[Performance] UI lags minutes behind actual file writes for ~800 line files

[weiwei2027]

Describe the bug

When writing long files in Kimi CLI v1.30, the UI refresh progressively slows down during write operations, lagging minutes to tens of minutes behind actual disk completion. The file content is already fully written to disk (verified by opening in external editors), but the CLI UI continues to slowly refresh, creating severe workflow disruption.

To Reproduce

Steps to reproduce the behavior:

1. Run Kimi CLI v1.30 on Ubuntu 24.04
2. Request generation of a file ~800 lines (code or documentation)
3. Observe the UI write progress indicator
4. During the "slow refresh" phase, open the target file in an external editor (e.g., VS Code, vim, cat)
5. Observe: File is complete on disk while CLI UI continues to lag for minutes to tens of minutes

Expected behavior

UI should reflect write progress in near real-time, with seconds of delay at most—not minutes.

Actual behavior

Metric	Value
File size tested	~800 lines
UI lag duration	Several minutes to tens of minutes
Disk write status	Complete (verified externally)
Occurrence frequency	High / consistent
Affected modes	Both ACP and Web mode
Affected file types	Code and documentation

Environment

Kimi CLI: 1.30
OS: Ubuntu 24.04
Modes affected: ACP, Web

Severity

High — This makes long file operations practically unusable, as users cannot reliably determine when the operation is actually complete.

Additional context

• This is clearly a UI rendering/buffering bottleneck, not a disk I/O issue
• The delay scales with file length (shorter files less affected)
• No visible error messages or crashes—just extreme UI slowness

Screencast.from.2026-04-08.11-38-38.webm

[weiwei2027]

确认是WriteFile工具及其相关UI问题，直接让kimi使用该工具写200行文件即可复现和验证。希望能尽快修复，这个问题很影响工作效率，谢谢！

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It is confirmed that it is a problem with the WriteFile tool and its related UI. Just ask kimi to use the tool to write a 200-line file to reproduce and verify. I hope it can be fixed as soon as possible. This problem greatly affects work efficiency. Thank you!