refactor: only include agentId in tool calls for subagents

Conditionally add agentId to tool call metadata only when the agent has a parent. This prevents the base agent from unnecessarily including its ID in tool calls while maintaining proper tracking for spawned subagents.

Also simplified CLI agent block logic by removing unused helper and using existing recursive update function.

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

Author: brandonkachen

backend/src/tools/stream-parser.ts

@@ -160,7 +160,8 @@ export async function processStreamWithTools(
             toolCallId,
             toolName,
             input,
-            agentId: agentState.agentId,
+            // Only include agentId for subagents (agents with a parent)
+            ...(agentState.parentId && { agentId: agentState.agentId }),
           })
         } else {
           // First non-str_replace tool marks end of str_replace phase

backend/src/tools/tool-executor.ts

@@ -193,7 +193,8 @@ export function executeToolCall<T extends ToolName>(
     toolCallId: toolCall.toolCallId,
     toolName,
     input: toolCall.input,
-    agentId: state.agentState?.agentId,
+    // Only include agentId for subagents (agents with a parent)
+    ...(state.agentState?.parentId && { agentId: state.agentState.agentId }),
   })
 
   toolCalls.push(toolCall)
@@ -430,7 +431,8 @@ export async function executeCustomToolCall(
     toolCallId: toolCall.toolCallId,
     toolName,
     input: toolCall.input,
-    agentId: state.agentState?.agentId,
+    // Only include agentId for subagents (agents with a parent)
+    ...(state.agentState?.parentId && { agentId: state.agentState.agentId }),
   })
 
   toolCalls.push(toolCall)

cli/src/hooks/use-send-message.ts

@@ -24,24 +24,6 @@ const hiddenToolNames = new Set<ToolName | 'spawn_agent_inline'>([
   'spawn_agents',
 ])
 
-// Helper function to check if an agent block exists
-const findAgentBlock = (
-  blocks: ContentBlock[],
-  targetAgentId: string,
-): boolean => {
-  for (const block of blocks) {
-    if (block.type === 'agent' && block.agentId === targetAgentId) {
-      return true
-    }
-    if (block.type === 'agent' && block.blocks) {
-      if (findAgentBlock(block.blocks, targetAgentId)) {
-        return true
-      }
-    }
-  }
-  return false
-}
-
 // Helper function to recursively update blocks
 const updateBlocksRecursively = (
   blocks: ContentBlock[],
@@ -532,15 +514,12 @@ export const useSendMessage = ({
                     setMessages((prev) =>
                       prev.map((msg) => {
                         if (msg.id === aiMessageId && msg.blocks) {
-                          const blocks = msg.blocks.map((block) => {
-                            if (
-                              block.type === 'agent' &&
-                              block.agentId === tempId
-                            ) {
-                              return { ...block, agentId: event.agentId }
-                            }
-                            return block
-                          })
+                          // Use recursive update to rename nested agents too
+                          const blocks = updateBlocksRecursively(
+                            msg.blocks,
+                            tempId,
+                            (block) => ({ ...block, agentId: event.agentId }),
+                          )
                           return { ...msg, blocks }
                         }
                         return msg
@@ -732,22 +711,8 @@ export const useSendMessage = ({
                 agentId: agentId || 'none',
               })
 
-              // Check if this tool call should be nested in a subagent
-              // Only nest if the agent block actually exists
-              const shouldNestInAgent = agentId && setMessages.length > 0
-              let agentBlockExists = false
-
-              if (shouldNestInAgent) {
-                setMessages((prev) => {
-                  const msg = prev.find((m) => m.id === aiMessageId)
-                  if (msg?.blocks) {
-                    agentBlockExists = findAgentBlock(msg.blocks, agentId)
-                  }
-                  return prev
-                })
-              }
-
-              if (agentBlockExists) {
+              // If this tool call belongs to a subagent, add it to that agent's blocks
+              if (agentId) {
                 logger.info('setMessages: tool_call for subagent', {
                   agentId,
                   toolName,