Function extractSideQuestionResponse

src/utils/sideQuestion.ts:125–155

* Extract a display string from forked agent messages. * * IMPORTANT: claude.ts yields one AssistantMessage PER CONTENT BLOCK, not one * per API response. With adaptive thinking enabled (inherited from the main * thread to preserve the cache key), a thinking response arrives as: * messages[0]

(messages: Message[])

 *     interruption, no assistant message at all.
 */
function extractSideQuestionResponse(messages: Message[]): string | null {
  // Flatten all assistant content blocks across the per-block messages.
  const assistantBlocks = messages.flatMap(m =>
    m.type === 'assistant' ? m.message.content : [],
  )

  if (assistantBlocks.length > 0) {
    // Concatenate all text blocks (there's normally at most one, but be safe).
    const text = extractTextContent(assistantBlocks, '\n\n').trim()
    if (text) return text

    // No text — check if the model tried to call a tool despite instructions.
    const toolUse = assistantBlocks.find(b => b.type === 'tool_use')
    if (toolUse) {
      const toolName = 'name' in toolUse ? toolUse.name : 'a tool'
      return `(The model tried to call ${toolName} instead of answering directly. Try rephrasing or ask in the main conversation.)`
    }
  }

  // No assistant content — likely API error exhausted retries. Surface the
  // first system api_error message so the user sees what happened.
  const apiErr = messages.find(
    (m): m is SystemAPIErrorMessage =>
      m.type === 'system' && 'subtype' in m && m.subtype === 'api_error',
  )
  if (apiErr) {
    return `(API error: ${formatAPIError(apiErr.error)})`
  }

  return null
}