Reloading swagger page causes 500 error.

[arontier-master]

I observed the problem described in the title on Cromwell 86 and 90 on Google Chrome, Microsoft Edge, and Arc.
To reload http://localhost:8000, I press Cmd+R on Mac.
And the status code is alternating between 200 and 500 whenever I reload the page.
Reload a normal page, I get 500.
Reload again, I get 200 with a normal page.
Reload again, 500.
Reload again, 200 with a normal page. and so on.

I tried without and with Nginx in front of Cromwell to find the same problem.

I never experienced this problem with Cromwell 75.

The error log is:

2025-06-11 03:36:30 cromwell-system-akka.actor.default-dispatcher-27 ERROR - Error during processing of request: 'requirement failed: Responses with this status code must have an empty entity'. Completing with 500 Internal Server Error response. To change default exception handling behavior, provide a custom ExceptionHandler.
java.lang.IllegalArgumentException: requirement failed: Responses with this status code must have an empty entity
  at scala.Predef$.require(Predef.scala:337)
  at akka.http.scaladsl.model.HttpResponse.<init>(HttpMessage.scala:458)
  at akka.http.scaladsl.model.HttpResponse.copy(HttpMessage.scala:493)
  at akka.http.scaladsl.model.HttpResponse.withEntity(HttpMessage.scala:479)
  at akka.http.scaladsl.model.HttpResponse.mapEntity(HttpMessage.scala:483)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapResponseEntity$1(BasicDirectives.scala:116)
  at akka.http.scaladsl.server.directives.BasicDirectives$$anonfun$mapResponse$1.applyOrElse(BasicDirectives.scala:110)
  at akka.http.scaladsl.server.directives.BasicDirectives$$anonfun$mapResponse$1.applyOrElse(BasicDirectives.scala:110)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRouteResultPF$1(BasicDirectives.scala:80)
  at akka.http.scaladsl.util.FastFuture$.$anonfun$map$1(FastFuture.scala:23)
  at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
  at akka.http.scaladsl.util.FastFuture$.transformWith$extension(FastFuture.scala:45)
  at akka.http.scaladsl.util.FastFuture$.map$extension(FastFuture.scala:23)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRouteResult$2(BasicDirectives.scala:68)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRouteResult$2(BasicDirectives.scala:68)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRequestContext$2(BasicDirectives.scala:45)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$1(RouteConcatenation.scala:44)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$1(RouteConcatenation.scala:44)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$1(RouteConcatenation.scala:44)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$2(RouteConcatenation.scala:47)
  at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
  at akka.http.scaladsl.util.FastFuture$.transformWith$extension(FastFuture.scala:45)
  at akka.http.scaladsl.util.FastFuture$.flatMap$extension(FastFuture.scala:26)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$1(RouteConcatenation.scala:44)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$2(RouteConcatenation.scala:47)
  at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
  at akka.http.scaladsl.util.FastFuture$.transformWith$extension(FastFuture.scala:45)
  at akka.http.scaladsl.util.FastFuture$.flatMap$extension(FastFuture.scala:26)
  at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$1(RouteConcatenation.scala:44)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRouteResultWith$2(BasicDirectives.scala:74)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
  at akka.http.scaladsl.server.directives.ExecutionDirectives.$anonfun$handleExceptions$2(ExecutionDirectives.scala:32)
  at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
  at akka.http.scaladsl.server.Route$.$anonfun$asyncHandler$1(Route.scala:86)
  at akka.stream.impl.fusing.MapAsyncUnordered$$anon$31.onPush(Ops.scala:1376)
  at akka.stream.impl.fusing.GraphInterpreter.processPush(GraphInterpreter.scala:523)
  at akka.stream.impl.fusing.GraphInterpreter.execute(GraphInterpreter.scala:409)
  at akka.stream.impl.fusing.GraphInterpreterShell.runBatch(ActorGraphInterpreter.scala:606)
  at akka.stream.impl.fusing.GraphInterpreterShell$AsyncInput.execute(ActorGraphInterpreter.scala:485)
  at akka.stream.impl.fusing.GraphInterpreterShell.processEvent(ActorGraphInterpreter.scala:581)
  at akka.stream.impl.fusing.ActorGraphInterpreter.akka$stream$impl$fusing$ActorGraphInterpreter$$processEvent(ActorGraphInterpreter.scala:749)
  at akka.stream.impl.fusing.ActorGraphInterpreter$$anonfun$receive$1.applyOrElse(ActorGraphInterpreter.scala:764)
  at akka.actor.Actor.aroundReceive(Actor.scala:539)
  at akka.actor.Actor.aroundReceive$(Actor.scala:537)
  at akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive(ActorGraphInterpreter.scala:671)
  at akka.actor.ActorCell.receiveMessage(ActorCell.scala:614)
  at akka.actor.ActorCell.invoke(ActorCell.scala:583)
  at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:268)
  at akka.dispatch.Mailbox.run(Mailbox.scala:229)
  at akka.dispatch.Mailbox.exec(Mailbox.scala:241)
  at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
  at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
  at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
  at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

Please help.

[nevoodoo]

Can confirm this to be an issue for us too, I assumed it was transient but the alternating seems to be consistent

[aednichols]

I encounter this too, it's very annoying and I've never been able to figure it out. Pull requests welcome!

[aednichols]

I can tell you that I think it started after some Swagger version upgrade. (Downgrading is not an option as we need a maintained, security-patched version.)