Engines wrote to a pipe of the agent's. An agent that restarted and
adopted them left that pipe with no reader, and an engine's next write
past its buffer failed with EPIPE — in a Python engine, inside whatever it
was reporting on. Each process now writes to its own file in the agent's
work directory (0600), followed into the shard's log; an adopted engine's
file is read from the start, so its output from before the restart is in
its log too. A file past 64 MB is emptied in place; the files go with the
shard.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
