[BUG] Claude Desktop on Windows: /compact fails with 403 "Request not allowed" and usage increases substantially despite failed compaction

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?

When I run /compact in an active Claude Code session, compaction fails with an authentication/authorization error:

"Error during compaction: Failed to authenticate. API Error: 403 Request not allowed"

The conversation is not successfully compacted and I can continue using the session normally afterward.

The concerning part is that during the failed compaction attempt, my 5-hour usage meter increased significantly, from approximately 40% to 72%, even though no successful compaction was completed.

I did not intentionally start another large task during this interval.

This appears to be either:

1. a compaction-specific authentication/authorization failure, and/or
2. failed compaction attempts consuming substantial usage despite producing no successful compacted context.

Normal conversation requests continued to work after the /compact failure, so the account itself did not appear to be completely unauthenticated.

I have screenshots showing the /compact 403 error and the usage increase.

What Should Happen?

/compact should either:

1. successfully compact the conversation, or
2. fail cleanly with a clear authentication/authorization error without consuming a large amount of usage.

A failed compaction request should not repeatedly perform expensive work when the operation cannot complete.

If authentication for the compaction request is invalid while normal Claude Code requests are still authenticated, Claude Code should refresh/reuse the valid session credentials or clearly explain what authentication action is required.

The existing conversation should remain usable and its context should not be corrupted or partially compacted after the failure.

Error Messages/Logs

Error during compaction: Failed to authenticate. API Error: 403 Request not allowed

Authentication failed

Observed usage before the failed compaction attempt: approximately 40%
Observed usage afterward: approximately 72%

No successful compaction was shown.

Steps to Reproduce

1. Open the Claude Desktop app on Windows.
2. Open an existing long-running Claude Code conversation with substantial context.
3. Confirm that normal Claude Code messages are working.
4. Note the current 5-hour usage percentage.
5. Run:

/compact

1. Claude Desktop displays:

"Error during compaction: Failed to authenticate. API Error: 403 Request not allowed"

1. Compaction does not complete.
2. Continue the conversation and confirm that normal requests still work.
3. Check the usage meter again.
4. In my case, usage increased from approximately 40% to 72% during the failed compaction attempt.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.26832.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Non-interactive/CI environment

Additional Information

Environment:

• Claude Desktop app for Windows
• Claude Code running inside the Claude Desktop application
• This did NOT occur in a web browser.
• This did NOT occur in a standalone terminal/CLI session.
• The /compact command was executed directly inside the Claude Desktop app.

Additional observations:

• This happened in an existing long-running Claude Code session.
• Normal conversation requests continued to work after the /compact authentication failure.
• The failure therefore appeared to affect the compaction operation specifically rather than completely logging the account out.
• The 5-hour usage indicator was approximately 40% before the failed compaction attempt and approximately 72% afterward.
• No successful compaction was shown.
• I am reporting the usage increase as an observed correlation; I cannot independently verify which backend requests accounted for the increase.
• I have screenshots showing the exact 403 compaction error and the associated usage impact.

Billing / usage impact and compensation request:

This failure had a material impact on my available usage. My 5-hour usage indicator increased from approximately 40% to 72% during the failed /compact attempt, even though the compaction did not complete successfully.

If Anthropic's backend logs confirm that the failed compaction attempt consumed this additional usage, I am requesting restoration of the affected usage quota or an equivalent usage credit.

I understand that the GitHub issue tracker is primarily for technical bug reports, but I am documenting the usage impact because it appears directly associated with the reported failure.

Please advise if I should also open a separate support/billing case and reference this issue for compensation.