diff --git a/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/selectors.ts b/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/selectors.ts
index 9f4ba7f78c4e7..47c00dc7e93b3 100644
--- a/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/selectors.ts
+++ b/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/selectors.ts
@@ -51,11 +51,17 @@ export const selectWorkflowDefinition = createSelector(
   (computed) => computed?.workflowDefinition
 );
 
-// Only checks if the current workflow yaml can be parses, does check the schema, only the yaml syntax
+// Only checks if the current workflow yaml can be parsed, does not check the schema, only the yaml syntax
 export const selectIsYamlSyntaxValid = createSelector(selectYamlComputed, (computed): boolean =>
   Boolean(computed?.workflowDefinition)
 );
 
+// Checks whether validation errors (from strict schema + custom validations) are present
+export const selectHasYamlSchemaValidationErrors = createSelector(
+  selectDetail,
+  (detail): boolean => detail.hasYamlSchemaValidationErrors
+);
+
 export const selectFocusedStepId = createSelector(selectDetail, (detail) => detail.focusedStepId);
 
 export const selectHighlightedStepId = createSelector(
diff --git a/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/slice.ts b/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/slice.ts
index 404a98f6e877d..88aad8972d9e8 100644
--- a/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/slice.ts
+++ b/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/slice.ts
@@ -31,6 +31,7 @@ const initialState: WorkflowDetailState = {
   highlightedStepId: undefined,
   isTestModalOpen: false,
   loading: initialLoadingState,
+  hasYamlSchemaValidationErrors: false,
   connectorFlyout: {
     isOpen: false,
     connectorType: undefined,
@@ -89,6 +90,10 @@ const workflowDetailSlice = createSlice({
       state.activeTab = action.payload;
     },
 
+    setHasYamlSchemaValidationErrors: (state, action: { payload: boolean }) => {
+      state.hasYamlSchemaValidationErrors = action.payload;
+    },
+
     // Connector flyout actions
     openCreateConnectorFlyout: (
       state,
@@ -151,6 +156,7 @@ export const {
   setExecution,
   clearExecution,
   setActiveTab,
+  setHasYamlSchemaValidationErrors,
   openCreateConnectorFlyout,
   openEditConnectorFlyout,
   closeConnectorFlyout,
diff --git a/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/types.ts b/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/types.ts
index cf3fd51b051b9..7312ad9c68666 100644
--- a/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/types.ts
+++ b/src/platform/plugins/shared/workflows_management/public/entities/workflows/store/workflow_detail/types.ts
@@ -49,6 +49,8 @@ export interface WorkflowDetailState {
   schema: WorkflowZodSchemaType;
   /** Loading states for async operations */
   loading: LoadingStates;
+  /** Whether the editor has validation errors (strict schema + custom validations) */
+  hasYamlSchemaValidationErrors: boolean;
   /** Connector flyout state */
   connectorFlyout: {
     isOpen: boolean;
diff --git a/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.test.tsx b/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.test.tsx
index 865421b7eea96..dc019721d3619 100644
--- a/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.test.tsx
+++ b/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.test.tsx
@@ -13,7 +13,8 @@ import type { WorkflowDetailHeaderProps } from './workflow_detail_header';
 import { WorkflowDetailHeader } from './workflow_detail_header';
 import { createMockStore } from '../../../entities/workflows/store/__mocks__/store.mock';
 import {
-  _setComputedDataInternal,
+  _clearComputedData,
+  setHasYamlSchemaValidationErrors,
   setWorkflow,
   setYamlString,
 } from '../../../entities/workflows/store/workflow_detail/slice';
@@ -72,27 +73,33 @@ describe('WorkflowDetailHeader', () => {
 
   const renderWithProviders = (
     component: React.ReactElement,
-    { isValid = true, hasChanges = false }: { isValid?: boolean; hasChanges?: boolean } = {}
+    {
+      isValid = true,
+      hasChanges = false,
+      hasYamlSchemaValidationErrors = false,
+      serverValid = true,
+    }: {
+      isValid?: boolean;
+      hasChanges?: boolean;
+      hasYamlSchemaValidationErrors?: boolean;
+      serverValid?: boolean;
+    } = {}
   ) => {
     const store = createMockStore();
 
