diff --git a/apps/sim/lib/workflows/credentials/credential-extractor.ts b/apps/sim/lib/workflows/credentials/credential-extractor.ts
index df1812872..014febabc 100644
--- a/apps/sim/lib/workflows/credentials/credential-extractor.ts
+++ b/apps/sim/lib/workflows/credentials/credential-extractor.ts
@@ -161,6 +161,49 @@ function formatFieldName(fieldName: string): string {
     .join(' ')
 }
 
+/**
+ * Remove malformed subBlocks from a block that may have been created by bugs.
+ * This includes subBlocks with:
+ * - Key "undefined" (caused by assigning to undefined key)
+ * - Missing required `id` field
+ * - Type "unknown" (indicates malformed data)
+ */
+function removeMalformedSubBlocks(block: any): void {
+  if (!block.subBlocks) return
+
+  const keysToRemove: string[] = []
+
+  Object.entries(block.subBlocks).forEach(([key, subBlock]: [string, any]) => {
+    // Flag subBlocks with invalid keys (literal "undefined" string)
+    if (key === 'undefined') {
+      keysToRemove.push(key)
+      return
+    }
+
+    // Flag subBlocks that are null or not objects
+    if (!subBlock || typeof subBlock !== 'object') {
+      keysToRemove.push(key)
+      return
+    }
+
+    // Flag subBlocks with type "unknown" (malformed data)
+    if (subBlock.type === 'unknown') {
+      keysToRemove.push(key)
+      return
+    }
+
+    // Flag subBlocks missing required id field
+    if (!subBlock.id) {
+      keysToRemove.push(key)
+    }
+  })
+
+  // Remove the flagged keys
+  keysToRemove.forEach((key) => {
+    delete block.subBlocks[key]
+  })
+}
+
 /**
  * Sanitize workflow state by removing all credentials and workspace-specific data
  * This is used for both template creation and workflow export to ensure consistency
@@ -183,6 +226,9 @@ export function sanitizeWorkflowForSharing(
   Object.values(sanitized.blocks).forEach((block: any) => {
     if (!block?.type) return
 
+    // First, remove any malformed subBlocks that may have been created by bugs
+    removeMalformedSubBlocks(block)
+
     const blockConfig = getBlock(block.type)
 
     // Process subBlocks with config
diff --git a/apps/sim/stores/workflows/json/importer.ts b/apps/sim/stores/workflows/json/importer.ts
index bb119e989..f2243c76c 100644
--- a/apps/sim/stores/workflows/json/importer.ts
+++ b/apps/sim/stores/workflows/json/importer.ts
@@ -5,9 +5,14 @@ import type { WorkflowState } from '../workflow/types'
 const logger = createLogger('WorkflowJsonImporter')
 
 /**
- * Normalize subblock values by converting empty strings to null.
+ * Normalize subblock values by converting empty strings to null and filtering out invalid subblocks.
  * This provides backwards compatibility for workflows exported before the null sanitization fix,
  * preventing Zod validation errors like "Expected array, received string".
+ *
+ * Also filters out malformed subBlocks that may have been created by bugs in previous exports:
+ * - SubBlocks with key "undefined" (caused by assigning to undefined key)
+ * - SubBlocks missing required fields like `id`
+ * - SubBlocks with `type: "unknown"` (indicates malformed data)
  */
 function normalizeSubblockValues(blocks: Record<string, any>): Record<string, any> {
   const normalizedBlocks: Record<string, any> = {}
@@ -19,6 +24,34 @@ function normalizeSubblockValues(blocks: Record<string, any>): Record<string, an
       const normalizedSubBlocks: Record<string, any> = {}
 
       Object.entries(block.subBlocks).forEach(([subBlockId, subBlock]: [string, any]) => {
+        // Skip subBlocks with invalid keys (literal "undefined" string)
+        if (subBlockId === 'undefined') {
+          logger.warn(`Skipping malformed subBlock with key "undefined" in block ${blockId}`)
+          return
+        }
+
+        // Skip subBlocks that are null or not objects
+        if (!subBlock || typeof subBlock !== 'object') {
+          logger.warn(`Skipping invalid subBlock ${subBlockId} in block ${blockId}: not an object`)
+          return
+        }
+
+        // Skip subBlocks with type "unknown" (malformed data)
+        if (subBlock.type === 'unknown') {
+          logger.warn(
+            `Skipping malformed subBlock ${subBlockId} in block ${blockId}: type is "unknown"`
+          )
+          return
+        }
+
+        // Skip subBlocks missing required id field
+        if (!subBlock.id) {
+          logger.warn(
+            `Skipping malformed subBlock ${subBlockId} in block ${blockId}: missing id field`
+          )
+          return
+        }
+
         const normalizedSubBlock = { ...subBlock }
 
         // Convert empty strings to null for consistency