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/fanfan-de/anybox/frontend-testing-debuggingnpx skills add fanfan-de/anybox --skill frontend-testing-debugginggit clone --depth 1 https://github.com/fanfan-de/anyboxWrote 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.
[](https://agentmods.dev/skills/fanfan-de/anybox/frontend-testing-debugging)<a href="https://agentmods.dev/skills/fanfan-de/anybox/frontend-testing-debugging"><img src="https://agentmods.dev/badge/skills/fanfan-de/anybox/frontend-testing-debugging.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00075 | $0.01975 |
| Opus 5 | $0.00037 | $0.00988 |
| Sonnet 5 | $0.00015 | $0.00395 |
| Haiku 4.5 | $0.00007 | $0.00198 |
Grade A, and why
frontend-testing-debugging 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 4d 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.
How it starts
The opening of the file, as written. The whole thing — 143 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Frontend Testing Debugging
Invocation Contract
This skill should work from normal user prompts. Do not require the user to spell out Browser routing, screenshots, report shape, or fallback policy.
Use this skill when the user asks to use the Build Web Apps plugin, web dev plugin, frontend dev plugin, or frontend testing/debugging skill for a rendered frontend change, test, or bug investigation.
Examples that should trigger this full workflow:
please make an improvement to the web dashboard transaction search area and use the web dev pluginuse the frontend dev plugin to polish this dashboarddebug this UI with the Build Web Apps plugintest this localhost app and fix the broken interaction
From a brief prompt, infer the target surface from the repo, currently open app/browser URL, nearby files, or running dev server. If the target URL is unclear, inspect the repo scripts and running local ports before asking the user.
For any code change to a rendered frontend surface, do the validation loop by default:
- Identify the target flow.
- Choose the Browser path below.
- Make the smallest useful edit.
- Validate the rendered behavior.
- Reply with the QA final response report.
Choose The Browser Path
First classify Browser availability:
- Available: the Chrome plugin and its
chromeskill are listed in the session. Read and follow that skill before any browser action. - Absent: the Chrome plugin or
chromeskill is not listed. Use regular Playwright and recordChrome plugin not available. - Invocation failed: Browser appears available, but the skill/runtime, Node REPL JavaScript setup, tab acquisition, or navigation fails. Treat this as a Browser-path blocker.
Do not use regular Playwright, external Chrome, or shell open first when Browser is available.
Only switch from a failed Browser invocation to regular Playwright if the user already allowed fallback or the task explicitly permits non-Browser validation. In that case, report the exact Browser failure and the fallback decision.
What ships with it
1 file 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.
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.
- 4d ago First seen · 143 lines · 75 tokens per session scan A 01db440e9c85
frontend-testing-debugging is a skill published in the GitHub repository fanfan-de/anybox (58 stars, last pushed 21d ago), licensed MIT. It adds 75 tokens to every session and 1,975 once invoked, about $0.0004 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 2026-08-30.
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