AB-3008 not_yet_supported
| Class | Validation |
| HTTP status | 400 |
| Retryable | no |
When it happens
The envelope uses a scheme or feature the schema accepts but the gateway does not ship yet (for example topic:// addresses before topics launch).
Hint
{feature}is not available yet. See the roadmap in docs.
Troubleshooting
Post-MVP feature; see 14-MVP-PLAN.md.