That's your answer. Your prompt length barely matters; every message re-sends the whole conversation so far. Message 200 of a session costs way more than message 5 of a fresh one.
/clearwhenever you switch task. New feature = new conversation.- Don't paste full logs; paste the 10 relevant lines.
- Don't let it read whole folders "to understand the project". Put the overview in CLAUDE.md once.
- Use a lighter model (
/model) for routine edits and keep the big one for planning and hard bugs.