tx_sibling_3 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_mempool_parent["new_utxos"][1],
+            version=3,
+            fee_rate=0,
+        )
+        tx_bumps_parent_with_sibling = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_sibling_3["new_utxo"],
+            version=3,
+            fee_rate=DEFAULT_FEE*300,
+        )
+
+        # Fails with another non-related transaction via testmempoolaccept
+        tx_unrelated = self.wallet.create_self_transfer(version=3)
+        result_test_unrelated = node.testmempoolaccept([tx_sibling_1["hex"], tx_unrelated["hex"]])
+        assert_equal(result_test_unrelated[0]["reject-reason"], "TRUC-violation")
+
+        # Fails in a package via testmempoolaccept
+        result_test_1p1c = node.testmempoolaccept([tx_sibling_1["hex"], tx_has_mempool_uncle["hex"]])
+        assert_equal(result_test_1p1c[0]["reject-reason"], "TRUC-violation")
+
+        # Allowed when tx is submitted in a package and evaluated individually.
+        # Note that the child failed since it would be the 3rd generation.
+        result_package_indiv = node.submitpackage([tx_sibling_1["hex"], tx_has_mempool_uncle["hex"]])
+        self.check_mempool([tx_mempool_parent["txid"], tx_sibling_1["txid"]])
+        expected_error_gen3 = f"TRUC-violation, tx {tx_has_mempool_uncle['txid']} (wtxid={tx_has_mempool_uncle['wtxid']}) would have too many ancestors"
+
+        assert_equal(result_package_indiv["tx-results"][tx_has_mempool_uncle['wtxid']]['error'], expected_error_gen3)
+
+        # Allowed when tx is submitted in a package with in-mempool parent (which is deduplicated).
+        node.submitpackage([tx_mempool_parent["hex"], tx_sibling_2["hex"]])
+        self.check_mempool([tx_mempool_parent["txid"], tx_sibling_2["txid"]])
+
+        # Child cannot pay for sibling eviction for parent, as it violates TRUC topology limits
+        result_package_cpfp = node.submitpackage([tx_sibling_3["hex"], tx_bumps_parent_with_sibling["hex"]])
+        self.check_mempool([tx_mempool_parent["txid"], tx_sibling_2["txid"]])
+        expected_error_cpfp = f"TRUC-violation, tx {tx_mempool_parent['txid']} (wtxid={tx_mempool_parent['wtxid']}) would exceed descendant count limit"
+
+        assert_equal(result_package_cpfp["tx-results"][tx_sibling_3['wtxid']]['error'], expected_error_cpfp)
+
+
+    @cleanup(extra_args=["-datacarriersize=1000"])
+    def test_truc_package_inheritance(self):
+        self.log.info("Test that TRUC inheritance is checked within package")
+        node = self.nodes[0]
+        tx_v3_parent = self.wallet.create_self_transfer(
+            fee_rate=0,
+            target_weight=4004,
+            version=3
+        )
+        tx_v2_child = self.wallet.create_self_transfer_multi(
+            utxos_to_spend=[tx_v3_parent["new_utxo"]],
+            fee_per_output=10000,
+            version=2
+        )
+        self.check_mempool([])
+        result = node.submitpackage([tx_v3_parent["hex"], tx_v2_child["hex"]])
+        assert_equal(result['package_msg'], f"TRUC-violation, non-version=3 tx {tx_v2_child['txid']} (wtxid={tx_v2_child['wtxid']}) cannot spend from version=3 tx {tx_v3_parent['txid']} (wtxid={tx_v3_parent['wtxid']})")
+        self.check_mempool([])
+
+    @cleanup(extra_args=None)
+    def test_truc_in_testmempoolaccept(self):
+        node = self.nodes[0]
+
+        self.log.info("Test that TRUC inheritance is accurately assessed in testmempoolaccept")
+        tx_v2 = self.wallet.create_self_transfer(version=2)
+        tx_v2_from_v2 = self.wallet.create_self_transfer(utxo_to_spend=tx_v2["new_utxo"], version=2)
+        tx_v3_from_v2 = self.wallet.create_self_transfer(utxo_to_spend=tx_v2["new_utxo"], version=3)
+        tx_v3 = self.wallet.create_self_transfer(version=3)
+        tx_v2_from_v3 = self.wallet.create_self_transfer(utxo_to_spend=tx_v3["new_utxo"], version=2)
+        tx_v3_from_v3 = self.wallet.create_self_transfer(utxo_to_spend=tx_v3["new_utxo"], version=3)
+
+        # testmempoolaccept paths don't require child-with-parents topology. Ensure that topology
+        # assumptions aren't made in inheritance checks.
