diff --git a/nimbus/p2p/chain.nim b/nimbus/p2p/chain.nim
index 706cc550b..f0bc7bd5a 100644
--- a/nimbus/p2p/chain.nim
+++ b/nimbus/p2p/chain.nim
@@ -1,6 +1,6 @@
 import ../db/[db_chain, state_db], eth_common, chronicles, ../vm_state, ../vm_types, ../transaction, ranges,
   ../vm/[computation, interpreter_dispatch, message], ../constants, stint, nimcrypto,
-  ../vm_state_transactions, sugar, ../utils, eth_trie/db
+  ../vm_state_transactions, sugar, ../utils, eth_trie/db, ../tracer, ./executor, json
 
 type
   Chain* = ref object of AbstractChainDB
@@ -30,72 +30,6 @@ method getSuccessorHeader*(c: Chain, h: BlockHeader, output: var BlockHeader): b
 method getBlockBody*(c: Chain, blockHash: KeccakHash): BlockBodyRef =
   result = nil
 
-proc processTransaction*(db: var AccountStateDB, t: Transaction, sender: EthAddress, vmState: BaseVMState): UInt256 =
-  ## Process the transaction, write the results to db.
-  ## Returns amount of ETH to be rewarded to miner
-  echo "Sender: ", sender
-  echo "txHash: ", t.rlpHash
-  # Inct nonce:
-  db.setNonce(sender, db.getNonce(sender) + 1)
-  var transactionFailed = false
-
-  #t.dump
-
-  # TODO: combine/refactor re validate
-  let upfrontGasCost = t.gasLimit.u256 * t.gasPrice.u256
-  let upfrontCost = upfrontGasCost + t.value
-  var balance = db.getBalance(sender)
-  if balance < upfrontCost:
-    if balance <= upfrontGasCost:
-      result = balance
-      balance = 0.u256
-    else:
-      result = upfrontGasCost
-      balance -= upfrontGasCost
-    transactionFailed = true
-  else:
-    balance -= upfrontCost
-
-  db.setBalance(sender, balance)
-  if transactionFailed:
-    return
-
-  var gasUsed = t.payload.intrinsicGas.GasInt # += 32000 appears in Homestead when contract create
-
-  if gasUsed > t.gasLimit:
-    echo "Transaction failed. Out of gas."
-    transactionFailed = true
-  else:
-    if t.isContractCreation:
-      # TODO: re-derive sender in callee for cleaner interface, perhaps
-      return applyCreateTransaction(db, t, vmState, sender)
-
-    else:
-      let code = db.getCode(t.to)
-      if code.len == 0:
-        # Value transfer
-        echo "Transfer ", t.value, " from ", sender, " to ", t.to
-
-        db.addBalance(t.to, t.value)
-      else:
-        # Contract call
-        echo "Contract call"
-
-        debug "Transaction", sender, to = t.to, value = t.value, hasCode = code.len != 0
-        let msg = newMessage(t.gasLimit, t.gasPrice, t.to, sender, t.value, t.payload, code.toSeq)
-        # TODO: Run the vm
-
-  if gasUsed > t.gasLimit:
-    gasUsed = t.gasLimit
-
-  var refund = (t.gasLimit - gasUsed).u256 * t.gasPrice.u256
-  if transactionFailed:
-    refund += t.value
-
-  db.addBalance(sender, refund)
-
-  return gasUsed.u256 * t.gasPrice.u256
-
 method persistBlocks*(c: Chain, headers: openarray[BlockHeader], bodies: openarray[BlockBody]) =
   # Run the VM here
   assert(headers.len == bodies.len)
@@ -149,6 +83,10 @@ method persistBlocks*(c: Chain, headers: openarray[BlockHeader], bodies: openarr
 
     if headers[i].stateRoot != stateDb.rootHash:
       echo "Wrong state root in block ", headers[i].blockNumber, ". Expected: ", headers[i].stateRoot, ", Actual: ", stateDb.rootHash, " arrived from ", c.db.getCanonicalHead().stateRoot
+      let trace = traceTransaction(c.db, headers[i], bodies[i], bodies[i].transactions.len - 1, {})
+      echo "NIMBUS TRACE"
+      echo trace.pretty()
+
     assert(headers[i].stateRoot == stateDb.rootHash)
 
