Real app runtime transcript
Commit: f03db4fbef59c42113e37c32897bf4d25d31cb2b
Environment: Linux web dev client, fresh isolated database; glab 1.124.0 signed in to gitlab.com.
Repository: synthetic main branch; origin https://gitlab.com/julius54/t3-triage-missing-22342.git

$ glab mr list --source-branch main --output json
Exit: 1
ERROR  
          
  404 Not Found.

Server warning after opening the thread:
[17:56:10.213] WARN (#13958) http.span=128640ms: PR lookup failed.
  operation: lookupStatusPr
  branch: main
  errorTag: SourceControlProviderError
  provider: gitlab
  providerOperation: listChangeRequests
  providerCommand: glab
  errorDetail: GitLab CLI command failed.

Create MR error toast:
Source control provider gitlab failed in listChangeRequests: GitLab CLI command failed.