fix(workflow): seed structured-output JSON ref and centralize EMPTY_SUBBLOCK_VALUES

- Use null sentinel for prevDataJsonRef and lazily stringify prevDataRef on first compare so the optimization holds on the first stream refresh after mount
- Export EMPTY_SUBBLOCK_VALUES from the subblock store; remove three duplicated module constants

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/general/components/api-info-modal.tsx

@@ -23,13 +23,11 @@ import { useDeploymentInfo, useUpdatePublicApi } from '@/hooks/queries/deploymen
 import { useUpdateWorkflow, useWorkflowMap } from '@/hooks/queries/workflows'
 import { usePermissionConfig } from '@/hooks/use-permission-config'
 import { useWorkflowRegistry } from '@/stores/workflows/registry/store'
-import { useSubBlockStore } from '@/stores/workflows/subblock/store'
+import { EMPTY_SUBBLOCK_VALUES, useSubBlockStore } from '@/stores/workflows/subblock/store'
 import { useWorkflowStore } from '@/stores/workflows/workflow/store'
 
 type NormalizedField = InputFormatField & { name: string }
 
-const EMPTY_SUBBLOCK_VALUES: Record<string, Record<string, unknown>> = {}
-
 interface ApiInfoModalProps {
   open: boolean
   onOpenChange: (open: boolean) => void

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/mcp/mcp.tsx

@@ -27,16 +27,14 @@ import {
   type WorkflowMcpServer,
   type WorkflowMcpTool,
 } from '@/hooks/queries/workflow-mcp-servers'
-import { useSubBlockStore } from '@/stores/workflows/subblock/store'
+import { EMPTY_SUBBLOCK_VALUES, useSubBlockStore } from '@/stores/workflows/subblock/store'
 import { useWorkflowStore } from '@/stores/workflows/workflow/store'
 
 const logger = createLogger('McpToolDeploy')
 
 /** InputFormatField with guaranteed name (after normalization) */
 type NormalizedField = InputFormatField & { name: string }
 
-const EMPTY_SUBBLOCK_VALUES: Record<string, Record<string, unknown>> = {}
-
 interface McpDeployProps {
   workflowId: string
   workflowName: string

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/components/sub-block/components/tag-dropdown/tag-dropdown.tsx

@@ -33,7 +33,7 @@ import { normalizeName } from '@/executor/constants'
 import { useVariablesStore } from '@/stores/variables/store'
 import type { Variable } from '@/stores/variables/types'
 import { useWorkflowRegistry } from '@/stores/workflows/registry/store'
-import { useSubBlockStore } from '@/stores/workflows/subblock/store'
+import { EMPTY_SUBBLOCK_VALUES, useSubBlockStore } from '@/stores/workflows/subblock/store'
 import { useWorkflowStore } from '@/stores/workflows/workflow/store'
 import type { BlockState } from '@/stores/workflows/workflow/types'
 
@@ -167,8 +167,6 @@ const TAG_PREFIXES = {
   VARIABLE: 'variable.',
 } as const
 
-const EMPTY_SUBBLOCK_VALUES: Record<string, Record<string, unknown>> = {}
-
 /**
  * Ensures the root tag is present in the tags array
  */

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/terminal/components/output-panel/components/structured-output.tsx

@@ -682,7 +682,7 @@ export const StructuredOutput = memo(function StructuredOutput({
     computeInitialPaths(data, isError)
   )
   const prevDataRef = useRef(data)
-  const prevDataJsonRef = useRef<string>('')
+  const prevDataJsonRef = useRef<string | null>(null)
   const prevIsErrorRef = useRef(isError)
   const internalRef = useRef<HTMLDivElement>(null)
   const listRef = useListRef(null)
@@ -723,10 +723,11 @@ export const StructuredOutput = memo(function StructuredOutput({
 
     if (prevDataRef.current !== data) {
       const newJson = JSON.stringify(data)
-      if (prevDataJsonRef.current !== newJson) {
-        prevDataJsonRef.current = newJson
+      const prevJson = prevDataJsonRef.current ?? JSON.stringify(prevDataRef.current)
+      if (prevJson !== newJson) {
         setExpandedPaths(computeInitialPaths(data, isError))
       }
+      prevDataJsonRef.current = newJson
       prevDataRef.current = data
     }
   }, [data, isError])

apps/sim/stores/workflows/subblock/store.ts

@@ -6,11 +6,18 @@ import { getBlock } from '@/blocks'
 import type { SubBlockConfig } from '@/blocks/types'
 import { populateTriggerFieldsFromConfig } from '@/hooks/use-trigger-config-aggregation'
 import { useWorkflowRegistry } from '@/stores/workflows/registry/store'
-import type { SubBlockStore } from '@/stores/workflows/subblock/types'
+import type { SubBlockStore, SubBlockValue } from '@/stores/workflows/subblock/types'
 import { isTriggerValid } from '@/triggers'
 
 const logger = createLogger('SubBlockStore')
 
+/**
+ * Stable empty fallback for `state.workflowValues[workflowId]` selectors.
+ * Using a module-level constant avoids returning a fresh `{}` on every
+ * selector call, which would defeat Zustand's `Object.is` equality.
+ */
+export const EMPTY_SUBBLOCK_VALUES: Record<string, Record<string, SubBlockValue>> = {}
+
 /**
  * SubBlockState stores values for all subblocks in workflows
  *