refactor(core): make LegacyAgentSession dependencies optional

Allows LegacyAgentProtocol to fall back to the global Config object to resolve its dependencies, making it easier to instantiate in the CLI.

docs/reference/configuration.md

@@ -1605,6 +1605,12 @@ their corresponding top-level category object in your `settings.json` file.
   - **Default:** `false`
   - **Requires restart:** Yes
 
+- **`experimental.adk.agentSessionInteractiveEnabled`** (boolean):
+  - **Description:** Enable the agent session implementation for the interactive
+    CLI.
+  - **Default:** `false`
+  - **Requires restart:** Yes
+
 - **`experimental.enableAgents`** (boolean):
   - **Description:** Enable local and remote subagents.
   - **Default:** `true`

packages/cli/src/config/settingsSchema.ts

@@ -1970,6 +1970,16 @@ const SETTINGS_SCHEMA = {
             description: 'Enable non-interactive agent sessions.',
             showInDialog: false,
           },
+          agentSessionInteractiveEnabled: {
+            type: 'boolean',
+            label: 'Interactive Agent Session Enabled',
+            category: 'Experimental',
+            requiresRestart: true,
+            default: false,
+            description:
+              'Enable the agent session implementation for the interactive CLI.',
+            showInDialog: false,
+          },
         },
       },
       enableAgents: {

packages/cli/src/nonInteractiveCliAgentSession.ts

@@ -37,6 +37,7 @@ import {
   LegacyAgentSession,
   ToolErrorType,
   geminiPartsToContentParts,
+  debugLogger,
 } from '@google/gemini-cli-core';
 
 import type { Part } from '@google/genai';
@@ -599,6 +600,7 @@ export async function runNonInteractive({
             // Explicitly ignore these non-interactive events
             break;
           default:
+            debugLogger.error('Unknown agent event type:', event);
             event satisfies never;
             break;
         }

packages/cli/src/ui/components/messages/__snapshots__/ToolGroupMessage.test.tsx.snap

@@ -78,7 +78,7 @@ exports[`<ToolGroupMessage /> > Golden Snapshots > renders header when scrolled
 
 exports[`<ToolGroupMessage /> > Golden Snapshots > renders mixed tool calls including update_topic 1`] = `
 "
-  Testing Topic: This is the description
+  Testing Topic: This is the summary
 
 ╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  read_file Read a file                                                 │
@@ -142,12 +142,6 @@ exports[`<ToolGroupMessage /> > Golden Snapshots > renders two tool groups where
 "
 `;
 
-exports[`<ToolGroupMessage /> > Golden Snapshots > renders update_topic tool call using TopicMessage > update_topic_tool 1`] = `
-"
-  Testing Topic: This is the description
-"
-`;
-
 exports[`<ToolGroupMessage /> > Golden Snapshots > renders with limited terminal height 1`] = `
 "╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  tool-with-result Tool with output                                     │

packages/core/src/agent/event-translator.ts

@@ -432,6 +432,7 @@ function isStructuredError(error: unknown): error is StructuredError {
   return (
     typeof error === 'object' &&
     error !== null &&
+    'status' in error &&
     'message' in error &&
     typeof error.message === 'string'
   );

packages/core/src/agent/legacy-agent-session.test.ts

@@ -17,6 +17,9 @@ import type {
   ToolCallRequestInfo,
 } from '../scheduler/types.js';
 import { CoreToolCallStatus } from '../scheduler/types.js';
+import type { GeminiClient } from '../core/client.js';
+import type { Scheduler } from '../scheduler/scheduler.js';
+import type { Config } from '../config/config.js';
 
