Method updateHistory

src/node/services/historyService.ts:1533–1604

* Update an existing message in history by historySequence * Reads the active chat.jsonl, replaces the matching message, and rewrites the file. * * This runs on every stream end, so it must stay O(active epoch): targets are * always in the active epoch (stream placeholders, compaction su

(workspaceId: string, message: MuxMessage)

   * never in the sealed archive.
   */
  async updateHistory(workspaceId: string, message: MuxMessage): Promise<Result<void>> {
    return this.fileLocks.withLock(workspaceId, async () => {
      try {
        const historyPath = this.getChatHistoryPath(workspaceId);

        // Read the active epoch — structural rewrite requires full file content
        const messages = await this.readChatHistory(workspaceId);
        const targetSequence = message.metadata?.historySequence;

        if (targetSequence === undefined) {
          return Err("Cannot update message without historySequence");
        }

        assert(
          isNonNegativeInteger(targetSequence),
          "updateHistory requires historySequence to be a non-negative integer"
        );

        // Find and replace the message with matching historySequence
        let found = false;
        let persistedMessage: MuxMessage | undefined;
        for (let i = 0; i < messages.length; i++) {
          if (messages[i].metadata?.historySequence === targetSequence) {
            const existingMessage = messages[i];
            assert(existingMessage, "updateHistory matched message must exist");

            // Preserve compaction boundary metadata during late in-place rewrites.
            // Compaction may update an assistant row first, then a late stream rewrite can
            // update that same historySequence and accidentally drop compaction markers.
            const preservedCompactionMetadata = getCompactionMetadataToPreserve(
              workspaceId,
              existingMessage,
              message
            );

            // Preserve the historySequence, update everything else.
            messages[i] = {
              ...message,
              metadata: {
                ...message.metadata,
                ...(preservedCompactionMetadata ?? {}),
                historySequence: targetSequence,
              },
            };
            persistedMessage = messages[i];
            found = true;
            break;
          }
        }

        if (!found || !persistedMessage) {
          return Err(`No message found with historySequence ${targetSequence}`);
        }

        // Rewrite entire file
        const historyEntries = this.serializeHistoryEntries(messages, workspaceId);

        // Atomic write prevents corruption if app crashes mid-write