mining: add getTransactionsByWitnessID() IPC method

diff --git a/src/interfaces/mining.h b/src/interfaces/mining.h
index 7f69c758..884a1e16 100644
--- a/src/interfaces/mining.h
+++ b/src/interfaces/mining.h
@@ -189,6 +189,15 @@ public:
      */
     virtual std::vector<CTransactionRef> getTransactionsByTxID(const std::vector<Txid>& txids) = 0;
 
+    /**
+     * Fetch raw transactions from the mempool by wtxid.
+     *
+     * @param[in] wtxids   witness transaction ids to look up
+     * @returns            one entry per requested wtxid containing the
+     *                     transaction if found, otherwise nullptr
+     */
+    virtual std::vector<CTransactionRef> getTransactionsByWitnessID(const std::vector<Wtxid>& wtxids) = 0;
+
     //! Get internal node context. Useful for RPC and testing,
     //! but not accessible across processes.
     virtual const node::NodeContext* context() { return nullptr; }
diff --git a/src/ipc/capnp/mining.capnp b/src/ipc/capnp/mining.capnp
index e1c9e116..5f0347fc 100644
--- a/src/ipc/capnp/mining.capnp
+++ b/src/ipc/capnp/mining.capnp
@@ -27,6 +27,7 @@ interface Mining $Proxy.wrap("interfaces::Mining") {
     interrupt @6 () -> ();
     submitBlock @7 (context :Proxy.Context, block: Data) -> (reason: Text, debug: Text, result: Bool);
     getTransactionsByTxID @8 (context :Proxy.Context, txids: List(Data)) -> (result: List(Data));
+    getTransactionsByWitnessID @9 (context :Proxy.Context, wtxids: List(Data)) -> (result: List(Data));
 }
 
 interface BlockTemplate $Proxy.wrap("interfaces::BlockTemplate") {
diff --git a/src/node/interfaces.cpp b/src/node/interfaces.cpp
index 33473fbf..dafca125 100644
--- a/src/node/interfaces.cpp
+++ b/src/node/interfaces.cpp
@@ -1048,6 +1048,19 @@ public:
         return results;
     }
 
+    std::vector<CTransactionRef> getTransactionsByWitnessID(const std::vector<Wtxid>& wtxids) override
+    {
+        if (!m_node.mempool) return {};
+
+        std::vector<CTransactionRef> results;
+        results.reserve(wtxids.size());
+        LOCK(m_node.mempool->cs);
+        for (const auto& wtxid : wtxids) {
+            results.emplace_back(m_node.mempool->get(wtxid));
+        }
+        return results;
+    }
+
     const NodeContext* context() override { return &m_node; }
     ChainstateManager& chainman() { return *Assert(m_node.chainman); }
     KernelNotifications& notifications() { return *Assert(m_node.notifications); }
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index a366e5e4..17644dea 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -194,6 +194,17 @@ void MinerTestingSetup::TestPackageSelection(const CScript& scriptPubKey, const
     BOOST_CHECK(raw_txs[0]);
     BOOST_CHECK(raw_txs[0]->GetHash() == hashParentTx);
     BOOST_CHECK(!raw_txs[1]);
+    // Test getTransactionsByWitnessID()
+    // tx has no witness, so just cast to Wtxid
+    const std::vector<Wtxid> wtx_id_list{
+        Wtxid::FromUint256(hashParentTx.ToUint256()),
+        Wtxid::FromUint256(uint256::ZERO)
+    };
+    raw_txs = mining->getTransactionsByWitnessID(wtx_id_list);
+    BOOST_REQUIRE_EQUAL(raw_txs.size(), tx_id_list.size());
+    BOOST_CHECK(raw_txs[0]);
+    BOOST_CHECK(raw_txs[0]->GetHash() == hashParentTx);
+    BOOST_CHECK(!raw_txs[1]);
     block_template = mining->createNewBlock(options, /*cooldown=*/false);
     BOOST_REQUIRE(block_template);
     block = block_template->getBlock();
diff --git a/test/functional/interface_ipc_mining.py b/test/functional/interface_ipc_mining.py
index a81e76da..f023b12d 100755
--- a/test/functional/interface_ipc_mining.py
+++ b/test/functional/interface_ipc_mining.py
@@ -673,7 +673,7 @@ class IPCMiningTest(BitcoinTestFramework):
         asyncio.run(capnp.run(async_routine()))
 
     def run_transaction_lookup_test(self):
-        """Test getTransactionsByTxID()."""
+        """Test getTransactionsByTxID() and getTransactionsByWitnessID()."""
         self.log.info("Running transaction lookup test")
 
         async def async_routine():
@@ -688,11 +688,20 @@ class IPCMiningTest(BitcoinTestFramework):
             assert_equal(raw_txs_txid.result[1].hex(), tx2["hex"])
             assert_equal(raw_txs_txid.result[2], b'')
 
+            self.log.debug("getTransactionsByWitnessID() returns mempool txs and nulls")
+            raw_txs_wtxid = await mining.getTransactionsByWitnessID(ctx, [tx1["tx"].wtxid, tx2["tx"].wtxid, bytes(32)])
+            assert_equal(len(raw_txs_wtxid.result), 3)
+            assert_equal(raw_txs_wtxid.result[0].hex(), tx1["hex"])
+            assert_equal(raw_txs_wtxid.result[1].hex(), tx2["hex"])
+            assert_equal(raw_txs_wtxid.result[2], b'')
+
             self.log.debug("Mined transactions are not returned")
             self.generate(self.nodes[0], 1)
             self.sync_all()
             raw_txs = await mining.getTransactionsByTxID(ctx, [tx1["tx"].txid])
             assert_equal(raw_txs.result[0], b'')
+            raw_txs = await mining.getTransactionsByWitnessID(ctx, [tx1["tx"].wtxid])
+            assert_equal(raw_txs.result[0], b'')
 
         asyncio.run(capnp.run(async_routine()))
 
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index 7614bd92..9c5b15ec 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -687,15 +687,20 @@ class CTransaction:
     def serialize(self):
         return self.serialize_with_witness()
 
+    @property
+    def wtxid(self):
+        """Return wtxid (transaction hash with witness) as little-endian bytes."""
+        return hash256(self.serialize_with_witness())
+
     @property
     def wtxid_hex(self):
         """Return wtxid (transaction hash with witness) as hex string."""
-        return hash256(self.serialize())[::-1].hex()
+        return self.wtxid[::-1].hex()
 
     @property
     def wtxid_int(self):
         """Return wtxid (transaction hash with witness) as integer."""
-        return uint256_from_str(hash256(self.serialize_with_witness()))
+        return uint256_from_str(self.wtxid)
 
     @property
     def txid(self):