GraphRAG Routing in .NET: Safe Fallback Between Classic RAG and LangGraph

Introduction

Agentic retrieval is powerful, but production reliability still wins over novelty. BlueRobin added a routing layer so GraphRAG can be enabled safely while preserving a deterministic fallback path to the existing .NET RAG pipeline.

What Changed in the Codebase

• 35a98e7: GraphRAG Python service introduced with LangGraph + hybrid retrieval nodes.
• 1bc3d89: CI updated so GraphRAG is built and shipped in shared service pipelines.
• Application routing added in src/Archives.Application/Services/GraphRagRoutingService.cs.

Routing Pattern

The production pattern is simple:

1. Check GraphRAG feature flag and health.
2. Route query to GraphRAG when healthy.
3. Fall back to classic RAG when unavailable or timed out.
4. Emit telemetry for route decisions.

This keeps rollout risk low while collecting real traffic signals.

Why This Matters

• You can launch agentic features without a full migration freeze.
• Incidents stay contained because fallback behavior is explicit.
• Teams get measurable adoption before hard-cutting to new pipelines.

Conclusion

GraphRAG adoption should be incremental, not all-or-nothing. A health-aware router creates the safety rail needed to evolve toward agentic systems in production.

Related reading:

• /semantic-kernel-agents-orchestration/
• /improving-rag-query-quality-and-relevance/