I can confirm that RStudio Connect is truncating process logs when showing/downloading logs in the RStudio Connect dashboard. The full logs for both stdout and stderr are retained on-disk without truncation.
Log truncation is helpful when using the RStudio Connect dashboard. Unfortunately, we are also performing the same truncation when the log is downloaded.
We seek to 10k bytes from the end-of-log for both stdout and stderr (tracked separately) and then seek for the first line-start from that point. Those two streams are then interleaved. We may trim one of the two streams if they are from very different points in time (stdout data appearing before 100k of stderr data, for example).
If stdout and stderr fit into 10k bytes each, the full log content is returned.
We will address this problem in an upcoming release.