fix(backend): validate configured model provider pair

backend/src/app.ts

@@ -23,7 +23,7 @@ export interface BuildAppDeps {
 }
 
 export function buildApp(config: AppConfig, deps?: BuildAppDeps): FastifyInstance {
-  const app = Fastify({ logger: false });
+  const app = Fastify({ logger: { level: "warn" }, disableRequestLogging: true });
 
   // Allow any origin in dev/e2e; tighten in production via config if needed.
   app.register(cors, {
@@ -45,7 +45,12 @@ export function buildApp(config: AppConfig, deps?: BuildAppDeps): FastifyInstanc
     Math.round(config.ollamaEnsureTimeoutMs / 1000),
   );
 
-  const listModels = deps?.listModels ?? createPiModelLister(config);
+  const listModels = deps?.listModels ?? createPiModelLister(config, {
+    warn: (detail) => app.log.warn(
+      { component: "pi-model-list", detail },
+      "Pi enabled-model configuration warning",
+    ),
+  });
   const getSettings = deps?.getSettings ?? (() => effectiveSettings(config, loadSettings(config)));
 
   const authenticate = authPreHandler(config.authMode);

backend/src/routes/meta.ts

@@ -34,7 +34,11 @@ export function metaRoutes(
     const fn = deps.listModels ?? (async () => []);
     try {
       return { models: await fn() };
-    } catch {
+    } catch (error) {
+      app.log.warn({
+        component: "pi-model-list",
+        errorType: error instanceof Error ? error.name : typeof error,
+      }, "Pi model listing failed");
       // Graceful fallback: Pi may not be running; don't crash the server.
       return { models: [] as PiModel[] };
     }

backend/src/routes/settings.ts

@@ -25,15 +25,19 @@ export function settingsRoutes(
   app.put("/settings", async (req, reply) => {
     const b = (req.body ?? {}) as Settings;
     if (b.model) {
-      let available: { id: string }[] = [];
+      let available: { provider: string; id: string }[] = [];
       try {
         available = await deps.listModels();
       } catch {
         available = [];
       }
       // Only validate when Pi gave us a non-empty list; otherwise allow (degraded).
-      if (available.length > 0 && !available.some((m) => m.id === b.model)) {
-        return reply.code(400).send({ error: `Unknown model: ${b.model}` });
+      if (available.length > 0 && !available.some(
+        (candidate) => candidate.provider === b.provider && candidate.id === b.model,
+      )) {
+        return reply.code(400).send({
+          error: `Unknown model: ${b.provider ?? "unknown"}/${b.model}`,
+        });
       }
     }
     const next: Settings = {

backend/test/routes-settings.test.ts

@@ -64,6 +64,33 @@ test("PUT /settings rejects an unknown model when a model list is available", as
   }
 });
 
+test("PUT /settings validates provider and model as one composite identifier", async () => {
+  const { app, dir } = appWithTmpSettings({}, {
+    listModels: async () => [
+      { provider: "provider-a", id: "shared-id", name: "A", reasoning: false },
+    ],
+  });
+  try {
+    const wrongProvider = await app.inject({
+      method: "PUT", url: "/settings",
+      payload: {
+        workspace: "psd", provider: "provider-b", model: "shared-id", thinking: "low",
+      },
+    });
+    expect(wrongProvider.statusCode).toBe(400);
+
+    const exactPair = await app.inject({
+      method: "PUT", url: "/settings",
+      payload: {
+        workspace: "psd", provider: "provider-a", model: "shared-id", thinking: "low",
+      },
+    });
+    expect(exactPair.statusCode).toBe(200);
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
 test("PUT /settings allows any model when model list is empty (Pi unavailable)", async () => {
   const { app, dir } = appWithTmpSettings({}, { listModels: async () => [] });
   try {

backend/test/routes-sql-meta.test.ts

@@ -1,4 +1,4 @@
-import { test, expect } from "vitest";
+import { test, expect, vi } from "vitest";
 import { buildApp } from "../src/app.js";
 import { loadConfig } from "../src/config.js";
 
@@ -148,6 +148,20 @@ test("GET /models returns {models:[]} when listModels throws (graceful fallback)
   expect(res.json()).toEqual({ models: [] });
 });
 
+test("GET /models logs a sanitized warning when listing fails", async () => {
+  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
+    thtRunner: {} as any,
+    listModels: async () => { throw new Error("credential-value-must-not-appear"); },
+  });
+  const warn = vi.spyOn(app.log, "warn");
+
+  const res = await app.inject({ method: "GET", url: "/models" });
+
+  expect(res.json()).toEqual({ models: [] });
+  expect(JSON.stringify(warn.mock.calls)).not.toContain("credential-value-must-not-appear");
+  expect(warn).toHaveBeenCalled();
+});
+
 test("GET /models with empty listModels stub returns empty array", async () => {
   const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
     thtRunner: {} as any,