feat: AI沙箱流式对话+引导学习+静态服务优化

- 后端: AI沙箱流式对话(SSE), reasoning_content 回退支持
- 前端: 沙箱页流式渲染, 引导学习面板, 默认场景/Starter兜底
- 优化: 前端改用静态文件服务器(node server.js)替代next dev, CSS永不丢失
- 修复: 通用模型默认改为可用模型, predev不再删.next缓存

backend/src/modules/admin/operations.controller.ts

@@ -107,13 +107,18 @@ export class OperationsController {
   }
 
   @Put('config/:key')
-  async updateConfig(@Param('key') key: string, @Body() body: { value: string }) {
+  async updateConfig(@Param('key') key: string, @Body() body: { value: string; description?: string; category?: string }) {
     const existing = await this.prisma.systemConfig.findUnique({ where: { key } });
     if (existing) {
-      return this.prisma.systemConfig.update({ where: { key }, data: { value: body.value } });
+      return this.prisma.systemConfig.update({ where: { key }, data: { value: body.value, ...(body.description !== undefined ? { description: body.description } : {}) } });
     }
     return this.prisma.systemConfig.create({
-      data: { key, value: body.value, category: 'other' },
+      data: { key, value: body.value, category: body.category || 'other', description: body.description || '' },
     });
   }
+
+  @Delete('config/:key')
+  async deleteConfig(@Param('key') key: string) {
+    return this.prisma.systemConfig.delete({ where: { key } });
+  }
 }

backend/src/modules/ai/ai-gateway.service.ts

@@ -21,6 +21,7 @@ export interface ModelInfo {
 interface AIProvider {
   name: string;
   chat(messages: ChatMessage[], options?: ChatOptions): Promise<string>;
+  chatStream?(messages: ChatMessage[], options?: ChatOptions): AsyncIterable<string>;
 }
 
 const MODEL_CATALOG: Record<string, ModelInfo> = {
@@ -114,6 +115,54 @@ export class AIGatewayService {
     return this.fallback(messages);
   }
 
+  async *chatStream(model: string, messages: ChatMessage[], options?: ChatOptions): AsyncIterable<string> {
+    const modelMap: Record<string, string> = {
+      'general': 'openai',
+      'openai': 'openai',
+      'gpt-3.5': 'openai',
+      'gpt-4': 'openai',
+      'longcat': 'openai',
+      'meituan/longcat-flash-lite': 'openai',
+      'deepseek-v4-flash': 'deepseek-v4-flash',
+      'sensenova-6.7-flash-lite': 'sensenova-6.7-flash-lite',
+      'sensenova-u1-fast': 'sensenova-u1-fast',
+    };
+
+    const providerKey = modelMap[model.toLowerCase()] || (model.includes('/') ? 'openai' : model);
+    const provider = this.providers.get(providerKey);
+
+    if (!this.usageStats[providerKey]) this.usageStats[providerKey] = { total: 0, success: 0, failed: 0 };
+    this.usageStats[providerKey].total++;
+
+    if (provider?.chatStream) {
+      try {
+        let hasContent = false;
+        for await (const chunk of provider.chatStream(messages, options)) {
+          hasContent = true;
+          yield chunk;
+        }
+        if (!hasContent) throw new Error('AI 返回内容为空');
+        this.usageStats[providerKey].success++;
+      } catch (err: any) {
+        this.logger.error(`${provider.name} 流式调用失败: ${err.message}`);
+        this.usageStats[providerKey].failed++;
+        yield this.fallback(messages);
+      }
+    } else if (provider) {
+      try {
+        const reply = await provider.chat(messages, options);
+        this.usageStats[providerKey].success++;
+        yield reply;
+      } catch (err: any) {
+        this.logger.error(`${provider.name} 调用失败: ${err.message}`);
+        this.usageStats[providerKey].failed++;
+        yield this.fallback(messages);
+      }
+    } else {
+      yield this.fallback(messages);
+    }
+  }
+
   private fallback(messages: ChatMessage[]): string {
     const lastMsg = typeof messages[messages.length - 1]?.content === 'string'
       ? messages[messages.length - 1]?.content as string : '';
@@ -188,6 +237,55 @@ class OpenAICompatibleProvider implements AIProvider {
     }
 
