Instruction file imported from artem-ibragimov/dicom_viewer_online (.github/instructions/api.instructions.md). Copyright stays with the author.

API boundary rules

• fetch belongs in *.api.ts wrappers or in existing server-side API boundaries such as Next.js route handlers.
• Keep request construction, response parsing, and transport-level error handling centralized here.
• Return typed DTOs or typed domain payloads.
• Do not leak transport parsing into containers or presentational components.
• Normalize failures explicitly and return deterministic error shapes.
• Keep user-visible text out of transport code unless intentionally returned as localized content by design.
• Do not prefix promise-returning calls with void just to discard the result. In route handlers, either await, return, or call directly for intentional fire-and-forget work with explicit failure handling in the callee.
• Do not use while (true) or for (;;) for polling or waiting. Prefer recursion or explicitly bounded iteration with a visible deadline or exit condition.
• Prefer guard-style if + return with braces over switch/case for request branching and response mapping.
• Do not use braceless if statements in route handlers or API wrappers.