diff --git a/src/modules/ai-runtime/ai-runtime.module.ts b/src/modules/ai-runtime/ai-runtime.module.ts
index 18255bc..c0f8ce9 100644
--- a/src/modules/ai-runtime/ai-runtime.module.ts
+++ b/src/modules/ai-runtime/ai-runtime.module.ts
@@ -6,11 +6,12 @@ import { UserAiService } from './user-ai.service';
 import { CredentialEncryptionService } from './credential-encryption.service';
 import { RuntimeInternalController } from './internal/runtime-internal.controller';
 import { RuntimeInternalService } from './internal/runtime-internal.service';
+import { UserAiQuotaService } from './user-ai-quota.service';
 
 @Module({
   imports: [ConfigModule, PrismaModule],
   controllers: [UserAiController, RuntimeInternalController],
-  providers: [UserAiService, CredentialEncryptionService, RuntimeInternalService],
-  exports: [UserAiService, CredentialEncryptionService, RuntimeInternalService],
+  providers: [UserAiService, CredentialEncryptionService, RuntimeInternalService, UserAiQuotaService],
+  exports: [UserAiService, CredentialEncryptionService, RuntimeInternalService, UserAiQuotaService],
 })
 export class AiRuntimeModule {}
diff --git a/src/modules/ai-runtime/user-ai-quota.service.ts b/src/modules/ai-runtime/user-ai-quota.service.ts
new file mode 100644
index 0000000..f2287df
--- /dev/null
+++ b/src/modules/ai-runtime/user-ai-quota.service.ts
@@ -0,0 +1,97 @@
+import { Injectable, BadRequestException } from '@nestjs/common';
+import { PrismaService } from '../../infrastructure/database/prisma.service';
+
+@Injectable()
+export class UserAiQuotaService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  /** Get today's date truncated to midnight UTC */
+  private today(): Date {
+    const d = new Date();
+    return new Date(Date.UTC(d.getFullYear(), d.getMonth(), d.getDate()));
+  }
+
+  /** Check if user can create a new AI job, throw if over limit */
+  async checkAndReserve(userId: string, apiKeyMode: string): Promise<void> {
+    const settings = await this.prisma.userAiSettings.findUnique({ where: { userId } });
+    const maxJobs = settings?.maxDailyAiJobs ?? 20;
+    const maxTokens = settings?.maxDailyTokenBudget ?? 100_000;
+
+    const localDate = this.today();
+
+    const usage = await this.prisma.userAiUsageDaily.findUnique({
+      where: { userId_localDate_apiKeyMode: { userId, localDate, apiKeyMode } },
+    });
+
+    const jobCount = usage?.jobCount ?? 0;
+    const totalTokens = usage?.totalTokens ?? 0;
+
+    if (jobCount >= maxJobs) {
+      throw new BadRequestException({
+        errorCode: 'DAILY_JOB_LIMIT_EXCEEDED',
+        message: `Daily AI job limit (${maxJobs}) exceeded. Current: ${jobCount}`,
+      });
+    }
+
+    if (totalTokens >= maxTokens) {
+      throw new BadRequestException({
+        errorCode: 'DAILY_TOKEN_BUDGET_EXCEEDED',
+        message: `Daily token budget (${maxTokens}) exceeded. Current: ${totalTokens}`,
+      });
+    }
+  }
+
+  /** Increment job count (called on job creation) */
+  async incrementJobCount(userId: string, apiKeyMode: string): Promise<void> {
+    const localDate = this.today();
+    await this.prisma.userAiUsageDaily.upsert({
+      where: { userId_localDate_apiKeyMode: { userId, localDate, apiKeyMode } },
+      create: { userId, localDate, apiKeyMode, jobCount: 1 },
+      update: { jobCount: { increment: 1 } },
+    });
+  }
+
+  /** Record token consumption from invocation log (called after Runtime call) */
+  async recordTokenUsage(
+    userId: string,
+    apiKeyMode: string,
+    inputTokens: number,
+    outputTokens: number,
+    totalTokens: number,
+    costEstimate?: number,
+  ): Promise<void> {
+    const localDate = this.today();
+    await this.prisma.userAiUsageDaily.upsert({
+      where: { userId_localDate_apiKeyMode: { userId, localDate, apiKeyMode } },
+      create: {
+        userId, localDate, apiKeyMode,
+        inputTokens, outputTokens, totalTokens,
+        costEstimate: costEstimate ?? 0,
+        jobCount: 0,
+      },
+      update: {
+        inputTokens: { increment: inputTokens },
+        outputTokens: { increment: outputTokens },
+        totalTokens: { increment: totalTokens },
+        costEstimate: { increment: costEstimate ?? 0 },
+      },
+    });
+  }
+
+  /** Get today's usage summary for a user */
+  async getUsage(userId: string) {
+    const localDate = this.today();
+    const [platform, userKey] = await Promise.all([
+      this.prisma.userAiUsageDaily.findUnique({
+        where: { userId_localDate_apiKeyMode: { userId, localDate, apiKeyMode: 'platform_key' } },
+      }),
+      this.prisma.userAiUsageDaily.findUnique({
+        where: { userId_localDate_apiKeyMode: { userId, localDate, apiKeyMode: 'user_deepseek_key' } },
+      }),
+    ]);
+    return {
+      platformKey: platform ?? { jobCount: 0, totalTokens: 0 },
+      userDeepseekKey: userKey ?? { jobCount: 0, totalTokens: 0 },
+    };
+  }
+}