fix: harden model catalog projections

backend/test/pi-process-manager.test.ts

@@ -718,6 +718,54 @@ test.each([["OpenAI", "openai"], ["gemini", "google"]])(
   },
 );
 
+test("set_model translates a canonical catalog key to its upstream Pi model ID", async () => {
+  const root = mkdtempSync(path.join(tmpdir(), "thothii-upstream-model-"));
+  const agentDir = path.join(root, "agent");
+  mkdirSync(agentDir, { mode: 0o700 });
+  writeFileSync(path.join(agentDir, "models.json"), JSON.stringify({
+    providers: {
+      local: {
+        baseUrl: "http://ollama:11434/v1", apiKey: "local",
+        models: [{ id: "qwen2.5:7b" }],
+      },
+    },
+  }), { mode: 0o600 });
+  vi.stubEnv("PI_CODING_AGENT_DIR", agentDir);
+  const child = recordingChild();
+  child.stderr.resume = () => {};
+  child.stdin.write = (data: unknown) => {
+    const request = JSON.parse(String(data));
+    child._writes.push(String(data));
+    if (request.id) {
+      queueMicrotask(() => child.stdout.emit("data", `${JSON.stringify({
+        type: "response", id: request.id, success: true,
+      })}\n`));
+    }
+    return true;
+  };
+  const model: RuntimeModel = {
+    id: "local/qwen", provider: "local", model: "qwen", label: "Qwen",
+    upstreamModel: "qwen2.5:7b", endpoint: { baseUrl: "http://ollama:11434/v1" },
+    authentication: { mode: "none" }, sessionAdapter: { mode: "openai_compatible" },
+    session: { reasoning: false, contextWindow: 32768, maxTokens: 8192 },
+  };
+  const modelCatalog: RuntimeModelCatalog = {
+    defaultSession: model.id, defaultMetadataGeneration: null, embedding: null,
+    sessionModels: () => [model], metadataModels: () => [], hasSession: (id) => id === model.id,
+  };
+  const mgr = new PiProcessManager(loadConfig({ PI_BIN: "/usr/local/bin/pi" }), {
+    modelCatalog, authProviders: () => new Set(), spawnFn: () => child as any,
+  });
+  try {
+    await mgr.spawnFor("upstream-model", { provider: "local", model: "qwen" });
+    expect(child._writes.join("")).toContain('"modelId":"qwen2.5:7b"');
+  } finally {
+    mgr.teardown("upstream-model");
+    vi.unstubAllEnvs();
+    rmSync(root, { recursive: true, force: true });
+  }
+});
+
 test.each(["installation-local", "private-compatible"])(
   "provider %s configured with a literal apiKey spawns without a managed key",
   async (provider) => {