typescript-guidelineslisted

# TypeScript Guidelines Shared TypeScript/JavaScript rubric for agents. Prefer repo-local conventions (import style, runtime, path aliases) when deliberate; push back when they defeat the type system or hide async bugs. ## Source Of Truth - The repo's `tsconfig.json` — `strict` and its sub-flags are the contract - TypeScript handbook for language semantics; the runtime's docs (Node, Bun, edge, browser) for platform APIs ## Core Rubric - Compile clean under `strict`. Honor `noUncheckedIndexedAccess` and `exactOptionalPropertyTypes` when enabled. - No `any`. Use `unknown` for genuinely unknown values and narrow with guards. Never use `as` to silence a type error; reserve casts for cases the compiler provably can't see, with a comment. - No `@ts-ignore` / `@ts-expect-error` without a cited reason. - `type` for unions/computed shapes; `interface` for shapes meant to be extended. `const` by default; `let` only when mutation is required. - Async: explicit `Promise<T>` return types; never leave floating promises; always `await` inside `try/catch`; no async work in constructors. Don't swallow rejections with empty `.catch()`. - Null safety: don't paper over `undefined` with optional chaining where downstream code assumes a value. Justify every non-null assertion (`!`). - Errors: throw typed error classes or return a `Result<T, E>` shape — never silently return `undefined` on failure. - React: function components + hooks; explicit prop types; `useEffect` that opens a connection/s