Function buildSubagentLookups

src/utils/messages.ts:1373–1416

(
  messages: { message: AssistantMessage | NormalizedUserMessage }[],
)

 * `AssistantMessage | NormalizedUserMessage`.
 */
export function buildSubagentLookups(
  messages: { message: AssistantMessage | NormalizedUserMessage }[],
): { lookups: MessageLookups; inProgressToolUseIDs: Set<string> } {
  const toolUseByToolUseID = new Map<string, ToolUseBlockParam>()
  const resolvedToolUseIDs = new Set<string>()
  const toolResultByToolUseID = new Map<
    string,
    NormalizedUserMessage & { type: 'user' }
  >()

  for (const { message: msg } of messages) {
    if (msg.type === 'assistant') {
      for (const content of msg.message.content) {
        if (content.type === 'tool_use') {
          toolUseByToolUseID.set(content.id, content as ToolUseBlockParam)
        }
      }
    } else if (msg.type === 'user') {
      for (const content of msg.message.content) {
        if (content.type === 'tool_result') {
          resolvedToolUseIDs.add(content.tool_use_id)
          toolResultByToolUseID.set(content.tool_use_id, msg)
        }
      }
    }
  }

  const inProgressToolUseIDs = new Set<string>()
  for (const id of toolUseByToolUseID.keys()) {
    if (!resolvedToolUseIDs.has(id)) {
      inProgressToolUseIDs.add(id)
    }
  }

  return {
    lookups: {
      ...EMPTY_LOOKUPS,
      toolUseByToolUseID,
      resolvedToolUseIDs,
      toolResultByToolUseID,
    },
    inProgressToolUseIDs,
  }
}

/**
 * Get sibling tool use IDs using pre-computed lookup. O(1).