Remix v2 Data Flow Code Review

Targets TypeScript route modules importing from @remix-run/*. See remix-v2-data-flow for canonical patterns.

Scope

In scope: route modules under app/routes/ exporting loader, action, shouldRevalidate, or headers; components that consume useLoaderData, useActionData, useNavigation, useFetcher, useRevalidator, <Await>.
Out of scope: form ergonomics (<Form> markup, accessibility, useFetcher UI patterns) → covered by remix-v2-forms-review. Route module conventions, file naming, nested routing, error boundary placement → covered by remix-v2-routing-review.
Imports expected: @remix-run/node (or @remix-run/cloudflare / @remix-run/deno) for server utilities; @remix-run/react for hooks and components.

Issue Type	Reference
Mutations in loader, missing validation, leaked server fields, throwing primitives, missing param checks	references/loaders.md
Unvalidated FormData, `json` instead of `redirect` on success, missing error case, leaked actionData	references/actions.md
`useTransition` v1 holdover, missing pending state, blanket `shouldRevalidate: false`, misused `useRevalidator`	references/revalidation.md
`defer` for already-fast data, missing `<Suspense>`, no `errorElement` on `<Await>`, awaiting what should stream	references/defer-await.md