Shared Preview

The default preview is same-tab iframe preview with postMessage. Detached tabs, shared stakeholder URLs, and multi-user preview require a realtime transport in addition to the same message contract.

Shared preview should preserve the same architecture:

• The admin FormView remains authoritative.
• The iframe or detached preview is a mirror.
• Save, autosave, Cmd+S, workflow transitions, locks, history, and actions stay in the existing form lifecycle.
• Realtime carries the same snapshot, patch, commit, focus, block, and resync concepts used by same-tab preview.

When Realtime Helps

Use realtime transport when:

• the preview opens in a separate browser tab or monitor
• a stakeholder opens a shared preview URL
• multiple preview clients should follow one editor session
• a physical mobile device should mirror the editor session

For normal split-screen editing, same-tab postMessage is simpler and lower latency.

Transport Model

Rendering diagram...

The channel should be scoped by collection, record, locale, and active preview session. Messages must still be session-bound and validated before applying any edit request to the form.

Publication Reads

Shared preview must not make draft data public by default. Public routes read stage: "published" when workflow controls publishing. Preview routes read the working stage only when the request is authorized through the preview token or equivalent session-bound preview mechanism.