Retrieval & RAG Systems
Hybrid semantic search with reranking over owned vector infrastructure — and the judgment to know when retrieval is premature.
Executive summary
Retrieval built as infrastructure, not a framework demo: pgvector on owned hardware, multilingual embeddings with cross-encoder reranking, tier-filtered results — plus documented maturity ladders that start retrieval-free on purpose.
What this capability means
RAG is the most commoditized term in AI — and the most commonly botched system. The failure mode is always the same: retrieval bolted on before the data model is right, evaluated by vibes.
Axis Bridge builds retrieval the other way around. The document store comes first (owned, backed up, access-controlled), embeddings and rerankers are replaceable components around it, and — where a corpus is still small — v1 ships retrieval-free with the upgrade path written down. That restraint is itself the capability: knowing what the next rung is, and not pretending to be on it.
Maturity ladder
- 01
Basic — Context stuffing
● demonstratedRelevant documents selected by plain SQL and packed into the prompt — deliberately chosen for v1 systems where corpus size doesn't yet justify vectors.
Query → SQL selection → Prompt context → LLM - 02
Intermediate — Hybrid semantic retrieval
● demonstratedDense embeddings plus reranking over chunked documents, with access-tier filtering and whole-document handback.
Query → BGE-M3 embedding → pgvector search → Reranker → Tier filter → Results - 03
Advanced — Evaluated, agentic retrieval
○ nextRetrieval quality measured by eval suites; agents choosing retrieval strategies and tools per query.
Query → Strategy selection → Multi-source retrieval → Eval-scored results → Agent
Evidence
- Hybrid search live behind an authenticated doorway — BGE-M3 embeddings (1024-dim) with bge-reranker-v2-m3 cross-encoder ordering, over PostgreSQL 18 + pgvector. me-inc-os-knowledge / engine (deployed on Coolify)
- Chunks inherit document privacy tiers; search finds a chunk, the doorway decides whether the whole parent document may be returned. me-inc-os-knowledge / PLAN.md §5
- A written retrieval maturity ladder for the concierge platform — retrieval-free v1 → token-budgeted window → ANN retrieval → agentic tools — chosen deliberately, not by omission. whatsapp-concierge / README "Reply (v1)"
- Knowledge packs structured for retrieval priority (numeric prefix ordering within knowledge bases). llm-knowledge-base conventions