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Engineering notes.

Public writing on building LLM products — applied AI, retrieval, evaluation, and the systems that keep them reliable in production.

  1. 2026-05-02

    How AI answer engines actually resolve your @graph

    ChatGPT, Perplexity, Claude, Gemini, and Google AI Overviews each parse JSON-LD differently. The deltas matter. Here's what I've measured running the same @graph through all five.

    read
  2. 2026-05-02

    10 JSON-LD bugs I find in every commerce audit (and what they cost)

    Field-level JSON-LD bugs that fail silently across 45K+ PDP catalogs. Each one mapped to the rich result it kills, the AI engine that drops you, and the dollar cost I model for clients.

    read
  3. 2026-05-02

    Schema decays. Here's the half-life I've measured.

    Production schema goes invisible to AI engines on its own, with no obvious failure. Here's the regression timeline I've measured across client engagements, and why CI gates aren't optional.

    read
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smlee.dev

AI Product Engineer — applied AI & full-stack. I build LLM products from idea to production, plus the reliability layer that makes them hold up.

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© 2026 Sangmin Lee · US East Coast / Remote

// AI Product Engineer · applied AI & full-stack · LLM products 0→1 · since 1996