fix(coding-agent): mention oauth exemption in apiKey validation error; add validation tests

packages/coding-agent/src/config/models-config.ts

@@ -71,7 +71,7 @@ export function validateProviderConfiguration(
 			throw new Error(
 				mode === "runtime-register"
 					? `Provider ${providerName}: "apiKey" or "oauth" is required when defining models.`
-					: `Provider ${providerName}: "apiKey" is required when defining custom models unless auth is "none".`,
+					: `Provider ${providerName}: "apiKey" is required when defining custom models unless auth is "none" or "oauth".`,
 			);
 		}
 	}

packages/coding-agent/test/config/models-config-validation.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, test } from "bun:test";
+import { validateProviderConfiguration } from "@oh-my-pi/pi-coding-agent/config/models-config";
+
+const models = [{ id: "grok-4", api: "openai-completions" as const }];
+const baseUrl = "https://api.example.invalid/v1";
+
+describe("validateProviderConfiguration (models-config auth)", () => {
+	test("auth: oauth allows custom models without apiKey", () => {
+		expect(() =>
+			validateProviderConfiguration("xai-oauth", { baseUrl, auth: "oauth", models }, "models-config"),
+		).not.toThrow();
+	});
+
+	test("auth: none allows custom models without apiKey", () => {
+		expect(() =>
+			validateProviderConfiguration("local", { baseUrl, auth: "none", models }, "models-config"),
+		).not.toThrow();
+	});
+
+	test("default auth (apiKey) still requires apiKey for custom models", () => {
+		expect(() => validateProviderConfiguration("custom", { baseUrl, models }, "models-config")).toThrow(
+			'Provider custom: "apiKey" is required when defining custom models unless auth is "none" or "oauth".',
+		);
+	});
+
+	test("explicit auth: apiKey with apiKey set passes", () => {
+		expect(() =>
+			validateProviderConfiguration("custom", { baseUrl, auth: "apiKey", apiKey: "sk-test", models }, "models-config"),
+		).not.toThrow();
+	});
+});