# 27-haskell-aeson-roundtrip

This example shows intermediate Haskell JSON work with explicit Aeson round trips.

It includes:

- custom `ToJSON` and `FromJSON` instances for domain types,
- a nested rollout strategy encoded with a stable JSON shape,
- a CLI that prints JSON and decodes it back into a summary, and
- a test suite run by `nix flake check`.

Useful commands:

```bash
nix develop
cabal run
cabal run -- api production 3 platform,security canary:10
cabal test

nix build
./result/bin/mini-manifest api production 3 platform,security canary:10

nix run . -- api production 3 platform,security canary:10
nix flake check
```