[Bug] Terminal output lag and duplication in Claude Code TUI rendering

Bug Description
Terminal rendering issues / output lag and duplication in Claude Code

I'm experiencing persistent rendering problems in the terminal UI during long sessions:

1. Output lag: Tool results (Bash command output, Read tool output) don't appear in sync with the

tool call that produced them. They arrive one turn late — I run a command, the assistant
continues, and the result from the previous call shows up underneath the current one. This makes
it very hard to follow what's actually happening.

1. Duplicated / out-of-order output: The same tool output sometimes renders multiple times, and

blocks appear out of the order they were executed in. A single Read or Bash result can show up two
or three times in the scrollback.

1. Garbled rendering: Output occasionally appears corrupted/interleaved, especially when multiple

tool calls run in the same turn or when results are large.

Impact: The lag forces a workaround where the assistant ends up issuing extra no-op commands (e.g.
echo markers) just to "flush" the pending output and confirm what landed — which adds noise and
wastes turns. It also makes it genuinely difficult to verify results before acting on them.

Environment:

• OS: Arch Linux (kernel 7.0.9-arch2-1)
• Shell: bash
• Long-running session with frequent multi-tool turns and large tool outputs
• The problem worsens as the conversation/context grows; it was not clearly fixed by /compact,

which suggests it's a terminal/harness rendering issue rather than a context-size issue.

What would help: Confirmation of whether this is a known issue with the TUI rendering pipeline,
and whether it's related to terminal emulator, output buffering, or the way concurrent/large tool
results are streamed and reconciled. (Terminal: Ghostty)

Environment Info

• Platform: linux
• Terminal: ghostty
• Version: 2.1.159
• Feedback ID: 4bd778d8-3581-4948-882a-fb1c413336ba

Errors

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