     discard c.db.persistHeaderToDb(headers[i])
diff --git a/nimbus/p2p/executor.nim b/nimbus/p2p/executor.nim
new file mode 100644
index 000000000..b87f95be3
--- /dev/null
+++ b/nimbus/p2p/executor.nim
@@ -0,0 +1,69 @@
+import ../db/[db_chain, state_db], ../transaction, eth_common,
+  ../vm_state, ../vm_types, ../vm_state_transactions, ranges,
+  chronicles, ../vm/[computation, interpreter_dispatch, message]
+
+proc processTransaction*(db: var AccountStateDB, t: Transaction, sender: EthAddress, vmState: BaseVMState): UInt256 =
+  ## Process the transaction, write the results to db.
+  ## Returns amount of ETH to be rewarded to miner
+  echo "Sender: ", sender
+  echo "txHash: ", t.rlpHash
+  # Inct nonce:
+  db.setNonce(sender, db.getNonce(sender) + 1)
+  var transactionFailed = false
+
+  #t.dump
+
+  # TODO: combine/refactor re validate
+  let upfrontGasCost = t.gasLimit.u256 * t.gasPrice.u256
+  let upfrontCost = upfrontGasCost + t.value
+  var balance = db.getBalance(sender)
+  if balance < upfrontCost:
+    if balance <= upfrontGasCost:
+      result = balance
+      balance = 0.u256
+    else:
+      result = upfrontGasCost
+      balance -= upfrontGasCost
+    transactionFailed = true
+  else:
+    balance -= upfrontCost
+
+  db.setBalance(sender, balance)
+  if transactionFailed:
+    return
+
+  var gasUsed = t.payload.intrinsicGas.GasInt # += 32000 appears in Homestead when contract create
+
+  if gasUsed > t.gasLimit:
+    echo "Transaction failed. Out of gas."
+    transactionFailed = true
+  else:
+    if t.isContractCreation:
+      # TODO: re-derive sender in callee for cleaner interface, perhaps
+      return applyCreateTransaction(db, t, vmState, sender)
+
+    else:
+      let code = db.getCode(t.to)
+      if code.len == 0:
+        # Value transfer
+        echo "Transfer ", t.value, " from ", sender, " to ", t.to
+
+        db.addBalance(t.to, t.value)
+      else:
+        # Contract call
+        echo "Contract call"
+
+        debug "Transaction", sender, to = t.to, value = t.value, hasCode = code.len != 0
+        let msg = newMessage(t.gasLimit, t.gasPrice, t.to, sender, t.value, t.payload, code.toSeq)
+        # TODO: Run the vm
+
+  if gasUsed > t.gasLimit:
+    gasUsed = t.gasLimit
+
+  var refund = (t.gasLimit - gasUsed).u256 * t.gasPrice.u256
+  if transactionFailed:
+    refund += t.value
+
+  db.addBalance(sender, refund)
+
+  return gasUsed.u256 * t.gasPrice.u256
diff --git a/nimbus/tracer.nim b/nimbus/tracer.nim
index abed86f80..b3d7b99ca 100644
--- a/nimbus/tracer.nim
+++ b/nimbus/tracer.nim
@@ -1,6 +1,6 @@
 import
   db/[db_chain, state_db, capturedb], eth_common, utils, json,
-  constants, vm_state, vm_types, transaction, p2p/chain,
+  constants, vm_state, vm_types, transaction, p2p/executor,
   eth_trie/db, nimcrypto
 
 proc getParentHeader(self: BaseChainDB, header: BlockHeader): BlockHeader =
@@ -10,7 +10,7 @@ proc prefixHex(x: openArray[byte]): string =
   "0x" & toHex(x, true)
 
 proc traceTransaction*(db: BaseChainDB, header: BlockHeader,
-                       body: BlockBody, txIndex: int, tracerFlags: set[TracerFlags]): JsonNode =
+                       body: BlockBody, txIndex: int, tracerFlags: set[TracerFlags] = {}): JsonNode =
   let
     parent = db.getParentHeader(header)
     # we add a memory layer between backend/lower layer db