Verbose command output can overwhelm session and consume excessive tokens

[walkyri]

Description

Verbose command output from long-running processes (e.g., Kopia backup progress) can overwhelm a Claude Code session, causing the interface to lock up and consuming excessive tokens.

Steps to Reproduce

1. Run a backup command (e.g., kopia snapshot create) that outputs continuous progress updates
2. The terminal floods with thousands of lines like:

   hashing, 8429 hashed (673.9 MB), 0 cached (0 B), uploaded 473.0 MB, estimating...
   

3. Session becomes unresponsive; keyboard input locks up
4. Token usage spikes significantly from processing all the output text

Expected Behavior

• Output should be rate-limited, truncated, or buffered to prevent session lockup
• Warning when command output exceeds a threshold
• Token consumption should be bounded for command output

Actual Behavior

• Session locks up completely
• All output text is processed, consuming tokens
• User must force-quit or switch to another terminal

Environment

• macOS (Darwin 25.2.0)
• Claude Code CLI
• Model: claude-opus-4-5-20251101

Workaround

Redirect verbose command output to a file:

command > /tmp/log.txt 2>&1 &

Suggestion

Consider implementing:

1. Output truncation after a configurable threshold
2. A warning when output volume is high
3. Documentation noting the risk of verbose commands in-session

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] bash_progress events not compacted, causing multi-MB transcripts and resume hang #19199
2. Claude Code stores all bash output in memory causing 90GB+ memory usage and crashes #11155
3. [BUG] Session freezes when reading persisted-output tool-results file after large Bash output #18095

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🤖 Generated with Claude Code

[walkyri]

Additionally, I am confident the usage spike was so massive it doubled my daily token consumption in a few minutes. Before the text flood I was at 15% usage for the day with three hours or so before reset, and after the flood and lockup-crash of Claude Code it ws 33%. Again, this was without any indication, warning, or crash report other than non-responsive keyboard entry only in the Claude Code window. I did not think to look for a log entry, but I will add one after this comment.

[walkyri]

Additional diagnostic info

The debug log from this session is 52 MB (~/.claude/debug/*.txt), which itself demonstrates the scale of the problem.

Relevant log entries showing the failure:

High write volume detected:

[DEBUG] High write ratio: blit=0, write=755818 (100.0% writes), screen=5979x159

Session eventually timed out and aborted:

[ERROR] Error in non-streaming fallback: Request was aborted.
[ERROR] AxiosError: timeout of 5000ms exceeded
[ERROR] Operation timed out.

Event logging also failed due to the volume:

[ERROR] 1P event logging: 10 events failed to export

The 755,818 writes to a 5979x159 screen buffer in a single cycle indicates the terminal was being flooded with output faster than it could render, eventually causing the session to become unresponsive and time out.

[github-actions]

Closing for now — inactive for too long. Please open a new issue if this is still relevant.

[github-actions]

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.