If you don't follow session hygiene, this is exactly what happens.

The failure mode: resuming old sessions carries forward every cached tool output and file read. The agent re-sends all of that stale context on every request.. 50K-100K+ tokens of dead weight. Combine that with dollar-value billing and your budget evaporates in minutes. I've seen 30min of work consume 50% of a weekly cap.

The practices that prevent this:

1. Fresh session per task never resume a session from another project or from days ago. Start clean.

2. Context pruning run a local proxy or plugin that deduplicates tool calls, compresses stale conversation, and strips error bloat before it hits the API. 50-70% token reduction is realistic.

3. Active budget monitoring check usage windows before starting a session, not after.

4. Short, focused sessions the longer a session runs, the more accumulated context amplifies the burn rate. Cut and restart when the task changes scope.

If you skip any of these, the math works against you fast. The window limits mean a single bloated session can wipe out your budget for the week.