Companion to saas_template_playbook.md . That file covers everything every SaaS needs. This file covers what changes — and what's new — when AI is core to the product. Practical-first. Code snippets, decision tables, real defaults, no buzzwords. If a section doesn't help you ship next week, it doesn't belong here. 📋 Table of Contents ⚡ The Shift in 60 Seconds 🎯 Pick One: AI-Native vs AI-Augmented 🚪 2.5 Two Starting Points: Greenfield vs Retrofit 🏗️ Reference Architecture 🤖 Agents as First-Class Actors 🔌 The LLM Gateway (Provider Abstraction) 📝 Prompts as Code 🛠️ Tools, Function Calling & MCP 🧠 Memory & RAG (the practical version) 📐 Structured Outputs 💧 Streaming UX 💵 Cost Control, Budgets & Model Routing 🧾 Outcome-Based & Metered Pricing — the implementation ✅ Evals — how to actually test agents 🔭 Observability for Agents ⚡ Caching (Prompt + Semantic) 🛡️ Safety, Abuse & PII 🙋 Human-in-the-Loop & Autonomy Levels ⏳ Long-Running Agent Jobs 🏢 AI-Specific Multi-Tenancy…