Editor Spec: Date MDX And Media/Embed Gaps

Goal

Run the editor-spec workflow for the markdown-adjacent feature gaps currently listed in docs/editor-behavior/markdown-parity-matrix.md:

• date MDX expansion beyond current behavior
• media/embed expansion beyond current behavior

Decide whether current evidence is already sufficient to tighten law/protocol for these deferred rows, or whether they should stay deferred with sharper boundaries.

Scope

• current editor-behavior law
• compiled research relevant to date, media, embed, and markdown-adjacent authoring
• current package/demo/test surfaces for date and media/embed
• minimal honest doc updates across standards/spec/protocol/parity/audit

Phases

Phase	Status	Notes
Load required editor-spec stack	in_progress	README, standards, spec, protocol, parity, audit, research, solutions
Inspect current date/media/embed repo surfaces	pending	package/test/demo grounding
Decide authority + node model + permanent home	pending	evidence vs gap
Patch docs if evidence is sufficient	pending	smallest honest stack changes
Verify cross-doc consistency	pending	terminology, links, contradictions

Findings

• Current Date, Media embed, and Image / file / audio / video blocks are already locked current contracts in the parity matrix; the vague gap row was about expansion beyond those contracts, not missing baseline law.
• Date already has real current evidence for:
  • inline void atom model
  • insert/delete boundary behavior
  • plain <date>value</date> MDX round-trip
• Date does not have strong enough evidence to lock richer MDX payloads, attribute-bearing date tags, display-vs-value splits, or calendar/localized UI semantics as editor-behavior law.
• Media already has real current evidence for:
  • url-centric MDX round-trip for file/audio/video/embed nodes
  • supported MDX attribute preservation
  • embed-url / iframe normalization
  • placeholder-to-media replacement with upload-history rewriting
• Media does not yet have strong enough cross-reference evidence to lock richer provider metadata, richer source-entry behavior, or broader embed chrome as stable editor-behavior law.
• No standards winner-map change was justified.
• No audit-history patch was justified; this was a law/protocol/parity cleanup, not a new external-reference disagreement.

Progress Log

• 2026-04-09: Started editor-spec pass for the two markdown-adjacent deferred feature gaps.
• 2026-04-09: Read the required editor-spec stack, research command docs, and the current date/media/embed package and docs surfaces.
• 2026-04-09: Tightened readable law for current-vs-deferred date MDX and media/embed behavior.
• 2026-04-09: Added missing protocol coverage for current date MDX round-trip and current media embed/upload flows, plus explicit deferred rows for richer expansion.
• 2026-04-09: Narrowed the parity-matrix feature-gap wording so it names the actual remaining deferred contracts instead of one vague bucket.