diff --git a/Cargo.lock b/Cargo.lock
index 57ad742b..4fc88aee 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5691,6 +5691,7 @@ dependencies = [
  "rolling-file",
  "salt",
  "serde",
+ "serde_json",
  "stateless-core",
  "stateless-r2",
  "stateless-test-utils",
diff --git a/crates/stateless-common/Cargo.toml b/crates/stateless-common/Cargo.toml
index bb2ea816..0d27b893 100644
--- a/crates/stateless-common/Cargo.toml
+++ b/crates/stateless-common/Cargo.toml
@@ -51,6 +51,7 @@ zstd.workspace = true
 [dev-dependencies]
 jsonrpsee.workspace = true
 kanal.workspace = true
+serde_json.workspace = true
 stateless-test-utils = { path = "../stateless-test-utils", features = ["mock-rpc"] }
 tokio-util.workspace = true
 
diff --git a/crates/stateless-common/src/rpc_client.rs b/crates/stateless-common/src/rpc_client.rs
index 6a480bc5..6aa2d875 100644
--- a/crates/stateless-common/src/rpc_client.rs
+++ b/crates/stateless-common/src/rpc_client.rs
@@ -40,7 +40,7 @@ use std::{
     time::{Duration, Instant},
 };
 
-use alloy_primitives::{B256, Bytes, U64};
+use alloy_primitives::{B256, Bytes, U64, keccak256};
 use alloy_provider::{Provider, RootProvider};
 use alloy_rpc_client::ClientBuilder;
 use alloy_rpc_types_eth::{Block, BlockId, BlockNumberOrTag, Header};
@@ -1575,13 +1575,19 @@ fn verify_block_integrity(block: &Block<Transaction>) -> Result<()> {
 
     // Verify transaction hashes and transactions root
     if let BlockTransactions::Full(ref transactions) = block.transactions {
+        // The RPC `hash` field seeds the envelope's cached hash, so it is only trusted once keccak
+        // of the envelope's own encoding reproduces it; the same bytes then feed the ordered trie
+        // for the transactions-root check.
+        let mut encoded_txs = Vec::with_capacity(transactions.len());
         for tx in transactions {
-            let tx_envelope = tx.inner.clone().into_inner();
+            let tx_envelope = tx.inner.inner.inner();
+            let encoded = tx_envelope.encoded_2718();
+            let computed_hash = keccak256(&encoded);
             ensure!(
-                tx_envelope.trie_hash() == *tx_envelope.hash(),
+                computed_hash == *tx_envelope.hash(),
                 "Transaction hash mismatch: expected {:?}, computed {:?}",
                 tx_envelope.hash(),
-                tx_envelope.trie_hash()
+                computed_hash
             );
 
             let recovered = tx_envelope
@@ -1594,10 +1600,11 @@ fn verify_block_integrity(block: &Block<Transaction>) -> Result<()> {
                 tx.from(),
                 recovered
             );
+            encoded_txs.push(encoded);
         }
 
-        let computed_tx_root = ordered_trie_root_with_encoder(transactions, |tx, buf| {
-            tx.inner.clone().into_inner().encode_2718(buf)
+        let computed_tx_root = ordered_trie_root_with_encoder(&encoded_txs, |tx_bytes, buf| {
+            buf.extend_from_slice(tx_bytes)
         });
         ensure!(
             computed_tx_root == block.header.transactions_root,
@@ -1629,7 +1636,10 @@ mod tests {
         find_divergence_point,
         pipeline::{BlockFetcher, DivergenceLookups},
     };
-    use stateless_test_utils::mock_rpc::{header_stub, parse_hex_u64, serve};
+    use stateless_test_utils::{
+        fixtures::TestFixtures,
+        mock_rpc::{header_stub, parse_hex_u64, serve},
+    };
     use tokio_util::sync::CancellationToken;
 
     use super::*;
@@ -2977,4 +2987,30 @@ mod tests {
         }
         assert!(found, "witness failure log must carry the block_number span field, got:\n{logs}");
     }
+
+    /// The deserializer seeds each envelope's cached hash from the RPC `hash` field, so
+    /// `trie_hash()` reproduces the claim by construction; only keccak over the envelope's own
+    /// encoding can tell a hash that does not belong to the bytes. Forging one hash leaves the
+    /// transactions root intact, so the hash check is the only thing that rejects the block.
+    /// The first transaction is the deposit (`Sealed`) and the last a signed envelope.
+    #[test]
+    fn verify_block_integrity_rejects_a_forged_transaction_hash() {
+        let fx = TestFixtures::mainnet_shared();
+        let block = fx
+            .paired_blocks()
+            .iter()
+            .map(|(_, hash)| &fx.blocks[hash])
+            .find(|block| !block.transactions.is_empty())
+            .expect("a paired mainnet fixture with transactions");
+        verify_block_integrity(block).expect("untampered fixture block verifies");
+
+        let last = block.transactions.len() - 1;
+        for index in [0, last] {
+            let mut json = serde_json::to_value(block).unwrap();
+            json["transactions"][index]["hash"] = serde_json::to_value(B256::ZERO).unwrap();
+            let forged: Block<Transaction> = serde_json::from_value(json).unwrap();
+            let err = verify_block_integrity(&forged).unwrap_err();
+            assert!(err.to_string().contains("Transaction hash mismatch"), "tx {index}: {err:?}");
+        }
+    }
 }
diff --git a/crates/stateless-core/src/executor.rs b/crates/stateless-core/src/executor.rs
index 0b1d15c8..58194078 100644
--- a/crates/stateless-core/src/executor.rs
+++ b/crates/stateless-core/src/executor.rs
@@ -492,8 +492,9 @@ where
     let logs_bloom =
         execution_result.receipts.iter().fold(Bloom::ZERO, |acc, receipt| acc | receipt.bloom());
 
-    // Gas used is the cumulative gas used of the last receipt
-    let gas_used = execution_result.receipts.last().map(|r| r.cumulative_gas_used()).unwrap_or(0);
+    // mega-evm's `finish()` sets this to the last receipt's cumulative gas;
+    // `verify_replay_outputs` pins it against the header's claim.
+    let gas_used = execution_result.gas_used;
 
     let receipts_root = calculate_receipt_root(&execution_result.receipts);
 
@@ -1062,6 +1063,9 @@ mod tests {
         assert!(matches!(err, ValidationError::BlockIncomplete), "{err:?}");
     }
 
+    /// Every paired mainnet fixture must validate end to end, which pins the replayed withdrawals
+    /// root, receipts root, logs bloom and gas used against the header's claims through
+    /// `verify_replay_outputs`.
     #[test]
     fn validate_block_mainnet_fixtures() {
         let _logging = init_test_logging("stateless_core");