Add Full Slice (backend → frontend)

The kit's accelerator: deliver a feature from database to UI in one pass. This skill composes add-feature (backend) and add-react-page (frontend) — follow each for the detailed code; this file is the order of operations and the contract that keeps the two halves in sync.

Order of operations

1. Backend slice — add-feature (and add-entity first if a new entity is needed):
   • Command/Query + response DTO in Modules.{X}.Contracts/v1/{Area}/ (+ Contracts/Dtos/).
   • Handler (public sealed, injects {X}DbContext), Validator, Endpoint (internal static Map…Endpoint, .RequirePermission(...)).
   • Wire in {X}Module.MapEndpoints. Build + test backend green.
2. Lock the contract — note the final route path, HTTP method, request shape, and response DTO field names/casing. The React side must match these exactly.
3. Frontend page — add-react-page in the chosen app:
   • API module calls the same path; hand-write TS types mirroring the response DTO (the API serializes C# records as camelCase JSON — TS fields are camelCase even though admin query params are PascalCase).
   • Page (useQuery/useMutation), route (RouteGuard for admin / withSuspense for dashboard).
4. Permission — if the endpoint is gated, mirror the constant into admin's lib/permissions.ts and gate the route (add-permission). Dashboard relies on the server 403.
5. Tests both sides — backend handler/validator test (xUnit/Shouldly/NSubstitute) + frontend Playwright spec (route-mocked).

The contract (the thing that breaks if you're sloppy)

Verify end-to-end

dotnet build src/FSH.Starter.slnx && dotnet test src/Tests/{X}.Tests
cd clients/{app} && npm run lint && npm run test:e2e
# optional manual check: dotnet run --project src/Host/FSH.Starter.AppHost  (brings up API + both apps)

Checklist

• Backend slice complete + green (add-feature)
• Contract locked: route, request shape, response DTO field names
• Frontend api module path + TS types match the contract (body JSON camelCase)
• Page + route added (add-react-page); admin permission mirrored + gated (add-permission)
• Backend test + Playwright test added; both suites green