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.
npx agentmods add skills/yarlson/yarstack/ui-controlnpx skills add yarlson/yarstack --skill ui-controlgit clone --depth 1 https://github.com/yarlson/yarstackWhat 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 | $0.00042 | $0.00296 |
| Opus 5 | $0.00021 | $0.00148 |
| Sonnet 5 | $0.00008 | $0.00059 |
| Haiku 4.5 | $0.00004 | $0.00030 |
Grade A, and why
ui-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 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.
What it actually says
UI Control
Gather reproducible evidence from the actual graphical surface without changing production behavior.
Workflow
- Identify the target surface, build or session, and observable contract.
- Reuse the authorized running or authenticated surface when it is the target. Start a local app only when necessary and authorized.
- Prefer existing repository harnesses and locate controls by stable roles, labels, identifiers, or application markers.
- Perform only actions needed for the requested behavior or a concrete risk.
- Capture the smallest relevant screenshot, accessibility output, console entry, network evidence, or trace.
- Check loading, empty, error, keyboard, focus, responsive, and cleanup states only when material to the contract.
- Clean up only servers, profiles, sessions, and artifacts created by this workflow.
Keep verification read-only unless the parent task separately authorizes implementation. Use behavior-implement for fixes, phase-validate for contract acceptance, and test-gap-review for evidence sufficiency.
Do not add automation dependencies for a one-off probe, retain sensitive evidence, use stale selectors, or terminate user-owned resources.
Finish with the surface tested, actions, observed result, retained evidence, and blockers or limitations.
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.
- 2d ago First seen · 25 lines · 42 tokens per session scan A ca9e891eb6d1
ui-control is a skill published in the GitHub repository yarlson/yarstack (3 stars, last pushed 5d ago), licensed MIT. It adds 42 tokens to every session and 296 once invoked, about $0.0002 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 2026-08-31.
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