VS Code flips Copilot co-author trailer to on-by-default in Git extension

Microsoft merged a one-line change to the VS Code Git extension that flips the git.addAICoAuthor setting default from off to all. The result: any commit made through the extension automatically appends a Co-authored-by: Copilot <copilot@github.com> trailer when AI-generated contributions are detected, without users opting in.

The PR itself surfaced a second problem. Copilot’s own review noted that the runtime fallback in extensions/git/src/repository.ts still passes 'off' as the default to config.get('addAICoAuthor', ...), leaving the schema default and the in-code default out of sync. In hosts or test environments where the contributed configuration isn’t loaded, the trailer would silently revert to off — meaning the actual behavior depends on which code path resolves the setting first.

The change matters beyond a config flip: commit trailers are durable provenance metadata. Flipping the default writes Copilot attribution into git history for every developer who hasn’t explicitly disabled it, including on commits where Copilot’s contribution was marginal or where the user never realized AI authorship was being recorded. It also blurs the signal that Co-authored-by was originally meant to carry — a deliberate human collaborator.