A skill for controlling a running NullPlayer application and observing its window. It can launch and configure the app, perform actions such as clicks and drags, reproduce on-screen problems, take screenshots, and measure what is shown.

Use it to start NullPlayer, open a skin, set up a test scenario, reproduce a visible defect, capture the window, or provide an interactive session.

It removes the need to describe UI actions without actually checking the running application.

app-control — Skill for Claude Code and Codex by ad-repo/nullplayer

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add ad-repo/nullplayer --skill app-control

Clone the repo

git clone --depth 1 https://github.com/ad-repo/nullplayer

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/ad-repo/nullplayer/app-control/github.svg)](https://agentmods.dev/skills/ad-repo/nullplayer/app-control)

Your own site

<a href="https://agentmods.dev/skills/ad-repo/nullplayer/app-control"><img src="https://agentmods.dev/badge/skills/ad-repo/nullplayer/app-control/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/ad-repo/nullplayer/app-control"><img src="https://agentmods.dev/badge/skills/ad-repo/nullplayer/app-control.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 126 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 11,340 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 unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00126	$0.11340
Opus 5.5	$0.00050	$0.04536
Sonnet 5.5	$0.00025	$0.02268
Haiku 4.5	$0.00013	$0.01134

Measured yesterday against content hash a36dd6f53351, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

app-control 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 yesterday.

The scan reads SKILL.md. This mod also ships 10 executable files (scripts/bento_tabs.sh, scripts/build.sh, scripts/launch.sh, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/app-control/SKILL.md · 585 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

Files

What ships with it

18 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

yesterday Changed · +25 lines a36dd6f53351
4d ago Changed · +2 lines facc08f01b1e
8d ago Changed · +5 lines 0cbc44fdf7b7
11d ago Changed · +1 lines · +6 tokens per session 7ed1e2aa76d4
14d ago Changed · +6 lines 01afc5b8602a
20d ago Changed · -1 lines e791cd69c4b6
21d ago Changed · +14 lines 5316fbe20a07
22d ago Changed 0be5c15eda0e
28d ago Changed · +3 lines · +4 tokens per session 7e7a6fbd9e4e
28d ago First seen · 530 lines · 116 tokens per session scan A c85742dc2acf

Subscribe to this mod's changes

app-control is a skill published in the GitHub repository ad-repo/nullplayer (178 stars, last pushed yesterday), with no licence file. It adds 126 tokens to every session and 11,340 once invoked, about $0.0005 per session on Opus 5.5. 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 2026-09-27.

Debugging

app-control next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
app-controlad-repo/nullplayer	Skill	178	yesterday	none	A	126	Claude Code, Codex
systematic-debuggingopen-metadata/OpenMetadata	Skill	16k	yesterday	Apache-2.0	A	37	Claude Code
log-error-digestzebbern/claude-code-guide	Skill	4.7k	3d ago	MIT	A	71	Claude Code, Codex
cwv-optimizeradobe/skills	Skill	319	yesterday	Apache-2.0	A	112	Claude Code
ci-fixersipyourdrink-ltd/bernstein	Skill	1.2k	yesterday	Apache-2.0	A	15	Claude Code, Codex
incident-response-incident-responsermyndharis/antigravity-skills	Skill	1.9k	23d ago	MIT	A	36	Claude Code
triaging-web-analytics-supportPostHog/posthog	Skill	41k	yesterday	none	A	151	Claude Code, Codex