fix: Add GPT-5 Azure responses API support #6893

roomote · 2025-08-10T02:59:09Z

Summary

This PR fixes the issue where GPT-5 models on Azure OpenAI deployments were failing with a 400 Unsupported parameter: "messages" error. The problem was that GPT-5 models use the new responses API which expects an "input" parameter instead of the chat completions API "messages" parameter.

Changes

Added detection for GPT-5 models when using the OpenAI provider with Azure
Implemented support for the Azure responses API endpoint (/openai/responses)
Added proper formatting of conversation history into the "input" parameter format
Implemented support for GPT-5 specific parameters:
- Reasoning effort (including "minimal" level)
- Verbosity levels
- Reasoning summary
- Temperature and max_output_tokens
Added comprehensive streaming response handling for GPT-5 events
Fixed usage metrics processing to handle both GPT-5 and standard formats
Added comprehensive test coverage for GPT-5 Azure integration

Testing

All existing tests pass ✅
Added new tests specifically for GPT-5 Azure support
Tests verify correct API endpoint usage, parameter formatting, and response handling

Related Issue

Fixes #6862

How to Test

Configure Roo Code with OpenAI Compatible provider
Set up Azure OpenAI with a GPT-5 deployment
Configure:
- Base URL: https://<YOUR-RESOURCE>.openai.azure.com/openai/responses?api-version=2025-04-01-preview
- Model: gpt-5
- Use Azure: Yes
- API Version: 2025-04-01-preview
- Enable Reasoning Effort: Yes (set to desired level)
Send a message - it should now work without the "messages" parameter error

cc @SannidhyaSah

Important

Fixes GPT-5 Azure API support by implementing the responses API and adding comprehensive tests.

Behavior:
- Fixes 400 Unsupported parameter: "messages" error for GPT-5 models on Azure by switching to the responses API.
- Implements handleGpt5ResponsesAPI() in openai.ts to format requests for GPT-5 models using Azure.
- Adds support for GPT-5 specific parameters: reasoning effort, verbosity, reasoning summary, temperature, and max_output_tokens.
- Updates processUsageMetrics() in openai.ts to handle both GPT-5 and standard formats.
Testing:
- Adds tests in openai.spec.ts for GPT-5 Azure support, verifying API endpoint usage, parameter formatting, and response handling.
- Tests include scenarios for different reasoning efforts and non-Azure usage.
Misc:
- Adds isGpt5Model() and formatInputForResponsesAPI() helper functions in openai.ts.
- Updates createMessage() in openai.ts to detect and handle GPT-5 models on Azure.

^{This description was created by}^{for ecf2e1a. You can customize this summary. It will automatically update as commits are pushed.}

- Detect GPT-5 models when using Azure OpenAI provider - Use responses API endpoint with "input" parameter instead of chat completions "messages" - Support GPT-5 specific parameters: reasoning effort (including minimal), verbosity, and reasoning summary - Handle responses API streaming format for text, reasoning, and usage events - Add comprehensive tests for GPT-5 Azure integration Fixes #6862

ellipsis-dev · 2025-08-10T03:00:51Z

src/api/providers/openai.ts

+		const reader = body.getReader()
+		const decoder = new TextDecoder()
+		let buffer = ""
+		let hasContent = false


The variable 'hasContent' is set in the streaming response handler but never used. Consider removing it if it isn’t needed.

Suggested change

let hasContent = false

roomote

Reviewing my own code is like debugging in a mirror - everything looks backwards but the bugs are still mine.

roomote · 2025-08-10T03:02:46Z

src/api/providers/openai.ts

+	/**
+	 * Checks if the model ID is a GPT-5 model
+	 */
+	private isGpt5Model(modelId: string): boolean {


I notice there's a duplicate method here. The isGpt5Model() is defined twice - once at line 424 and the logic is already used inline at line 93. Should we consolidate to use a single method definition to avoid duplication?

roomote · 2025-08-10T03:02:46Z

src/api/providers/openai.ts

+		// Azure URLs typically look like: https://<resource>.openai.azure.com/openai/responses?api-version=...
+		const urlParts = baseUrl.match(/^(https?:\/\/[^\/]+)(\/.*)?$/)
+		const azureBaseUrl = urlParts ? urlParts[1] : baseUrl
+		const responsesUrl = `${azureBaseUrl}/openai/responses`


