Describe the problem/error/question
We have a flow that works like a map-reduce: It takes an object containing an array, splits the array into several items, then aggregates them back in order to perform a code-node summary.
What we have found, is that the aggregate step “invents” items. This looks like an workflow isolation bug because these invented rows seem to bleed in from previous workflow runs.
What is the error message (if any)?
Please share your workflow
Share the output returned by the last node
Here you can see two different executions, one with 1 item and one with 14 items. The aggregate step always produces an array of 18 items.
Information on your n8n setup
instance information
Debug info
core
- n8nVersion: 2.1.1
- platform: docker (self-hosted)
- nodeJsVersion: 22.21.1
- nodeEnv: production
- database: postgres
- executionMode: scaling (single-main)
- concurrency: -1
- license: enterprise (production)
- consumerId: 2d4ac391-ed5e-4c37-9e68-911c31a108a5
storage
- success: all
- error: all
- progress: false
- manual: true
- binaryMode: s3
pruning
- enabled: true
- maxAge: 336 hours
- maxCount: 10000 executions
client
- userAgent: mozilla/5.0 (macintosh; intel mac os x 10_15_7) applewebkit/537.36 (khtml, like gecko) chrome/143.0.0.0 safari/537.36
- isTouchDevice: false
Generated at: 2025-12-24T15:16:08.070Z