setup RAG (#6146)

engine/config/.env.example

@@ -8,6 +8,24 @@ STIRLING_FAST_MODEL=anthropic:claude-haiku-4-5
 STIRLING_SMART_MODEL_MAX_TOKENS=8192
 STIRLING_FAST_MODEL_MAX_TOKENS=2048
 
+# RAG Configuration — retrieval-augmented generation is always on.
+# Embedding provider credentials are handled natively (e.g. VOYAGE_API_KEY for VoyageAI).
+STIRLING_RAG_EMBEDDING_MODEL=voyageai:voyage-4
+
+# Vector store backend: "sqlite" (embedded) or "pgvector" (external Postgres).
+STIRLING_RAG_BACKEND=sqlite
+
+# Path to the sqlite-vec database file (used when backend=sqlite).
+STIRLING_RAG_STORE_PATH=data/rag.db
+
+# Postgres DSN for pgvector (used when backend=pgvector). Leave empty when backend=sqlite.
+# Example: postgresql://user:password@host:5432/dbname
+STIRLING_RAG_PGVECTOR_DSN=
+
+STIRLING_RAG_CHUNK_SIZE=512
+STIRLING_RAG_CHUNK_OVERLAP=64
+STIRLING_RAG_TOP_K=5
+
 # PostHog analytics. Set STIRLING_POSTHOG_ENABLED=true and provide an API key to enable.
 STIRLING_POSTHOG_ENABLED=false
 STIRLING_POSTHOG_API_KEY=phc_VOdeYnlevc2T63m3myFGjeBlRcIusRgmhfx6XL5a1iz