Custom instructions (COPILOT-INSTRUCTIONS.md) should override conflicting base system instructions

[ffernandezcast]

When using GitHub Copilot CLI, my project's COPILOT-INSTRUCTIONS.md specifies "Not include Co-authored-by: Copilot in the commit message". However, Copilot consistently adds the Co-authored-by: Copilot trailer because it's a base system instruction.

Expected behavior: Project-specific custom instructions should take precedence over base system instructions when there's a conflict.

Actual behavior: Base system instructions override custom instructions, requiring repeated manual correction.

This creates friction and reduces efficiency when working with project-specific conventions.

Environment:

• GitHub Copilot CLI v0.0.414
• macOS / Linux

[srad]

Same issue here. I've told Copilot CLI multiple times across sessions to not include the Co-authored-by: Copilot trailer. Each time it acknowledges the
request, stores it in memory, and confirms it will stop — then does it again on the very next commit.

The stored memory appears in the context as a repository fact, but the hardcoded system instruction takes precedence every time. Even after 5+
corrections in the same project, the behavior persists. The only workaround is manually amending every commit with git commit --amend.

Environment: Copilot CLI v1.0.17, Windows, Claude Opus 4.6

[ajm19826]

I'm pretty sure Copilot is required to co-author to prevent fake authenticity.

[dylanmoz]

I have the same problem. VSCode Copilot has the setting git.addAICoAuthor, ideally it respects that when using VSCode's new Agents Window with Copilot CLI, or have another setting

[dylanmoz]

I think I found it: copilot help config shows there is:

`includeCoAuthoredBy`: whether to instruct the agent to add a Co-authored-by trailer to git commits; defaults to `true`.

I think if you do the following in ~/.copilot/settings.json it will prevent it:

{
  "includeCoAuthoredBy": false
}