[idea] Reduce the CPU load when agent is running

[txchen]

idea / problem

I noticed that when codex or claude code is running, herdr is using significant amount of CPU. I am using MBP (m3 max), herdr is using 15-25% CPU (1 core), it will impact the battery life. The spinner is also making ghostty/kitty to use GPU because it needs to keep rendering new frames.

requested change

Add settings to:

• Tune the spinner update frequency
• Disable spinner
• Reduce the agent state polling rate to reduce cpu load.

why you want this

Reduce CPU usage, improve battery life.

[txchen]

I guess it is because when agent is running, herdr is rendering the UI with 60fps, if we can make the 16ms value configurable, we can easily tune and see the result.
IMHO, most people don't need a 60fps spinner.

[txchen]

I tried running this script:

#!/usr/bin/env bash
set -euo pipefail

i=0
while true; do
  printf 'output line %d\n' "$i"
  i=$((i + 1))
  sleep 0.015
done

In herdr, then both ghostty and herdr will cause high CPU usage, ghostty will also take GPU resources.
In tmux, tmux is only using very very low CPU, and ghostty's CPU/GPU usage will be also lower (about 50% compared to herdr case)

I guess ratatui or herdr's rendering logic might be the root cause.

[tdi]

@txchen are you sure this is actually herd not the agent running in it ? I often see ghosttty CPU utilization where in fact this is claude code running in

[txchen]

@tdi yes, it is herdr. Actually when agent is running: all of the 3 are having high cpu usage: claude code itself, herdr and ghostty.

[ogulcancelik]

i did some optimizations, but main bottlenecks are kitty graphics, which causes more heavy render costs. so if you want more perf, dont enable kitty graphics. however beyond that, i updated lib-ghostty vendor and using more efficient apis now.

next release should drop busy load by like half, hopefully. at least did on my m2 max :)

[Castrozan]

i found the agent-state handler was forcing a full frame redraw on every republish even when the agent had no visible change to show, so i added a gate on my fork to only render when something visible actually changes, and it's running lighter

Castrozan#6