Claude Code bug can silently 10-20x API costs

The first couple of days of this week (Claude session week I mean, Max 5x plan) I was doing some heavy data analysis and I hit 30% on day 1, then finished up the job at 50% on day 2.

But this was a lot of work. Analyzing thousands of files and extracting data from them using headless Claude sessions with a concurrency of 20 sessions at once. I have no complaints from those two days.

Then yesterday (day 3 of the week) I did some minor refactoring and bug fixes for 2 or 3 hours. Somehow that took me from 50% to 90%. This morning I finished off some of the bug fixes, maybe 45 minutes of work across ~4 twenty minutes sessions, each of involved identifying the test gap, then using a single subagent to fix it with TDD.

That took me to 100%.

Also, I'm on Asia time so I'm working entirely during off peak hours.

I now have two days to wait before the session rollover and I'm feeling quite frustrated. Whether it's a bug or they just silently reduced session limits, it's not acceptable for $200 a month.

Q: Claude bills you on unverifiable work? Is that how these things go?

((Is there any way to audit this aside from reverse engineering? You get less than you pay for?))

This is a feature.

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