Phase 0: A1 Wayland baseline + state snapshot — major reframing

3 in-session reps of chromium-fourier 149 / brave_drops_test.html /
Plasma Wayland 6.6.4 (kwin-fourier 6.6.4-3 + qt6-base-fourier
6.11.0-3 carry-overs intact). Tight cluster IQR=0:
drops_total=0, drops_post_warmup=0, frames_total=1685, kwin %CPU
median=0.00, mean=0.04. Perf samples on kwin (~30 over 70s) show
zero composite/dmabuf/GL symbols — only event-loop bookkeeping.

Most likely mechanism: KWin direct-scanout fast-path engaged for
the single-visible-client video case. The campaign's load-bearing
hypothesis ("X11 + non-compositing WM avoids per-frame GL composite
of NV12") is structurally weakened — KWin already avoids that work
under Wayland for this workload. Phase 1 needs to add a
multi-window A1' variant and drm_info-during-playback to confirm
direct-scanout, then revisit matrix cell design.

revert.log entry 6: SDDM autologin + state.conf swap that landed
the Plasma Wayland session for the A1 reps. Backup of original
state.conf preserved at /var/lib/sddm/state.conf.x11-research-bak;
single-command revert documented.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

phase0_evidence/wayland_baseline_2026-05-03/a1_rep2/capture_start.txt

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+2026-05-03T12:28:10Z