ADR-0081: Block Editor Inline Rich Text via Markdown

Status: Accepted Date: 2026-06-25 Author: @johalputt

Context

The block editor stored and rendered block text as plain, HTML-escaped strings, so there was no inline formatting at all — no bold, italic, links or inline code. Authors expected a Ghost-style writing experience.

Decision

1. Render inline Markdown (**bold**, *italic*, `code`, [links](url), ~~strike~~) for paragraph/heading/quote/callout/list text in internal/blockrender, using a dedicated goldmark instance (inlineMD, GFM strikethrough + linkify) and stripping the outer <p>.
2. The assembled fragment continues through the existing bluemonday UGC sanitiser, so the change upgrades plain-escaped text to safe rich inline HTML without widening the XSS surface (goldmark escapes raw HTML and bluemonday re-validates). Regression tests assert formatting renders and that <script>/javascript: are still stripped.
3. The editor (admin-os-editor.js) gains a selection toolbar, leading-Markdown shortcuts, continuous Enter/Backspace block flow, a filterable slash menu, and image paste / drag-and-drop upload via the existing media endpoint.

Consequences

• Positive: real rich-text authoring; block model and storage contract are unchanged; security posture preserved (sanitiser is the single trust boundary).
• Trade-off: literal */_/` in pre-existing content now render as Markdown (matches Ghost); authors escape with \* when a literal is intended.