Keep the native model when importing sessions (#8948)

* fix(server): preserve the selected model when importing sessions

Import preparation resolved a new-session catalog default and sent it as an explicit resume override. Keep import selections with the resumed provider and persist its reported model for subsequent reloads.

* fix(codex): allow the first reply after importing a session

Resolve collaboration settings again when default model and effort are applied so imported sessions send a complete first-turn request.

---------

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

packages/server/src/server/agent/agent-manager.test.ts

@@ -4699,6 +4699,51 @@ test("resumeAgentFromPersistence keeps metadata config, applies overrides, and p
   });
 });
 
+test("importProviderSession preserves the native model instead of applying the new-session default", async () => {
+  const workdir = mkdtempSync(join(tmpdir(), "agent-manager-import-model-"));
+  onTestFinished(() => rmSync(workdir, { recursive: true, force: true }));
+  const storage = new AgentStorage(join(workdir, "agents"), logger);
+  const nativeModel = "native-selected-model";
+
+  class ImportClient extends TestAgentClient {
+    importConfig: AgentSessionConfig | undefined;
+
+    async importSession(input: ImportProviderSessionInput, context: ImportProviderSessionContext) {
+      this.importConfig = context.config;
+      // A resumable provider applies explicit selections but otherwise retains its model.
+      const session = new TestAgentSession({
+        ...context.config,
+        model: context.config.model ?? nativeModel,
+      });
+      return {
+        session,
+        config: context.storedConfig,
+        persistence: { provider: this.provider, sessionId: input.providerHandleId },
+        timeline: [],
+      };
+    }
+  }
+
+  const client = new ImportClient();
+  const manager = new AgentManager({ clients: { codex: client }, registry: storage, logger });
+  const imported = await manager.importProviderSession({
+    provider: "codex",
+    providerHandleId: "native-session",
+    cwd: workdir,
+    workspaceId: "import-model",
+  });
+  await manager.flush();
+
+  expect(imported.runtimeInfo?.model).toBe(nativeModel);
+  expect(imported.config.model).toBe(nativeModel);
+  expect(client.importConfig?.model).toBeUndefined();
+  expect((await storage.get(imported.id))?.config.model).toBe(nativeModel);
+
+  await manager.reloadAgentSession(imported.id);
+  expect(client.resumeOverrides.at(-1)?.model).toBe(nativeModel);
+  await manager.getAgent(imported.id)?.session?.close();
+});
+
 test("importProviderSession imports the selected session without listing and publishes ready state", async () => {
   const workdir = mkdtempSync(join(tmpdir(), "agent-manager-import-session-"));
   const storagePath = join(workdir, "agents");

packages/server/src/server/agent/agent-manager.ts

@@ -1679,6 +1679,7 @@ export class AgentManager {
         cwd: input.cwd,
       },
       resolvedAgentId,
+      { resolveDefaultModel: false },
     );
     this.paseoToolPolicies.set(resolvedAgentId, paseoToolPolicy);
     const launchContext = await this.buildLaunchContext(
@@ -1705,8 +1706,13 @@ export class AgentManager {
     await this.requireExternalMcpSupport(imported.session, providerLaunchConfig, launchContext);
     let handedToRegistration = false;
     try {
+      const runtimeInfo = await imported.session.getRuntimeInfo();
       const importedConfig = await this.normalizeConfig(
-        stripInternalPaseoMcpServer(imported.config),
+        stripInternalPaseoMcpServer({
+          ...imported.config,
+          model: runtimeInfo.model ?? imported.config.model,
+        }),
+        { resolveDefaultModel: false },
       );
       const timelineRows = buildImportedTimelineRows(imported.timeline);
       const initialTitle = resolveImportedAgentTitle(importedConfig, timelineRows);
@@ -5723,11 +5729,12 @@ export class AgentManager {
   private async prepareSessionConfig(
     config: AgentSessionConfig,
     agentId: string,
-    options: { env?: Record<string, string>; purpose?: AgentResumePurpose } = {},
+    options: NormalizeConfigOptions = {},
   ): Promise<PreparedSessionConfig> {
     const storedConfig = await this.normalizeConfig(stripInternalPaseoMcpServer(config), {
       env: options.env,
       purpose: options.purpose,
+      resolveDefaultModel: options.resolveDefaultModel,
     });
     const paseoToolPolicy = this.paseoToolsEnabled
       ? this.resolvePaseoToolPolicy(storedConfig.provider)

packages/server/src/server/agent/providers/codex-app-server-agent.test.ts

@@ -1379,6 +1379,42 @@ describe("Codex app-server provider", () => {
     }
   });
 
+  test.each([undefined, "configured-model"])(
+    "import resolves model %s before the first collaboration turn",
+    async (configuredModel) => {
+      const appServer = createFakeCodexAppServer({
+        "config/read": () => ({
+          config: { model: configuredModel, model_reasoning_effort: "low" },
+        }),
+        "collaborationMode/list": () => ({
+          data: [{ name: "Code", mode: "default", model: null, reasoning_effort: null }],
+        }),
+      });
+      const provider = createProviderWithFakeAppServer(appServer);
+      const config = createConfig({ model: undefined, thinkingOptionId: undefined });
+      const imported = await provider.importSession(
+        { providerHandleId: "native-thread", cwd: config.cwd! },
+        { config, storedConfig: config },
+      );
+
+      try {
+        await imported.session.startTurn("first follow-up after import");
+        await expect(appServer.waitForTurnStart()).resolves.toMatchObject({
+          threadId: "native-thread",
+          model: configuredModel ?? "gpt-5.4",
+          effort: "low",
+          collaborationMode: {
+            mode: "default",
+            settings: { model: configuredModel ?? "gpt-5.4", reasoning_effort: "low" },
+          },
+        });
+        appServer.assertNoErrors();
+      } finally {
+        await imported.session.close();
+      }
+    },
+  );
+
   test("provider persistence leaves options owned by the stored agent config", async () => {
     const appServer = createFakeCodexAppServer();
     const provider = createProviderWithFakeAppServer(appServer);

packages/server/src/server/agent/providers/codex-app-server-agent.ts

@@ -5554,6 +5554,7 @@ export class CodexAppServerAgentSession implements AgentSession {
     this.config.model = model;
     this.reconcileServiceTier();
     this.config.thinkingOptionId = thinkingOptionId;
+    this.refreshResolvedCollaborationMode();
     return model;
   }