anthropics
[BUG] 2.1.9 is unusable
Preflight Checklist
- [x] I have searched existing issues and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code
What's Wrong?
I'm on macOS 26.2 (25C56) using Ghostty (latest) and using Claude Code inside tmux.
Performance on long-running tasks has always been unreasonably bad. In general, it's not uncommon for CC to use over 10 GIGS of RAM for 3-4 instances if they're running subagents.
But today, with 2.1.9, it's simply unusable.
I'm seeing:
- CC instances completely freezing
- CC instances NOT being saved to history
- The flickering bug is worse than ever & appears on shorter conversations
One of my CC sessions hit 30 gigs of ram usage (I'm at 64, conveniently) and 200% CPU usage. This is absolutely ridiculous and it's 100% coming from the harness rendering, not the actual IO operations or the tiny amount of actual data CC can operate with at any given time.
Oh, I have the verbose flag on. That shouldn't matter, but I'll validate; the rendering engine is finicky so it's worth testing.
What Should Happen?
I would expect: <1GB of ram usage for a CC session, no matter how subagents I run in it <30% CPU usage
No scrolling bug. No blowing up my machine because of the TUI.
Error Messages/Logs
Steps to Reproduce
Run a code review of a branch with 8 parallel subagents.
Claude Model
Opus
Is this a regression?
Yes, this worked in a previous version
Last Working Version
2.1.8
Claude Code Version
2.1.9
Platform
Anthropic API
Operating System
macOS
Terminal/Shell
Other
Additional Information
No response
Found 3 possible duplicate issues:
- https://github.com/anthropics/claude-code/issues/18532
- https://github.com/anthropics/claude-code/issues/18471
- https://github.com/anthropics/claude-code/issues/18488
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crazy flicker happening for me as well. Basically ctrl+o is the only way to get even just an idea of what's happening
(same platform as OP; also tmux inside ghostty, same for tmux inside wezterm)
I am hitting this also and had to downgrade, 2.0.76 is the last version that works for me
I had to revert to an older version.
The full UI rerendering is a massive performance bottleneck & is just a few lines away from breaking performance in general. Tmux blows up with any version and 2x more so with the latest ones for some reason.
Long chats are still unstable after the revert.
David's "Claude Chill" (https://github.com/davidbeesley/claude-chill) helps a lot but it also adds jank to an otherwise nice workflow.
This needs a proper source fix & rendering optimization.
