I burned a week of Claude quota in 3 days. Then I found the setting eating it.

I burned a full week of my Claude Ultra quota in 3 days.

My first instinct was to blame the model. So I did what any normal person would do: I benchmarked my own AI, and I let a script grade every answer so I couldn't lie to myself.

100 runs later, I had a number I didn't believe.

Same problem. Same model. Ten times the price.

A routing algorithm with mandatory stops and a toll quota. Opus solved it correctly both ways:

• at the lowest effort: $0.19
• at the highest effort: $2.03

I reran the logic in my head looking for what the $1.84 had bought. Nothing. Same verdict from the grader, and a much longer wait.

Past medium, the bars only do one thing: get longer. max cost up to 9.3 times high, for the same result, and took 4 to 7 times as long.

That should have been the headline. It wasn't, because of what the cheapest model did next.

2 cents

I gave Haiku, on its lowest effort, a task I expected it to fail: write a regex engine from scratch, without re.

Then I compared it with Python's re on 3,000 random patterns.

It matched all of them. Three runs out of three. For $0.02.

And I had been paying Opus to find values in files.

Then I checked my everyday work

Finding a value in a repo. Renaming across files. Fixing a parser. The boring work that fills a week, and that I was running on the most expensive brain I had.

$0.352 became $0.041. 88% less, and the same 6 passes out of 6.

Before you turn everything down

Don't. This is the part most cost posts skip.

These tasks were well specified, and something could check the answer. That is exactly where low effort is safe. When nothing can check the work, like design or review, the numbers say nothing, and my samples are small. My credit also ran out mid-benchmark, so 21 runs were excluded and Haiku is only partly measured on the hard tasks.

So the lesson was never "use the cheap setting". It was this: when a check proves the result, the check guarantees the quality, not the effort.

So we built rightsize

It's that sentence turned into a Claude Code skill. Free and open source. It picks the model and effort for every step, and saves the heavy thinking for the work that truly needs it.

It also runs only the tests a change touches (0.7 s instead of 11.4 s on a 40-module repo), and ships an audit that reads your local transcripts and shows where your tokens went. Nothing leaves your machine. I recommend it, unless you prefer not knowing.

/plugin marketplace add spar-x-fr/spar-x-skills /plugin install spar-x-skills@spar-x-skills 

github.com/spar-x-fr/spar-x-skills, maintained with Zakaria Khchiche.

It costs nothing. But you can pay us in GitHub stars, the only currency Claude hasn't found a way to burn yet.