Claude Code has a built-in file clerk, and on Opus 5.5 it bills like a senior engineer. It's called Explore. When Claude says it's exploring your codebase, this helper opens and reads your files. It can't edit anything, and it runs on the same model as your chat, so on Opus it reads on Opus and eats the same limit. Opus 5.5 costs $4 per million tokens in. Haiku 5.5 costs $0.10. In my own logs, Opus just reading files and pages came to $723 in 3 months. Anthropic's docs give the fix. Make your own helper named Explore, and it replaces the built-in one, model included: 1. copy the file from the reply 2. tell Claude Code "save this as ~/.claude/agents/Explore.md" 3. restart Claude Code 4. next time it explores, type /tasks. The Explore row names the model, it should say Haiku One trap: there's also a setting that moves every helper to Haiku at once. Skip it, because it moves your planner to Haiku too. Move only the clerk. Do it before your next long session.