The logging utilities are just a frontend to a bunch of supported logging/tracing providers, many but not all of which accept plain text. So yes, it was technic

The logging utilities are just a frontend to a bunch of supported logging/tracing providers, many but not all of which accept plain text. So yes, it was technically a separate system (Honeycomb) doing the rejection, but one that was blessed by the vendor. And the only debugging facility I had available, which was duplicating the payload to stdout and tailing that, masked the issue because stdout is an actual stream. And to be clear, the system would be broken for the plaintext providers too, just more obviously broken as you'd presumably have a bunch of JSON tokens (or segments of a format string or whatever) show up as individual log lines.