Based on the available documentation, Permit.io callbacks do not support gRPC. The callback mechanism uses HTTP/REST endpoints (1) . The

PDP_DATA_UPDATE_CALLBACKS

configuration shows that callbacks are configured with HTTP-based parameters :

[  
 {  
 "url": "<http://example.com/callback>",  
 "key": "example",
 "config": {
 "headers": {  
 "Authorization": "Bearer token"  
 },  
 "method": "GET",  
 "data": {  
 "key": "value"  
 }  
 }  
 }  
]

The default configuration specifies

{"method": "POST"}

, which indicates HTTP methods. The callback endpoint

/data/callback_report

also accepts standard HTTP POST requests with JSON payloads (2) . If you need gRPC support for your use case, I'd recommend reaching out to the Permit.io team to discuss alternative integration approaches or potential feature requests.

To learn more, see the sources I considered: [[1] Configurations](https://docs.permit.io/concepts/pdp/configuration) [[2] POST /data/callback_report](https://opal-v2.permit.io/redoc#tag/Data-Updates/operation/log_client_update_report_data_callback_report_post)