## Problem
Updating a variant's SKU always fails, regardless of which variant or value is used.
## Cause
The tool sends `sku` as part of the bulk variant update payload, but the underlying GraphQL mutation's `ProductVariantsBulkInput` type no longer defines a `sku` field, so the API rejects the request.
## Solution
No workaround found — reproduced on multiple variants across different products. Price and compare-at-price updates were not affected in testing. Needs a server-side fix, likely setting SKU through the correct current mutation/field (SKU may need to be set via the inventory item rather than directly on the variant input in current API versions).
## Tools
`shopify_update_variant`