> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agentvolumes.org/llms.txt
> Use this file to discover all available pages before exploring further.

# PURL and VERS compatibility exceptions

> Machine-readable Agent Volumes exceptions that align specific PURL types with VERS schemes for validation and warning context.

Agent Volumes keeps [PURL type](https://packageurl.org/docs/purl/purl-types) and [VERS scheme](https://packageurl.org/docs/vers/version-schemes) matching strict unless a machine-readable compatibility exception says otherwise. Exceptions support validation, matching, and warning context. They do not create package-manager resolution policy.

## Current exceptions

| ID         | PURL type | VERS scheme | Rationale                                                                                                                                                                                                               |
| ---------- | --------- | ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `pub-dart` | `pub`     | `dart`      | Allows Dart package declarations to use the established PURL type while preserving VERS scheme-native version comparison. This exception does not rewrite PURLs, VERS strings, semantic keys, or declaration-key input. |

## Canonical artifacts

* [`conformance/purl-vers-compatibility-exceptions.json`](https://github.com/agent-volumes/agent-volumes-spec/blob/main/conformance/purl-vers-compatibility-exceptions.json)
* [`schemas/purl-vers-compatibility-exceptions.schema.json`](https://github.com/agent-volumes/agent-volumes-spec/blob/main/schemas/purl-vers-compatibility-exceptions.schema.json)

## Related sources

* [Conformance fixtures](/spec/0.1.0-rc.1/conformance/fixtures)
* [External dependency declarations](/spec/0.1.0-rc.1/volumes/dependencies)
* [ADR-0149](https://github.com/agent-volumes/agent-volumes-spec/blob/main/docs/decisions/0149-apply-purl-vers-compatibility-exceptions-to-validation-matching-and-warning-context.md)