+        test_accept_v2_and_v3 = node.testmempoolaccept([tx_v2["hex"], tx_v3["hex"]])
+        assert all([result["allowed"] for result in test_accept_v2_and_v3])
+
+        test_accept_v3_from_v2 = node.testmempoolaccept([tx_v2["hex"], tx_v3_from_v2["hex"]])
+        expected_error_v3_from_v2 = f"TRUC-violation, version=3 tx {tx_v3_from_v2['txid']} (wtxid={tx_v3_from_v2['wtxid']}) cannot spend from non-version=3 tx {tx_v2['txid']} (wtxid={tx_v2['wtxid']})"
+        assert all([result["package-error"] == expected_error_v3_from_v2 for result in test_accept_v3_from_v2])
+
+        test_accept_v2_from_v3 = node.testmempoolaccept([tx_v3["hex"], tx_v2_from_v3["hex"]])
+        expected_error_v2_from_v3 = f"TRUC-violation, non-version=3 tx {tx_v2_from_v3['txid']} (wtxid={tx_v2_from_v3['wtxid']}) cannot spend from version=3 tx {tx_v3['txid']} (wtxid={tx_v3['wtxid']})"
+        assert all([result["package-error"] == expected_error_v2_from_v3 for result in test_accept_v2_from_v3])
+
+        test_accept_pairs = node.testmempoolaccept([tx_v2["hex"], tx_v3["hex"], tx_v2_from_v2["hex"], tx_v3_from_v3["hex"]])
+        assert all([result["allowed"] for result in test_accept_pairs])
+
+        self.log.info("Test that descendant violations are caught in testmempoolaccept")
+        tx_v3_independent = self.wallet.create_self_transfer(version=3)
+        tx_v3_parent = self.wallet.create_self_transfer_multi(num_outputs=2, version=3)
+        tx_v3_child_1 = self.wallet.create_self_transfer(utxo_to_spend=tx_v3_parent["new_utxos"][0], version=3)
+        tx_v3_child_2 = self.wallet.create_self_transfer(utxo_to_spend=tx_v3_parent["new_utxos"][1], version=3)
+        test_accept_2children = node.testmempoolaccept([tx_v3_parent["hex"], tx_v3_child_1["hex"], tx_v3_child_2["hex"]])
+        expected_error_2children = f"TRUC-violation, tx {tx_v3_parent['txid']} (wtxid={tx_v3_parent['wtxid']}) would exceed descendant count limit"
+        assert all([result["package-error"] == expected_error_2children for result in test_accept_2children])
+
+        # Extra TRUC transaction does not get incorrectly marked as extra descendant
+        test_accept_1child_with_exra = node.testmempoolaccept([tx_v3_parent["hex"], tx_v3_child_1["hex"], tx_v3_independent["hex"]])
+        assert all([result["allowed"] for result in test_accept_1child_with_exra])
+
+        # Extra TRUC transaction does not make us ignore the extra descendant
+        test_accept_2children_with_exra = node.testmempoolaccept([tx_v3_parent["hex"], tx_v3_child_1["hex"], tx_v3_child_2["hex"], tx_v3_independent["hex"]])
+        expected_error_extra = f"TRUC-violation, tx {tx_v3_parent['txid']} (wtxid={tx_v3_parent['wtxid']}) would exceed descendant count limit"
+        assert all([result["package-error"] == expected_error_extra for result in test_accept_2children_with_exra])
+        # Same result if the parent is already in mempool
+        node.sendrawtransaction(tx_v3_parent["hex"])
+        test_accept_2children_with_in_mempool_parent = node.testmempoolaccept([tx_v3_child_1["hex"], tx_v3_child_2["hex"]])
+        assert all([result["package-error"] == expected_error_extra for result in test_accept_2children_with_in_mempool_parent])
+
+    @cleanup(extra_args=None)
+    def test_reorg_2child_rbf(self):
+        node = self.nodes[0]
+        self.log.info("Test that children of a TRUC transaction can be replaced individually, even if there are multiple due to reorg")
+
+        ancestor_tx = self.wallet.send_self_transfer_multi(from_node=node, num_outputs=2, version=3)
+        self.check_mempool([ancestor_tx["txid"]])
+
+        block = self.generate(node, 1)[0]
+        self.check_mempool([])
+
+        child_1 = self.wallet.send_self_transfer(from_node=node, version=3, utxo_to_spend=ancestor_tx["new_utxos"][0])
+        child_2 = self.wallet.send_self_transfer(from_node=node, version=3, utxo_to_spend=ancestor_tx["new_utxos"][1])
+        self.check_mempool([child_1["txid"], child_2["txid"]])
+
+        self.generate(node, 1)
+        self.check_mempool([])
+
+        # Create a reorg, causing ancestor_tx to exceed the 1-child limit
+        node.invalidateblock(block)
+        self.check_mempool([ancestor_tx["txid"], child_1["txid"], child_2["txid"]])
+        assert_equal(node.getmempoolentry(ancestor_tx["txid"])["descendantcount"], 3)
+
+        # Create a replacement of child_1. It does not conflict with child_2.
