fix: non-string toolbar button text, like JSX, crashes rendering (#7120) (now warns and falls back to the button name. use v7's iconContent for custom button content)
fix: style injection crashes when calendar is mounted in an iframe (#7301)
fix: crash when inline styles are blocked by a Content Security Policy (#7353) (now warns instead. styles must be provided another way, or upgrade to v7, which distributes plain CSS files)
fix: crash in Salesforce LWC with Lightning Web Security when querying CSP nonce (#7439)
fix: in list view, clicking event with url and custom eventContent crashes instead of navigating (#6133)
fix: batchRendering missing from CalendarApi type, e.g. for React's getApi() (#7227)

fix: event.setProp('resourceEditable', ...) ignored with a warning (#5166)
fix: React "Maximum update depth exceeded" when validRange, visibleRange or hiddenDays is a new-but-equal value each render and datesSet sets state (#7069)
fix: when slotMaxTime is beyond 24h, now-indicator disappears after midnight in timeline views, and its arrow disappears in timegrid views (#6394)
fix: eventDrop reports oldResource/newResource when an event that isn't resource-editable is dragged over another resource, even though its resource doesn't change (#4943)
fix: event time cut off by long title with eventDisplay:'block' (#6457)

feature: passing a v6 plugin to FullCalendar v7 now fails with a clear message naming the v7 import (v6 plugins carry a majorVersionError property. in TypeScript, the error replaces a cryptic one about premiumReleaseDate)
docs: READMEs and npm descriptions of the v6-only packages, like @fullcalendar/daygrid, now say they're for v6 and name their v7 replacement