one of my mappings json files is 1.8M in size - do I need to specify an option to support this file size?

There is no limitation for the file size, but there is a limitation for response size.

There’s no technical limitation in WireMock OSS on response size. If it’s the response that’s very large it’s usually a good idea to move it to its own file under

__files

as then it’ll be streamed straight from storage rather than held in memory.

There's still a Jetty default limit AFAIK. At least header size limits are overridable in the CLI

I don’t think there is for response bodies. I’ve had conversations with people sending 300Mb response bodies via files.