fix(coding-agent): apply modelOverrides to extension providers

closes #6367

packages/coding-agent/test/model-registry.test.ts

@@ -8,7 +8,7 @@ import type {
 	Model,
 	OpenAICompletionsCompat,
 } from "@earendil-works/pi-ai/compat";
-import { getApiProvider } from "@earendil-works/pi-ai/compat";
+import { getApiProvider, getSupportedThinkingLevels } from "@earendil-works/pi-ai/compat";
 import { getOAuthProvider } from "@earendil-works/pi-ai/oauth";
 import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 import { AuthStorage } from "../src/core/auth-storage.ts";
@@ -938,6 +938,63 @@ describe("ModelRegistry", () => {
 			expect(registry.getProviderDisplayName("oauth-provider")).toBe("OAuth Provider");
 		});
 
+		test("modelOverrides apply to dynamically registered provider models", async () => {
+			writeRawModelsJson({
+				"extension-provider": {
+					modelOverrides: {
+						"extension-model": {
+							name: "Overridden Extension Model",
+							thinkingLevelMap: {
+								off: null,
+								minimal: null,
+								low: null,
+								medium: null,
+								xhigh: "max",
+							},
+							headers: { "x-model-override": "enabled" },
+						},
+					},
+				},
+			});
+
+			const registry = ModelRegistry.create(authStorage, modelsJsonPath);
+			registry.registerProvider("extension-provider", {
+				baseUrl: "https://provider.test/v1",
+				apiKey: "test-key",
+				api: "openai-completions",
+				models: [
+					{
+						id: "extension-model",
+						name: "Extension Model",
+						reasoning: true,
+						input: ["text"],
+						cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+						contextWindow: 128000,
+						maxTokens: 4096,
+					},
+				],
+			});
+
+			const model = registry.find("extension-provider", "extension-model");
+			expect(model).toBeDefined();
+			if (!model) {
+				throw new Error("extension model was not registered");
+			}
+			expect(model.name).toBe("Overridden Extension Model");
+			expect(model.thinkingLevelMap).toEqual({
+				off: null,
+				minimal: null,
+				low: null,
+				medium: null,
+				xhigh: "max",
+			});
+			expect(getSupportedThinkingLevels(model)).toEqual(["high", "xhigh"]);
+			expect(await registry.getApiKeyAndHeaders(model)).toMatchObject({
+				ok: true,
+				headers: { "x-model-override": "enabled" },
+			});
+		});
+
 		test("stored API key env propagates to request auth and resolves headers", async () => {
 			authStorage.set("cloudflare-ai-gateway", {
 				type: "api_key",