9. Versioning

The versioning model defines how chkpt evolves over time. It establishes compatibility expectations, forward‑compatibility guarantees, and the principles governing future extensions of the execution substrate. Versioning ensures that institutions can adopt new versions of chkpt without disrupting certified workflows or compromising deterministic execution.

9.1 Purpose of Versioning

Versioning provides a structured approach for evolving the chkpt specification. It ensures that changes are predictable, reviewable, and compatible with existing institutional processes. Versioning also enables institutions to understand the behavioural context of each execution by associating it with a specific execution version. This association is essential for evidence integrity, as defined in the Evidence Model.

9.2 Execution Version

The execution version identifies the behaviour of the chkpt substrate itself. Each execution must record the execution version used, enabling reviewers to understand the substrate behaviour that governed the Application. Execution versions are not certified artefacts; they exist solely for traceability and evidence association. Their role is introduced in the Conceptual Model.

9.3 Workflow Version Independence

Workflow versions are defined and certified externally. chkpt does not influence workflow versioning; it binds to whatever version is provided by the adopting organisation. This separation ensures that workflow governance remains independent of chkpt’s evolution and preserves the strict governance–execution boundary described in the Workflow Certification Context.

9.4 Compatibility Expectations

New versions of chkpt must maintain compatibility with existing certified workflows unless a breaking change is explicitly declared. Institutions must be able to rely on chkpt to apply previously certified workflows without modification. Compatibility expectations ensure long‑term stability, reduce operational burden, and support predictable execution across substrate versions.

9.5 Forward‑Compatibility Guarantees

chkpt provides forward‑compatibility guarantees for non‑breaking changes. These guarantees ensure that workflows certified under earlier versions of chkpt can continue to be executed under newer versions without behavioural drift. Forward‑compatibility supports gradual adoption of new substrate capabilities while preserving determinism and admissible behaviour enforcement, as defined in the Execution Model.

9.6 Extensions

Future extensions to chkpt may introduce new capabilities, evidence requirements, or execution‑side controls. Extensions must not alter the behaviour of existing features unless explicitly declared as breaking changes. All extensions must preserve determinism, admissible behaviour enforcement, and evidence integrity. Extensions operate within the applicability boundaries defined in Applicability.

9.7 Deprecation

Deprecated features must remain functional for a defined period to support institutional transition. Deprecation notices must clearly indicate when a feature will be removed and what alternatives are available. Deprecation must not compromise execution determinism, evidence integrity, or version alignment. Deprecation rules ensure predictable evolution of the substrate.