fix(mothership): parallel subagent rendering

apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx

@@ -161,6 +161,18 @@ function parseBlocks(blocks: ContentBlock[]): MessageSegment[] {
     segments.push({ ...nextGroup, isOpen })
   }
 
+  const lastSubagentBlockIndex = new Map<string, number>()
+  for (let i = 0; i < blocks.length; i++) {
+    const block = blocks[i]
+    if (block.type === 'subagent' && block.content) {
+      lastSubagentBlockIndex.set(block.content, i)
+    }
+  }
+  const hasSubagentBlockAfter = (name: string, index: number): boolean => {
+    const last = lastSubagentBlockIndex.get(name)
+    return last !== undefined && last > index
+  }
+
   for (let i = 0; i < blocks.length; i++) {
     const block = blocks[i]
 
@@ -267,6 +279,9 @@ function parseBlocks(blocks: ContentBlock[]): MessageSegment[] {
       const isDispatch = SUBAGENT_KEYS.has(tc.name) && !tc.calledBy
 
       if (isDispatch) {
+        if (hasSubagentBlockAfter(tc.name, i)) {
+          continue
+        }
         if (!group || group.agentName !== tc.name) {
           if (group) {
             pushGroup(group)

apps/sim/lib/copilot/request/go/stream.ts

@@ -361,29 +361,26 @@ export async function runStreamLoop(
           flushSubagentThinkingBlock(context)
           flushThinkingBlock(context)
           if (spanEvt === MothershipStreamV1SpanLifecycleEvent.start) {
-            const lastParent = context.subAgentParentStack[context.subAgentParentStack.length - 1]
-            const lastBlock = context.contentBlocks[context.contentBlocks.length - 1]
             if (toolCallId) {
-              if (lastParent !== toolCallId) {
+              if (!context.subAgentParentStack.includes(toolCallId)) {
                 context.subAgentParentStack.push(toolCallId)
               }
               context.subAgentParentToolCallId = toolCallId
               context.subAgentContent[toolCallId] ??= ''
               context.subAgentToolCalls[toolCallId] ??= []
             }
-            if (
-              subagentName &&
-              !(
-                lastParent === toolCallId &&
-                lastBlock?.type === 'subagent' &&
-                lastBlock.content === subagentName
+            if (subagentName) {
+              const alreadyOpen = context.contentBlocks.some(
+                (b) =>
+                  b.type === 'subagent' && b.content === subagentName && b.endedAt === undefined
               )
-            ) {
-              context.contentBlocks.push({
-                type: 'subagent',
-                content: subagentName,
-                timestamp: Date.now(),
-              })
+              if (!alreadyOpen) {
+                context.contentBlocks.push({
+                  type: 'subagent',
+                  content: subagentName,
+                  timestamp: Date.now(),
+                })
+              }
             }
             return
           }