After the chill stereo bus rebuild, --stems <dir> writes each engine bus (bass / pad / lead-drums / sfx / extras / ambient) as its own 24-bit/48k stereo WAV, before the global-story filter and master chain — clean multitrack stems that sum roughly back to the pre-master mix. Chill-only and flag-gated, so trancenwaltz stays byte-identical when the flag is absent. Used to cut the trancepenta stem package. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>