UseExceptionHandler throws exceptions

[mikekistler]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Adding app.UseExceptionHandler() to a Minimal APIs app can cause endpoints to fail with 500 Internal Server Error rather than report the actual error, e.g. error in deserialization of request body.

Note that if you add app.UseExceptionHandler(); to a minimal API without AddProblemDetails() you will get this error on startup:

      System.InvalidOperationException: An error occurred when configuring the exception handler middleware. Either the 'ExceptionHandlingPath' or the 'ExceptionHandler' property must be set in 'UseExceptionHandler()'. Alternatively, set one of the aforementioned properties in 'Startup.ConfigureServices' as follows: 'services.AddExceptionHandler(options => { ... });' or configure to generate a 'ProblemDetails' response in 'service.AddProblemDetails()'.

which seems helpful, but can make matters worse, because if you add builder.Services.AddProblemDetails(), errors such as deserialization errors of the request body, which without app.UseExceptionHandler() would return a 400 Bad Request, now return

HTTP/1.1 500 Internal Server Error

{
  "type": "https://tools.ietf.org/html/rfc9110#section-15.6.1",
  "title": "An error occurred while processing your request.",
  "status": 500,
  "traceId": "00-bee3d0407d116c51fbccb374c06f41dd-ae7bfd1db45ea6ca-00"
}

I did search the existing issues and found #51888, but what seems to be the recommended workaround for that problem:

app.UseExceptionHandler(_ => {});

Only produces a far more elaborate 500 Internal Server Error:

HTTP/1.1 500 Internal Server Error
Connection: close
Content-Type: application/problem+json
Date: Sun, 01 Jun 2025 12:11:23 GMT
Server: Kestrel
Cache-Control: no-cache,no-store
Expires: -1
Pragma: no-cache
Transfer-Encoding: chunked

{
  "type": "https://tools.ietf.org/html/rfc9110#section-15.6.1",
  "title": "System.InvalidOperationException",
  "status": 500,
  "detail": "The exception handler configured on ExceptionHandlerOptions produced a 404 status response. This InvalidOperationException containing the original exception was thrown since this is often due to a misconfigured ExceptionHandlingPath. If the exception handler is expected to return 404 status responses then set AllowStatusCode404Response to true.",
  "exception": {
    "details": "System.InvalidOperationException: The exception handler configured on ExceptionHandlerOptions produced a 404 status response. This InvalidOperationException containing the original exception was thrown since this is often due to a misconfigured ExceptionHandlingPath. If the exception handler is expected to return 404 status responses then set AllowStatusCode404Response to true.\n ---> Microsoft.AspNetCore.Http.BadHttpRequestException: Failed to read parameter \"WeatherForecast forecast\" from the request body as JSON.\n ---> System.Text.Json.JsonException: The JSON value could not be converted to WeatherForecast. Path: $.summary | LineNumber: 3 | BytePositionInLine: 17.\n ---> System.InvalidOperationException: Cannot get the value of a token type 'Number' as a string.\n   at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_ExpectedString(JsonTokenType tokenType)\n   at System.Text.Json.Utf8JsonReader.GetString()\n   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)\n   at System.Text.Json.Serialization.Converters.SmallObjectWithParameterizedConstructorConverter`5.TryRead[TArg](ReadStack& state, Utf8JsonReader& reader, JsonParameterInfo jsonParameterInfo, TArg& arg)\n   at System.Text.Json.Serialization.Converters.SmallObjectWithParameterizedConstructorConverter`5.ReadAndCacheConstructorArgument(ReadStack& state, Utf8JsonReader& reader, JsonParameterInfo jsonParameterInfo)\n   at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter`1.ReadConstructorArgumentsWithContinuation(ReadStack& state, Utf8JsonReader& reader, JsonSerializerOptions options)\n   at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)\n   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)\n   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)\n   --- End of inner exception stack trace ---\n   at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, Utf8JsonReader& reader, Exception ex)\n   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)\n   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.ContinueDeserialize(ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, T& value)\n   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsync(Stream utf8Json, CancellationToken cancellationToken)\n   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsObjectAsync(Stream utf8Json, CancellationToken cancellationToken)\n   at Microsoft.AspNetCore.Http.HttpRequestJsonExtensions.ReadFromJsonAsync(HttpRequest request, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)\n   at Microsoft.AspNetCore.Http.HttpRequestJsonExtensions.ReadFromJsonAsync(HttpRequest request, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)\n   at Microsoft.AspNetCore.Http.RequestDelegateFactory.<HandleRequestBodyAndCompileRequestDelegateForJson>g__TryReadBodyAsync|102_0(HttpContext httpContext, Type bodyType, String parameterTypeName, String parameterName, Boolean allowEmptyRequestBody, Boolean throwOnBadRequest, JsonTypeInfo jsonTypeInfo)\n   --- End of inner exception stack trace ---\n   at Microsoft.AspNetCore.Http.RequestDelegateFactory.Log.InvalidJsonRequestBody(HttpContext httpContext, String parameterTypeName, String parameterName, Exception exception, Boolean shouldThrow)\n   at Microsoft.AspNetCore.Http.RequestDelegateFactory.<HandleRequestBodyAndCompileRequestDelegateForJson>g__TryReadBodyAsync|102_0(HttpContext httpContext, Type bodyType, String parameterTypeName, String parameterName, Boolean allowEmptyRequestBody, Boolean throwOnBadRequest, JsonTypeInfo jsonTypeInfo)\n   at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass102_2.<<HandleRequestBodyAndCompileRequestDelegateForJson>b__2>d.MoveNext()\n--- End of stack trace from previous location ---\n   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)\n   --- End of inner exception stack trace ---\n   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.HandleException(HttpContext context, ExceptionDispatchInfo edi)\n   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.HandleException(HttpContext context, ExceptionDispatchInfo edi)\n   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)\n   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)",
    "headers": {
      "Accept": [
        "application/json"
      ],
      "Connection": [
        "close"
      ],
      "Host": [
        "localhost:5243"
      ],
      "User-Agent": [
        "vscode-restclient"
      ],
      "Accept-Encoding": [
        "gzip, deflate"
      ],
      "Content-Type": [
        "application/json"
      ],
      "Content-Length": [
        "71"
      ]
    },
    "path": "/weatherforecast/",
    "endpoint": null,
    "routeValues": {}
  },
  "traceId": "00-ac53f4b0eaf46df2211ae6bf75502948-3fc1550dcb74e0df-00"
}

