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Add support for OpenAI Responses API to all OpenAI-related plugins #1447

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Add support for OpenAI Responses API to all OpenAI-related plugins #1447

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54b96dc
Initial plan
Copilot Nov 16, 2025
1f426b5
Add OpenAI Responses API support to all five plugins
Copilot Nov 16, 2025
fcec6d3
Merge branch 'main' into copilot/add-support-for-responses-api
waldekmastykarz Nov 16, 2025
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78 changes: 77 additions & 1 deletion DevProxy.Abstractions/LanguageModel/OpenAIModels.cs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,15 @@ public static bool TryGetOpenAIRequest(string content, ILogger logger, out OpenA

var rawRequest = JsonSerializer.Deserialize<JsonElement>(content, ProxyUtils.JsonSerializerOptions);

// Responses API request (check first as it's the recommended API)
if (rawRequest.TryGetProperty("input", out _) &&
rawRequest.TryGetProperty("modalities", out _))
{
logger.LogDebug("Request is a Responses API request");
request = JsonSerializer.Deserialize<OpenAIResponsesRequest>(content, ProxyUtils.JsonSerializerOptions);
return true;
}

// Check for completion request (has "prompt", but not specific to image)
if (rawRequest.TryGetProperty("prompt", out _) &&
!rawRequest.TryGetProperty("size", out _) &&
Expand All @@ -63,7 +72,8 @@ public static bool TryGetOpenAIRequest(string content, ILogger logger, out OpenA
// Embedding request
if (rawRequest.TryGetProperty("input", out _) &&
rawRequest.TryGetProperty("model", out _) &&
!rawRequest.TryGetProperty("voice", out _))
!rawRequest.TryGetProperty("voice", out _) &&
!rawRequest.TryGetProperty("modalities", out _))
{
logger.LogDebug("Request is an embedding request");
request = JsonSerializer.Deserialize<OpenAIEmbeddingRequest>(content, ProxyUtils.JsonSerializerOptions);
Expand Down Expand Up @@ -409,3 +419,69 @@ public class OpenAIImageData
[JsonPropertyName("revised_prompt")]
public string? RevisedPrompt { get; set; }
}

#region Responses API

public class OpenAIResponsesRequest : OpenAIRequest
{
public object? Input { get; set; }
public IEnumerable<string>? Modalities { get; set; }
public string? Instructions { get; set; }
public bool? Store { get; set; }
[JsonPropertyName("previous_response_id")]
public string? PreviousResponseId { get; set; }
public object? Tools { get; set; }
[JsonPropertyName("max_output_tokens")]
public long? MaxOutputTokens { get; set; }
}

public class OpenAIResponsesResponse : OpenAIResponse
{
public IEnumerable<OpenAIResponsesOutputItem>? Output { get; set; }
[JsonPropertyName("created_at")]
public long CreatedAt { get; set; }
public string? Status { get; set; }

public override string? Response
{
get
{
if (Output is null || !Output.Any())
{
return null;
}

// Find the last message-type output item with text content
var lastMessage = Output
.Where(item => item.Type == "message")
.LastOrDefault();

if (lastMessage?.Content is null)
{
return null;
}

// Extract text from content array
var textContent = lastMessage.Content
.Where(c => c.Type == "output_text")
.LastOrDefault();

return textContent?.Text;
}
}
}

public class OpenAIResponsesOutputItem
{
public string? Type { get; set; }
public string? Role { get; set; }
public IEnumerable<OpenAIResponsesContentPart>? Content { get; set; }
}

public class OpenAIResponsesContentPart
{
public string? Type { get; set; }
public string? Text { get; set; }
}

#endregion
77 changes: 38 additions & 39 deletions DevProxy.Plugins/Behavior/LanguageModelFailurePlugin.cs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
return;
}

if (!TryGetOpenAIRequest(request.BodyString, out var openAiRequest))
if (!OpenAIRequest.TryGetOpenAIRequest(request.BodyString, Logger, out var openAiRequest))
{
Logger.LogRequest("Skipping non-OpenAI request", MessageType.Skipped, new(e.Session));
return;
Expand Down Expand Up @@ -116,53 +116,52 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
Logger.LogRequest($"Simulating fault {faultName}", MessageType.Chaos, new(e.Session));
e.Session.SetRequestBodyString(JsonSerializer.Serialize(newRequest, ProxyUtils.JsonSerializerOptions));
}
else
{
Logger.LogDebug("Unknown OpenAI request type. Passing request as-is.");
}

await Task.CompletedTask;

