Package Dependency Rules

Layers (lower -> higher)

1. exceptions, utils, logging — no internal dependencies
2. config, io, security — depend only on layer 1
3. foundation — depends only on exceptions
4. core — depends on foundation, exceptions
5. math — depends on foundation, exceptions
6. runtime, compiler, providers — depend on core, foundation, exceptions
7. optimization — depends on math, foundation, exceptions
8. simulation — depends on foundation, core, math
9. Domain packages: quantum (+runtime/compiler/providers), physics, chemistry (-> physics), biology (-> chemistry), astronomy (-> physics), cosmology (-> astronomy, physics), ai, finance (-> math, optimization, ai)
10. visualization, datasets, plugins, telemetry — depend on lower layers only, never on domain packages

Hard rules

• No circular imports between packages, ever.
• Domain packages never import each other except via the explicit arrows above (e.g. chemistry -> physics is allowed; physics -> chemistry is not).
• Only providers may reference vendor-specific SDKs, and only behind optional extras in pyproject.toml.