     const data = await res.json() as any;
-    return data.choices[0].message.content;
+    const msg = data.choices[0].message;
+    return msg.content || msg.reasoning_content || '';
+  }
+
+  async *chatStream(messages: ChatMessage[], options?: ChatOptions): AsyncIterable<string> {
+    const res = await fetch(this.apiUrl, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'Authorization': `Bearer ${this.apiKey}`,
+      },
+      body: JSON.stringify({
+        model: this.defaultModel,
+        messages,
+        temperature: options?.temperature ?? 0.7,
+        top_p: options?.top_p ?? 1,
+        max_tokens: options?.max_tokens ?? 2000,
+        stream: true,
+      }),
+    });
+
+    if (!res.ok) {
+      throw new Error(`${this.name} API error: ${res.status} ${await res.text()}`);
+    }
+
+    const reader = res.body!.getReader();
+    const decoder = new TextDecoder();
+    let buffer = '';
+
+    while (true) {
+      const { done, value } = await reader.read();
+      if (done) break;
+
+      buffer += decoder.decode(value, { stream: true });
+      const lines = buffer.split('\n');
+      buffer = lines.pop() || '';
+
+      for (const line of lines) {
+        const trimmed = line.trim();
+        if (!trimmed || !trimmed.startsWith('data:')) continue;
+        const data = trimmed.slice(5).trim();
+        if (data === '[DONE]') return;
+        try {
+          const json = JSON.parse(data);
+          const delta = json.choices?.[0]?.delta || {};
+          const content = delta.content || delta.reasoning_content || '';
+          if (content) yield content;
+        } catch {}
+      }
+    }
   }
 }

backend/src/modules/sandbox/sandbox.controller.ts

@@ -1,8 +1,9 @@
-import { Controller, Post, Get, Delete, Patch, Body, Param, Query, UseGuards, Req, ParseIntPipe } from '@nestjs/common';
+import { Controller, Post, Get, Delete, Patch, Body, Param, Query, UseGuards, Req, ParseIntPipe, Res } from '@nestjs/common';
 import { ApiTags, ApiBearerAuth, ApiBody } from '@nestjs/swagger';
 import { AuthGuard } from '@nestjs/passport';
 import { SandboxService } from './sandbox.service';
 import { ChatOptions } from '../ai/ai-gateway.service';
+import { Response } from 'express';
 
 @ApiTags('AI沙箱')
 @Controller('sandbox')
@@ -12,9 +13,25 @@ export class SandboxController {
   constructor(private sandboxService: SandboxService) {}
 
   @Post('chat')
-  @ApiBody({ schema: { example: { conversationId: 'uuid', model: 'general', messages: [{ role: 'user', content: 'hi' }], images: ['https://example.com/img.png'], temperature: 0.7, top_p: 1, max_tokens: 2000 } } })
-  async chat(@Req() req: any, @Body() body: { conversationId?: string; model: string; messages: { role: string; content: string }[]; images?: string[] } & ChatOptions) {
-    return this.sandboxService.chat(req.user.userId, body.conversationId, body.model, body.messages, body, body.images);
+  @ApiBody({ schema: { example: { conversationId: 'uuid', model: 'general', messages: [{ role: 'user', content: 'hi' }], images: ['https://example.com/img.png'], temperature: 0.7, top_p: 1, max_tokens: 2000, stream: false } } })
+  async chat(@Req() req: any, @Body() body: { conversationId?: string; model: string; messages: { role: string; content: string }[]; images?: string[]; stream?: boolean } & ChatOptions, @Res() res: Response) {
+    if (body.stream) {
+      res.setHeader('Content-Type', 'text/event-stream');
+      res.setHeader('Cache-Control', 'no-cache');
+      res.setHeader('Connection', 'keep-alive');
+      res.setHeader('X-Accel-Buffering', 'no');
+
+      try {
+        for await (const chunk of this.sandboxService.chatStream(req.user.userId, body.conversationId, body.model, body.messages, body, body.images)) {
+          res.write(`data: ${chunk}\n\n`);
+        }
+      } catch (err: any) {
+        res.write(`data: ${JSON.stringify({ type: 'error', message: err.message })}\n\n`);
+      }
+      res.end();
+    } else {
+      return this.sandboxService.chat(req.user.userId, body.conversationId, body.model, body.messages, body, body.images);
+    }
   }
 
