diff --git a/src/main/java/it/cnr/isti/workflow/manager/assistant/AssistantFlowValidation.java b/src/main/java/it/cnr/isti/workflow/manager/assistant/AssistantFlowValidation.java
new file mode 100644
index 0000000..893ee35
--- /dev/null
+++ b/src/main/java/it/cnr/isti/workflow/manager/assistant/AssistantFlowValidation.java
@@ -0,0 +1,52 @@
+package it.cnr.isti.workflow.manager.assistant;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+import it.cnr.isti.workflow.manager.flows.model.FlowCreateRequest;
+import it.cnr.isti.workflow.manager.flows.validation.FlowExecutionValidator;
+import it.cnr.isti.workflow.manager.flows.validation.ValidationError;
+import it.cnr.isti.workflow.manager.flows.validation.ValidationErrorCodec;
+import jakarta.validation.ConstraintViolation;
+import jakarta.validation.Validator;
+
+final class AssistantFlowValidation {
+
+    private AssistantFlowValidation() {
+    }
+
+    static List<ValidationError> validate(FlowCreateRequest flow, Validator validator,
+            FlowExecutionValidator flowExecutionValidator) {
+        List<ValidationError> errors = new ArrayList<>();
+
+        Set<ConstraintViolation<FlowCreateRequest>> violations = validator.validate(flow);
+        for (ConstraintViolation<FlowCreateRequest> violation : violations) {
+            List<ValidationError> decoded = ValidationErrorCodec.decode(violation.getMessage());
+            if (decoded.isEmpty()) {
+                errors.add(toFallbackError(violation));
+                continue;
+            }
+            for (ValidationError error : decoded) {
+                if (error.message() == null || Objects.equals(error.message(), violation.getMessage())) {
+                    errors.add(toFallbackError(violation));
+                } else {
+                    errors.add(error);
+                }
+            }
+        }
+
+        // Bean validation alone misses structural/execution issues (dangling connections,
+        // an unconnected BranchRejoin input, global-input reference mismatches, container
+        // subflow rules, ...) that only surface at actual execution time otherwise.
+        if (flow != null && flow.flow() != null) {
+            errors.addAll(flowExecutionValidator.collectErrors(flow.flow()));
+        }
+        return errors;
+    }
+
+    private static ValidationError toFallbackError(ConstraintViolation<FlowCreateRequest> violation) {
+        return new ValidationError("flow", null, violation.getPropertyPath().toString(), violation.getMessage());
+    }
+}
diff --git a/src/main/java/it/cnr/isti/workflow/manager/assistant/FlowAssistantService.java b/src/main/java/it/cnr/isti/workflow/manager/assistant/FlowAssistantService.java
index 3847c28..5fc21d3 100644
--- a/src/main/java/it/cnr/isti/workflow/manager/assistant/FlowAssistantService.java
+++ b/src/main/java/it/cnr/isti/workflow/manager/assistant/FlowAssistantService.java
@@ -61,12 +61,10 @@ import it.cnr.isti.workflow.manager.flows.model.FlowData;
 import it.cnr.isti.workflow.manager.flows.validation.FlowExecutionValidator;
 import it.cnr.isti.workflow.manager.flows.validation.ValidationError;
 import it.cnr.isti.workflow.manager.flows.validation.ValidationErrorCode;
-import it.cnr.isti.workflow.manager.flows.validation.ValidationErrorCodec;
 import it.cnr.isti.workflow.manager.ios.IODescriptor;
 import it.cnr.isti.workflow.manager.ios.IOType;
 import it.cnr.isti.workflow.manager.llms.providers.LLMProvider;
 import it.cnr.isti.workflow.manager.vault.UserSecretService;
-import jakarta.validation.ConstraintViolation;
 import jakarta.validation.Validator;
 
 @Service
@@ -355,7 +353,7 @@ public class FlowAssistantService {
 
     public AssistantFlowResponse fix(AssistantFixRequest request, String owner, ProgressListener progressListener) {
         List<ValidationError> initialErrors = request.validationErrors() == null || request.validationErrors().isEmpty()
-                ? validate(request.flow())
+                ? AssistantFlowValidation.validate(request.flow(), validator, flowExecutionValidator)
                 : request.validationErrors();
         boolean directMdc = ensureAssistantRequestMdc(OperationMode.FIX.name());
         try {
@@ -416,7 +414,7 @@ public class FlowAssistantService {
             assembled = assembleFlow(provider, authorization, assistantModel, generatedFlowProvider, generatedFlowModel,
                     phaseModels, mode, userPrompt, flowContext, errorContext, progressListener);
             progressListener.onProgress("validating", "Validating the assembled flow");
-            errors = validate(assembled.flow());
+            errors = AssistantFlowValidation.validate(assembled.flow(), validator, flowExecutionValidator);
             if (errors.isEmpty() || repairs >= allowedRepairs) {
                 break;
             }
@@ -1038,39 +1036,6 @@ public class FlowAssistantService {
         return SharedMemoryIntentClassifier.isSharedMemoryRequest(flowText.toString());
     }
 
-    private List<ValidationError> validate(FlowCreateRequest flow) {
-        List<ValidationError> errors = new ArrayList<>();
-
-        Set<ConstraintViolation<FlowCreateRequest>> violations = validator.validate(flow);
-        for (ConstraintViolation<FlowCreateRequest> violation : violations) {
-            List<ValidationError> decoded = ValidationErrorCodec.decode(violation.getMessage());
-            if (decoded.isEmpty()) {
-                errors.add(toFallbackError(violation));
-                continue;
-            }
-            for (ValidationError error : decoded) {
-                if (error.message() == null || Objects.equals(error.message(), violation.getMessage())) {
-                    errors.add(toFallbackError(violation));
-                } else {
-                    errors.add(error);
-                }
-            }
-        }
-
-        // Bean validation alone misses structural/execution issues (dangling connections,
-        // an unconnected BranchRejoin input, global-input reference mismatches, container
-        // subflow rules, ...) that only surface at actual execution time otherwise.
-        if (flow != null && flow.flow() != null) {
-            errors.addAll(flowExecutionValidator.collectErrors(flow.flow()));
-        }
-        return errors;
-    }
-
-    private ValidationError toFallbackError(ConstraintViolation<FlowCreateRequest> violation) {
-        return new ValidationError("flow", null, violation.getPropertyPath().toString(), violation.getMessage());
-    }
-
-
     private void appendRationale(List<String> target, String rationale) {
         if (rationale != null && !rationale.isBlank()) {
             target.add(rationale.trim());