What probably matters to youSection of the release
A new --append-subagent-system-prompt-file <file> flag lets a subagent system-prompt append be supplied from a file instead of inline. It's mutually exclusive with the existing --append-subagent-system-prompt flag.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeAdded --append-subagent-system-prompt-file to read the subagent system prompt from a file, for prompts too large to pass on the command line
