diff --git a/packages/host/app/components/ai-assistant/panel.gts b/packages/host/app/components/ai-assistant/panel.gts
index 72e5d81f1b..4691186a65 100644
--- a/packages/host/app/components/ai-assistant/panel.gts
+++ b/packages/host/app/components/ai-assistant/panel.gts
@@ -24,6 +24,8 @@ import { aiBotUsername } from '@cardstack/runtime-common';
 
 import ENV from '@cardstack/host/config/environment';
 
+import OperatorModeStateService from '@cardstack/host/services/operator-mode-state-service';
+
 import AddSkillsToRoomCommand from '../../commands/add-skills-to-room';
 import CreateAIAssistantRoomCommand from '../../commands/create-ai-assistant-room';
 import { Message } from '../../lib/matrix-classes/message';
@@ -40,6 +42,8 @@ import RenameSession from '../ai-assistant/rename-session';
 import Room from '../matrix/room';
 import DeleteModal from '../operator-mode/delete-modal';
 
+import { Submodes } from '../submode-switcher';
+
 import assistantIcon from './ai-assist-icon.webp';
 
 import type MatrixService from '../../services/matrix-service';
@@ -368,6 +372,7 @@ export default class AiAssistantPanel extends Component<Signature> {
   @service private declare monacoService: MonacoService;
   @service private declare router: RouterService;
   @service private declare commandService: CommandService;
+  @service private declare operatorModeStateService: OperatorModeStateService;
 
   @tracked private isShowingPastSessions = false;
   @tracked private roomToRename: SessionRoomData | undefined = undefined;
@@ -545,6 +550,9 @@ export default class AiAssistantPanel extends Component<Signature> {
   @action
   private enterRoom(roomId: string, hidePastSessionsList = true) {
     this.matrixService.currentRoomId = roomId;
+    if (this.operatorModeStateService.state.submode === Submodes.Code) {
+      this.matrixService.setLLMModelForCodeMode();
+    }
     if (hidePastSessionsList) {
       this.hidePastSessions();
     }
diff --git a/packages/host/app/resources/room.ts b/packages/host/app/resources/room.ts
index 792b83d3da..d8a8202f1a 100644
--- a/packages/host/app/resources/room.ts
+++ b/packages/host/app/resources/room.ts
@@ -228,6 +228,9 @@ export class RoomResource extends Resource<Args> {
   }
 
   activateLLM(model: string) {
+    if (this.activeLLM === model) {
+      return;
+    }
     this._activeLLM = model;
     this.activateLLMTask.perform(model);
   }
diff --git a/packages/host/app/services/matrix-service.ts b/packages/host/app/services/matrix-service.ts
index 2e896d28e3..7b44b9f0fb 100644
--- a/packages/host/app/services/matrix-service.ts
+++ b/packages/host/app/services/matrix-service.ts
@@ -48,6 +48,7 @@ import {
   APP_BOXEL_REALMS_EVENT_TYPE,
   APP_BOXEL_ACTIVE_LLM,
   LEGACY_APP_BOXEL_REALMS_EVENT_TYPE,
+  DEFAULT_LLM_LIST,
 } from '@cardstack/runtime-common/matrix-constants';
 
 import {
@@ -1337,6 +1338,25 @@ export default class MatrixService extends Service {
       await this.client?.scrollback(room);
     }
   }
+
+  async setLLMModelForCodeMode() {
+    this.setLLMModel('anthropic/claude-3.5-sonnet');
+  }
+
+  private async setLLMModel(model: string) {
+    if (!DEFAULT_LLM_LIST.includes(model)) {
+      throw new Error(`Cannot find LLM model: ${model}`);
+    }
+    if (!this.currentRoomId) {
+      return;
+    }
+    let roomResource = this.roomResources.get(this.currentRoomId);
+    if (!roomResource) {
+      return;
+    }
+    await roomResource.loading;
+    roomResource.activateLLM(model);
+  }
 }
 
 function saveAuth(auth: LoginResponse) {
diff --git a/packages/host/app/services/operator-mode-state-service.ts b/packages/host/app/services/operator-mode-state-service.ts
index 0be9a0fedc..86b4a02dd9 100644
--- a/packages/host/app/services/operator-mode-state-service.ts
+++ b/packages/host/app/services/operator-mode-state-service.ts
@@ -34,6 +34,7 @@ import { type Stack } from '../components/operator-mode/interact-submode';
 
 import { removeFileExtension } from '../components/search-sheet/utils';
 
+import MatrixService from './matrix-service';
 import NetworkService from './network';
 
 import type CardService from './card-service';
@@ -97,6 +98,7 @@ export default class OperatorModeStateService extends Service {
   @service private declare router: RouterService;
   @service private declare reset: ResetService;
   @service private declare network: NetworkService;
+  @service private declare matrixService: MatrixService;
 
   constructor(owner: Owner) {
     super(owner);
@@ -310,6 +312,10 @@ export default class OperatorModeStateService extends Service {
   updateSubmode(submode: Submode) {
     this.state.submode = submode;
     this.schedulePersist();
+
+    if (submode === Submodes.Code) {
+      this.matrixService.setLLMModelForCodeMode();
+    }
   }
 
   updateCodePathWithCodeSelection(
diff --git a/packages/host/tests/acceptance/ai-assistant-test.gts b/packages/host/tests/acceptance/ai-assistant-test.gts
index 9d328594fc..02cd6a6f6e 100644
--- a/packages/host/tests/acceptance/ai-assistant-test.gts
+++ b/packages/host/tests/acceptance/ai-assistant-test.gts
@@ -1,4 +1,4 @@
-import { click, fillIn } from '@ember/test-helpers';
+import { click, fillIn, waitFor } from '@ember/test-helpers';
 
 import { module, test } from 'qunit';
 
@@ -326,4 +326,29 @@ module('Acceptance | AI Assistant tests', function (hooks) {
     let roomState = getRoomState('mock_room_1', APP_BOXEL_ACTIVE_LLM, '');
     assert.strictEqual(roomState.model, 'google/gemini-pro-1.5');
   });
+
+  test('defaults to anthropic/claude-3.5-sonnet in code mode', async function (assert) {
+    await visitOperatorMode({
+      stacks: [
+        [
+          {
+            id: `${testRealmURL}index`,
+            format: 'isolated',
+          },
+        ],
+      ],
+    });
+
+    await click('[data-test-submode-switcher] button');
+    await click('[data-test-boxel-menu-item-text="Code"]');
+    await click('[data-test-open-ai-assistant]');
+    assert.dom('[data-test-llm-select-selected]').hasText('claude-3.5-sonnet');
+
+    createAndJoinRoom('@testuser:staging', 'room-test-2');
+
+    await click('[data-test-past-sessions-button]');
+    await waitFor("[data-test-enter-room='mock_room_2']");
+    await click('[data-test-enter-room="mock_room_2"]');
+    assert.dom('[data-test-llm-select-selected]').hasText('claude-3.5-sonnet');
+  });
 });