 // ---------------------------------------------------------------------------
 // Mock helpers
@@ -24,7 +27,7 @@ import { CoreToolCallStatus } from '../scheduler/types.js';
 
 function createMockDeps(
   overrides?: Partial<LegacyAgentSessionDeps>,
-): LegacyAgentSessionDeps {
+): Required<LegacyAgentSessionDeps> {
   const mockClient = {
     sendMessageStream: vi.fn(),
     getChat: vi.fn().mockReturnValue({
@@ -40,18 +43,22 @@ function createMockDeps(
   const mockConfig = {
     getMaxSessionTurns: vi.fn().mockReturnValue(-1),
     getModel: vi.fn().mockReturnValue('gemini-2.5-pro'),
+    getGeminiClient: vi.fn().mockReturnValue(mockClient),
+    getMessageBus: vi.fn().mockImplementation(() => ({
+      subscribe: vi.fn(),
+      unsubscribe: vi.fn(),
+    })),
   };
 
   return {
-    client: mockClient as unknown as LegacyAgentSessionDeps['client'],
-
-    scheduler: mockScheduler as unknown as LegacyAgentSessionDeps['scheduler'],
-
-    config: mockConfig as unknown as LegacyAgentSessionDeps['config'],
+    client: mockClient as unknown as GeminiClient,
+    scheduler: mockScheduler as unknown as Scheduler,
+    config: mockConfig as unknown as Config,
     promptId: 'test-prompt',
     streamId: 'test-stream',
+    getPreferredEditor: vi.fn().mockReturnValue(undefined),
     ...overrides,
-  };
+  } as Required<LegacyAgentSessionDeps>;
 }
 
 async function* makeStream(
@@ -129,7 +136,7 @@ async function collectEvents(
 // ---------------------------------------------------------------------------
 
 describe('LegacyAgentSession', () => {
-  let deps: LegacyAgentSessionDeps;
+  let deps: Required<LegacyAgentSessionDeps>;
 
   beforeEach(() => {
     deps = createMockDeps();

packages/core/src/agent/legacy-agent-session.ts

@@ -14,10 +14,11 @@ import type { Part } from '@google/genai';
 import type { GeminiClient } from '../core/client.js';
 import type { Config } from '../config/config.js';
 import type { ToolCallRequestInfo } from '../scheduler/types.js';
-import type { Scheduler } from '../scheduler/scheduler.js';
+import { Scheduler } from '../scheduler/scheduler.js';
 import { recordToolCallInteractions } from '../code_assist/telemetry.js';
 import { ToolErrorType, isFatalToolError } from '../tools/tool-error.js';
 import { debugLogger } from '../utils/debugLogger.js';
+import type { EditorType } from '../utils/editor.js';
 import {
   buildToolResponseData,
   contentPartsToGeminiParts,
@@ -45,14 +46,15 @@ function isAbortLikeError(err: unknown): boolean {
 }
 
 export interface LegacyAgentSessionDeps {
-  client: GeminiClient;
-  scheduler: Scheduler;
   config: Config;
-  promptId: string;
+  client?: GeminiClient;
+  scheduler?: Scheduler;
+  promptId?: string;
   streamId?: string;
+  getPreferredEditor?: () => EditorType | undefined;
 }
 
-class LegacyAgentProtocol implements AgentProtocol {
+export class LegacyAgentProtocol implements AgentProtocol {
   private _events: AgentEvent[] = [];
   private _subscribers = new Set<(event: AgentEvent) => void>();
   private _translationState: TranslationState;
@@ -69,10 +71,16 @@ class LegacyAgentProtocol implements AgentProtocol {
   constructor(deps: LegacyAgentSessionDeps) {
     this._translationState = createTranslationState(deps.streamId);
     this._nextStreamIdOverride = deps.streamId;
-    this._client = deps.client;
-    this._scheduler = deps.scheduler;
     this._config = deps.config;
-    this._promptId = deps.promptId;
+    this._client = deps.client ?? deps.config.getGeminiClient();
+    this._promptId = deps.promptId ?? deps.config.promptId ?? '';
+    this._scheduler =
+      deps.scheduler ??
+      new Scheduler({
+        context: deps.config,
+        schedulerId: 'legacy-agent-scheduler',
+        getPreferredEditor: deps.getPreferredEditor ?? (() => undefined),
+      });
   }
 
