From the peek side, this is the command that creates the output:

def render_json(
    tds: Iterable[TargetData], exclude_defaults: bool = False, include_dep_rules: bool = False
) -> str:
    return f"{json.dumps([td.to_dict(exclude_defaults, include_dep_rules) for td in tds], indent=2, cls=_PeekJsonEncoder)}\n"

I haven't really ever looked at the custom encoder before, but between that or the Pants stdout writer - not sure where else the problem could be. Does an array end or get created on a specific target? Or is it length based? Have you identified any patterns that could help debug? For example, if you have a large repo, and you only peek a subset of it

pants peek myfolder::

Inherently, something about the code strikes me as odd, since the function is wrapped in

{ }

- but at the console, I never see that, I only see

[ ]

- but yeah, will need to investigate more

Oh, also, why aren't you just using

pants peek ::

? Why list first?

Do you get the same behaviour on a straight

pants peek ::

though?