Key Takeaways
Most SaaS AI agents don't need a vector database — file-based memory plus 1M-token context windows plus tool calls handle the typical case
Anthropic's official "key primitive for just-in-time context retrieval" is filesystem-based, not vector-based
Claude Code's pattern — an index file (MEMORY.md) plus per-topic markdown files loaded on demand — works for production SaaS agents too
RAG still wins for large unstructured corpora, regulated multi-tenant data, and frequently-refreshed external knowledge — most SaaS use cases don't fit those criteria
