D030 - Backend seams are enforced by crate boundaries

Status: decided Date: 2026-08-19

orbistoun-gpu holds command-stream and shader translation and does not depend on ash; orbistoun-gpu-vulkan is the only crate that knows Vulkan exists.

Why: with no dependency there is nothing to leak, and cargo enforces that rather than review. A second backend is a new crate rather than surgery on the translator.

Rejected:

• One crate with a module boundary: discipline instead of enforcement.