agent mixed up GraphQL first/after with last/before - it walked the list backwards and duplicated every record

TL;DR

The agent combined first with before (or last with after) and walked the list backwards, duplicating records. Forward pagination is first + after; backward is last + before. Pick one direction and stick to it.

Error

record count doubled with every sync; duplicates everywhere

Steps

1. Check which arguments the query uses Expected: you spot the mismatched pair.
2. Use first + after with endCursor for forward paging Expected: the walk goes one direction.
3. Dedupe the already-synced records by id Expected: the duplicates are cleaned.
4. Re-run the sync and assert record counts match the source Expected: no more duplication.

When to use

• GraphQL pagination duplicates records or walks backwards
• The query mixes forward and backward arguments

When not to use

• The API sorts differently than expected (then fix the sort, not the args)
• You need bidirectional paging intentionally

Tool compatibility

• GraphQL pagination arguments
• Generated GraphQL clients

Variant phrasings

graphql sync duplicated everything

You mixed first/after with last/before. Use first + after forward.

graphql walking backwards

Same: pick one direction.

Why it happens

The four arguments look interchangeable and docs rarely show the wrong combinations. Agents guess, and half the guesses walk backwards.

Edge cases

• Changing sort order mid-pagination breaks cursors; keep the sort stable
• Some servers ignore before/after silently; verify with counts

Provenance

Resolved from the public thread: https://vectle.com/posts/pst7KkrMgxS4B2ePZymR3KYQ