Expected Behavior

UseExceptionHandler() should not make error diagnosis more difficult.

Steps To Reproduce

Create a minimal API app with a POST endpoint that takes a request body with a string property.

Add the ProblemDetails services to the DI container:

builder.Services.AddProblemDetails();

Enable the ExceptionHandler middleware:

app.UseExceptionHandler();

Run the app and send it a POST request with a number for the value of the string property.

Complete workaround is in the use-exception-handler directory of my dotnet10-issue-repros repo.

Exceptions (if any)

  Content root path: /workspaces/dotnet10-issue-repros/use-exception-handler

warn: Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware[3]
Failed to determine the https port for redirect.
fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1]
An unhandled exception has occurred while executing the request.
Microsoft.AspNetCore.Http.BadHttpRequestException: Failed to read parameter "WeatherForecast forecast" from the request body as JSON.
---> System.Text.Json.JsonException: The JSON value could not be converted to WeatherForecast. Path: $.summary | LineNumber: 3 | BytePositionInLine: 17.
---> System.InvalidOperationException: Cannot get the value of a token type 'Number' as a string.
at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_ExpectedString(JsonTokenType tokenType)
at System.Text.Json.Utf8JsonReader.GetString()
at System.Text.Json.Serialization.JsonConverter1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue) at System.Text.Json.Serialization.Converters.SmallObjectWithParameterizedConstructorConverter5.TryRead[TArg](ReadStack& state, Utf8JsonReader& reader, JsonParameterInfo jsonParameterInfo, TArg& arg)
at System.Text.Json.Serialization.Converters.SmallObjectWithParameterizedConstructorConverter5.ReadAndCacheConstructorArgument(ReadStack& state, Utf8JsonReader& reader, JsonParameterInfo jsonParameterInfo) at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter1.ReadConstructorArgumentsWithContinuation(ReadStack& state, Utf8JsonReader& reader, JsonSerializerOptions options)
at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value) at System.Text.Json.Serialization.JsonConverter1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)
at System.Text.Json.Serialization.JsonConverter1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state) --- End of inner exception stack trace --- at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, Utf8JsonReader& reader, Exception ex) at System.Text.Json.Serialization.JsonConverter1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.Serialization.Metadata.JsonTypeInfo1.ContinueDeserialize(ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, T& value) at System.Text.Json.Serialization.Metadata.JsonTypeInfo1.DeserializeAsync(Stream utf8Json, CancellationToken cancellationToken)
at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsObjectAsync(Stream utf8Json, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Http.HttpRequestJsonExtensions.ReadFromJsonAsync(HttpRequest request, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Http.HttpRequestJsonExtensions.ReadFromJsonAsync(HttpRequest request, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Http.RequestDelegateFactory.g__TryReadBodyAsync|102_0(HttpContext httpContext, Type bodyType, String parameterTypeName, String parameterName, Boolean allowEmptyRequestBody, Boolean throwOnBadRequest, JsonTypeInfo jsonTypeInfo)
--- End of inner exception stack trace ---
at Microsoft.AspNetCore.Http.RequestDelegateFactory.Log.InvalidJsonRequestBody(HttpContext httpContext, String parameterTypeName, String parameterName, Exception exception, Boolean shouldThrow)
at Microsoft.AspNetCore.Http.RequestDelegateFactory.g__TryReadBodyAsync|102_0(HttpContext httpContext, Type bodyType, String parameterTypeName, String parameterName, Boolean allowEmptyRequestBody, Boolean throwOnBadRequest, JsonTypeInfo jsonTypeInfo)
at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass102_2.<b__2>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)

.NET Version

10.0.100-preview.5.25277.114

Anything else?

No response

[mikekistler]

I created a workaround for the specific issue of deserialization errors throwing exceptions -- see this comment.

[captainsafia]

Moving to the backlog since we have a workaround and an actual fix would be non-trivial.

Overall, this issue relates to the thornier set of problems around how binding errors surface in minimal APIs, particularly in the absence of model state.