> A couple years later, they want to upgrade the validator now that supports the 2025 specification. However in that 2025 specification, we added database-field-id as a keyword, and its value is expected to be a string. Suddenly the user's schema is no longer valid. We've broken a user by adding a new keyword.
No you haven't. They chose to change. Same as if they change to another schema format altogether (eg XML). Is this implying a user is going commit to a schema (pragmatic laziness, notwithstanding) that they haven't read? Regardless, their following solution baffles...
> Therefore, no keyword addition can be considered safe, making forward compatibility impossible to guarantee.
Correct.
> Using the vocabulary requires writing a custom meta-schema that adds the vocabulary URI and references the associated meta-schema, and referencing that custom meta-schema in the schema.
I just can't fathom this ceaseless drive toward cruft. Now a meta-vocabulary (a sub-schema). That's supposed to be better? Change will come, in 10 years, 50 years, etc. Semantic versioning normalizes it in the json-schema itself. It's as good a system as any and definitely better than adding another versioned dependency.