fix: append /v1 to OpenAI Compatible base URLs for llama.cpp compatibility

- Automatically append /v1 to base URLs that are plain URLs without a path
- This fixes compatibility with llama.cpp servers that expose OpenAI-compatible endpoints
- Added tests to verify the URL handling works correctly

Fixes #7065

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

@@ -99,6 +99,41 @@ describe("OpenAiNativeHandler", () => {
 			})
 			expect(handlerWithoutKey).toBeInstanceOf(OpenAiNativeHandler)
 		})
+
+		it("should append /v1 to base URL when it's a plain URL without path", () => {
+			// Test with plain URL (like llama.cpp server)
+			const handler1 = new OpenAiNativeHandler({
+				apiModelId: "gpt-4.1",
+				openAiNativeApiKey: "test-api-key",
+				openAiNativeBaseUrl: "http://127.0.0.1:8080",
+			})
+			expect(handler1).toBeInstanceOf(OpenAiNativeHandler)
+			// The client should have the /v1 appended internally
+
+			// Test with URL that already has /v1
+			const handler2 = new OpenAiNativeHandler({
+				apiModelId: "gpt-4.1",
+				openAiNativeApiKey: "test-api-key",
+				openAiNativeBaseUrl: "http://localhost:8080/v1",
+			})
+			expect(handler2).toBeInstanceOf(OpenAiNativeHandler)
+
+			// Test with URL that has a different path
+			const handler3 = new OpenAiNativeHandler({
+				apiModelId: "gpt-4.1",
+				openAiNativeApiKey: "test-api-key",
+				openAiNativeBaseUrl: "https://api.openai.com/v1",
+			})
+			expect(handler3).toBeInstanceOf(OpenAiNativeHandler)
+
+			// Test with URL with trailing slash
+			const handler4 = new OpenAiNativeHandler({
+				apiModelId: "gpt-4.1",
+				openAiNativeApiKey: "test-api-key",
+				openAiNativeBaseUrl: "http://localhost:11434/",
+			})
+			expect(handler4).toBeInstanceOf(OpenAiNativeHandler)
+		})
 	})
 
 	describe("createMessage", () => {

src/api/providers/openai-native.ts

@@ -57,7 +57,23 @@ export class OpenAiNativeHandler extends BaseProvider implements SingleCompletio
 			this.options.enableGpt5ReasoningSummary = true
 		}
 		const apiKey = this.options.openAiNativeApiKey ?? "not-provided"
-		this.client = new OpenAI({ baseURL: this.options.openAiNativeBaseUrl, apiKey })
+
+		// Handle base URL - append /v1 if it's a plain URL without a path
+		let baseURL = this.options.openAiNativeBaseUrl
+		if (baseURL && !baseURL.includes("/v1")) {
+			// Check if it's a URL without any path (just protocol://host:port)
+			try {
+				const url = new URL(baseURL)
+				// If the pathname is just '/', append /v1
+				if (url.pathname === "/") {
+					baseURL = baseURL.replace(/\/$/, "") + "/v1"
+				}
+			} catch {
+				// If URL parsing fails, leave it as is
+			}
+		}
+
+		this.client = new OpenAI({ baseURL, apiKey })
 	}
 
 	private normalizeGpt5Usage(usage: any, model: OpenAiNativeModel): ApiStreamUsageChunk | undefined {