-    // Set up the workflow in the store
-    store.dispatch(setWorkflow(mockWorkflow));
+    // Set up the workflow in the store (with server-side valid flag)
+    store.dispatch(setWorkflow({ ...mockWorkflow, valid: serverValid }));
     store.dispatch(setYamlString(hasChanges ? 'modified yaml' : mockWorkflow.yaml));
 
-    // Set computed data to control syntax validation
-    if (isValid) {
-      store.dispatch(
-        _setComputedDataInternal({
-          workflowDefinition: {
-            version: '1',
-            name: 'Test Workflow',
-            enabled: true,
-            triggers: [],
-            steps: [],
-          },
-        })
-      );
+    if (!isValid) {
+      // Clear the computed data that the middleware auto-generated from the yaml,
+      // so that selectIsYamlSyntaxValid returns false
+      store.dispatch(_clearComputedData());
+    }
+
+    // Simulate strict validation errors from Monaco
+    if (hasYamlSchemaValidationErrors) {
+      store.dispatch(setHasYamlSchemaValidationErrors(true));
     }
 
     const wrapper = ({ children }: { children: React.ReactNode }) => {
@@ -158,15 +165,39 @@ describe('WorkflowDetailHeader', () => {
     expect(container).toBeTruthy();
   });
 
-  // We shouldn't rely on parseResult to determine if the yaml is valid now
-  // instead we should move validationErrors to the store and use it to determine it
-  it.skip('disables run workflow button when yaml is invalid', () => {
+  it('disables run workflow button when yaml has syntax errors', () => {
     const result = renderWithProviders(<WorkflowDetailHeader {...defaultProps} />, {
       isValid: false,
     });
     expect(result.getByTestId('runWorkflowHeaderButton')).toBeDisabled();
   });
 
+  it('disables run workflow button when yaml has validation errors', () => {
+    const result = renderWithProviders(<WorkflowDetailHeader {...defaultProps} />, {
+      isValid: true,
+      hasYamlSchemaValidationErrors: true,
+    });
+    expect(result.getByTestId('runWorkflowHeaderButton')).toBeDisabled();
+  });
+
+  it('disables enabled toggle when yaml has validation errors', () => {
+    const result = renderWithProviders(<WorkflowDetailHeader {...defaultProps} />, {
+      isValid: true,
+      hasYamlSchemaValidationErrors: true,
+    });
+    const toggle = result.getByRole('switch');
+    expect(toggle).toBeDisabled();
+  });
+
+  it('disables enabled toggle when server reports workflow as invalid (e.g. initial page load)', () => {
+    const result = renderWithProviders(<WorkflowDetailHeader {...defaultProps} />, {
+      isValid: true,
+      serverValid: false,
+    });
+    const toggle = result.getByRole('switch');
+    expect(toggle).toBeDisabled();
+  });
+
   it('enables run workflow button when yaml is valid', () => {
     const result = renderWithProviders(<WorkflowDetailHeader {...defaultProps} />);
     const button = result.getByTestId('runWorkflowHeaderButton');
diff --git a/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.tsx b/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.tsx
index e4cf63209909b..afb35966b37e2 100644
--- a/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.tsx
+++ b/src/platform/plugins/shared/workflows_management/public/pages/workflow_detail/ui/workflow_detail_header.tsx
@@ -37,6 +37,7 @@ import { useSaveYaml } from '../../../entities/workflows/model/use_save_yaml';
 import { useUpdateWorkflow } from '../../../entities/workflows/model/use_update_workflow';
 import {
   selectHasChanges,
+  selectHasYamlSchemaValidationErrors,
   selectIsExecutionsTab,
   selectIsSavingYaml,
   selectIsYamlSynced,
@@ -105,6 +106,7 @@ export const WorkflowDetailHeader = React.memo(
 
     const workflow = useSelector(selectWorkflow);
     const isSyntaxValid = useSelector(selectIsYamlSyntaxValid);
+    const hasYamlSchemaValidationErrors = useSelector(selectHasYamlSchemaValidationErrors);
     const hasUnsavedChanges = useSelector(selectHasChanges);
     const isExecutionsTab = useSelector(selectIsExecutionsTab);
     const isYamlSynced = useSelector(selectIsYamlSynced);
@@ -135,13 +137,17 @@ export const WorkflowDetailHeader = React.memo(
 
     const [showRunConfirmation, setShowRunConfirmation] = useState(false);
 
