The L2 render cache used objectId(this.#theme) as part of the key.
After setTheme(), the same Markdown instance still holds the old
theme reference (same objectId) but the closures now read a different
palette — so the cache returned pre-switch styled lines (F3).
Export clearRenderCache() from markdown.ts and call it from the
onThemeChange handler in interactive-mode.ts so all L2 entries are
dropped on every theme switch, forcing a clean re-render.
cognitive
e9d70260f4