In the AI-for-research era, GPT and friends answer math questions in Markdown. Android had no clean reader that renders all four common TeX/LaTeX math delimiter styles — so this simple app now exists.

A minimal Android markdown reader (with light editing) built for mathematicians. It renders TeX/LaTeX math correctly in all four common delimiter styles:

Inline:  $x_i$  and  \(u \in C^k\)
Display: $$...$$  and  \[ ... \]

Most Android markdown editors either render no math at all, or break on real mathematical documents: the markdown parser runs first and eats \(...\) / \[...\] backslashes (CommonMark escape rules) and mangles _-containing formulas like $\bar{\mu}_{n}$ into emphasis spans before any math renderer sees them.

MathMD extracts math segments before markdown parsing (a protection/placeholder pass), so all four delimiter styles survive intact. The pass is written in TypeScript and covered by a regression suite (including $\{x\}$, inline pairs, $W^{1,p}_0(\Omega)$, and code spans/fences that must stay literal).

• Four math delimiter styles, rendered by bundled KaTeX (fully offline)
• Edit / Preview flip toggle; configurable startup mode
• In-document search with match highlighting and next/previous navigation, working in both the editor and the rendered preview
• New blank document; open via system file picker or "Open with…" from other apps; save in place or as a copy
• Light/dark/system theme; per-pane font family and editor font size
• Fixed line width in characters (optional): the page wraps once at that column and the default zoom fits it exactly to the screen (no horizontal panning); pinch-zoom scales the whole page uniformly — zooming past the fit level enables global horizontal panning, wrap never changes. Over-wide formulas scroll horizontally under a line-pinned \tag
• No network permission usage for the preview; the WebView is asset-sandboxed
• No accounts, no telemetry, no ads

There is deliberately no currency special-casing. Every unescaped $ interacts with the math pass: two unescaped $ pair into a formula no matter what sits between them (I have $12 and he have $23 renders 12 and he have as math), and only a lone $ with no partner stays literal. All dedicated dollar signs must therefore be written escaped (\$) or inside code spans — a literal $ is never safe.

Requirements: JDK 17, Android SDK (platform 37 + build-tools 36), Node 20+.

# Preview pipeline (TypeScript → assets) + regression tests
(cd tools && npm install)
./scripts/build-preview.sh
node tools/mdtest/run.js

# Android app
gradle :app:assembleDebug     # APK: app/build/outputs/apk/debug/

• app/ — Android app (Kotlin, Jetpack Compose, Material 3)
• tools/preview-src/ — math-protection scanner + render pipeline (TypeScript)
• tools/mdtest/ — node regression harness for the preview pipeline
• docs/ — architecture decision record, research notes, signing setup
• scripts/ — esbuild bundle step, keystore generator

• KaTeX (MIT) — math rendering
• markdown-it (MIT) — markdown parsing
• Material Symbols glyph paths (Apache-2.0) — icons
• Definitely a vibe coding result: every line of this repository was written by an AI agent; the human owner designed, tested on real hardware, and directed ~15 review rounds.

MIT — see LICENSE.