GitHub CLI v2.99.0 adds --attach for PR images

Until now, GitHub CLI had no way to upload images, so anyone letting Claude Code open a pull request had to finish the job in a browser by dragging screenshots in by hand. Version 2.99.0 closes that gap: the --attach flag can be repeated within one command, and because it replaces a local image path in the body with the uploaded URL, before-and-after tables can be composed in a markdown file and posted as-is.

It also shows how to make Claude Code use the flag on its own. Writing rules into CLAUDE.md — capture before-and-after screenshots for UI changes, keep them outside the repository or in a .gitignore'd directory, and create the pull request with --body-file plus --attach — prompts the agent to include them. One rule matters because gh pr create --attach still creates the pull request when some uploads fail, but exits with a non-zero code; an agent that reads only the exit code may retry and hit an error on the same branch, so the guidance is to add failed images later with gh pr edit instead of recreating the pull request.

Because --attach is a feature of the gh command itself, the same approach extends to other coding agents. Codex and Antigravity CLI can attach screenshots the same way if the equivalent rules are written in AGENTS.md rather than CLAUDE.md. The main limits are that the user needs write access to the target repository, the flag is unavailable on GitHub Enterprise Server, and videos are displayed as a player without alt text.