Some Copilot CLI base instructions issued to a subagent prevent it from writing output to a file

[CezaryKlus]

Describe the bug

• I created a set of agents forming an orchestrator pattern for the full Work Item implementation
• When orchestrator executes a subagent responsible for functional testing this subagent consistently reports that it either could not write a test result file or was instructed not to write output to a file
• In either orchestrator or functional tester there are absolutely no instructions to prevent writing output files
• Orchestrator invokes the functional testing subagent only with the Work Item ID (no other runSubagent additional instructions)
• In other subagents for phases like Implementation everything works perfectly fine

Sample response from functional testing subagent (GPT 5.3 Codex) "...but I could not write the required notes file due the active session constraint: “Do NOT write output to files.”"

Related bug report: #3049

Affected version

No response

Steps to reproduce the behavior

No response

Expected behavior

No response

Additional context

The same workflow works 100% fine when run via VS Code.