exec3_parallel: eliminate IBS round-trip in finalize path

execution/exec/state.go

@@ -282,9 +282,9 @@ func (rw *Worker) resetTx(chainTx kv.TemporalTx) error {
 		case withTx:
 			typedWriter.SetTx(rw.chainTx)
 		default:
-			if rw.stateWriter != nil {
-				return fmt.Errorf("can't set tx for writer: %T", rw.stateWriter)
-			}
+			// Writers that don't implement withPutter or withTx (e.g.
+			// NoopWriter, LightCollector) don't need a DB transaction —
+			// they accumulate writes in memory only. This is not an error.
 		}
 
 		rw.chain = consensuschain.NewReader(rw.chainConfig, rw.chainTx, rw.blockReader, rw.logger)
@@ -442,6 +442,13 @@ func (rw *Worker) RunTxTaskNoLock(txTask Task) *TxResult {
 		result.TraceTos = callTracer.Tos()
 	}
 
+	// Capture collector-format writes from LightCollector (parallel workers).
+	// MakeWriteSet already wrote to rw.stateWriter; extract the accumulated
+	// writes so finalize can use them directly without IBS reconstruction.
+	if lc, ok := rw.stateWriter.(*state.LightCollector); ok {
+		result.CollectorWrites = lc.TakeWrites()
+	}
+
 	return result
 }
 

execution/exec/txtask.go

@@ -111,6 +111,12 @@ type TxResult struct {
 	TraceFroms        map[accounts.Address]struct{}
 	TraceTos          map[accounts.Address]struct{}
 	AccessedAddresses state.AccessSet
+
+	// CollectorWrites holds collector-format writes (all 4 account fields per
+	// address) produced by MakeWriteSet during worker execution. Used by the
+	// parallel finalize path to skip full IBS reconstruction: fee-calc balance
+	// adjustments are applied directly to these writes.
+	CollectorWrites state.VersionedWrites
 }
 
 func (r *TxResult) compare(other *TxResult) int {