After upgrading to a later version of the Bitbucket Branch Source plugin (which includes the changes from https://github.com/jenkinsci/bitbucket-branch-source-plugin/commit/156beebf299050e191b13837d89f94733eb31339), we are encountering the following error in the server logs:

"Fail to retrieve the timestamp for tag event <tag>".

This issue occurs because the webhook event sent by Bitbucket (version 8.19) follows the following format:

{  
  "eventKey":"repo:refs_changed",
  "date":"2025-03-10T09:47:32+1000",
  "actor":{ ...  },
  "repository":{  ...  },
  "changes":[  
    {  
      "ref":{  
        "id":"refs/tags/0.1.0",
        "displayId":"0.1.0",
        "type":"TAG"
      },
      "refId":"refs/tags/0.1.0",
      "fromHash":"0000000000000000000000000000000000000000",
      "toHash":"b82dd854c413d8e09aaf68c3c286f11ec6780be6",
      "type":"ADD"
    }
  ]
} 

In the current implementation of ServerPushEvent, the call to client.resolveCommit(change.getFromHash()) is making a request to Bitbucket's commits endpoint using "0000000000000000000000000000000000000000" as the parameter. This always results in a 404 error and a SERVER-log in Jenkins. 

Instead, if the toHash value is used, Bitbucket returns the commit the tag points to, which works correctly. At least for Bitbucket Server 8.19.