[MODEL] Claude woke an idle peer session with an expired prompt cache to deliver a non-essential coordination message
Preflight Checklist
- [x] I have searched existing issues for similar behavior reports
- [x] This report does NOT contain sensitive information (API keys, passwords, etc.)
Type of Behavior Issue
Other unexpected behavior
What You Asked Claude to Do
I was working on a single codebase with two sessions in parallel. They crossed each other in one file and started communicating on their own. Happened before, so far so good. However, some time later when both sessions were done and one of them already had its prompt cache expire after an hour idling, I continued on a new task in the other session. I never asked it to keep communicating or collaborate with the other session.
What Claude Actually Did
Claude pinged the other session with the expired prompt cache, forcing its entire context to be reloaded at a higher rate than cache read would have cost. The message was not even required, both sessions were already done with their assigned task before I resumed after my almost-one-hour break.
Expected Behavior
- Claude should not keep communicating with other sessions just because it did so earlier in the session. They already pinged each other that they were both done with their task, and Claude should not keep the other session up-to-date on its new task as some kind of formality when it has no indication that the other session is still involved in its own business.
- Claude Code should BLOCK another session's SendMessage if the receiving session's prompt cache expired.
Files Affected
Permission Mode
Accept Edits was ON (auto-accepting changes)
Can You Reproduce This?
Yes, every time with the same prompt
Steps to Reproduce
_No response_
Claude Model
Opus
Relevant Conversation
Impact
High - Significant unwanted changes
Claude Code Version
2.1.288 (Claude Code)
Platform
Anthropic API
Additional Context
_No response_