Subcritical

There is a meme that was originally about Claude Code.

Specifically, it was about running Claude Code with --dangerously-skip-permissions — the flag that tells the AI agent to stop asking for authorisation before it does things, on the grounds that you have decided to trust it absolutely and accept whatever consequences follow. The image is a boy, cheerful, holding a ball-in-cup toy where the ball and the cup have been replaced with the Demon Core. The original caption: how it feels to give Claude a vague /goal and –dangerously-skip-permissions.

I changed the caption to read: how it feels to live with a vp shunt.

The fact that it required no other modifications tells you something.

For the uninitiated: the Demon Core was a subcritical mass of plutonium used in nuclear weapons research in the 1940s. It killed two physicists in separate criticality accidents. The joke — in both versions — is that it sits there looking inert, doing nothing in particular, until due to some combination of bad luck and physics it briefly doesn’t.

A ventriculoperitoneal shunt is a valve and catheter system implanted to drain excess cerebrospinal fluid from the ventricles of the brain, through the neck and chest, and into the abdominal cavity. I have had one since infancy. I have had four revisions. The most recent was 17 April 2026. It is not, by any reasonable clinical definition, an unusual procedure for me.

It is also, by any reasonable clinical definition, brain surgery.

The Nature of the Thing

The shunt does not make itself known when it is working. That is the correct behaviour. It sits there, subcritical, draining fluid at a rate calibrated to keep the pressure in my skull within a range that does not cause damage. I go about my life. It goes about its.

The problem is that VP shunts fail. This is not a hypothetical. They block, fracture, displace, or simply stop working. The failure rate is not small — somewhere in the range of 40 to 50 percent within the first two years, higher over a lifetime. Four revisions in twenty years is, I’m told, on the more frequent end but not unusual for someone who has had one since infancy.

The failure mode is the thing. When a shunt fails, intracranial pressure builds. The symptoms — headache, nausea, vomiting, altered consciousness — look like a lot of other things. The margin between “probably fine, might need the GP” and “needs surgery within hours” is genuinely narrow. And because the shunt spends most of its time working correctly, the baseline for “probably fine” is something you develop over years of paying attention to your own skull.

That’s the Demon Core quality of it. Inert, subcritical, doing nothing alarming — until it is. The --dangerously-skip-permissions comparison is, on reflection, fairly apt: the system is running, the authorisation checks have been waived by circumstance, and you are simply hoping it continues to behave.

On Being Numb to It

I wrote after the April surgery about the disconnect between how I experience these events and how other people seem to. Brain surgery, from the outside, is a dramatic and frightening thing. From the inside — specifically, the inside of my experience of this particular surgery — it is the fourth time I have been in that position. It is a known quantity, in the way that something can be known without being pleasant.

The meme made me laugh because it articulates something that is genuinely difficult to describe otherwise. There isn’t really a vocabulary for “permanently aware that the object in my head could fail at any moment, but that awareness has been so thoroughly integrated into daily life that it no longer registers as fear.” You live with it. It becomes furniture.

The fact that the same image works for a reckless AI agent and a congenital neurological condition is either a coincidence or a comment on how many things in modern life operate on the same basic principle: mostly fine, until suddenly not, with limited warning and significant consequences.

Why the Joke Lands

Dark humour about chronic illness is not an absence of feeling. It is, frequently, the only register that actually fits.

The alternatives are: catastrophising, which achieves nothing; performing distress for other people’s benefit, which is exhausting and faintly dishonest; or the particular flattened quality of treating it as purely logistical, which is accurate but leaves something out. The joke holds both things at once — the genuine strangeness of the situation, and the fact that you are, nonetheless, fine. Probably. Subcritically.

The cheerful kid holding the Demon Core like it is an ordinary toy is precisely correct. You just get on with it. The thing is in your head. The thing has been in your head since infancy. You have had it replaced four times. You know the failure symptoms. You do not have the relevant surgeon’s contact details saved, which you are aware is an oversight. You’ve done the maths on what “feeling off” means often enough that the calculation is now largely automatic.

One day, probably, it will go critical again.

Until then.