+        child_1_conflict = self.wallet.send_self_transfer(from_node=node, version=3, utxo_to_spend=ancestor_tx["new_utxos"][0], fee_rate=Decimal("0.01"))
+
+        # Ensure child_1 and child_1_conflict are different transactions
+        assert (child_1_conflict["txid"] != child_1["txid"])
+        self.check_mempool([ancestor_tx["txid"], child_1_conflict["txid"], child_2["txid"]])
+        assert_equal(node.getmempoolentry(ancestor_tx["txid"])["descendantcount"], 3)
+
+    @cleanup(extra_args=None)
+    def test_truc_sibling_eviction(self):
+        self.log.info("Test sibling eviction for TRUC")
+        node = self.nodes[0]
+        tx_v3_parent = self.wallet.send_self_transfer_multi(from_node=node, num_outputs=2, version=3)
+        # This is the sibling to replace
+        tx_v3_child_1 = self.wallet.send_self_transfer(
+            from_node=node, utxo_to_spend=tx_v3_parent["new_utxos"][0], fee_rate=DEFAULT_FEE * 2, version=3
+        )
+        assert tx_v3_child_1["txid"] in node.getrawmempool()
+
+        self.log.info("Test tx must be higher feerate than sibling to evict it")
+        tx_v3_child_2_rule6 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_v3_parent["new_utxos"][1], fee_rate=DEFAULT_FEE, version=3
+        )
+        rule6_str = f"insufficient fee (including sibling eviction), rejecting replacement {tx_v3_child_2_rule6['txid']}; new feerate"
+        assert_raises_rpc_error(-26, rule6_str, node.sendrawtransaction, tx_v3_child_2_rule6["hex"])
+        self.check_mempool([tx_v3_parent['txid'], tx_v3_child_1['txid']])
+
+        self.log.info("Test tx must meet absolute fee rules to evict sibling")
+        tx_v3_child_2_rule4 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_v3_parent["new_utxos"][1], fee_rate=2 * DEFAULT_FEE + Decimal("0.00000001"), version=3
+        )
+        rule4_str = f"insufficient fee (including sibling eviction), rejecting replacement {tx_v3_child_2_rule4['txid']}, not enough additional fees to relay"
+        assert_raises_rpc_error(-26, rule4_str, node.sendrawtransaction, tx_v3_child_2_rule4["hex"])
+        self.check_mempool([tx_v3_parent['txid'], tx_v3_child_1['txid']])
+
+        self.log.info("Test tx cannot cause more than 100 evictions including RBF and sibling eviction")
+        # First add 4 groups of 25 transactions.
+        utxos_for_conflict = []
+        txids_v2_100 = []
+        for _ in range(4):
+            confirmed_utxo = self.wallet.get_utxo(confirmed_only=True)
+            utxos_for_conflict.append(confirmed_utxo)
+            # 25 is within descendant limits
+            chain_length = int(MAX_REPLACEMENT_CANDIDATES / 4)
+            chain = self.wallet.create_self_transfer_chain(chain_length=chain_length, utxo_to_spend=confirmed_utxo)
+            for item in chain:
+                txids_v2_100.append(item["txid"])
+                node.sendrawtransaction(item["hex"])
+        self.check_mempool(txids_v2_100 + [tx_v3_parent["txid"], tx_v3_child_1["txid"]])
+
+        # Replacing 100 transactions is fine
+        tx_v3_replacement_only = self.wallet.create_self_transfer_multi(utxos_to_spend=utxos_for_conflict, fee_per_output=4000000)
+        # Override maxfeerate - it costs a lot to replace these 100 transactions.
+        assert node.testmempoolaccept([tx_v3_replacement_only["hex"]], maxfeerate=0)[0]["allowed"]
+        # Adding another one exceeds the limit.
