Keep docs truthful when the library changes — treat every doc sentence as an assertion. Use after renaming identifiers, changing operator/overload semantics, altering error messages, or adding features; also when writing new reference docs.
Audit the library's friendly compile-time diagnostics end-to-end — trigger each one, verify the message fires before raw template noise, and prove its recommended remedy actually compiles. Use after changing concepts/asserts/operators, or when a user reports a confusing compile error.
Add or upgrade a MIP++ solver backend, or add a new capability test suite, and prove conformance through the shared typed test suites. Use when wiring a new solver, bumping a solver API version, or when a backend fails/skips shared suites.