fix: address Claude code review feedback on PR #519

- Handle iterationFailCount > 0 with firstError == nil (fallback message)
- Add nil guard for vm.smartWalletConfig on ERC20 injection path
- Demote debug/trace logs from Info to Debug level
- Add comment explaining slot 51 (Compound cToken contracts)

Author: weilicious

core/taskengine/engine.go

@@ -2989,7 +2989,7 @@ func (n *Engine) SimulateTask(user *model.User, trigger *avsproto.TaskTrigger, n
 	if shouldContinue {
 		// Inject simulated state overrides so downstream Tenderly simulations see
 		// the balance changes implied by the trigger event.
-		n.logger.Info("SimulateTask: state override check",
+		n.logger.Debug("SimulateTask: state override check",
 			"triggerType", triggerType,
 			"isEventTrigger", triggerType == avsproto.TriggerType_TRIGGER_TYPE_EVENT,
 			"simulationStateNil", vm.simulationState == nil)
@@ -3082,9 +3082,8 @@ func (n *Engine) injectEventTriggerStateOverrides(triggerOutput map[string]inter
 		return
 	}
 
-	n.logger.Info("injectEventTriggerStateOverrides: called",
-		"triggerOutputKeys", GetMapKeys(triggerOutput),
-		"simulationStateEmpty", vm.simulationState.IsEmpty())
+	n.logger.Debug("injectEventTriggerStateOverrides: called",
+		"triggerOutputKeys", GetMapKeys(triggerOutput))
 
 	// Only process if there is parsed event data
 	rawData := triggerOutput["data"]
@@ -3100,7 +3099,7 @@ func (n *Engine) injectEventTriggerStateOverrides(triggerOutput map[string]inter
 	}
 
 	eventName, _ := data["eventName"].(string)
-	n.logger.Info("injectEventTriggerStateOverrides: resolved eventName",
+	n.logger.Debug("injectEventTriggerStateOverrides: resolved eventName",
 		"eventName", eventName,
 		"dataKeys", GetMapKeys(data))
 
@@ -3166,6 +3165,11 @@ func (n *Engine) injectTransferEventState(data map[string]interface{}, vm *VM) {
 	}
 
 	// ERC20 transfer
+	if vm.smartWalletConfig == nil || vm.smartWalletConfig.EthRpcUrl == "" {
+		n.logger.Warn("No smart wallet config for ERC20 balance injection, skipping")
+		return
+	}
+
 	holderAddress := common.HexToAddress(walletAddr)
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()

core/taskengine/simulation_state.go

@@ -154,6 +154,8 @@ func erc20BalanceSlot(holder common.Address, mappingSlot int64) common.Hash {
 }
 
 // Common ERC20 balance mapping slot indices across different implementations.
+// 0: standard OpenZeppelin ERC20, 1-3: various token implementations,
+// 9: USDC (FiatTokenV2 proxy), 51: Compound cToken-style contracts.
 var commonBalanceSlots = []int64{0, 1, 2, 3, 9, 51}
 
 // ProbeERC20BalanceSlot discovers which storage slot a token contract uses for

core/taskengine/vm.go

@@ -4904,14 +4904,19 @@ func (v *VM) executeLoopWithQueue(stepID string, taskNode *avsproto.TaskNode, no
 		}
 	}
 
-	if iterationFailCount > 0 && firstError != nil {
+	if iterationFailCount > 0 {
 		// Some or all iterations failed — mark the loop step as failed so
 		// AnalyzeExecutionResult can detect partial_success at the execution level.
 		// Pass the error via the `err` parameter (not `errorMessage`) so that
 		// finalizeStep uses err.Error() directly without wrapping it in
 		// NewInvalidRequestError which adds an "invalid request: " prefix.
-		innerMsg := strings.TrimPrefix(firstError.Error(), "invalid request: ")
-		errorMsg := fmt.Sprintf("%d of %d iterations failed: %s", iterationFailCount, len(results), innerMsg)
+		var errorMsg string
+		if firstError != nil {
+			innerMsg := strings.TrimPrefix(firstError.Error(), "invalid request: ")
+			errorMsg = fmt.Sprintf("%d of %d iterations failed: %s", iterationFailCount, len(results), innerMsg)
+		} else {
+			errorMsg = fmt.Sprintf("%d of %d iterations failed", iterationFailCount, len(results))
+		}
 		loopErr := NewStructuredError(
 			avsproto.ErrorCode_INVALID_REQUEST,
 			errorMsg,