desktop-screenshot

desktop-screenshot is a skill for Claude Code, Codex from block/buzz. It costs 20 tokens per session (947 once invoked), scanned A, original, Apache-2.0.

A workflow for capturing desktop application screenshots and attaching them to GitHub pull requests, which are proposed code changes for review.

In plain words
What is it for?
Use it to build the frontend, capture named or clipped screens with Playwright, check image links in pull-request text, and post the results.
Why use it?
It avoids broken or unreliable image links by hosting screenshots at fixed URLs tied to Git commits.

Skill for Claude CodeCodex ✓ vendor

Written for no agent in particular: nothing here depends on one.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is ./scripts/post-screenshots.sh <PR-number> test-results/screenshots.

Good fit Use it to build the frontend, capture named or clipped screens with…

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View source ↗ block/buzz
About the project

Buzz is a self-hostable workspace where people and AI agents share rooms, communicate through signed events, and collaborate on repositories, workflows, canvases, and code reviews. It is for teams that want humans and agents to work together on software through a relay they control. The catalogue entries are agents, skills, and instructions for using Buzz’s collaborative workflows.

block/buzz · 32,211 stars · on GitHub

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/block/buzz
agentmods
npx agentmods add skills/block/buzz/screenshot

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for desktop-screenshot

README.md
[![agentmods](https://agentmods.dev/badge/skills/block/buzz/screenshot.svg)](https://agentmods.dev/skills/block/buzz/screenshot)
Your own site
<a href="https://agentmods.dev/skills/block/buzz/screenshot"><img src="https://agentmods.dev/badge/skills/block/buzz/screenshot.svg" alt="Measured on agentmods" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 947 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00020 $0.00947
Opus 5 $0.00010 $0.00474
Sonnet 5 $0.00004 $0.00189
Haiku 4.5 $0.00002 $0.00095

Measured 2d ago against content hash 8dc4bd6a0047, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

desktop-screenshot scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

desktop/src-tauri/src/managed_agents/screenshot_skill.md · 104 lines

How it starts

The opening of the file, as written. The whole thing — 104 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Desktop Screenshot Skill

CRITICAL: How to Host Screenshots for PRs

NEVER use buzz upload, the relay media endpoint, or any third-party image host (imgur, imgbb, etc.) for PR screenshots. Relay media URLs fail through GitHub's camo proxy (Non-Image content-type returned). External hosts are unreliable and may expose content.

ALWAYS use scripts/post-screenshots.sh — it hosts PNGs on a per-developer git branch with immutable commit-SHA URLs that render correctly on GitHub. If you manually compose or edit PR markdown, run scripts/check-pr-image-urls.sh <markdown-file> before posting. The checker fails on Buzz/relay media URLs so broken images are caught locally.

This hosting rule applies to any PNG you want in a PR, including mobile simulator screenshots captured outside the desktop Playwright helper.

Step 1 — Capture Screenshots

just desktop-screenshot builds the frontend, starts a preview server, and runs Playwright with the mock bridge (no relay needed).

just desktop-screenshot --name home
just desktop-screenshot --name channel --route /channels/general
just desktop-screenshot --name ctx-menu --right-click channel-random --clip 0,200,320,300
just desktop-screenshot --name sidebar --active-channel general --messages /tmp/msgs.json --clip 0,0,256,720

Flags: --name (filename, required), --route (client route), --active-channel (channel to view), --click/--right-click/--hover (interact before capture), --clip (crop as x,y,w,h), --messages (JSON file), --wait (ms, default 2000), --viewport (WxH, default 1280x720), --outdir (default test-results/screenshots).

Output: PNG path on stdout.

Injecting Messages

Write a JSON array to a temp file. channelName and content are required:

[
  {"channelName": "random", "content": "Hey check this out", "kind": 40002},
  {"channelName": "random", "content": "Another message"}
]

Without --active-channel, the helper navigates to the message channel (for showing content). With --active-channel, messages can target other channels while the camera stays put (for unread indicators, badges).

Read the full file on GitHub · 104 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 104 lines · 20 tokens per session scan A 8dc4bd6a0047

Subscribe to this mod's changes

desktop-screenshot is a skill published in the GitHub repository block/buzz (32,211 stars, last pushed yesterday), licensed Apache-2.0. It adds 20 tokens to every session and 947 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.