+        utxos_for_conflict.append(tx_v3_parent["new_utxos"][1])
+        tx_v3_child_2_rule5 = self.wallet.create_self_transfer_multi(utxos_to_spend=utxos_for_conflict, fee_per_output=4000000, version=3)
+        rule5_str = f"too many potential replacements (including sibling eviction), rejecting replacement {tx_v3_child_2_rule5['txid']}; too many potential replacements (101 > 100)"
+        assert_raises_rpc_error(-26, rule5_str, node.sendrawtransaction, tx_v3_child_2_rule5["hex"])
+        self.check_mempool(txids_v2_100 + [tx_v3_parent["txid"], tx_v3_child_1["txid"]])
+
+        self.log.info("Test sibling eviction is successful if it meets all RBF rules")
+        tx_v3_child_2 = self.wallet.create_self_transfer(
+            utxo_to_spend=tx_v3_parent["new_utxos"][1], fee_rate=DEFAULT_FEE*10, version=3
+        )
+        node.sendrawtransaction(tx_v3_child_2["hex"])
+        self.check_mempool(txids_v2_100 + [tx_v3_parent["txid"], tx_v3_child_2["txid"]])
+
+        self.log.info("Test that it's possible to do a sibling eviction and RBF at the same time")
+        utxo_unrelated_conflict = self.wallet.get_utxo(confirmed_only=True)
+        tx_unrelated_replacee = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=utxo_unrelated_conflict)
+        assert tx_unrelated_replacee["txid"] in node.getrawmempool()
+
+        fee_to_beat = max(int(tx_v3_child_2["fee"] * COIN), int(tx_unrelated_replacee["fee"]*COIN))
+
+        tx_v3_child_3 = self.wallet.create_self_transfer_multi(
+            utxos_to_spend=[tx_v3_parent["new_utxos"][0], utxo_unrelated_conflict], fee_per_output=fee_to_beat*2, version=3
+        )
+        node.sendrawtransaction(tx_v3_child_3["hex"])
+        self.check_mempool(txids_v2_100 + [tx_v3_parent["txid"], tx_v3_child_3["txid"]])
+
+    @cleanup(extra_args=None)
+    def test_reorg_sibling_eviction_1p2c(self):
+        node = self.nodes[0]
+        self.log.info("Test that sibling eviction is not allowed when multiple siblings exist")
+
+        tx_with_multi_children = self.wallet.send_self_transfer_multi(from_node=node, num_outputs=3, version=3, confirmed_only=True)
+        self.check_mempool([tx_with_multi_children["txid"]])
+
+        block_to_disconnect = self.generate(node, 1)[0]
+        self.check_mempool([])
+
+        tx_with_sibling1 = self.wallet.send_self_transfer(from_node=node, version=3, utxo_to_spend=tx_with_multi_children["new_utxos"][0])
+        tx_with_sibling2 = self.wallet.send_self_transfer(from_node=node, version=3, utxo_to_spend=tx_with_multi_children["new_utxos"][1])
+        self.check_mempool([tx_with_sibling1["txid"], tx_with_sibling2["txid"]])
+
+        # Create a reorg, bringing tx_with_multi_children back into the mempool with a descendant count of 3.
+        node.invalidateblock(block_to_disconnect)
+        self.check_mempool([tx_with_multi_children["txid"], tx_with_sibling1["txid"], tx_with_sibling2["txid"]])
+        assert_equal(node.getmempoolentry(tx_with_multi_children["txid"])["descendantcount"], 3)
+
+        # Sibling eviction is not allowed because there are two siblings
+        tx_with_sibling3 = self.wallet.create_self_transfer(
+            version=3,
+            utxo_to_spend=tx_with_multi_children["new_utxos"][2],
+            fee_rate=DEFAULT_FEE*50
+        )
+        expected_error_2siblings = f"TRUC-violation, tx {tx_with_multi_children['txid']} (wtxid={tx_with_multi_children['wtxid']}) would exceed descendant count limit"
+        assert_raises_rpc_error(-26, expected_error_2siblings, node.sendrawtransaction, tx_with_sibling3["hex"])
+
+        # However, an RBF (with conflicting inputs) is possible even if the resulting cluster size exceeds 2
+        tx_with_sibling3_rbf = self.wallet.send_self_transfer(
+            from_node=node,
+            version=3,
+            utxo_to_spend=tx_with_multi_children["new_utxos"][0],
+            fee_rate=DEFAULT_FEE*50
+        )
+        self.check_mempool([tx_with_multi_children["txid"], tx_with_sibling3_rbf["txid"], tx_with_sibling2["txid"]])
+
+
+    def run_test(self):
+        self.log.info("Generate blocks to create UTXOs")
+        node = self.nodes[0]
+        self.wallet = MiniWallet(node)
+        self.generate(self.wallet, 120)
+        self.test_truc_max_vsize()
+        self.test_truc_acceptance()
+        self.test_truc_replacement()
+        self.test_truc_bip125()
+        self.test_truc_reorg()
+        self.test_nondefault_package_limits()
+        self.test_truc_ancestors_package()
+        self.test_truc_ancestors_package_and_mempool()
+        self.test_sibling_eviction_package()
+        self.test_truc_package_inheritance()
+        self.test_truc_in_testmempoolaccept()
+        self.test_reorg_2child_rbf()
+        self.test_truc_sibling_eviction()
+        self.test_reorg_sibling_eviction_1p2c()
+
+
+if __name__ == "__main__":
+    MempoolTRUC().main()