Method performCompaction

src/node/services/compactionHandler.ts:1009–1188

* Perform history compaction by persisting a durable summary boundary. * * Steps: * 1. Delete partial state to avoid stale partial replay * 2. Persist post-compaction attachment state * 3. Prefer updating the streamed summary in-place, otherwise append a fallback summary * 4. Emit

(
    summary: string,
    metadata: {
      model: string;
      usage?: LanguageModelV2Usage;
      contextUsage?: LanguageModelV2Usage;
      duration?: number;
      providerMetadata?: Record<string, unknown>;
      contextProviderMetadata?: Record<string, unknown>;
      systemMessageTokens?: number;
    },
    messages: MuxMessage[],
    streamedSummaryMessageId: string,
    compactionRequestMessageId: string,
    isIdleCompaction = false,
    pendingFollowUp?: CompactionFollowUpRequest
  )

   * 4. Emit summary message to frontend
   */
  private async performCompaction(
    summary: string,
    metadata: {
      model: string;
      usage?: LanguageModelV2Usage;
      contextUsage?: LanguageModelV2Usage;
      duration?: number;
      providerMetadata?: Record<string, unknown>;
      contextProviderMetadata?: Record<string, unknown>;
      systemMessageTokens?: number;
    },
    messages: MuxMessage[],
    streamedSummaryMessageId: string,
    compactionRequestMessageId: string,
    isIdleCompaction = false,
    pendingFollowUp?: CompactionFollowUpRequest
  ): Promise<Result<CompactionCompletionMetadata, string>> {
    assert(summary.trim().length > 0, "performCompaction requires a non-empty summary");
    assert(metadata.model.trim().length > 0, "Compaction summary requires a model");
    assert(
      streamedSummaryMessageId.trim().length > 0,
      "performCompaction requires streamed summary message ID"
    );

    // CRITICAL: Delete partial.json BEFORE persisting compaction summary.
    // This prevents a race condition where:
    // 1. CompactionHandler persists summary
    // 2. sendQueuedMessages triggers commitPartial
    // 3. commitPartial finds stale partial.json and appends it to history
    // By deleting partial first, commitPartial becomes a no-op
    const deletePartialResult = await this.historyService.deletePartial(this.workspaceId);
    if (!deletePartialResult.success) {
      log.warn(`Failed to delete partial before compaction: ${deletePartialResult.error}`);
      // Continue anyway - the partial may not exist, which is fine
    }

    // Extract diffs from the latest compaction epoch only, so append-only history
    // does not re-inject stale pre-boundary edits after subsequent compactions.
    // If boundary markers are malformed, slicing self-heals by falling back to
    // full history instead of crashing or dropping all diffs.
    await this.preparePendingStateFromMessages(messages);

    const nextCompactionEpoch = getNextCompactionEpoch(messages);
    assert(Number.isInteger(nextCompactionEpoch), "next compaction epoch must be an integer");

    const previousBoundaryHistorySequence = getLatestBoundaryHistorySequence(messages);
    const maxExistingHistorySequence = this.getMaxExistingHistorySequence(messages);

    // For idle compaction, preserve the original recency timestamp so the workspace
    // doesn't appear "recently used" in the sidebar. Use the shared recency utility
    // to ensure consistency with how the sidebar computes recency.
    let timestamp = Date.now();
    if (isIdleCompaction) {
      const recency = computeRecencyFromMessages(messages);
      if (recency !== null) {
        timestamp = recency;
      }
    }