OneMark

GitHub-identical Markdown rendering — offline, on every platform.

One engine. Six targets. No server.

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Status: pre-implementation. Scope is locked, architecture is decided, no code has been written yet. Everything below is a commitment, not a claim. See docs/02-PRD.md.

The problem

Markdown renders differently everywhere. You write GitHub Flavored Markdown, you know that dialect, and you rely on how github.com renders it — but that rendering only exists inside github.com.

Open the same .md file on your Mac and you get a different dialect, or a browser round-trip. Open it on your iPad and you get another one. Every web editor either ships the document to a server to render it, or renders a flavor that isn't GFM.

What OneMark does

Renders GFM exactly as GitHub does, entirely on your device, identically on every platform you own — and proves it with a test suite that diffs against GitHub's own renderer.

Fidelity is verified, not claimed

Level	Method	Gate
CommonMark spec suite	~650 cases	≥ 99%
GFM extension spec suite	full suite	100%
Golden corpus	100 real READMEs diffed against GitHub's POST /markdown API	≥ 98%
Reference engine	cmark-gfm (GitHub's actual C engine) as a triage oracle	diagnostic

cmark-gfm never ships. It exists only to be diffed against.

Architecture

                    ┌──────────────────────────┐
                    │   comrak  (Rust)         │   ← ONE parser, everywhere
                    │   CommonMark + GFM → AST │
                    └────────────┬─────────────┘
                                 │  AST
                    ┌────────────┴─────────────┐
                    │   OneMark renderer (TS)  │   ← Shiki · KaTeX · Mermaid
                    │   AST → sanitized HTML   │     GitHub CSS · all bundled
                    └────────────┬─────────────┘
                                 │
     ┌──────────┬────────────┬───┴────┬───────────┬──────────┐
     │   Web    │   macOS    │  Win   │   Linux   │ iOS/Andr │
     │  (WASM)  │  (native)  │(native)│  (native) │ (native) │
     └──────────┴────────────┴────────┴───────────┴──────────┘
                    all six via ONE TypeScript UI

Layer	Choice
Parser	comrak — Rust, CommonMark + GFM
Runtime	Tauri v2 — Rust shell, ~5–10 MB binaries
Editor	CodeMirror 6
Highlighting / math / diagrams	Shiki · KaTeX · Mermaid — all bundled, never CDN
Package managers	pnpm (TypeScript) + cargo (Rust)

Targets

Milestone	Platform	Storage
M1	Web	OPFS
M2	macOS	folders + security-scoped bookmarks
M3	Windows · Linux	folders
M4	iOS · iPadOS · Android	Files app / SAF

What OneMark is not

Not a note app · not a PKM tool · not a sync service · not a git client · not a publishing platform · not a plugin host · not WYSIWYG.

Full list with reasoning: docs/02-PRD.md §3.1.

Documentation

Doc	What
docs/00-README.md	Documentation index
docs/01-Brief.md	Why this exists — pain, differentiator, audience
docs/02-PRD.md	Scope, requirements, metrics, risks
docs/03-Technical-Spec.md	Interfaces, repo layout, data flow
docs/04-Build-Plan.md	Milestones, each independently shippable
docs/05-Learning-Roadmap.md	Rust · WASM · Tauri · CM6, in the order you'll need them
docs/adr/	Architecture decisions — including the rejected alternatives
HANDOFF.md	Read this first when picking the project back up

License

PolyForm Noncommercial 1.0.0 — free for noncommercial use, commercial rights reserved.