newtA backend framework for Bun

Bounded contexts, use cases, entities and domain events with a transactional outbox, in stores you can swap.

Rules the machine checks

A use case writes to its own module, one module per transaction, a save that reads rows takes a guard. newt refuses the rest at runtime, and its lint before you run.

The anatomy and the lint

Saves you can trust

Every row has a version; two people changing one thing never lose a change. A conflict runs the use case again on its own, and a rule over several rows holds on every store.

Two people, one card

Events that are never lost

An event is written in the same transaction as the change that tells it. A worker runs each reaction until it succeeds, with retries, backoff and dead jobs you can retry.

The outbox

Stores you can swap

SQLite, plain files, Postgres and MySQL behind one port. Modules never know which one; a contract suite proves a store of your own keeps every promise.

From files to SQLite

Time you can move

One clock per context drives timestamps, jobs and schedules. A cron fires once even with several processes, and a test moves the clock instead of waiting.

Invitations and time

HTTP that is closed by default

Every route needs a session unless it says otherwise. CORS, idempotent POSTs, OAuth-style errors, health that answers 503 while the server drains.

Asking twice

Ready for coding agents

newt ships an AGENTS.md versioned with the code. newt init points an application's agents at it; newt add module writes a module the lint already accepts.

The command line

Your system, drawn

newt-graph reads an application and draws its contexts, modules, use cases and events. Pick a use case and watch its side effects travel, worker after worker.

newt-graph

Learn it by building

Thirty chapters build cooper, a small Trello with an OAuth server, an MCP server and a backoffice. Each chapter ends at a git tag that runs and passes its tests.

Start