Function appendMessageTagToUserMessage

src/utils/messages.ts:1620–1670

* Appends a [id:...] message ID tag to the last text block of a user message. * Only mutates the API-bound copy, not the stored message. * This lets Claude reference message IDs when calling the snip tool.

(message: UserMessage)

 * This lets Claude reference message IDs when calling the snip tool.
 */
function appendMessageTagToUserMessage(message: UserMessage): UserMessage {
  if (message.isMeta) {
    return message
  }

  const tag = `\n[id:${deriveShortMessageId(message.uuid)}]`

  const content = message.message.content

  // Handle string content (most common for simple text input)
  if (typeof content === 'string') {
    return {
      ...message,
      message: {
        ...message.message,
        content: content + tag,
      },
    }
  }

  if (!Array.isArray(content) || content.length === 0) {
    return message
  }

  // Find the last text block
  let lastTextIdx = -1
  for (let i = content.length - 1; i >= 0; i--) {
    if (content[i]!.type === 'text') {
      lastTextIdx = i
      break
    }
  }
  if (lastTextIdx === -1) {
    return message
  }

  const newContent = [...content]
  const textBlock = newContent[lastTextIdx] as TextBlockParam
  newContent[lastTextIdx] = {
    ...textBlock,
    text: textBlock.text + tag,
  }

  return {
    ...message,
    message: {
      ...message.message,
      content: newContent as typeof content,
    },
  }
}

/**
 * Strips tool_reference blocks from tool_result content in a user message.