   get events(): readonly AgentEvent[] {

packages/core/src/agent/types.ts

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import type { Kind } from '../tools/tools.js';
+
 export type WithMeta = { _meta?: Record<string, unknown> };
 
 export type Unsubscribe = () => void;
@@ -180,6 +182,16 @@ export interface ToolRequest {
   name: string;
   /** The arguments for the tool. */
   args: Record<string, unknown>;
+  /** UI specific metadata */
+  _meta?: {
+    legacyState?: {
+      displayName?: string;
+      isOutputMarkdown?: boolean;
+      description?: string;
+      kind?: Kind;
+    };
+    [key: string]: unknown;
+  };
 }
 
 /**
@@ -192,6 +204,18 @@ export interface ToolUpdate {
   displayContent?: ContentPart[];
   content?: ContentPart[];
   data?: Record<string, unknown>;
+  /** UI specific metadata */
+  _meta?: {
+    legacyState?: {
+      status?: string;
+      progressMessage?: string;
+      progress?: number;
+      progressTotal?: number;
+      pid?: number;
+      description?: string;
+    };
+    [key: string]: unknown;
+  };
 }
 
 export interface ToolResponse {
@@ -205,6 +229,13 @@ export interface ToolResponse {
   data?: Record<string, unknown>;
   /** When true, the tool call encountered an error that will be sent to the model. */
   isError?: boolean;
+  /** UI specific metadata */
+  _meta?: {
+    legacyState?: {
+      outputFile?: string;
+    };
+    [key: string]: unknown;
+  };
 }
 
 export type ElicitationRequest = {

packages/core/src/config/config.ts

@@ -225,6 +225,7 @@ export interface GemmaModelRouterSettings {
 
 export interface ADKSettings {
   agentSessionNoninteractiveEnabled?: boolean;
+  agentSessionInteractiveEnabled?: boolean;
 }
 
 export interface ExtensionSetting {
@@ -892,6 +893,7 @@ export class Config implements McpContext, AgentLoopContext {
 
   private readonly gemmaModelRouter: GemmaModelRouterSettings;
   private readonly agentSessionNoninteractiveEnabled: boolean;
+  private readonly agentSessionInteractiveEnabled: boolean;
 
   private readonly continueOnFailedApiCall: boolean;
   private readonly retryFetchErrors: boolean;
@@ -1314,6 +1316,8 @@ export class Config implements McpContext, AgentLoopContext {
 
     this.agentSessionNoninteractiveEnabled =
       params.adk?.agentSessionNoninteractiveEnabled ?? false;
+    this.agentSessionInteractiveEnabled =
+      params.adk?.agentSessionInteractiveEnabled ?? false;
     this.retryFetchErrors = params.retryFetchErrors ?? true;
     this.maxAttempts = Math.min(
       params.maxAttempts ?? DEFAULT_MAX_ATTEMPTS,
@@ -3377,6 +3381,10 @@ export class Config implements McpContext, AgentLoopContext {
     return this.agentSessionNoninteractiveEnabled;
   }
 
+  getAgentSessionInteractiveEnabled(): boolean {
+    return this.agentSessionInteractiveEnabled;
+  }
+
   /**
    * Get override settings for a specific agent.
    * Reads from agents.overrides.<agentName>.

schemas/settings.schema.json

@@ -2775,6 +2775,13 @@
               "markdownDescription": "Enable non-interactive agent sessions.\n\n- Category: `Experimental`\n- Requires restart: `yes`\n- Default: `false`",
               "default": false,
               "type": "boolean"
+            },
+            "agentSessionInteractiveEnabled": {
+              "title": "Interactive Agent Session Enabled",
+              "description": "Enable the agent session implementation for the interactive CLI.",
+              "markdownDescription": "Enable the agent session implementation for the interactive CLI.\n\n- Category: `Experimental`\n- Requires restart: `yes`\n- Default: `false`",
+              "default": false,
+              "type": "boolean"
             }
           },
           "additionalProperties": false