Recommended Open-source stack

Open-source stack
Layer 
 
 
 Recommended Options 
 
 
 
 
 LLMs 
 
 
 LLaMA 4, Qwen 3, Mixtral, DeepSeek 
 
 
 
 
 Fast Inference 
 
 
 Groq, vLLM, Ollama 
 
 
 
 
 Agent Framework 
 
 
 LlamaIndex 
 
 
 
 
 Workflow Engine 
 
 
 LlamaIndex Workflows 
 
 
 
 
 API Layer 
 
 
 FastAPI 
 
 
 
 
 Vector DB 
 
 
 Qdrant, Chroma 
 
 
 
 
 Graph DB 
 
 
 Neo4j, Memgraph 
 
 
 
 
 SQL DB 
 
 
 PostgreSQL 
 
 
 
 
 Policy Engine 
 
 
 OPA (Open Policy Agent) / Cedar 
 
 
 
 
 Observability 
 
 
 Langfuse / OpenTelemetry 
 
 
 
 
 Queueing 
 
 
 Redis / Kafka 
 
 
 
 
 Automation 
 
 
 N8N 
 
 
 
 
 Auth 
 
 
 OAuth2 / Keycloak 
 
 
 
 
 Tool interoperability  
 
 
 MCP (Model Context Protocol) — now under the Agentic AI Foundation / Linux Foundation 
 
 
 
 
 Agent memory  
 
 
 Mem0, Zep, or a self-hosted tiered store (working / episodic / semantic) 
 
 
 
 
 
 NEW IN 2026  
 Anthropic donated MCP to the newly formed Agentic AI Foundation under the Linux Foundation in December 2025, with OpenAI and Block as co-founders and AWS, Google, Microsoft, Cloudflare, GitHub, and Bloomberg as supporting members. It is now a vendor-neutral standard rather than a single-vendor protocol, which is why it belongs in the stack table above rather than only in the tool layer section. 
  

Recommended Winning Stack (2026)
Layer 
 
 
 Choice 
 
 
 
 
 API 
 
 
 FastAPI 
 
 
 
 
 Agent Framework 
 
 
 LlamaIndex 
 
 
 
 
 Workflow 
 
 
 LlamaIndex Workflows 
 
 
 
 
 Tool Interoperability 
 
 
 MCP (2026-07-28 spec, stateless) 
 
 
 
 
 Vector Memory 
 
 
 ChromaDB 
 
 
 
 
 Graph Memory 
 
 
 Neo4j 
 
 
 
 
 Agent Memory Layer 
 
 
 Mem0 / Zep (tiered, benchmarked) 
 
 
 
 
 SQL 
 
 
 PostgreSQL 
 
 
 
 
 Models 
 
 
 Groq / vLLM served OSS models 
 
 
 
 
 Policies 
 
 
 OPA 
 
 
 
 
 Observability 
 
 
 Langfuse + OpenTelemetry 
 
 
 
 
 Queue 
 
 
 Redis 
 
 
 
 
 Automation 
 
 
 N8N