diff --git a/apps/sim/app/api/workflows/[id]/deploy/route.ts b/apps/sim/app/api/workflows/[id]/deploy/route.ts
index 1dd8798a3f2..aae32b15d6d 100644
--- a/apps/sim/app/api/workflows/[id]/deploy/route.ts
+++ b/apps/sim/app/api/workflows/[id]/deploy/route.ts
@@ -20,6 +20,7 @@ import {
   createSchedulesForDeploy,
   validateWorkflowSchedules,
 } from '@/lib/workflows/schedules'
+import { validateWorkflowState } from '@/lib/workflows/sanitization/validation'
 import { validateWorkflowPermissions } from '@/lib/workflows/utils'
 import { createErrorResponse, createSuccessResponse } from '@/app/api/workflows/utils'
 import type { WorkflowState } from '@/stores/workflows/workflow/types'
@@ -134,6 +135,22 @@ export async function POST(request: NextRequest, { params }: { params: Promise<{
       return createErrorResponse('Failed to load workflow state', 500)
     }
 
+    // Validate workflow state (block types, edges, tool references)
+    const workflowValidation = validateWorkflowState({
+      blocks: normalizedData.blocks,
+      edges: normalizedData.edges,
+      loops: normalizedData.loops,
+      parallels: normalizedData.parallels,
+      variables: {},
+    } as WorkflowState)
+    if (!workflowValidation.valid) {
+      const errorSummary = workflowValidation.errors.join('; ')
+      logger.warn(
+        `[${requestId}] Workflow validation failed for ${id}: ${errorSummary}`
+      )
+      return createErrorResponse(`Workflow validation failed: ${errorSummary}`, 400)
+    }
+
     const scheduleValidation = validateWorkflowSchedules(normalizedData.blocks)
     if (!scheduleValidation.isValid) {
       logger.warn(
diff --git a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/hooks/use-deployment.ts b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/hooks/use-deployment.ts
index b6a5d585e32..216582412ac 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/hooks/use-deployment.ts
+++ b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/hooks/use-deployment.ts
@@ -28,16 +28,13 @@ export function useDeployment({
 
   /**
    * Handle deploy button click
-   * First deploy: calls API to deploy, then opens modal on success
-   * Already deployed: opens modal directly (validation happens on Update in modal)
+   * First deploy: runs pre-deploy checks, calls API to deploy, then opens modal on success
+   * Already deployed: runs pre-deploy checks, then opens modal (redeployment happens in modal)
    */
   const handleDeployClick = useCallback(async () => {
     if (!workflowId) return { success: false, shouldOpenModal: false }
 
-    if (isDeployed) {
-      return { success: true, shouldOpenModal: true }
-    }
-
+    // Always run pre-deploy checks, even for redeployments
     const { blocks, edges, loops, parallels } = useWorkflowStore.getState()
     const liveBlocks = mergeSubblockState(blocks, workflowId)
     const checkResult = runPreDeployChecks({
@@ -56,6 +53,10 @@ export function useDeployment({
       return { success: false, shouldOpenModal: false }
     }
 
+    if (isDeployed) {
+      return { success: true, shouldOpenModal: true }
+    }
+
     setIsDeploying(true)
     try {
       const response = await fetch(`/api/workflows/${workflowId}/deploy`, {
diff --git a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/panel.tsx b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/panel.tsx
index 47e6e420709..8b71c9b7cee 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/panel.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/panel.tsx
@@ -356,7 +356,14 @@ export const Panel = memo(function Panel() {
   // Compute run button state
   const canRun = userPermissions.canRead // Running only requires read permissions
   const isLoadingPermissions = userPermissions.isLoading
-  const hasValidationErrors = false // TODO: Add validation logic if needed
+
+  // Validate workflow has connected blocks when multiple blocks exist.
+  // A single-block workflow (e.g. one starter or agent block) is valid without edges,
+  // but multiple blocks with no edges indicates a disconnected graph.
+  const blockCount = useWorkflowStore((state) => Object.keys(state.blocks).length)
+  const hasEdges = useWorkflowStore((state) => state.edges.length > 0)
+  const hasValidationErrors = blockCount > 1 && !hasEdges
+
   const isWorkflowBlocked = isExecuting || hasValidationErrors
   const isButtonDisabled = !isExecuting && (isWorkflowBlocked || (!canRun && !isLoadingPermissions))
 
@@ -373,7 +380,7 @@ export const Panel = memo(function Panel() {
         handler: () => {
           if (isExecuting) {
             void cancelWorkflow()
-          } else {
+          } else if (!isButtonDisabled) {
             void runWorkflow()
           }
         },