Shopify Metafield Schema Drift: Keep Definitions and Data Aligned

The problem

Metafield definitions are contracts. When a type changes from single-line text to JSON, when a namespace is renamed, or when an app writes values outside the declared definition, every consumer of that field — themes, feeds, ERP mappings, AI enrichment — starts failing in different, hard-to-correlate ways. Schema drift is slow-moving and expensive because the data still looks populated.

Diagnostic checklist

• Compare every metafield definition against the values actually stored on products.
• Flag values that fail the declared type (text in a number field, truncated JSON).
• Find namespaces written by apps but missing from the definitions list.
• Track definition changes that were never versioned or communicated to feed consumers.
• Verify that required metafield values exist on all variants, not just on parent products.