Since the beginning of this month (Nov, 2025) we have had several instances of the productVariantsBulkUpdate mutation response completely missing lines in the response file. We are using version 2025-04, and have been on this version for multiple months without issue.
We are still not 100% certain on precise reproduction steps, but it seems that large mutation files (those that target 6000+ products with varying amounts of variants) are most likely to encounter the bug.
The way this issue manifests is straight forward; the _lineNumber that is present as part of each object in the response will at some point in the file skip hundreds of positions forward. We have seen files where this has happened twice in the same response.
Another way to identify the issue is that the total number of lines in file is less than the highest lineNumber present in the file.
For our app in particular this is a major breaking issue as we use this mutation extensively, we have had to deal with many angry long term merchants regarding this.
Hi @Daniel_Moseley! This sounds like a regression if it’s consistently reproducible! The _lineNumber field you’re mentioning isn’t part of the standard mutation response though, that’s typically what you see in bulk operations JSONL files. Are you running this through a bulk operation, or calling the mutation directly?
Also trying to understand your scale here, when you say “6000+ products”, do you mean you’re making separate mutation calls for each product, or are you somehow batching? The mutation works on a single product at a time (up to 2,048 variants per product if you have Extended Variants enabled).
Can you share a request ID (or Bulk Operation ID) from one of the failed responses and maybe an example of where the line numbers jump? Like if you’re seeing line 100, then suddenly line 500, with nothing in between. That’ll help narrow down if this is a bulk operations file generation issue or something else.
If this is consistently happening since the beginning of the month and affecting multiple merchants, I’ll be sure to refer this issue to the team responsible internally. Thanks!
Hi @Donal-Shopify , thanks for getting back to me. Apologies for the lack of clarity, yes we are calling this mutation through a bulk operation - I hope that also explains where the 6000+ products number is coming from; we’re often running a mutation across all the products on a store where this number is feasible.
Here is an example of a bulk operation on a test store where we managed to reproduce the issue multiple times in a row gid://shopify/BulkOperation/6613572288816
Finding the exact number in the file can be hard because of the format, but if you search for __lineNumber":4365 in the response file you will notice that it is only a few lines after lineNumber":3847, suggesting a skip of around 500 products!
It’s worth noting we have not found a consistency in what line exactly causes this, we think it could be influenced by variant count to some extent.
As it stands this has impacted at least a dozen different merchants, with merchants reaching out to us with symptoms of this behaviour as recently as 12 hours ago.
I am also having this issue periodically on some stores. Usually it’s with thousands of products and there can be up to 10000 missing, but I’ve had just a few products missing from a small bulk mutation.
This is quite urgent as we have no error message or anything to explain to the user why the task failed to edit all items.
I can provide more recent failure examples with bulk operation IDs if desired. e.g. gid://shopify/BulkOperation/6387664552188 or gid://shopify/BulkOperation/6698591355155
Also I should mention this is happening on 2025-10 for productUpdate mutations as well, so not limited to just variant editing. The second ID provided is an example of that.
I reviewed the logs for each and referred the issue to our Bulk Operations team internally for review.
I’ll update this thread once I hear back from the team. If you do start to notice patterns in which operations are affected, and which are not, be sure to let us know here in the thread and I’ll pass it on to the team.
One pattern is we seem to have a couple tasks that are scheduled that consistently fail for one shop. I think that second ID I shared is from the same shop, but here’s another: gid://shopify/BulkOperation/6704219914515 In this case, there’s always userErrors with the task, but some of the lines are missing. The number of items that are missing always varies, even when the number to edit remains the same.
So it’s possible that it’s more likely to fail when there are useErrors in the bulk mutation, but it also happens without any.
Good news - our team identified and fixed the root cause. There was an issue in how bulk mutation jobs were processing lines when operations were interrupted and retried, which caused some lines to get skipped in the response file.
Can you confirm whether you’re still seeing missing lines in your bulk operations since then? If you run a new bulk operation now, you should see all lines present in the response.
Thanks for the detailed reproduction info and bulk operation IDs - that really helped the team track this down quickly!
Thanks @Donal-Shopify for escalating this and thanks @DavidT for sharing your findings also. Seems fixed from our recent experience too. Marked as solved.
I had same problem (bulk input contained 48K lines, I only received around 16K lines in response), i’m putting back the previous bulk limit (48K) and will keep you guys posted.
Hey @Gregory_Kapustin, have you noticed in improvement in bulk operations started since my last post? If not, if you can share some affected Bulk Operation IDs I can take a closer look!
