fix(copilot): persist thinking blocks on page refresh via sendBeacon

- Use navigator.sendBeacon in beforeunload handler to reliably persist
  in-progress messages (including thinking blocks) during page teardown
- Flush batched streaming updates before beacon persistence
- Fall back to sendBeacon in abortMessage when page is unloading
- Fix double-digit ordered list clipping in thinking block (pl-6 → pl-8)

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/copilot/components/copilot-message/components/thinking-block/thinking-block.tsx

@@ -108,7 +108,7 @@ const SmoothThinkingText = memo(
     return (
       <div
         ref={textRef}
-        className='[&_*]:!text-[var(--text-muted)] [&_*]:!text-[12px] [&_*]:!leading-[1.4] [&_p]:!m-0 [&_p]:!mb-1 [&_h1]:!text-[12px] [&_h1]:!font-semibold [&_h1]:!m-0 [&_h1]:!mb-1 [&_h2]:!text-[12px] [&_h2]:!font-semibold [&_h2]:!m-0 [&_h2]:!mb-1 [&_h3]:!text-[12px] [&_h3]:!font-semibold [&_h3]:!m-0 [&_h3]:!mb-1 [&_code]:!text-[11px] [&_ul]:!pl-5 [&_ul]:!my-1 [&_ol]:!pl-6 [&_ol]:!my-1 [&_li]:!my-0.5 [&_li]:!py-0 font-season text-[12px] text-[var(--text-muted)]'
+        className='[&_*]:!text-[var(--text-muted)] [&_*]:!text-[12px] [&_*]:!leading-[1.4] [&_p]:!m-0 [&_p]:!mb-1 [&_h1]:!text-[12px] [&_h1]:!font-semibold [&_h1]:!m-0 [&_h1]:!mb-1 [&_h2]:!text-[12px] [&_h2]:!font-semibold [&_h2]:!m-0 [&_h2]:!mb-1 [&_h3]:!text-[12px] [&_h3]:!font-semibold [&_h3]:!m-0 [&_h3]:!mb-1 [&_code]:!text-[11px] [&_ul]:!pl-5 [&_ul]:!my-1 [&_ol]:!pl-8 [&_ol]:!my-1 [&_li]:!my-0.5 [&_li]:!py-0 font-season text-[12px] text-[var(--text-muted)]'
       >
         <CopilotMarkdownRenderer content={displayedContent} />
       </div>
@@ -355,7 +355,7 @@ export function ThinkingBlock({
           isExpanded ? 'mt-1.5 max-h-[150px] opacity-100' : 'max-h-0 opacity-0'
         )}
       >
-        <div className='[&_*]:!text-[var(--text-muted)] [&_*]:!text-[12px] [&_*]:!leading-[1.4] [&_p]:!m-0 [&_p]:!mb-1 [&_h1]:!text-[12px] [&_h1]:!font-semibold [&_h1]:!m-0 [&_h1]:!mb-1 [&_h2]:!text-[12px] [&_h2]:!font-semibold [&_h2]:!m-0 [&_h2]:!mb-1 [&_h3]:!text-[12px] [&_h3]:!font-semibold [&_h3]:!m-0 [&_h3]:!mb-1 [&_code]:!text-[11px] [&_ul]:!pl-5 [&_ul]:!my-1 [&_ol]:!pl-6 [&_ol]:!my-1 [&_li]:!my-0.5 [&_li]:!py-0 font-season text-[12px] text-[var(--text-muted)]'>
+        <div className='[&_*]:!text-[var(--text-muted)] [&_*]:!text-[12px] [&_*]:!leading-[1.4] [&_p]:!m-0 [&_p]:!mb-1 [&_h1]:!text-[12px] [&_h1]:!font-semibold [&_h1]:!m-0 [&_h1]:!mb-1 [&_h2]:!text-[12px] [&_h2]:!font-semibold [&_h2]:!m-0 [&_h2]:!mb-1 [&_h3]:!text-[12px] [&_h3]:!font-semibold [&_h3]:!m-0 [&_h3]:!mb-1 [&_code]:!text-[11px] [&_ul]:!pl-5 [&_ul]:!my-1 [&_ol]:!pl-8 [&_ol]:!my-1 [&_li]:!my-0.5 [&_li]:!py-0 font-season text-[12px] text-[var(--text-muted)]'>
           <CopilotMarkdownRenderer content={cleanContent} />
         </div>
       </div>

apps/sim/lib/copilot/messages/persist.ts

@@ -5,7 +5,7 @@ import { serializeMessagesForDB } from './serialization'
 
 const logger = createLogger('CopilotMessagePersistence')
 
