Show HN: RAG Firewall – retrieval-time guardrails for LangChain/LlamaIndex

1 talbuilds 1 8/29/2025, 7:48:12 PM github.com ↗

RAG pipelines are great, but they can still retrieve "toxic" chunks: – prompt injection attempts – leaked API keys/secrets – stale or conflicting content – unapproved external URLs

We built an open-source "retrieval firewall" that scans chunks before they reach the LLM: – denies injection & secrets – flags/reranks PII, encoded blobs, untrusted URLs – audit log (JSONL) of all decisions – drop-in wrappers for LangChain and LlamaIndex retrievers

Install: pip install rag-firewall Repo: https://github.com/taladari/rag-firewall

Curious if others here handle retrieval-time risks, or just ingest/output filtering. Would love feedback and red-team payloads.

Comments (1)

talbuilds · 1h ago

A couple of extra notes I didn’t fit in the main post:

– The firewall runs entirely client-side, so no data ever leaves your environment.

– It focuses on *retrieval-time* risks, not output moderation — so the LLM never sees poisoned chunks in the first place.

– Policies are YAML: you can choose to deny, allow, or just re-rank risky docs (based on recency, provenance, relevance).

– Overhead is low: scanners are regex/heuristic, so for ~5–20 chunks it adds only a few ms.

I’d love feedback on two things in particular:

1. Do you think retrieval-time filtering belongs in the pipeline, or should it all be done at ingest/output?

2. If you’ve got prompt injection payloads or edge cases you use to test your own RAG stacks, I’d love to try them against this.

Thanks for taking a look — always happy to hear critique, especially from folks running LangChain/LlamaIndex in production.