fix(backend): validate configured model provider pair

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,