feat: add support for OpenAI gpt-5-chat-latest model

packages/types/src/providers/openai.ts

@@ -6,6 +6,18 @@ export type OpenAiNativeModelId = keyof typeof openAiNativeModels
 export const openAiNativeDefaultModelId: OpenAiNativeModelId = "gpt-5-2025-08-07"
 
 export const openAiNativeModels = {
+	"gpt-5-chat-latest": {
+		maxTokens: 128000,
+		contextWindow: 400000,
+		supportsImages: true,
+		supportsPromptCache: true,
+		supportsReasoningEffort: false,
+		inputPrice: 1.25,
+		outputPrice: 10.0,
+		cacheReadsPrice: 0.13,
+		description: "GPT-5 Chat Latest: Optimized for conversational AI and non-reasoning tasks",
+		supportsVerbosity: true,
+	},
 	"gpt-5-2025-08-07": {
 		maxTokens: 128000,
 		contextWindow: 400000,

src/api/providers/__tests__/openai-native-gpt5-chat.spec.ts

@@ -0,0 +1,147 @@
+import { describe, it, expect, vi, beforeEach } from "vitest"
+import { OpenAiNativeHandler } from "../openai-native"
+import { ApiHandlerOptions } from "../../../shared/api"
+import { Anthropic } from "@anthropic-ai/sdk"
+
+// Mock OpenAI
+vi.mock("openai", () => {
+	return {
+		default: class MockOpenAI {
+			responses = {
+				create: vi.fn(),
+			}
+			chat = {
+				completions: {
+					create: vi.fn(),
+				},
+			}
+		},
+	}
+})
+
+describe("OpenAiNativeHandler - GPT-5 Chat Latest", () => {
+	let handler: OpenAiNativeHandler
+	let mockOptions: ApiHandlerOptions
+
+	beforeEach(() => {
+		vi.clearAllMocks()
+		mockOptions = {
+			apiModelId: "gpt-5-chat-latest",
+			openAiNativeApiKey: "test-api-key",
+			openAiNativeBaseUrl: "https://api.openai.com",
+		}
+		handler = new OpenAiNativeHandler(mockOptions)
+	})
+
+	describe("Model Configuration", () => {
+		it("should correctly configure gpt-5-chat-latest model", () => {
+			const model = handler.getModel()
+
+			expect(model.id).toBe("gpt-5-chat-latest")
+			expect(model.info.maxTokens).toBe(128000)
+			expect(model.info.contextWindow).toBe(400000)
+			expect(model.info.supportsImages).toBe(true)
+			expect(model.info.supportsPromptCache).toBe(true)
+			expect(model.info.supportsReasoningEffort).toBe(false) // Non-reasoning model
+			expect(model.info.description).toBe(
+				"GPT-5 Chat Latest: Optimized for conversational AI and non-reasoning tasks",
+			)
+		})
+
+		it("should not include reasoning effort for gpt-5-chat-latest", () => {
+			const model = handler.getModel()
+
+			// Should not have reasoning parameters since it's a non-reasoning model
+			expect(model.reasoning).toBeUndefined()
+		})
+	})
+
+	describe("API Endpoint Selection", () => {
+		it("should use Responses API for gpt-5-chat-latest", async () => {
+			// Mock fetch for Responses API
+			const mockFetch = vi.fn().mockResolvedValue({
+				ok: true,
+				body: new ReadableStream({
+					start(controller) {
+						controller.enqueue(
+							new TextEncoder().encode('data: {"type":"response.text.delta","delta":"Hello"}\n\n'),
+						)
+						controller.enqueue(
+							new TextEncoder().encode(
+								'data: {"type":"response.done","response":{"id":"test-id","usage":{"input_tokens":10,"output_tokens":5}}}\n\n',
+							),
+						)
+						controller.enqueue(new TextEncoder().encode("data: [DONE]\n\n"))
+						controller.close()
+					},
+				}),
+			})
+			global.fetch = mockFetch
+
+			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Hello" }]
+
+			const stream = handler.createMessage("System prompt", messages)
+			const chunks = []
+			for await (const chunk of stream) {
+				chunks.push(chunk)
+			}
+
+			// Verify it called the Responses API endpoint
+			expect(mockFetch).toHaveBeenCalledWith(
+				"https://api.openai.com/v1/responses",
+				expect.objectContaining({
+					method: "POST",
+					headers: expect.objectContaining({
+						"Content-Type": "application/json",
+						Authorization: "Bearer test-api-key",
+					}),
+					body: expect.stringContaining('"model":"gpt-5-chat-latest"'),
+				}),
+			)
+
+			// Verify the request body doesn't include reasoning parameters
+			const requestBody = JSON.parse(mockFetch.mock.calls[0][1].body)
+			expect(requestBody.reasoning).toBeUndefined()
+		})
+	})
+
+	describe("Conversation Features", () => {
+		it("should support conversation continuity with previous_response_id", async () => {
+			// Mock fetch for Responses API
+			const mockFetch = vi.fn().mockResolvedValue({
+				ok: true,
+				body: new ReadableStream({
+					start(controller) {
+						controller.enqueue(
+							new TextEncoder().encode('data: {"type":"response.text.delta","delta":"Response"}\n\n'),
+						)
+						controller.enqueue(
+							new TextEncoder().encode(
+								'data: {"type":"response.done","response":{"id":"response-123","usage":{"input_tokens":10,"output_tokens":5}}}\n\n',
+							),
+						)
+						controller.enqueue(new TextEncoder().encode("data: [DONE]\n\n"))
+						controller.close()
+					},
+				}),
+			})
+			global.fetch = mockFetch
+
+			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Follow-up question" }]
+
+			const stream = handler.createMessage("System prompt", messages, {
+				taskId: "test-task",
+				previousResponseId: "previous-response-456",
+			})
+
+			const chunks = []
+			for await (const chunk of stream) {
+				chunks.push(chunk)
+			}
+
+			// Verify the request includes previous_response_id
+			const requestBody = JSON.parse(mockFetch.mock.calls[0][1].body)
+			expect(requestBody.previous_response_id).toBe("previous-response-456")
+		})
+	})
+})

src/api/providers/openai-native.ts

@@ -1139,7 +1139,8 @@ export class OpenAiNativeHandler extends BaseProvider implements SingleCompletio
 
 	private isResponsesApiModel(modelId: string): boolean {
 		// Both GPT-5 and Codex Mini use the v1/responses endpoint
-		return modelId.startsWith("gpt-5") || modelId === "codex-mini-latest"
+		// gpt-5-chat-latest also uses the Responses API
+		return modelId.startsWith("gpt-5") || modelId === "codex-mini-latest" || modelId === "gpt-5-chat-latest"
 	}
 
 	private async *handleStreamResponse(