visual-verification

A web and user-interface checking workflow that combines code checks with testing of real pages in a running development server.

In plain words
What is it for?
Use it to run type checks, unit tests, design scans, and smoke tests for key routes such as a home page or login form.
Why use it?
Unit tests may miss blank pages, broken routes, browser console errors, or missing page content. This workflow checks those problems and saves screenshots as evidence.

Skill for Claude CodeCodex

Part of the yoke plugin — 34 skills, 1 hook shipped together

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.

agentmods
npx agentmods add skills/hecer/yoke/visual-verification
Any agent
npx skills add HECer/yoke --skill visual-verification
Clone the repo
git clone --depth 1 https://github.com/HECer/yoke

Made for: Claude Code, Codex.

Or install yoke, the plugin that ships this one along with the rest of its 34 skills, 1 hook.

Per session 92 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 579 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00092 $0.00579
Opus 5 $0.00046 $0.00290
Sonnet 5 $0.00018 $0.00116
Haiku 4.5 $0.00009 $0.00058

Measured 2d ago against content hash 23f05b894856, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

visual-verification 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.

canon/skills/visual-verification/SKILL.md · 55 lines

What it actually says

Visual verification

Unit tests don't see a blank page, an unwired route, a runtime console error, or AI-slop design. Make the loop's gate catch them by widening verify, since the loop trusts verify as truth.

1. Compose the verify pipeline

Set verify.command (in .yoke/config.yaml) to chain, fail-fast:

<typecheck> && <unit tests> && yoke design-scan . && yoke flow-smoke .

e.g. tsc --noEmit && vitest run && yoke design-scan . && yoke flow-smoke .. Any red step blocks the story.

2. Flow-smoke with the built-in gate

Configure the key user flows once in .yoke/config.yaml:

smoke:
  baseUrl: http://localhost:3000
  flows:
    - name: home
      path: /
      landmark: "main h1"
    - name: login
      path: /login
      landmark: "form"

With that in place, the yoke flow-smoke . step from the section-1 pipeline is live. yoke flow-smoke loads each route against the running dev server, waits for the landmark, fails on any console error, and always saves a screenshot to .yoke/proof/<story>/ (the loop labels the folder with the current story id via YOKE_STORY; standalone runs use latest, or pass --label=). Requires Playwright in the project: npm i -D playwright && npx playwright install chromium. Start the dev server before verify (e.g. via start-server-and-test).

3. Video only when necessary

yoke flow-smoke records video per flow and keeps it only on failure (.yoke/proof/<story>/<flow>.webm). When a flow goes red: watch that clip first, then use the wired Playwright MCP to reproduce interactively. Never record every run manually — the gate already handles the failure case.

Rule

Green pipeline = types + units + no design-slop over budget + every flow renders without console errors, with a screenshot to prove it. Only then is the story actually done.

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 · 55 lines · 92 tokens per session scan A 23f05b894856

Subscribe to this mod's changes

visual-verification is a skill published in the GitHub repository HECer/yoke (2 stars, last pushed 12d ago), licensed MIT. It adds 92 tokens to every session and 579 once invoked, about $0.0005 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.