feat(HAI-098): add model selection and configuration support

- Extend Settings type with model provider and model name fields
- Add backend API endpoint to list available models
- Add frontend API client for fetching models
- Add model settings section to SettingsModal with provider/model dropdowns
- Update engine executor to use the selected model from settings

packages/dashboard/src/routes.test.ts

@@ -4,7 +4,7 @@ import http from "node:http";
 import { createApiRoutes } from "./routes.js";
 import type { TaskStore, TaskAttachment } from "@hai/core";
 import type { TaskDetail } from "@hai/core";
-import type { AuthStorageLike } from "./routes.js";
+import type { AuthStorageLike, ModelRegistryLike } from "./routes.js";
 
 function createMockStore(overrides: Partial<TaskStore> = {}): TaskStore {
   return {
@@ -376,6 +376,75 @@ describe("Attachment routes", () => {
   });
 });
 
+// --- Models route tests ---
+
+function createMockModelRegistry(overrides: Partial<ModelRegistryLike> = {}): ModelRegistryLike {
+  return {
+    refresh: vi.fn(),
+    getAvailable: vi.fn().mockReturnValue([
+      { id: "claude-sonnet-4-5", name: "Claude Sonnet 4.5", provider: "anthropic", reasoning: true, contextWindow: 200000 },
+      { id: "gpt-4o", name: "GPT-4o", provider: "openai", reasoning: false, contextWindow: 128000 },
+    ]),
+    ...overrides,
+  };
+}
+
+describe("GET /models", () => {
+  let store: TaskStore;
+
+  beforeEach(() => {
+    store = createMockStore();
+  });
+
+  function buildApp(modelRegistry?: ModelRegistryLike) {
+    const app = express();
+    app.use(express.json());
+    app.use("/api", createApiRoutes(store, { modelRegistry }));
+    return app;
+  }
+
+  it("returns available models from registry", async () => {
+    const modelRegistry = createMockModelRegistry();
+    const res = await GET(buildApp(modelRegistry), "/api/models");
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual([
+      { provider: "anthropic", id: "claude-sonnet-4-5", name: "Claude Sonnet 4.5", reasoning: true, contextWindow: 200000 },
+      { provider: "openai", id: "gpt-4o", name: "GPT-4o", reasoning: false, contextWindow: 128000 },
+    ]);
+    expect(modelRegistry.refresh).toHaveBeenCalled();
+  });
+
+  it("returns empty array when no model registry is provided", async () => {
+    const res = await GET(buildApp(), "/api/models");
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual([]);
+  });
+
+  it("returns empty array when registry has no available models", async () => {
+    const modelRegistry = createMockModelRegistry({
+      getAvailable: vi.fn().mockReturnValue([]),
+    });
+    const res = await GET(buildApp(modelRegistry), "/api/models");
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual([]);
+  });
+
+  it("returns 500 when registry throws", async () => {
+    const modelRegistry = createMockModelRegistry({
+      getAvailable: vi.fn().mockImplementation(() => {
+        throw new Error("registry error");
+      }),
+    });
+    const res = await GET(buildApp(modelRegistry), "/api/models");
+
+    expect(res.status).toBe(500);
+    expect(res.body.error).toBe("registry error");
+  });
+});
+
 // --- Auth route tests ---
 
 function createMockAuthStorage(overrides: Partial<AuthStorageLike> = {}): AuthStorageLike {

packages/dashboard/src/routes.ts

@@ -5,6 +5,17 @@ import type { TaskStore, Column, MergeResult } from "@hai/core";
 import { COLUMNS } from "@hai/core";
 import type { ServerOptions } from "./server.js";
 
+/**
+ * Minimal interface matching pi-coding-agent's ModelRegistry API surface
+ * used by the models route. Avoids a direct dependency on the pi-coding-agent package.
+ */
+export interface ModelRegistryLike {
+  /** Reload models from disk to pick up changes. */
+  refresh(): void;
+  /** Get models that have auth configured. */
+  getAvailable(): Array<{ id: string; name: string; provider: string; reasoning: boolean; contextWindow: number }>;
+}
+
 /**
  * Minimal interface matching pi-coding-agent's AuthStorage API surface
  * used by the auth routes. Avoids a direct dependency on the pi-coding-agent package.
@@ -65,6 +76,9 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
     }
   });
 
+  // Models
+  registerModelsRoute(router, options?.modelRegistry);
+
   // List all tasks
   router.get("/tasks", async (_req, res) => {
     try {
@@ -277,6 +291,33 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
   return router;
 }
 
+/**
+ * Register the GET /api/models route.
+ * Returns available AI models from the ModelRegistry for the UI model selector.
+ * If no ModelRegistry is provided, returns an empty array.
+ */
+function registerModelsRoute(router: Router, modelRegistry?: ModelRegistryLike): void {
+  router.get("/models", (_req, res) => {
+    try {
+      if (!modelRegistry) {
+        res.json([]);
+        return;
+      }
+      modelRegistry.refresh();
+      const models = modelRegistry.getAvailable().map((m) => ({
+        provider: m.provider,
+        id: m.id,
+        name: m.name,
+        reasoning: m.reasoning,
+        contextWindow: m.contextWindow,
+      }));
+      res.json(models);
+    } catch (err: any) {
+      res.status(500).json({ error: err.message });
+    }
+  });
+}
+
 /**
  * Register authentication status, login, and logout routes.
  * Uses pi-coding-agent's AuthStorage for credential management.

packages/dashboard/src/server.ts

@@ -3,7 +3,7 @@ import { join, dirname } from "node:path";
 import { existsSync } from "node:fs";
 import { fileURLToPath } from "node:url";
 import type { TaskStore, MergeResult } from "@hai/core";
-import type { AuthStorageLike } from "./routes.js";
+import type { AuthStorageLike, ModelRegistryLike } from "./routes.js";
 import { createApiRoutes } from "./routes.js";
 import { createSSE } from "./sse.js";
 import { rateLimit, RATE_LIMITS } from "./rate-limit.js";
@@ -17,6 +17,8 @@ export interface ServerOptions {
   maxConcurrent?: number;
   /** Optional AuthStorage instance for auth routes — if not provided, one is created internally */
   authStorage?: AuthStorageLike;
+  /** Optional ModelRegistry instance for the models API — if not provided, the endpoint returns an empty list */
+  modelRegistry?: ModelRegistryLike;
 }
 
 export function createServer(store: TaskStore, options?: ServerOptions): ReturnType<typeof express> {