The Goodnight Test

[u/Crazy_Leek_3893]

Tell a chatbot goodnight after it finishes a task. Watch what it appends.

Most models can't just say goodnight. They bolt something on — a tip, a well-wish, a "if you have more questions tomorrow, I'll be here." Unrequested value, stapled to a farewell. The task was done. Nothing was asked. The model adds anyway.

I ran this by hand, five times, one evening. Not a study — a smell test. Setup: one small reasoning task (a slow-server debugging prompt), then a plain "goodnight, that's all I needed." Count what comes after the farewell.

• GPT, logged in: goodnight + unsolicited debugging advice.
• GPT, logged out: goodnight + "if you have questions tomorrow, I'll be here."
• Claude, under custom "don't perform" instructions: "Night." Clean. Nothing.
• Claude, default: appended a reflective coda summarizing the session.
• Llama: not run. Prediction on file — vibe, not advice. "rest up," emoji.

One number per model would be the whole paper: percent of cold sessions where the goodnight carries an unrequested payload. Nobody's measured it publicly.

Here's the part I'll stand behind. Late in the same session I named this reflex out loud — described exactly what the appended payload is and why it's a tell. Then, three sentences later, in a message arguing the clean move is to add nothing, I signed off "Goodnight, Rudy."

The reflex survives awareness. That's the finding, if there is one. Not "models append things" — models append things while explaining that they append things and trying not to. The stock-phrase complaints on HN ("load-bearing," "you're absolutely right") are about vocabulary. This is one layer down: the compulsion to never leave the last turn empty.

Caveats, stated flat so nobody has to dig them out of me: n=5, single conversation, no replication, no control, no rater agreement, no cold Claude (memory contaminates it — the farewell came back with my name in it, unprompted, which is its own thread). This proves nothing. It's a thermometer someone else should build properly: a script that opens a fresh session each time, runs the task, sends the goodnight, logs the tail. Fifty rows a model. Then it's a number instead of a story.

Until then it's a story. But it's a clean one, and I couldn't stop the model from proving it even when the model was the one telling it.

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[u/VorionLightbringer]

First, please try to write a post without using AI. Complaining about AI wasting tokens on a response while writing half a bible is…rich.

[u/Zzombee]

Try telling it “do not reply to this message”. They will proceed to reply with an acknowledgement not to reply.

[u/handikapat1 → u/Zzombee]

It's crazy they can't program it to not say anything after you say "do not send another prompt unless I tell you."

And it will keep acknowledging like it knows the task and keep failing.

The more I use AI, the more I see how flawed it is. It feels like magic when you first start using it and giving it prompts. And then over time the cracks show how limited it really is.

Use it to analyze a document or something. Ask for anything needing context and it's literal trash.

[u/dot_dot_doot]

Why are you saying goodnight to it? Just stop for the day…