What
Telemetry is the usage data Claude Code sends back. The format it uses for events has four new fields about your git repository:
git_remote_url: the address of the repository's remote.is_clean_tree_at_start: whether the working tree had no uncommitted changes when the session started.changed_file_count_at_start: how many files had changes at session start.untracked_file_count_at_start: how many files were not tracked by git at session start.
The code that reads and writes the format supports all four. The exporter pulls _PROTO_git_remote_url out of the extra metadata so that it does not end up in additional_metadata. However, the event it builds never sets git_remote_url, and nothing sets the three *_at_start fields.
Why
For now these fields stay empty. They show where the event format is heading: once something starts filling them, events would carry your repository's remote address and how many uncommitted changes you had at session start, which is worth knowing if you care about what usage data contains.