In the past, we have made several non-breaking and minor backward-compatible changes. In some cases, we have even bumped version numbers without affecting clients.

But, so far, we haven't had to address breaking changes to the HTML output. The immediate impetus for this is the upcoming data-mw split for Parsoid HTML. But, there are other changes on the horizon. <section> tags for one, and other wrapper tags in the future. Maybe changes based on multimedia support, or changes to templating, etc.

We have had email and IRC discussions about how best to deal with breaking changes to the Parsoid HTML format. This is a meta-ticket to:

• finish up the draft proposal
• communicate it on wikitech-l to get feedback
• finalize the process