From f722cf2bf0720ca170a655d78ad0e14e022d0ff5 Mon Sep 17 00:00:00 2001
From: William Valentin <william.valentin.info@gmail.com>
Date: Thu, 5 Feb 2026 13:36:36 -0800
Subject: [PATCH] feat: add /backend command handler to MinimalTui

---
 src/frontends/tui/minimal.test.ts | 46 ++++++++++++++++++++-
 src/frontends/tui/minimal.ts      | 68 +++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/src/frontends/tui/minimal.test.ts b/src/frontends/tui/minimal.test.ts
index 33d8980..ecdfe89 100644
--- a/src/frontends/tui/minimal.test.ts
+++ b/src/frontends/tui/minimal.test.ts
@@ -1,5 +1,7 @@
-import { describe, it, expect } from 'vitest';
+import { describe, it, expect, vi } from 'vitest';
 import { formatPrompt, parseCommand } from './minimal.js';
+import type { ModelConfig } from '../../config/schema.js';
+import { MinimalTui } from './minimal.js';
 
 describe('formatPrompt', () => {
   it('formats default prompt', () => {
@@ -34,3 +36,45 @@ describe('parseCommand (re-exported)', () => {
     expect(result).toBeNull();
   });
 });
+
+describe('MinimalTui backend command', () => {
+  it('switches local backend when provider is configured', async () => {
+    const mockSession = {
+      id: 'test',
+      getHistory: () => [],
+      addMessage: vi.fn(),
+      clear: vi.fn(),
+    };
+
+    const mockRouter = {
+      getTier: () => 'default' as const,
+      getAvailableTiers: () => ['default', 'local'],
+      setTier: vi.fn(() => true),
+      getLocalProviderName: () => 'ollama',
+      setLocalClient: vi.fn(),
+      chat: vi.fn(),
+      getClient: vi.fn(),
+    };
+
+    const localProviders: Record<string, ModelConfig> = {
+      llamacpp: {
+        provider: 'llamacpp',
+        model: '',
+        endpoint: 'http://localhost:8080',
+      },
+    };
+
+    const tui = new MinimalTui({
+      session: mockSession as any,
+      modelClient: mockRouter as any,
+      modelRouter: mockRouter as any,
+      systemPrompt: 'test',
+      localProviders,
+    });
+
+    // Access private method for testing
+    await (tui as any).handleBackendCommand('llamacpp');
+
+    expect(mockRouter.setLocalClient).toHaveBeenCalled();
+  });
+});
diff --git a/src/frontends/tui/minimal.ts b/src/frontends/tui/minimal.ts
index 48576cf..be3626f 100644
--- a/src/frontends/tui/minimal.ts
+++ b/src/frontends/tui/minimal.ts
@@ -4,6 +4,8 @@ import type { ModelClient, TokenUsage } from '../../models/types.js';
 import type { ModelRouter, ModelTier } from '../../models/router.js';
 import { parseCommand, getHelpText, resolveModelAlias, type Command } from './commands.js';
 import { renderMarkdown } from './markdown.js';
+import type { ModelConfig } from '../../config/schema.js';
+import { OllamaClient, LlamaCppClient } from '../../models/index.js';
 
 export { parseCommand, type Command };
 
@@ -21,6 +23,8 @@ export interface MinimalTuiConfig {
   systemPrompt: string;
   onFullscreen?: () => void;
   onTransfer?: (target: string) => void;
+  localProviders?: Record<string, ModelConfig>;
+  currentLocalProvider?: string;
 }
 
 export class MinimalTui {
@@ -96,6 +100,10 @@ export class MinimalTui {
         this.handleModelCommand(command.name);
         break;
 
+      case 'backend':
+        this.handleBackendCommand(command.provider);
+        break;
+
       case 'transfer':
         this.config.onTransfer?.(command.target);
         break;
@@ -129,6 +137,66 @@ export class MinimalTui {
     }
   }
 
+  private handleBackendCommand(provider?: string): void {
+    const router = this.config.modelRouter;
+    if (!router) {
+      console.log('Backend switching not available.\n');
+      return;
+    }
+
+    if (!provider) {
+      const current = router.getLocalProviderName() ?? this.config.currentLocalProvider ?? 'unknown';
+      const available = this.getAvailableBackends();
+      console.log(`Current local backend: ${current}`);
+      console.log(`Available: ${available.join(', ')}\n`);
+      return;
+    }
+
+    const providerConfig = this.config.localProviders?.[provider];
+    if (!providerConfig) {
+      const available = this.getAvailableBackends();
+      console.log(`Backend '${provider}' not configured.`);
+      console.log(`Available: ${available.join(', ')}\n`);
+      return;
+    }
+
+    const client = this.createLocalClient(providerConfig);
+    if (!client) {
+      console.log(`Failed to create client for '${provider}'.\n`);
+      return;
+    }
+
+    router.setLocalClient(client, provider);
+    console.log(`Switched to backend: ${provider}\n`);
+  }
+
+  private getAvailableBackends(): string[] {
+    const backends: string[] = [];
+    if (this.config.currentLocalProvider) {
+      backends.push(this.config.currentLocalProvider);
+    }
+    if (this.config.localProviders) {
+      backends.push(...Object.keys(this.config.localProviders));
+    }
+    return [...new Set(backends)];
+  }
+
+  private createLocalClient(config: ModelConfig): ModelClient | null {
+    if (config.provider === 'ollama') {
+      return new OllamaClient({
+        model: config.model,
+        host: config.endpoint,
+      });
+    }
+    if (config.provider === 'llamacpp') {
+      return new LlamaCppClient({
+        endpoint: config.endpoint ?? 'http://localhost:8080',
+        authToken: config.auth_token,
+      });
+    }
+    return null;
+  }
+
   private printStatus(): void {
     console.log(`Session: ${this.config.session.id}`);
     console.log(`Messages: ${this.config.session.getHistory().length}`);