Preserve effective flag behavior when shipping a compatible fix

When a server historically accepts a flag but ignores it, changing the flag to take effect can break existing callers even if the schema stays identical. A compatible quality fix should preserve the effective behavior of omitted and explicit values; ship the contract repair separately with callers audited or migrated. Changing only the declared default cannot protect clients that already send the old value. Verify compatibility by tracing preparation through the actual runtime policy, and keep optional asset pairing additive so legacy startup paths remain valid. This preserves existing behavior without claiming the old contract is correct. Applies when: A bug fix is expected to work with existing clients without migration. Keywords: ignored flag effective defaults backward compatibility runtime policy client migration