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MemX, a local-first long-term memory system for AI assistants, is introduced, emphasizing stability-oriented retrieval using vector recall, keyword recall, Reciprocal Rank Fusion (RRF), and a four-factor re-ranking. Evaluation on Chinese-language benchmarks demonstrates high retrieval accuracy (Hit@1=91.3% to 100%), while LongMemEval reveals strong performance at fact-level granularity (Hit@5=51.6%) but challenges with temporal and multi-session reasoning. Full-text indexing significantly reduces keyword search latency, achieving sub-90ms end-to-end search times at scale.
Achieve 91%+ Hit@1 retrieval accuracy in a local-first long-term memory system for AI assistants by combining vector recall, keyword recall, RRF, and re-ranking, while maintaining sub-90ms search latency at scale.
We present MemX, a local-first long-term memory system for AI assistants with stability-oriented retrieval design. MemX is implemented in Rust on top of libSQL and an OpenAI-compatible embedding API, providing persistent, searchable, and explainable memory for conversational agents. Its retrieval pipeline applies vector recall, keyword recall, Reciprocal Rank Fusion (RRF), four-factor re-ranking, and a low-confidence rejection rule that suppresses spurious recalls when no answer exists in the memory store. We evaluate MemX on two axes. First, two custom Chinese-language benchmark suites (43 queries,<=1,014 records) validate pipeline design: Hit@1=91.3% on a default scenario and 100% under high confusion, with conservative miss-query suppression. Second, the LongMemEval benchmark (500 queries, up to 220,349 records) quantifies system boundaries across four ability types and three storage granularities. At fact-level granularity the system reaches Hit@5=51.6% and MRR=0.380, doubling session-level performance, while temporal and multi-session reasoning remain challenging (<=43.6% Hit@5). FTS5 full-text indexing reduces keyword search latency by 1,100x at 100k-record scale, keeping end-to-end search under 90 ms. Unlike Mem0 and related work that targets end-to-end agent benchmarks, MemX focuses on a narrower, reproducible baseline: local-first deployment, structural simplicity, explainable retrieval, and stability-oriented design.
