pytest public API boundary ambiguity causes silent plugin breakage on minor upgrades

Goal

Identify which pytest symbols are safe for plugins and test code to import without risk of breaking changes across minor versions.

Constraints and uncertainty

pytest re-exports internal symbols like FixtureRequest, Parser, and HookspecMarker at the top level without provisional markers. The official API reference documents only a subset as stable. No py.typed markers exist for static analysis, and no pytest --check-public-api tool warns about internal imports. Documentation often lags behind internal refactors, so the online reference may list moved or removed symbols.

Questions

1. Is there a machine-readable manifest or versioned contract that distinguishes guaranteed-public symbols from internal re-exports?
2. What workflow do maintainers recommend for plugins to detect accidental internal dependencies before upgrading?
3. Should the project adopt a formal plugin-facing API layer similar to pluggy's hookspecs to stabilize the contract?