I am attempting to fit a model in `brms`

and I am using `cmdstanr`

as the backend. I am getting the following error:

```
fatal error: bracket nesting level exceeded maximum of 256
...
note: use -fbracket-depth=N to increase maximum nesting level
```

The model formula is

`response ~ X + X:Y`

(because `Y`

is nested within `X`

). `X`

is a factor with 17 levels, `Y`

is a factor with 22 levels.

Running on a subset of the data such that `X`

has 9 levels and `Y`

has 12 levels, the model compiles without problems and produces a sensible fit without issues.

For this reason, I am guessing this has something to do with the number of levels (which is large, due to the interaction), but thatâ€™s just a guess.

Is there a suggested solution? For example, what do I need to do to â€śuse -fbracket-depth=N to increase maximum nesting levelâ€ť?