background-position can't run on the compositor, so every frame of the animated chat backgrounds repainted the whole chat area. That cost 51 to 72% main-thread busy while sitting idle in a room at 60 fps.
The drifts are slow: 3 to 22 px/s, under a pixel per frame. So each animation now uses steps(): about 12 updates/s for fireflies, stars and aurora, and about 24/s for the faster rain and pulse.
Measured headless (20 s idle in a room, CDP TaskDuration):
background
before
after
none
0.7%
0.9%
rain
50.7%
5.9%
stars
71.2%
4.5%
pulse
64.9%
5.8%
aurora
58.9%
4.2%
fireflies
71.7%
3.8%
Visual note: aurora and pulse used ease-in-out. With steps(), their motion is now even-paced. The layers and colours are unchanged, and Pause animations / reduced motion still remove the animation entirely.
tsc clean · unit tests pass · ESLint/Prettier clean.
Fixes #337.
`background-position` can't run on the compositor, so every frame of the animated chat backgrounds repainted the whole chat area. That cost **51 to 72% main-thread busy** while sitting idle in a room at 60 fps.
The drifts are slow: 3 to 22 px/s, under a pixel per frame. So each animation now uses `steps()`: about **12 updates/s** for fireflies, stars and aurora, and about **24/s** for the faster rain and pulse.
**Measured** headless (20 s idle in a room, CDP `TaskDuration`):
| background | before | after |
|---|---|---|
| none | 0.7% | 0.9% |
| rain | 50.7% | **5.9%** |
| stars | 71.2% | **4.5%** |
| pulse | 64.9% | **5.8%** |
| aurora | 58.9% | **4.2%** |
| fireflies | 71.7% | **3.8%** |
**Visual note:** aurora and pulse used `ease-in-out`. With `steps()`, their motion is now even-paced. The layers and colours are unchanged, and *Pause animations* / reduced motion still remove the animation entirely.
`tsc` clean · unit tests pass · ESLint/Prettier clean.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5
background-position can't run on the compositor, so every frame of the
animated chat backgrounds repainted the whole chat area: 51 to 72% main-thread
busy while idle in a room at 60 fps. The drifts are slow (3 to 22 px/s,
under a pixel per frame), so each animation now uses steps(): about 12
updates/s for fireflies, stars and aurora and about 24/s for rain and
pulse.
Measured headless (20 s idle in a room, CDP TaskDuration):
none 0.7% → 0.9%; rain 50.7 → 5.9; stars 71.2 → 4.5;
pulse 64.9 → 5.8; aurora 58.9 → 4.2; fireflies 71.7 → 3.8.
Aurora and pulse used ease-in-out; with steps() their motion is now
even-paced. Pause animations / reduced motion still strip the animation.
Fixes#337
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5
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Fixes #337.
background-positioncan't run on the compositor, so every frame of the animated chat backgrounds repainted the whole chat area. That cost 51 to 72% main-thread busy while sitting idle in a room at 60 fps.The drifts are slow: 3 to 22 px/s, under a pixel per frame. So each animation now uses
steps(): about 12 updates/s for fireflies, stars and aurora, and about 24/s for the faster rain and pulse.Measured headless (20 s idle in a room, CDP
TaskDuration):Visual note: aurora and pulse used
ease-in-out. Withsteps(), their motion is now even-paced. The layers and colours are unchanged, and Pause animations / reduced motion still remove the animation entirely.tscclean · unit tests pass · ESLint/Prettier clean.🤖 Generated with Claude Code
https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5