Function reorderMessagesInUI

src/utils/messages.ts:855–1026

(
  messages: (
    | NormalizedUserMessage
    | NormalizedAssistantMessage
    | AttachmentMessage
    | SystemMessage
  )[],
  syntheticStreamingToolUseMessages: NormalizedAssistantMessage[],
)

// Re-order, to move result messages to be after their tool use messages
export function reorderMessagesInUI(
  messages: (
    | NormalizedUserMessage
    | NormalizedAssistantMessage
    | AttachmentMessage
    | SystemMessage
  )[],
  syntheticStreamingToolUseMessages: NormalizedAssistantMessage[],
): (
  | NormalizedUserMessage
  | NormalizedAssistantMessage
  | AttachmentMessage
  | SystemMessage
)[] {
  // Maps tool use ID to its related messages
  const toolUseGroups = new Map<
    string,
    {
      toolUse: ToolUseRequestMessage | null
      preHooks: AttachmentMessage[]
      toolResult: NormalizedUserMessage | null
      postHooks: AttachmentMessage[]
    }
  >()

  // First pass: group messages by tool use ID
  for (const message of messages) {
    // Handle tool use messages
    if (isToolUseRequestMessage(message)) {
      const toolUseID = message.message.content[0]?.id
      if (toolUseID) {
        if (!toolUseGroups.has(toolUseID)) {
          toolUseGroups.set(toolUseID, {
            toolUse: null,
            preHooks: [],
            toolResult: null,
            postHooks: [],
          })
        }
        toolUseGroups.get(toolUseID)!.toolUse = message
      }
      continue
    }

    // Handle pre-tool-use hooks
    if (
      isHookAttachmentMessage(message) &&
      message.attachment.hookEvent === 'PreToolUse'
    ) {
      const toolUseID = message.attachment.toolUseID
      if (!toolUseGroups.has(toolUseID)) {
        toolUseGroups.set(toolUseID, {
          toolUse: null,
          preHooks: [],
          toolResult: null,
          postHooks: [],
        })
      }