Incremental Markdown Parser for LLM Streams

AI chat UIs re-parse entire markdown documents on each token arrival, causing performance lag. This is a lightweight parser that processes streaming markdown incrementally, only updating changed portions. Target: developers building AI chat interfaces and LLM applications.

LLM chat interfaces are now a commodity feature across SaaS products, and the rendering performance problem is real and widely reported — teams shipping chat UIs on top of GPT-4o or Claude frequently complain about jank during streaming, especially with long responses containing code blocks or tables. No clear incumbent owns this specific niche; most developers either tolerate the full-reparse cost or hack together brittle diffing on top of libraries like `marked` or `remark`. The $1k–5k/mo band is plausible as an open-source library with a paid hosted component or commercial license, though it's a stretch — this is the kind of utility most teams will either build themselves in a weekend or expect to find free on npm, which is also the core risk: the ceiling on willingness to pay for a parsing primitive is very low, and a single well-maintained open-source release from a motivated contributor could make a commercial version irrelevant overnight.