+    // Combined validity: syntax must parse AND no strict validation errors AND server considers it valid.
+    // workflow?.valid !== false covers the initial page load before Monaco validates.
+    const isValid = isSyntaxValid && !hasYamlSchemaValidationErrors && workflow?.valid !== false;
+
     const runWorkflowTooltipContent = useMemo(() => {
       return getTestRunTooltipContent({
         isExecutionsTab,
-        isValid: isSyntaxValid,
+        isValid,
         canRunWorkflow: canExecuteWorkflow,
       });
-    }, [isSyntaxValid, canExecuteWorkflow, isExecutionsTab]);
+    }, [isValid, canExecuteWorkflow, isExecutionsTab]);
 
     const saveWorkflowTooltipContent = useMemo(() => {
       const isCreate = !workflowId;
@@ -262,9 +268,9 @@ export const WorkflowDetailHeader = React.memo(
                       ? i18n.translate('workflows.workflowDetailHeader.unsaved', {
                           defaultMessage: 'Save changes to enable/disable workflow',
                         })
-                      : !isSyntaxValid
+                      : !isValid
                       ? i18n.translate('workflows.workflowDetailHeader.invalid', {
-                          defaultMessage: 'Fix errors to enable workflow',
+                          defaultMessage: 'Fix validation errors to enable workflow',
                         })
                       : undefined
                   }
@@ -274,7 +280,7 @@ export const WorkflowDetailHeader = React.memo(
                       !workflowId ||
                       isLoading ||
                       !canUpdateWorkflow ||
-                      !isSyntaxValid ||
+                      !isValid ||
                       hasUnsavedChanges
                     }
                     checked={isEnabled}
@@ -292,7 +298,7 @@ export const WorkflowDetailHeader = React.memo(
                     iconType="play"
                     size="s"
                     onClick={handleRunClickWithUnsavedCheck}
-                    disabled={isExecutionsTab || !canExecuteWorkflow || isLoading || !isSyntaxValid}
+                    disabled={isExecutionsTab || !canExecuteWorkflow || isLoading || !isValid}
                     aria-label={Translations.runWorkflow}
                     data-test-subj="runWorkflowHeaderButton"
                   />
diff --git a/src/platform/plugins/shared/workflows_management/public/widgets/workflow_yaml_editor/ui/workflow_yaml_editor.tsx b/src/platform/plugins/shared/workflows_management/public/widgets/workflow_yaml_editor/ui/workflow_yaml_editor.tsx
index 8aba9baeff69a..b63787a3646e9 100644
--- a/src/platform/plugins/shared/workflows_management/public/widgets/workflow_yaml_editor/ui/workflow_yaml_editor.tsx
+++ b/src/platform/plugins/shared/workflows_management/public/widgets/workflow_yaml_editor/ui/workflow_yaml_editor.tsx
@@ -53,7 +53,10 @@ import {
   selectStepExecutions,
   selectWorkflow,
 } from '../../../entities/workflows/store/workflow_detail/selectors';
-import { setIsTestModalOpen } from '../../../entities/workflows/store/workflow_detail/slice';
+import {
+  setHasYamlSchemaValidationErrors,
+  setIsTestModalOpen,
+} from '../../../entities/workflows/store/workflow_detail/slice';
 import { ActionsMenuPopover } from '../../../features/actions_menu_popover';
 import type { ActionOptionData } from '../../../features/actions_menu_popover/types';
 import { useMonacoMarkersChangedInterceptor } from '../../../features/validate_workflow_yaml/lib/use_monaco_markers_changed_interceptor';
@@ -256,6 +259,12 @@ export const WorkflowYAMLEditor = ({
       workflowYamlSchema: workflowYamlSchema as z.ZodSchema,
     });
 
+  // Sync validation error state to Redux so sibling components (e.g. header toggle) can react
+  useEffect(() => {
+    const hasErrors = validationErrors.some((e) => e.severity === 'error');
+    dispatch(setHasYamlSchemaValidationErrors(hasErrors));
+  }, [validationErrors, dispatch]);
+
   const handleErrorClick = useCallback((error: YamlValidationResult) => {
     if (!editorRef.current) {
       return;