-export async function persistMessages(params: {
+interface PersistParams {
   chatId: string
   messages: CopilotMessage[]
   sensitiveCredentialIds?: Set<string>
@@ -13,24 +13,29 @@ export async function persistMessages(params: {
   mode?: string
   model?: string
   conversationId?: string
-}): Promise<boolean> {
+}
+
+/** Builds the JSON body used by both fetch and sendBeacon persistence paths. */
+function buildPersistBody(params: PersistParams): string {
+  const dbMessages = serializeMessagesForDB(
+    params.messages,
+    params.sensitiveCredentialIds ?? new Set<string>()
+  )
+  return JSON.stringify({
+    chatId: params.chatId,
+    messages: dbMessages,
+    ...(params.planArtifact !== undefined ? { planArtifact: params.planArtifact } : {}),
+    ...(params.mode || params.model ? { config: { mode: params.mode, model: params.model } } : {}),
+    ...(params.conversationId ? { conversationId: params.conversationId } : {}),
+  })
+}
+
+export async function persistMessages(params: PersistParams): Promise<boolean> {
   try {
-    const dbMessages = serializeMessagesForDB(
-      params.messages,
-      params.sensitiveCredentialIds ?? new Set<string>()
-    )
     const response = await fetch(COPILOT_UPDATE_MESSAGES_API_PATH, {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({
-        chatId: params.chatId,
-        messages: dbMessages,
-        ...(params.planArtifact !== undefined ? { planArtifact: params.planArtifact } : {}),
-        ...(params.mode || params.model
-          ? { config: { mode: params.mode, model: params.model } }
-          : {}),
-        ...(params.conversationId ? { conversationId: params.conversationId } : {}),
-      }),
+      body: buildPersistBody(params),
     })
     return response.ok
   } catch (error) {
@@ -41,3 +46,27 @@ export async function persistMessages(params: {
     return false
   }
 }
+
+/**
+ * Persists messages using navigator.sendBeacon, which is reliable during page unload.
+ * Unlike fetch, sendBeacon is guaranteed to be queued even when the page is being torn down.
+ */
+export function persistMessagesBeacon(params: PersistParams): boolean {
+  try {
+    const body = buildPersistBody(params)
+    const blob = new Blob([body], { type: 'application/json' })
+    const sent = navigator.sendBeacon(COPILOT_UPDATE_MESSAGES_API_PATH, blob)
+    if (!sent) {
+      logger.warn('sendBeacon returned false — browser may have rejected the request', {
+        chatId: params.chatId,
+      })
+    }
+    return sent
+  } catch (error) {
+    logger.warn('Failed to persist messages via sendBeacon', {
+      chatId: params.chatId,
+      error: error instanceof Error ? error.message : String(error),
+    })
+    return false
+  }
+}

apps/sim/stores/panel/copilot/store.ts

@@ -39,6 +39,7 @@ import {
   buildToolCallsById,
   normalizeMessagesForUI,
   persistMessages,
+  persistMessagesBeacon,
   saveMessageCheckpoint,
 } from '@/lib/copilot/messages'
 import type { CopilotTransportMode } from '@/lib/copilot/models'
@@ -78,6 +79,28 @@ let _isPageUnloading = false
 if (typeof window !== 'undefined') {
   window.addEventListener('beforeunload', () => {
     _isPageUnloading = true
+
+    // Emergency persistence: flush any pending streaming updates to the store and
+    // persist via sendBeacon (which is guaranteed to be queued during page teardown).
+    // Without this, thinking blocks and in-progress content are lost on refresh.
+    try {
+      const state = useCopilotStore.getState()
+      if (state.isSendingMessage && state.currentChat) {
+        // Flush batched streaming updates into the store messages
+        flushStreamingUpdates(useCopilotStore.setState.bind(useCopilotStore))
+        const flushedState = useCopilotStore.getState()
+        persistMessagesBeacon({
+          chatId: flushedState.currentChat!.id,
+          messages: flushedState.messages,
+          sensitiveCredentialIds: flushedState.sensitiveCredentialIds,
+          planArtifact: flushedState.streamingPlanContent || null,
+          mode: flushedState.mode,
+          model: flushedState.selectedModel,
+        })
+      }
+    } catch {
+      // Best-effort — don't let errors prevent page unload
+    }
   })
 }
 function isPageUnloading(): boolean {
@@ -1461,19 +1484,26 @@ export const useCopilotStore = create<CopilotStore>()(
         // Immediately put all in-progress tools into aborted state
         abortAllInProgressTools(set, get)
 
-        // Persist whatever contentBlocks/text we have to keep ordering for reloads
+        // Persist whatever contentBlocks/text we have to keep ordering for reloads.
+        // During page unload, use sendBeacon which is guaranteed to be queued even
+        // as the page tears down. Regular async fetch won't complete in time.
         const { currentChat, streamingPlanContent, mode, selectedModel } = get()
         if (currentChat) {
           try {
             const currentMessages = get().messages
-            void persistMessages({
+            const persistParams = {
               chatId: currentChat.id,
               messages: currentMessages,
               sensitiveCredentialIds: get().sensitiveCredentialIds,
               planArtifact: streamingPlanContent || null,
               mode,
               model: selectedModel,
-            })
+            }
+            if (isPageUnloading()) {
+              persistMessagesBeacon(persistParams)
+            } else {
+              void persistMessages(persistParams)
+            }
           } catch (error) {
             logger.warn('[Copilot] Failed to queue abort snapshot persistence', {
               error: error instanceof Error ? error.message : String(error),