Upload images to GitHub (gh-image)

GitHub has no public API for image uploads — the web UI uses an internal endpoint that mints user-attachments URLs scoped to the repo's visibility. gh-image (MIT, © drogers0) replicates that flow as a gh CLI extension, so an agent can upload a local image from the terminal and get a ready-to-embed Markdown image line back.

Overview

This skill drives gh-image to turn a local image file into a hosted GitHub user-attachments URL, then embeds that URL into a pull request, issue, or comment. It is the missing "attach a screenshot" capability for terminal agents.

When to Use This Skill

Use this skill when asked to:

• "Attach a screenshot to the PR" or "add an image to the PR description"
• "Put this image in the issue" / "comment with these screenshots"
• "Show the test results / before-and-after in the PR"
• Embed any local image into GitHub Markdown without leaving the terminal

How It Works

Step 1: Verify prerequisites

gh auth status                                   # gh installed & authenticated
gh extension list | grep -q 'drogers0/gh-image' \
  || gh extension install drogers0/gh-image      # review/pin the extension source first

gh-image does not use the gh token for the upload (that endpoint rejects tokens). It needs a GitHub user_session cookie, resolved in this order: --token <value> flag → GH_SESSION_TOKEN env var (use in CI/headless) → a logged-in browser's cookie store (default for local use).

Step 2: Upload

# Use an absolute path; --repo is optional inside a repo working dir.
gh image "/abs/path/screenshot.png" --repo <owner>/<repo>

gh image prints Markdown to stdout, one line per image:

![screenshot.png](https://github.com/user-attachments/assets/<uuid>)

Capture that output — it is the embeddable reference.

Step 3: Embed into the PR / issue / comment

MD="$(gh image "/abs/path/shot.png" --repo owner/repo)"
BODY="$(gh pr view <pr> --repo owner/repo --json body -q .body)"
printf '%s\n\n## Screenshots\n\n%s\n' "$BODY" "$MD" \
  | gh pr edit <pr> --repo owner/repo --body-file -

Use gh pr comment, gh issue edit, or gh issue comment with --body-file - for other targets. Always pass --body-file - (not inline --body) so multi-line bodies and special characters can't break shell quoting.

Step 4: Verify

gh pr view <pr> --repo owner/repo --json body -q .body   # confirm URL present

Examples

• Attach a CleanShot screenshot to PR #42: upload the file, append it under a ## Screenshots heading in the PR body.
• Embed before/after images in a README: upload both, paste the two Markdown lines into the README at the relevant section.

Best Practices

• Resolve globs to absolute paths first; quote paths with spaces/Unicode.
• For display sizing, embed an HTML tag instead of bare Markdown: <img width="800" src="https://github.com/user-attachments/assets/<uuid>" />.
• In CI, set GH_SESSION_TOKEN from a dedicated bot account.

Limitations

• Session cookie required. A user_session cookie grants full account access (not scoped like a PAT) — treat it like a password; use a bot account in CI.
• Write access to the target repo is required; orgs that enforce SAML SSO need the session authorized at https://github.com/orgs/<org>/sso first.
• Private-repo images stay private: the user-attachments URL inherits repo visibility, so an anonymous fetch on a private repo returns 404/403 by design.
• Windows + Chrome 127+ cannot read cookies (library limitation) — use another browser or GH_SESSION_TOKEN.
• The skill embeds the Markdown itself; gh-image only prints the URL.