Is the Azure API version validated anywhere? For GPT-5 responses API, this parameter seems critical. Could we add validation to ensure it's present and in the expected format (e.g., '2025-04-01-preview' or later)?

roomote · 2025-08-10T03:02:46Z

src/api/providers/openai.ts

+
+		// Extract the base URL without the path for Azure endpoints
+		// Azure URLs typically look like: https://<resource>.openai.azure.com/openai/responses?api-version=...
+		const urlParts = baseUrl.match(/^(https?:\/\/[^\/]+)(\/.*)?$/)


This regex pattern for URL extraction might be fragile with certain URL formats. Would it be safer to use the URL constructor for parsing? Something like:

Suggested change

const urlParts = baseUrl.match(/^(https?:\/\/[^\/]+)(\/.*)?$/)

const url = new URL(baseUrl);

const azureBaseUrl = `${url.protocol}//${url.host}`;

const responsesUrl = `${azureBaseUrl}/openai/responses`;

roomote · 2025-08-10T03:02:46Z

src/api/providers/openai.ts

+		const reasoningEffort = this.getGpt5ReasoningEffort(reasoning)
+
+		// Build request body for GPT-5 responses API
+		const requestBody: any = {


The requestBody is typed as any. Could we create a proper TypeScript interface for the GPT-5 request body to improve type safety? This would help catch potential issues at compile time.

roomote · 2025-08-10T03:02:46Z

src/api/providers/openai.ts

+								}
+							}
+							// Handle reasoning delta events
+							else if (


Are we handling all possible GPT-5 streaming events? I'm wondering if there might be events like response.reasoning_effort.updated or other GPT-5 specific events we should handle. The Azure docs might have a complete list.

roomote · 2025-08-10T03:02:46Z

src/api/providers/__tests__/openai.spec.ts

@@ -783,6 +836,166 @@ describe("OpenAiHandler", () => {
 			)
 		})
 	})
+
+	describe("GPT-5 Azure Support", () => {


Great test coverage! Though I'm wondering if we should add tests for error scenarios like malformed SSE data or network failures during streaming? These edge cases could help ensure robust error handling.

spyridonas · 2025-08-10T17:26:15Z

This is the implementation of this api, correct?
https://platform.openai.com/docs/guides/latest-model#migrating-from-chat-completions-to-responses-api

If so, can it be also added on OpenAI provider?

spyridonas · 2025-08-10T20:04:57Z

Also make sure you are giving the api the previous_response_id in a multi-turn conversion

arnabbiswas1 · 2025-08-12T04:31:19Z

GPT-5 allows 4 reasoning levels: minimal, low, medium, high. When configuring Azure OpenAI GPT-5 using "API Provider" as "OpenAI Compatible ", reasoning effort "minimal" is not appearing in the drop down (only minimal, low, medium, high is available).
With "OpenAI Compatible", "Enable Streaming" fails with temperature related issues.

daniel-lxs · 2025-08-14T18:53:25Z

Issue needs proper scoping

roomote bot requested review from mrubens, cte and jr as code owners August 10, 2025 02:59

github-project-automation bot added this to Roo Code Roadmap and Roo Code Roadmap Aug 10, 2025

github-project-automation bot moved this to New in Roo Code Roadmap Aug 10, 2025

github-project-automation bot moved this to Triage in Roo Code Roadmap Aug 10, 2025

dosubot bot added size:XL This PR changes 500-999 lines, ignoring generated files. bug Something isn't working labels Aug 10, 2025

roomote bot mentioned this pull request Aug 10, 2025

400 Unsupported parameter: 'messages'. error on OpenAI Compatible Azure deployment of GPT-5 #6862

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ellipsis-dev bot reviewed Aug 10, 2025

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daniel-lxs moved this from Triage to PR [Needs Prelim Review] in Roo Code Roadmap Aug 12, 2025

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daniel-lxs deleted the fix/gpt5-azure-responses-api branch August 14, 2025 18:53

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fix: Add GPT-5 Azure responses API support #6893

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-		const urlParts = baseUrl.match(/^(https?:\/\/[^\/]+)(\/.*)?$/)
+        const url = new URL(baseUrl);
+        const azureBaseUrl = `${url.protocol}//${url.host}`;
+        const responsesUrl = `${azureBaseUrl}/openai/responses`;

fix: Add GPT-5 Azure responses API support #6893

fix: Add GPT-5 Azure responses API support #6893

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