Building Real AI Features in SaaS: Context, Streaming, Tool Use, and Cost Control

Most AI features in SaaS products are shallow: a text box that calls an API and displays the result. Real AI integration means the model has context about your user, can take actions in your system, and produces outputs that persist. Here's how to build that. The Context Problem An AI feature without user context is a generic chatbot. The difference between ChatGPT and a useful AI assistant in your product is the context you provide: // Bad -- no context const response = await anthropic.messages.create({ model: 'claude-sonnet-4-6', messages: [{ role: 'user', content: userMessage }], }) // Good -- rich context const user = await db.user.findUnique({ where: { id: session.userId }, include: { subscription: true, recentActivity: { take: 10 } }, }) const systemPrompt = [ `You are an AI assistant for ${user.name}'s account.`, `Their current plan: ${user.subscription.plan}`, `Recent activity: ${JSON.stringify(user.recentActivity)}`, `Today: ${new Date().toISOString()}`, ].join(' ') const resp