GitHub Copilot harness: agent-created file can’t be passed to an agent-flow tool when the agent runs from a workflow Agent node

Question

We have a Copilot Studio agent on the GitHub Copilot harness with skills that run Python scripts to generate Word documents (.docx). The agent saves each document to SharePoint through an agent-flow tool (“When an agent calls the flow” trigger) with a FILE-type input (contentBytes / name).

Works: in the agent’s test chat, the agent passes the generated file to the tool and it saves correctly.

Fails: when the same published agent is started unattended from an AI workflow (SharePoint trigger → Get file content → Agent node with “An existing agent” → Create file), the agent builds the documents but every save fails with: connector binary parameter $.file.contentBytes is not valid base64; retry with the exact file:// attachment path or complete base64 The agent tried file:///app/workspace/<file>.docx paths. It reports that /app/created and /app/uploads are not writable in this run, so it can’t produce an attachment path.

Question: in an unattended Agent-node run, is there a supported way for file bytes produced by the agent’s code to reach a tool’s file input without the model writing the base64 into the tool arguments? If not, is it on the roadmap? Also, can the Agent node return created files as an output?

Environment: Copilot Studio (default environment), Agent node “An existing agent”, agent published, workflow published.