Runtime selection

Before runtime-dependent work, read execution selection. In a verified T3 host follow the T3 contract and its method reference; the inline section below is the native Codex branch, not literal T3 dispatch. Outside T3, native Codex follows that inline branch unchanged. If the host is ambiguous or a required capability is unavailable, report the gap; a permission refusal never authorizes switching branches.

Native Codex branch

TypeScript best practices

Apply the cursor-principle-type-system-discipline skill first.