mastra-ai/mastra · error · Error

Item ${args.id} does not belong to dataset ${args.datasetId}

Error message

Item ${args.id} does not belong to dataset ${args.datasetId}

What it means

InMemory _doUpdateItem() verifies that the live item row's datasetId equals args.datasetId and throws this plain Error when the item belongs to a different dataset. This guards against moving or editing an item under the wrong parent dataset when the caller supplies mismatched ids.

Source

Thrown at packages/core/src/storage/domains/datasets/inmemory.ts:287

    // T3.11 — every mutation inserts exactly one dataset_version row
    await this.createDatasetVersion(args.datasetId, newVersion);

    return toDatasetItem(row);
  }

  protected async _doUpdateItem(args: UpdateDatasetItemInput): Promise<DatasetItem> {
    const rows = this.db.datasetItems.get(args.id);
    if (!rows || rows.length === 0) {
      throw new Error(`Item not found: ${args.id}`);
    }

    const currentRow = rows.find(r => r.validTo === null && !r.isDeleted);
    if (!currentRow) {
      throw new Error(`Item not found: ${args.id}`);
    }
    if (currentRow.datasetId !== args.datasetId) {
      throw new Error(`Item ${args.id} does not belong to dataset ${args.datasetId}`);
    }

    const dataset = this.db.datasets.get(args.datasetId);
    if (!dataset) {
      throw new Error(`Dataset not found: ${args.datasetId}`);
    }

    // Bump version (T3.26)
    const newVersion = dataset.version + 1;
    this.db.datasets.set(args.datasetId, { ...dataset, version: newVersion });

    // T3.8 — close old row
    currentRow.validTo = newVersion;

    // T3.8 — insert new row with same id
    const now = new Date();
    const newRow: DatasetItemRow = {
      id: args.id,

View on GitHub (pinned to 75dd419e61)

Solutions

1. Derive datasetId from the item itself (getItemById({id}).datasetId) instead of hardcoding it.
2. Fix the mapping in your update script so each item is paired with its actual parent dataset.
3. If the item truly must belong to another dataset, delete it there and re-insert it into the target dataset.
4. Log both ids in the message when debugging — the error names both the item and the dataset.

Example fix

// before
await storage.datasets.updateItem({ id: itemId, datasetId: 'ds-a', groundTruth });
// after
const item = await storage.datasets.getItemById({ id: itemId });
await storage.datasets.updateItem({ id: itemId, datasetId: item.datasetId, groundTruth });

const item = await storage.datasets.getItemById({ id: itemId });
if (item && item.datasetId !== datasetId) throw new Error(`Item '${itemId}' belongs to '${item.datasetId}', not '${datasetId}'`);

function belongsToDataset(item: { datasetId: string }, datasetId: string): boolean {
  return item.datasetId === datasetId;
}

try {
  await storage.datasets.updateItem({ id: itemId, datasetId, input });
} catch (e) {
  if (e instanceof Error && /does not belong to dataset/.test(e.message)) {
    // fix the item->dataset pairing in the caller before retrying
  } else throw e;
}

When it happens

Trigger: updateItem({id, datasetId}) where the item id exists (live row) but was created in a dataset other than the datasetId passed — e.g., ids swapped in config, an item id reused across datasets, or a copy/paste mixing dataset ids.

Common situations: Bulk update scripts iterating items while hardcoding one datasetId, test fixtures where item ids collide across datasets, or callers passing the wrong relationship (item of dataset A updated with dataset B's id).

Related errors

• Dataset not found: ${args.id}
• Dataset not found: ${args.datasetId}
• Item not found: ${args.id}
• DATASETS_STORAGE_NOT_CONFIGURED
• DATASETS_STORE_NOT_AVAILABLE

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/0347c7e2b2f6896a. Report an issue: GitHub.