fix(mothership): minor followups (#3709)

* fix(mothership): abort fix

* diff engine fix

Author: icecrasher321

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts

@@ -420,7 +420,6 @@ export function useChat(
     chatIdRef.current = undefined
     setResolvedChatId(undefined)
     appliedChatIdRef.current = undefined
-    abortControllerRef.current?.abort()
     abortControllerRef.current = null
     sendingRef.current = false
     setMessages([])
@@ -445,7 +444,26 @@ export function useChat(
 
     appliedChatIdRef.current = chatHistory.id
     const mappedMessages = chatHistory.messages.map(mapStoredMessage)
-    setMessages(mappedMessages)
+    const shouldPreserveActiveStreamingMessage =
+      sendingRef.current && Boolean(activeStreamId) && activeStreamId === streamIdRef.current
+
+    if (shouldPreserveActiveStreamingMessage) {
+      setMessages((prev) => {
+        const localStreamingAssistant = prev[prev.length - 1]
+        if (localStreamingAssistant?.role !== 'assistant') {
+          return mappedMessages
+        }
+
+        const nextMessages =
+          mappedMessages[mappedMessages.length - 1]?.role === 'assistant'
+            ? mappedMessages.slice(0, -1)
+            : mappedMessages
+
+        return [...nextMessages, localStreamingAssistant]
+      })
+    } else {
+      setMessages(mappedMessages)
+    }
 
     if (chatHistory.resources.some((r) => r.id === 'streaming-file')) {
       fetch('/api/copilot/chat/resources', {
@@ -1467,7 +1485,6 @@ export function useChat(
     return () => {
       streamReaderRef.current?.cancel().catch(() => {})
       streamReaderRef.current = null
-      abortControllerRef.current?.abort()
       abortControllerRef.current = null
       streamGenRef.current++
       sendingRef.current = false

apps/sim/lib/copilot/chat-streaming.ts

@@ -353,7 +353,6 @@ export function createSSEStream(params: StreamingOrchestrationParams): ReadableS
     },
     cancel() {
       clientDisconnected = true
-      abortController.abort()
       if (eventWriter) {
         eventWriter.flush().catch(() => {})
       }

apps/sim/lib/workflows/diff/diff-engine.ts

@@ -505,12 +505,21 @@ export class WorkflowDiffEngine {
       try {
         const baselineBlockIds = new Set(Object.keys(mergedBaseline.blocks))
 
-        // Identify blocks that need positioning: genuinely new blocks AND
-        // blocks inserted into subflows (position reset to 0,0). Extracted
-        // blocks are excluded — the server computes valid absolute positions
-        // from the container offset, so they don't need repositioning.
+        // Identify blocks that need positioning: genuinely new blocks that
+        // don't have valid positions yet. Blocks already positioned by a
+        // previous server-side layout (non-origin position) are skipped to
+        // avoid redundant client-side re-layout that can shift blocks when
+        // block metrics change between edits (e.g. condition handle offsets).
         const blocksNeedingLayout = Object.keys(finalBlocks).filter((id) => {
-          if (!baselineBlockIds.has(id)) return true
+          if (!baselineBlockIds.has(id)) {
+            const pos = finalBlocks[id]?.position
+            const hasValidPosition =
+              pos &&
+              Number.isFinite(pos.x) &&
+              Number.isFinite(pos.y) &&
+              !(pos.x === 0 && pos.y === 0)
+            return !hasValidPosition
+          }
           const baselineParent = mergedBaseline.blocks[id]?.data?.parentId ?? null
           const proposedParent = finalBlocks[id]?.data?.parentId ?? null
           if (baselineParent === proposedParent) return false