Logger.LogTrace("Left {Name}", nameof(BeforeRequestAsync));
}

private bool TryGetOpenAIRequest(string content, out OpenAIRequest? request)
{
request = null;

if (string.IsNullOrEmpty(content))
{
return false;
}

try
else if (openAiRequest is OpenAIResponsesRequest responsesRequest)
{
Logger.LogDebug("Checking if the request is an OpenAI request...");

var rawRequest = JsonSerializer.Deserialize<JsonElement>(content, ProxyUtils.JsonSerializerOptions);

if (rawRequest.TryGetProperty("prompt", out _))
// Handle Responses API
if (responsesRequest.Input is string inputString)
{
Logger.LogDebug("Request is a completion request");
request = JsonSerializer.Deserialize<OpenAICompletionRequest>(content, ProxyUtils.JsonSerializerOptions);
return true;
// Simple string input - append fault prompt
responsesRequest.Input = inputString + "\n\n" + faultPrompt;
Logger.LogDebug("Modified Responses API string input with fault prompt");
}

if (rawRequest.TryGetProperty("messages", out _))
else if (responsesRequest.Input is JsonElement inputElement)
{
Logger.LogDebug("Request is a chat completion request");
request = JsonSerializer.Deserialize<OpenAIChatCompletionRequest>(content, ProxyUtils.JsonSerializerOptions);
return true;
// Structured input - append as new message item
try
{
var items = JsonSerializer.Deserialize<List<JsonElement>>(inputElement.GetRawText(), ProxyUtils.JsonSerializerOptions) ?? [];
var faultItem = JsonSerializer.SerializeToElement(new
{
role = "user",
content = new[]
{
new { type = "input_text", text = faultPrompt }
}
}, ProxyUtils.JsonSerializerOptions);
items.Add(faultItem);
responsesRequest.Input = items;
Logger.LogDebug("Added fault prompt as new item to Responses API input");
}
catch (JsonException)
{
// If we can't parse as array, append to input as string
responsesRequest.Input = inputElement.GetRawText() + "\n\n" + faultPrompt;
Logger.LogDebug("Modified Responses API input with fault prompt (fallback)");
}
}

Logger.LogDebug("Request is not an OpenAI request.");
return false;
Logger.LogRequest($"Simulating fault {faultName}", MessageType.Chaos, new(e.Session));
e.Session.SetRequestBodyString(JsonSerializer.Serialize(responsesRequest, ProxyUtils.JsonSerializerOptions));
}
catch (JsonException ex)
else
{
Logger.LogDebug(ex, "Failed to deserialize OpenAI request.");
return false;
Logger.LogDebug("Unknown OpenAI request type. Passing request as-is.");
}

await Task.CompletedTask;

Logger.LogTrace("Left {Name}", nameof(BeforeRequestAsync));
}

private (string? Name, string? Prompt) GetFault()
Expand Down
56 changes: 14 additions & 42 deletions DevProxy.Plugins/Behavior/LanguageModelRateLimitingPlugin.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,7 @@ public override Task BeforeRequestAsync(ProxyRequestArgs e, CancellationToken ca
return Task.CompletedTask;
}

if (!TryGetOpenAIRequest(request.BodyString, out var openAiRequest))
if (!OpenAIRequest.TryGetOpenAIRequest(request.BodyString, Logger, out var openAiRequest))
{
Logger.LogRequest("Skipping non-OpenAI request", MessageType.Skipped, new(e.Session));
return Task.CompletedTask;
Expand Down Expand Up @@ -224,7 +224,7 @@ public override Task BeforeResponseAsync(ProxyResponseArgs e, CancellationToken
return Task.CompletedTask;
}

if (!TryGetOpenAIRequest(request.BodyString, out var openAiRequest))
if (!OpenAIRequest.TryGetOpenAIRequest(request.BodyString, Logger, out var openAiRequest))
{
Logger.LogDebug("Skipping non-OpenAI request");
return Task.CompletedTask;
Expand All @@ -239,7 +239,18 @@ public override Task BeforeResponseAsync(ProxyResponseArgs e, CancellationToken
{
try
{
var openAiResponse = JsonSerializer.Deserialize<OpenAIResponse>(responseBody, ProxyUtils.JsonSerializerOptions);
// Try to parse as Responses API first, then fall back to standard response
OpenAIResponse? openAiResponse = null;

if (openAiRequest is OpenAIResponsesRequest)
{
openAiResponse = JsonSerializer.Deserialize<OpenAIResponsesResponse>(responseBody, ProxyUtils.JsonSerializerOptions);
}
else
{
openAiResponse = JsonSerializer.Deserialize<OpenAIResponse>(responseBody, ProxyUtils.JsonSerializerOptions);
}

if (openAiResponse?.Usage != null)
{
var promptTokens = (int)openAiResponse.Usage.PromptTokens;
Expand Down Expand Up @@ -271,45 +282,6 @@ public override Task BeforeResponseAsync(ProxyResponseArgs e, CancellationToken
return Task.CompletedTask;
}

private bool TryGetOpenAIRequest(string content, out OpenAIRequest? request)
{
request = null;

if (string.IsNullOrEmpty(content))
{
return false;
}

try
{
Logger.LogDebug("Checking if the request is an OpenAI request...");

var rawRequest = JsonSerializer.Deserialize<JsonElement>(content, ProxyUtils.JsonSerializerOptions);

if (rawRequest.TryGetProperty("prompt", out _))
{
Logger.LogDebug("Request is a completion request");
request = JsonSerializer.Deserialize<OpenAICompletionRequest>(content, ProxyUtils.JsonSerializerOptions);
return true;
}

if (rawRequest.TryGetProperty("messages", out _))
{
Logger.LogDebug("Request is a chat completion request");
request = JsonSerializer.Deserialize<OpenAIChatCompletionRequest>(content, ProxyUtils.JsonSerializerOptions);
return true;
}

