How will this process work?
There are three key parts:
Firefox and platform developers should take add-on compatibility into account with any changes they make. Add-on compatibility will be included in the criteria for changes being promoted to Aurora and Beta channels. Its especially important to minimize breaking changes for Firefox 5 & 6 when the Add-on SDK is not yet stable. Once released this summer, the Add-on SDK will be an excellent alternative to dealing with compatibility.
Before any compatibility-breaking changes land, Firefox developers should follow a standardized compatibility notification process with a description of the change, the reasons for the change, and patterns we can look for in add-ons to identify those affected. This will be used to update documentation, make blog posts, and add the patterns to the AMO compatibility scanner.
The day before we branch for Aurora, AMOs compatibility scanner will be run on the latest versions of all add-ons compatible with the most recent release. Any add-ons flagged as potentially incompatible or that use binary components will not have their compatibility bumped and the authors will receive an email with the identified problems. After testing and fixing any problems, the author can then manually set compatibility and rejoin the automatic process for future releases. Add-ons that have not been flagged will have their compatibility bumped to the new version.