[Bug] CLAUDE_CODE_FORK_SUBAGENT=1 causes non-fork agents to be super expensive

Question

**Bug Description**
With CLAUDE_CODE_FORK_SUBAGENT=1 it seems like regular Agents (not forks) eat up my usage *extremely* quickly, i.e. two ~200k token agents using most of my 5 hour limit on the MAX 20x plan. I suspect they break the cache or don't use it properly

**Environment Info**
- Platform: darwin
- Terminal: WezTerm
- Version: 2.1.119
- Feedback ID: 762fea3f-fff2-47d7-b78f-fc3689f3eee5

**Errors**
```json
[]
```