I wrote about another solid case study this morning: https://simonwillison.net/2025/Dec/14/justhtml/
I genuinely don't understand how you can look at all of this evidence and still conclude that they aren't useful for people who learn how to use them.
Now let's make the analogy more accurate: let's imagine the blast furnace often ignores the operator controls, and just did what it "wanted" instead. Additionally, there are no gauges and there is no telemetry you can trust (it might have some that can the furnace will occasionally falsify, but you won't know when it's doing that).
Let's also imagine that the blast furnace changes behavior minute-to-minute (usually in the middle of the process) between useful output, useless output (requires scrapping), and counterproductive output (requires rework which exceeds the productivity gains of using the blast furnace to begin with).
Furthermore, the only way to tell which one of those 3 options you got, is to manually inspect every detail of every piece of every output. If you don't do this, the output might leak secrets (or worse) and bankrupt your company.
Finally, the operator would be charged for usage regardless of how often the furnace actually worked. At least this part of the analogy already fits.
What a weird blast furnace! Would anyone try to use this tool in such a scenario? Not most experienced metalworkers. Maybe a few people with money to burn. In particular, those who sing the highest praises of such a tool would likely be ignorant of all these pitfalls, or have a vested interest in the tool selling.
Absolutely wrong. If this blast furnace would cost a fraction of other blast furnaces, and would allow you to produce certain metals that were too expensive to produce previously (even with high error rate), almost everyone would use it.
Which is exactly what we're seeing right now.
Yes, you have to distinguish marketing message vs real value. But in terms of bang for buck, Claude Code is an absolute blast (pun intended)!
Totally incorrect: as we already mentioned, this blast furnace actually costs just as much as every other blast furnace to run all the time (which they do). The difference is only in the outputs, which I described in my post and now repeat below, with emphasis this time.
Let's also imagine that the blast furnace changes behavior minute-to-minute (usually in the middle of the process) between useful output, useless output (requires scrapping), and counterproductive output ——>(requires rework which exceeds the productivity gains of using the blast furnace to begin with)<——
Does this describe any currently-operating blast furnaces you are aware of? Like I said, probably not, for good reason.
I couldn't agree more.
I did not say that. I said that most metalworkers familiar with all the downsides (only 1 of which you are referring to here) would avoid using such an unpredictable, uncontrollable, uneconomical blast furnace entirely.
A regular blast furnace requires the user to be careful. A blast furnace which randomly does whatever it wants from minute to minute, producing bad output more often than good, including bad output that costs more to fix than the furnace cost to run, more than any cost savings, with no way to tell or meaningfully control it, is pretty useless.
Saying "be careful" using a machine with no effective observability or predictability or controls is a silly misnomer, when no amount of care will bestow the machine with them.
What other tools work this way, and are in widespread use? You mentioned horses, for example: What do you think usually happens to a deranged, rabid, syphilitic working horse which cannot effectively perform any job with any degree of reliability, and which often unpredictably acts out in dangerous and damaging ways? Is it usually kept on the job and 'run carefully'? Of course not.