type-safetylisted

# subroutine — type-safety discipline Applies to every TypeScript file touched, React or Hono, front or back. The collar. The repo's own `AGENTS.md` overrides this file when it states something stricter or different — read it first. Otherwise, this is the discipline. ## Non-negotiable - **No `any`.** Use `unknown` + narrowing. If a third-party type is `any`, wrap it and narrow at the boundary. - **No `as T` assertions.** Use type guards, discriminated unions, or schema parsing (`Schema.parse`) to _prove_ the type instead of asserting it. - **No `!` non-null assertions.** Use optional chaining, explicit null checks, or a local narrowed variable. - These three are typically enforced by the linter (oxlint/eslint). Treat a lint error here as a design smell, not a nuisance to silence. ## Inference & annotation - **Maximize inference.** Annotate only at public API boundaries (exported function signatures, lib entry points). Let internal code infer. - Prefer `as const` for literal types and value sets. ## Unions & value sets - **String literal unions over `enum`. Never use TS `enum`.** ```ts type Role = "platform_admin" | "admin" | "operator"; // ✓ ``` - For a named, symbol-accessible value set, prefer an **object-as-const** over an array-as-const (safer renames, IDE symbol access): ```ts export const DEPLOY_STATUS = { idle: "idle", running: "running" } as const; // ✓ type DeployStatus = (typeof DEPLOY_STATUS)[keyof typeof DEPLOY_STATUS]; ``` - **Dis