Logger.LogDebug("Request is not an OpenAI request.");
return false;
}
catch (JsonException ex)
{
Logger.LogDebug(ex, "Failed to deserialize OpenAI request.");
return false;
}
}

private ThrottlingInfo ShouldThrottle(Request request, string throttlingKey)
{
var throttleKeyForRequest = BuildThrottleKey(request);
Expand Down
74 changes: 74 additions & 0 deletions DevProxy.Plugins/Inspection/OpenAITelemetryPlugin.cs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,9 @@ private void AddResponseTypeSpecificTags(Activity activity, OpenAIRequest openAi
{
switch (openAiRequest)
{
case OpenAIResponsesRequest:
AddResponsesApiResponseTags(activity, openAiRequest, responseBody);
break;
case OpenAIChatCompletionRequest:
AddChatCompletionResponseTags(activity, openAiRequest, responseBody);
break;
Expand Down Expand Up @@ -541,6 +544,9 @@ private void AddRequestTypeSpecificTags(Activity activity, OpenAIRequest openAiR
{
switch (openAiRequest)
{
case OpenAIResponsesRequest responsesRequest:
AddResponsesApiRequestTags(activity, responsesRequest);
break;
case OpenAIChatCompletionRequest chatRequest:
AddChatCompletionRequestTags(activity, chatRequest);
break;
Expand Down Expand Up @@ -914,6 +920,7 @@ private static string GetOperationName(OpenAIRequest request)

return request switch
{
OpenAIResponsesRequest => "responses",
OpenAIChatCompletionRequest => "chat.completions",
OpenAICompletionRequest => "completions",
OpenAIEmbeddingRequest => "embeddings",
Expand All @@ -925,6 +932,73 @@ private static string GetOperationName(OpenAIRequest request)
};
}

private void AddResponsesApiRequestTags(Activity activity, OpenAIResponsesRequest responsesRequest)
{
Logger.LogTrace("AddResponsesApiRequestTags() called");

// OpenLIT
_ = activity.SetTag(SemanticConvention.GEN_AI_OPERATION, "responses")
// OpenTelemetry
.SetTag(SemanticConvention.GEN_AI_OPERATION_NAME, "responses");

if (Configuration.IncludePrompt && responsesRequest.Input != null)
{
var inputString = responsesRequest.Input is string str ? str : JsonSerializer.Serialize(responsesRequest.Input, ProxyUtils.JsonSerializerOptions);
_ = activity.SetTag(SemanticConvention.GEN_AI_CONTENT_PROMPT, inputString);
}

if (responsesRequest.Instructions != null)
{
_ = activity.SetTag("ai.request.instructions", responsesRequest.Instructions);
}

if (responsesRequest.Modalities != null)
{
_ = activity.SetTag("ai.request.modalities", string.Join(",", responsesRequest.Modalities));
}

Logger.LogTrace("AddResponsesApiRequestTags() finished");
}

private void AddResponsesApiResponseTags(Activity activity, OpenAIRequest openAIRequest, string responseBody)
{
Logger.LogTrace("AddResponsesApiResponseTags() called");

var responsesResponse = JsonSerializer.Deserialize<OpenAIResponsesResponse>(responseBody, ProxyUtils.JsonSerializerOptions);
if (responsesResponse is null)
{
return;
}

RecordUsageMetrics(activity, openAIRequest, responsesResponse);

_ = activity.SetTag(SemanticConvention.GEN_AI_RESPONSE_ID, responsesResponse.Id);

if (responsesResponse.Status != null)
{
_ = activity.SetTag("ai.response.status", responsesResponse.Status);
}

// Extract completion text from output items
if (Configuration.IncludeCompletion && responsesResponse.Output != null)
{
var textContent = responsesResponse.Output
.Where(item => item.Type == "message" && item.Content != null)
.SelectMany(item => item.Content!)
.Where(c => c.Type == "output_text")
.Select(c => c.Text)
.Where(t => !string.IsNullOrEmpty(t))
.LastOrDefault();

if (!string.IsNullOrEmpty(textContent))
{
_ = activity.SetTag(SemanticConvention.GEN_AI_CONTENT_COMPLETION, textContent);
}
}

Logger.LogTrace("AddResponsesApiResponseTags() finished");
}

public void Dispose()
{
_loader?.Dispose();
Expand Down
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