Preview: playback runs at the pace frames arrive when it can't keep up

docs/gaps.md

@@ -61,7 +61,7 @@ are grouped by area; the issue tracker has the rest.
 | 2 | **Fidelity unmeasured** beyond scalar ease | [fidelity/](fidelity/README.md): 168 samples, one property type; `compare_frames` helper exists, no corpus | Every "done" feature may still differ; users find the differences | 60–100 h harness + P0/P1 corpus; more per feature | G1 · [target-app-parity.md](target-app-parity.md) |
 | 3 | **Open crash reports** | Open: #580, #501, #426, #341, #234, #879. Now closed: #591, #306, #511 | A crash loses work; outranks features ([AGENTS.md](../AGENTS.md)) | 10–25 h | G3 · this file |
 | 4 | ~~**No CI gate on pull requests**~~ closed | `.github/workflows/ci.yml` runs `cargo xtask ci` (fmt, clippy, tests, layers, assets, wasm) on every pull request and push to `main` through craft-common-actions' shared `gate.yml` (#2204) | — | done | G3 · this file |
-| 5 | **Playback and scrubbing feel** | #595 stutter on cached frames (partly addressed: nearest-first RAM preview prefetch, cache bars at 1/3 resolution), #304, #504 / #335 audio late or crackling, #586 puppet lag (maintainers asked for details); #329 slow scrubbing (#784) and #554 closed | Preview is where motion designers spend their day | 25–50 h | G5 · [hardware-parity.md](hardware-parity.md) |
+| 5 | **Playback and scrubbing feel** | #595 stutter on cached frames (partly addressed: nearest-first RAM preview prefetch, cache bars at 1/3 resolution; an uncached first playback plays at the rate frames render instead of freezing between bursts, with frame lanes four threads wide), #304, #504 / #335 audio late or crackling, #586 puppet lag (maintainers asked for details); #329 slow scrubbing (#784) and #554 closed | Preview is where motion designers spend their day | 25–50 h | G5 · [hardware-parity.md](hardware-parity.md) |
 | 6 | **Linux and Windows interaction bugs** | Open: #488 rename arrows (hardening landed, reporter asked for details), #492 anchor drag, #268 file drops on Wayland (winit), #613 Direct3D 12 compositor. Now closed: #491, #493, #467, #320, #302, #596 | Many reports come from Linux; some Windows GPUs fail to start the compositor | 25–45 h | G2 · [ui-parity.md](ui-parity.md) |
 | 7 | **Animation presets: 76 against 621** | After Effects ships 621 `.ffx` presets (Behaviors, Backgrounds, Shapes, Synthetics, Text, Transitions…); we ship 76 original presets (8 text-animator; 23 Transitions: wipes, clock and fan reveals, blinds, dissolves, card flips, CC wipes, fades, #757; 23 Backgrounds: drifting gradients, fog, cloud and smoke, plasma and magma, cells, hexagons, scrolling grids and checks, pulse rings, bokeh, light sweep, #1096, driven by expressions so they keep moving, not seamless loops; 22 Behaviors: wiggle, shake, float, orbit, bounce, drift, pendulum, spin, pulse, heartbeat, blink, strobe, flicker on transform and opacity, #1510) and read only our `.ecpreset`. Missing: Shapes, Synthetics, Image and more Text | Presets are how many designers start; tutorials assume them | 15–35 h (original presets; `.ffx` reading is out of clean-room scope) | G8 · [effects-parity.md](effects-parity.md) |
 | 8 | **Mask and shape bugs** | Open: #1004 mask vertex multi-select, #999 auto-pan, #1042 / #1033 vertex nodes under the bounding box, #959 / #960 shape group toggles and operators. Now closed: #510, #513, #527, #509, #303, #553, #932 (Convert To Bezier Path on a shape layer's parametric path) | Masks are core compositing | 10–20 h | G2 · [target-app-parity.md](target-app-parity.md) |

docs/preferences.md

@@ -54,7 +54,8 @@ Commands (CLI, MCP, control channel):
 - `previews.adaptiveResolutionLimit`: Adaptive Resolution Limit (the lowest resolution Fast Previews ▸
   Adaptive Resolution drops to while you drag, and the lowest a playing preview steps down to)
 - `previews.adaptivePlayback`: Lower Resolution When Playback Can't Keep Up. On by default. A
-  preview at Resolution Auto that stalls on frames and shows under 80 % of its frame rate steps
+  preview at Resolution Auto that plays under 80 % of its frame rate (frames render slower than
+  that, so it plays them at the rate they arrive rather than freezing between them) steps
   down a resolution (half the scale after two seconds, a quarter two seconds later if still slow,
   no lower than the Adaptive Resolution Limit) for the rest of that play; stopping goes back to the viewer's resolution, and Cache
   Frames When Idle fills it in. An explicit Resolution (the comp's or the Preview panel's) is