Function buildSideQuestionTranscript

src/node/services/sideQuestionService.ts:579–654

(
  workspaceId: string,
  historyService: HistoryService,
  liveStream: ReturnType<AIService["getStreamInfo"]>
)

}

async function buildSideQuestionTranscript(
  workspaceId: string,
  historyService: HistoryService,
  liveStream: ReturnType<AIService["getStreamInfo"]>
): Promise<string> {
  // Read the active history window before applying the /btw cap. Prior side
  // questions are filtered below; capping the raw tail first would let many
  // side-question rows crowd out recent main-chat context.
  const result = await historyService.getHistoryFromLatestBoundary(workspaceId);
  if (!result.success) return "";

  const messages: MuxMessage[] = [...result.data];
  const partial = await historyService.readPartial(workspaceId);
  if (partial) messages.push(partial);

  // Partial files are throttled; merge the synchronous StreamManager snapshot
  // so /btw sees the main-agent text already visible in the UI.
  if (liveStream) {
    const liveMessage: MuxMessage = {
      id: liveStream.messageId,
      role: "assistant",
      metadata: {
        historySequence: liveStream.historySequence,
        model: liveStream.model,
      },
      parts: liveStream.parts,
    };
    const isLiveStreamMessage = (message: MuxMessage): boolean =>
      message.id === liveStream.messageId ||
      message.metadata?.historySequence === liveStream.historySequence;
    const existingIndex = messages.findIndex(isLiveStreamMessage);
    if (existingIndex === -1) {
      messages.push(liveMessage);
    } else {
      const existing = messages[existingIndex];
      messages[existingIndex] = {
        ...existing,
        metadata: {
          ...existing.metadata,
          historySequence: liveStream.historySequence,
          model: existing.metadata?.model ?? liveStream.model,
        },
        parts: liveStream.parts,
      };
      // Drop older partial.json copies for the same active stream; the live
      // snapshot above is the single source of truth for visible streamed text.
      for (let i = messages.length - 1; i >= 0; i--) {
        if (i !== existingIndex && isLiveStreamMessage(messages[i])) {
          messages.splice(i, 1);
        }
      }
    }
  }

  // Exclude PRIOR side-question exchanges from the transcript so /btw answers
  // don't pollute the context the model uses to answer the current side
  // question. Each /btw is independent — chained /btw turns would otherwise
  // amplify their own (potentially-wrong) prior answers. Then honor the same