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Hello world! Panproto is a data migration framework that can be used with a wide variety of schema languages: ATProto, JSON Schema, OpenAPI, Protobuf, GraphQL, SQL DDL, and a ton more.

The main idea is that every schema language it supports translates into one common graph format.

That means you can hand it two versions of a schema in any of the languages it supports, and it'll computes the diff, classify whether the change is breaking, and generate a converter that turns old records into new ones.

What's even better is that adding support for a new schema language just involves writing a description of it. Nothing about the underlying engine needs to change.

The generated converter goes both directions. The forward direction turns an old record into a new one; the backward direction converts it back, recovering whatever the forward path dropped (if anything) via a side channel called a complement.

You can also ask what changed without generating a migration. Panproto classifies each diff entry as breaking or non-breaking, using the rules of the specific schema language. This classification can be run from the panproto CLI in CI to gate PRs that touch a schema before they reach review.

Very importantly, migrations are composable. You can chain v1 to v2 to v3 to v4 into a single converter that walks records all the way through. When auto-generation needs help on a particular field, you can drop in a value-level transform written in a small built-in expression language.

The system flags what survives cleanly and what loses information when one language has no analogue for a construct in the other.

Source code in any programming language supported by treesitter also parses into the same graph format. So refactoring a Rust codebase and migrating an OpenAPI spec can be viewed as the same operation underneath.