Start model-less Pi agents on Pi's configured default model (#5343)

A Pi agent created without a model took the first entry of Pi's model
list, which ignores defaultProvider/defaultModel in Pi's settings. The Pi
catalog now marks the model a fresh Pi session reports in get_state as
the default, so the daemon's default-model fallback picks it.

Closes #4918

Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/server/src/server/agent/providers/pi/agent.test.ts

@@ -2505,6 +2505,26 @@ describe("PiRpcAgentClient", () => {
     expect(pi.recordedLaunches[0]).toMatchObject({ cwd: "/workspace/with-extension" });
   });
 
+  test("marks the model Pi resolves from its own settings as the catalog default", async () => {
+    const pi = new FakePi();
+    const unconfigured = { provider: "openai", id: "gpt-4", name: "GPT-4", reasoning: false };
+    const configured = { provider: "zai", id: "glm-5.3", name: "GLM-5.3", reasoning: true };
+    pi.queueSessionSetup((session) => {
+      session.models = [unconfigured, configured];
+      session.state = { ...session.state, model: configured };
+    });
+
+    const catalog = await createClient(pi).fetchCatalog({
+      scope: "workspace",
+      cwd: "/workspace/project",
+      force: false,
+    });
+
+    expect(catalog.models.filter((model) => model.isDefault).map((model) => model.id)).toEqual([
+      "zai/glm-5.3",
+    ]);
+  });
+
   test("honors per-model Pi thinking maps and clamps the catalog default upward", async () => {
     const pi = new FakePi();
     pi.queueSessionSetup((session) => {

packages/server/src/server/agent/providers/pi/agent.ts

@@ -2664,12 +2664,23 @@ export class PiRpcAgentClient implements AgentClient {
       });
       if (!runtimeSession) throw new Error("Pi catalog runtime did not start");
       const catalogSession = runtimeSession;
+      const piModels = await runProviderRefreshActivity(context, "get_available_models", () =>
+        catalogSession.getAvailableModels(null),
+      );
+      // A fresh Pi session starts on the model Pi resolves from its own settings.
+      const { model: configuredModel } = await runProviderRefreshActivity(
+        context,
+        "get_state",
+        () => catalogSession.getState(),
+      );
       const models = transformPiModels(
-        (
-          await runProviderRefreshActivity(context, "get_available_models", () =>
-            catalogSession.getAvailableModels(null),
-          )
-        ).map((model) => mapPiModel(model, PI_PROVIDER)),
+        piModels.map((model) => {
+          const mapped = mapPiModel(model, PI_PROVIDER);
+          const isConfigured =
+            model.provider === configuredModel?.provider && model.id === configuredModel?.id;
+          if (isConfigured) mapped.isDefault = true;
+          return mapped;
+        }),
       );
       return { models, modes: [] };
     } finally {