Six months in and my job stopped teaching me anything. Is a plateau this early a red flag?

First few months were a firehose. Now most of my tickets are muscle memory. The codebase isn't getting more complex, the work repeats, and the learning curve has gone flat.

I'm aware this is a comfortable problem to have. Stable job, paid to write code, plenty of people would trade places without blinking. But comfortable and stagnant look identical from the inside, and six months feels early to have hit the ceiling of what a role can teach me.

So I'm trying to read the signal correctly before I do anything rash. For those who've plateaued at a job early: how did you figure out which it was — the kind you fix by hunting down harder problems inside the same job, or the kind that means the job itself is done teaching you?