Wei Chen
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TECHNICAL WRITING

Learning in the open.

Notes on building reliable AI systems and the engineering decisions behind them.

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RAGEvaluation

Evaluate RAG at the Retrieval Boundary

Separate missing evidence from unsupported answers using relevance labels, retrieval metrics, and a small, reviewable evaluation set.

· ~2 min read
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RetrievalSearch Engineering

Hybrid Search: Give Exact Matches and Meaning a Vote

Why lexical retrieval still matters, how reciprocal rank fusion combines results, and what to measure before adding a reranker.

· ~2 min read
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LLMsContext Engineering

A Larger Context Window Is Not an Evidence Strategy

What long-context research tells us about evidence placement, and how to budget context without turning every request into a document dump.

· ~2 min read
Eyeglasses in front of computer screens displaying source code
AI AgentsBackend Engineering

Tool-Calling Agents Need Explicit Execution Boundaries

Design tools as contracts: validate arguments, enforce authorization, bound retries, and inspect outcomes outside the language model.

· ~2 min read