Hi, Following the advice I received here, I switched to using NSStagedMigrationManager instead of trying to drive a custom NSMappingModel entirely in code. I now have a staged migration pipeline with two stages: • Stage 1 (V1 → V2): a lightweight migration. • Stage 2 (V2 → V3): a custom migration where I re-archive a Transformable attribute (object) from a legacy ValueTransformer to a safe binary format (GraphArchiver). Both models are built entirely at runtime (no .xcdatamodeld files). Each model has a unique versionChecksum string (hardcoded identifiers: "GraphCK_MigrationV1", "GraphCK_MigrationV2", "GraphCK_MigrationV3"). When I run the staged migration manager with these two stages, I consistently hit this exception: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Duplicate version checksums across stages detected.' Debug logging shows: Stage1 checksums: ["GraphCK_MigrationV1", "GraphCK_MigrationV2"] Stage2 checksums: ["GraphCK_MigrationV2", "GraphCK_MigrationV3"] So the identifiers look correct and distinct, but the framework still complains about “duplicate checksums across stages”. Question: Is this error expected when building models entirely at runtime? Do we need to persist .mom files or .xcmappingmodel files so the checksums are stable? Or is there a supported way to run a staged migration pipeline from runtime-constructed models only? Any insight on how to avoid the “duplicate version checksums” error when using NSStagedMigrationManager with runtime models would be greatly appreciated.