Next.js 16 Server Action Requirements

Problem

Next.js 16 enforces strict rules for files with the "use server" directive. Violations cause build failures with cryptic error messages. Common issues include exporting non-async functions, constants, or using static imports of next/headers.

Context / Trigger Conditions

• Build Error: A 'use server' file can only export async functions, found object
• Build Error: Static imports of next/headers force modules into dynamic rendering
• TypeScript Error: Helper functions in server actions fail type checking
• Next.js Version: 16.x (these rules are stricter than Next.js 15)

Solution

Rule 1: All Exported Functions Must Be Async

Every exported function in a "use server" file must be async, even if it doesn't perform async operations.