Two runs per arm, about 81,000 frames each, order A B C C B A:
A step 1 as is 0.90% late, 20.1 per 10k two+ refreshes late
B switch_interval_ms 1 0.78% late, 15.8 per 10k
C prefetch_gate 0.60% late, 2.5 per 10k
No freezes in any arm, and the next group was ready at every strip
extension, so parking the prefetch thread (3-6s per 8-minute run) cost
nothing visible. The gate is now on unless vegas_scroll.prefetch_gate is
false; on a stock binding it cannot work and says so at INFO once a run
rather than warning on every install. switch_interval_ms stays off.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>