   @Get('sessions')

backend/src/modules/sandbox/sandbox.service.ts

@@ -3,6 +3,14 @@ import { PrismaService } from '../../prisma/prisma.service';
 import { AIGatewayService, ChatOptions } from '../ai/ai-gateway.service';
 import { randomUUID, createHmac } from 'crypto';
 
+interface StreamResult {
+  type: 'text' | 'done' | 'error';
+  content?: string;
+  sessionId?: number;
+  conversationId?: string;
+  message?: string;
+}
+
 @Injectable()
 export class SandboxService {
   constructor(
@@ -78,6 +86,84 @@ export class SandboxService {
     return { reply, conversationId: convId, sessionId: session.id };
   }
 
+  async *chatStream(userId: number, conversationId: string | undefined, model: string, messages: { role: string; content: string }[], options?: ChatOptions, images?: string[]): AsyncGenerator<string> {
+    const user = await this.prisma.user.findUnique({ where: { id: userId } });
+    if (!user || user.status !== 'ACTIVE') {
+      yield JSON.stringify({ type: 'error', message: '用户不可用' } as StreamResult);
+      return;
+    }
+
+    const convId = conversationId || randomUUID();
+
+    const today = new Date();
+    today.setHours(0, 0, 0, 0);
+    const existing = await this.prisma.sandboxSession.findUnique({
+      where: { userId_conversationId: { userId, conversationId: convId } },
+    });
+    if (!existing) {
+      const todayCount = await this.prisma.sandboxSession.count({
+        where: { userId, createdAt: { gte: today } },
+      });
+      if (todayCount >= (user.sandboxDaily || 10)) {
+        yield JSON.stringify({ type: 'error', message: '今日沙箱使用次数已用完' } as StreamResult);
+        return;
+      }
+    }
+
+    let aiMessages = messages as any[];
+    if (images && images.length > 0) {
+      aiMessages = messages.map(m => {
+        if (m.role === 'user' && m === messages[messages.length - 1]) {
+          const parts: any[] = [{ type: 'text', text: m.content }];
+          for (const img of images) {
+            parts.push({ type: 'image_url', image_url: { url: img } });
+          }
+          return { role: m.role, content: parts };
+        }
+        return m;
+      });
+    }
+
+    let fullReply = '';
+    try {
+      for await (const chunk of this.aiGateway.chatStream(model, aiMessages, options)) {
+        fullReply += chunk;
+        yield JSON.stringify({ type: 'text', content: chunk } as StreamResult);
+      }
+    } catch (err: any) {
+      yield JSON.stringify({ type: 'error', message: err.message } as StreamResult);
+      return;
+    }
+
+    if (typeof fullReply !== 'string' || fullReply.length === 0) {
+      fullReply = '抱歉，AI 返回了无效的回复，请重试。';
+    }
+
+    const allMessages = messages.concat({ role: 'assistant', content: fullReply });
+    const firstUserMsg = messages.find(m => m.role === 'user');
+    const title = firstUserMsg ? firstUserMsg.content.slice(0, 80) : 'AI 对话';
+
+    const session = await this.prisma.sandboxSession.upsert({
+      where: { userId_conversationId: { userId, conversationId: convId } },
+      create: {
+        userId,
+        conversationId: convId,
+        model,
+        title,
+        messages: JSON.stringify(allMessages),
+        tokens: Math.ceil(fullReply.length / 2),
+      },
+      update: {
+        model,
+        title,
+        messages: JSON.stringify(allMessages),
+        tokens: Math.ceil(fullReply.length / 2),
+      },
+    });
+
+    yield JSON.stringify({ type: 'done', sessionId: session.id, conversationId: convId } as StreamResult);
+  }
+
   async getSessions(userId: number, params: { page?: number; pageSize?: number; search?: string }) {
     const page = Number(params.page ?? 1);
     const pageSize = Number(params.pageSize ?? 50);