fix(tui): enable tool access in fullscreen mode via NativeAgent

Fullscreen TUI was calling modelClient directly, bypassing the NativeAgent
tool loop entirely. Pass the agent through FullscreenTuiConfig → App and
use agent.process() for message handling, which enables the full tool
registry and executor.

src/cli/tui.ts

@@ -216,6 +216,7 @@ export function registerTuiCommand(program: Command): void {
           modelRouter,
           systemPrompt,
           model: config.models.default.model,
+          agent,
           onExit: cleanup,
         });
       } else {
@@ -259,6 +260,7 @@ export function registerTuiCommand(program: Command): void {
             modelRouter,
             systemPrompt,
             model: config.models.default.model,
+            agent,
             onExit: cleanup,
           });
           return;

src/frontends/tui/components/App.tsx

@@ -7,6 +7,7 @@ import { parseCommand, getHelpText, resolveModelAlias, getCommandCompletions } f
 import type { Message, ModelClient, TokenUsage } from '../../../models/types.js';
 import type { ModelRouter } from '../../../models/router.js';
 import type { ManagedSession } from '../../../session/index.js';
+import type { NativeAgent } from '../../../backends/native/agent.js';
 
 export interface AppProps {
   session: ManagedSession;
@@ -14,6 +15,7 @@ export interface AppProps {
   modelRouter?: ModelRouter;
   systemPrompt: string;
   model: string;
+  agent?: NativeAgent;
   onExit?: () => void;
 }
 
@@ -23,6 +25,7 @@ export function App({
   modelRouter,
   systemPrompt,
   model,
+  agent,
   onExit,
 }: AppProps): React.ReactElement {
   const { exit } = useApp();
@@ -156,19 +159,33 @@ export function App({
 
     if (command.type !== 'message' || isStreaming) return;
 
-    // Add user message
+    // Add user message to UI (and session if no agent — agent adds it internally)
     const userMessage: Message = { role: 'user', content: command.content };
-    const messageWithTimestamp = session.addMessage(userMessage);
-    setMessages(prev => [...prev, messageWithTimestamp]);
+    if (!agent) {
+      const messageWithTimestamp = session.addMessage(userMessage);
+      setMessages(prev => [...prev, messageWithTimestamp]);
+    } else {
+      setMessages(prev => [...prev, { ...userMessage, timestamp: Date.now() }]);
+    }
     setScrollOffset(0); // Auto-scroll to bottom
 
-    // Stream response
+    // Process response
     setIsStreaming(true);
     setStreamingContent('');
     abortRef.current = false;
 
     try {
-      if (modelClient.chatStream) {
+      if (agent) {
+        // agent.process() handles session history internally
+        const response = await agent.process(command.content);
+
+        const usage = agent.getUsage();
+        setTokenUsage({ inputTokens: usage.inputTokens, outputTokens: usage.outputTokens });
+
+        // Sync UI with session history (agent already added messages to session)
+        setMessages(session.getHistory());
+      } else if (modelClient.chatStream) {
+        // Fallback: direct streaming without tools
         let fullContent = '';
 
         for await (const event of modelClient.chatStream({
@@ -199,7 +216,7 @@ export function App({
         const assistantWithTimestamp = session.addMessage(assistantMessage);
         setMessages(prev => [...prev, assistantWithTimestamp]);
       } else {
-        // Fallback to non-streaming
+        // Fallback: non-streaming without tools
         const response = await modelClient.chat({
           messages: session.getHistory(),
           system: systemPrompt,
@@ -225,7 +242,7 @@ export function App({
       setIsStreaming(false);
       setStreamingContent('');
     }
-  }, [isStreaming, session, modelClient, modelRouter, systemPrompt, exit, onExit, messages.length, tokenUsage]);
+  }, [isStreaming, session, agent, modelClient, modelRouter, systemPrompt, exit, onExit, messages.length, tokenUsage]);
 
   return (
     <Box flexDirection="column" height="100%">

src/frontends/tui/fullscreen.ts

@@ -4,6 +4,7 @@ import { App } from './components/index.js';
 import type { ManagedSession } from '../../session/index.js';
 import type { ModelClient } from '../../models/types.js';
 import type { ModelRouter } from '../../models/router.js';
+import type { NativeAgent } from '../../backends/native/agent.js';
 
 export interface FullscreenTuiConfig {
   session: ManagedSession;
@@ -11,6 +12,7 @@ export interface FullscreenTuiConfig {
   modelRouter?: ModelRouter;
   systemPrompt: string;
   model: string;
+  agent?: NativeAgent;
   onExit?: () => void;
 }
 
@@ -27,6 +29,7 @@ export async function startFullscreenTui(config: FullscreenTuiConfig): Promise<v
       modelRouter: config.modelRouter,
       systemPrompt: config.systemPrompt,
       model: config.model,
+      agent: config.agent,
       onExit: config.onExit,
     })
   );