web-preview

A preview marker for KiroCrew’s Browser tab, which embeds a locally running website in the chat’s side panel.

In plain words
What is it for?
It helps preview sites and apps started with tools such as Vite, Next.js, npm, or Python’s local web server.
Why use it?
It removes the need to copy a local address into a browser panel yourself. The marker is emitted only after the development server is confirmed running.

Skill for Claude CodeCodex

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/kirodotdev/kirocrew/web-preview
Any agent
npx skills add kirodotdev/KiroCrew --skill web-preview
Clone the repo
git clone --depth 1 https://github.com/kirodotdev/KiroCrew

Made for: Claude Code, Codex.

Per session 79 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 682 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 $0.00079 $0.00682
Opus 5 $0.00039 $0.00341
Sonnet 5 $0.00016 $0.00136
Haiku 4.5 $0.00008 $0.00068

Measured 3d ago against content hash c159d3a622cd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

web-preview 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 3d 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.

src/kiro_crew/builtin_skills/web-preview/SKILL.md · 62 lines

How it starts

The opening of the file, as written. The whole thing — 62 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Web Preview marker

KiroCrew's chat right-side panel has a Browser tab (+ menu → Browser) that embeds a URL in a live iframe. When you start a local web server so the user can preview a site/app, tell the dashboard which URL to load by emitting a single hidden marker in your reply.

The marker

Emit exactly this, on its own line, once the server is confirmed listening:

<!-- kirocrew:preview url="http://127.0.0.1:PORT" -->
  • It's an HTML comment, so the user never sees it in the rendered message — the dashboard parses it and auto-opens the Browser tab at that URL, contextual to the current session.
  • Use the actual URL the server binds to, including the real port (http://localhost:5173, http://127.0.0.1:8080, …). Prefer 127.0.0.1 / localhost — only loopback URLs are embeddable.
  • Emit it after you've confirmed the server is up (e.g. it returned HTTP 200), not before.
  • If you restart on a different port, emit a new marker with the new URL — the panel re-points to the newest one.

When NOT to emit it

  • When you're only discussing previews, explaining this feature, or showing an example URL — emit it solely when a server is genuinely running for the user to view.
  • You don't need it for public/remote URLs the user opens themselves; it's for the embedded local preview.

Fallback

If you forget the marker but mention a localhost URL in prose (e.g. "serving at http://localhost:5173"), the dashboard will still try to pick up the newest such URL — but the marker is precise, so prefer it.

The marker is for the user — verify it yourself too

The marker only points the user's panel at the URL; it gives you no pixels. If the server is showing a front-end change you just made, also run the web-verify skill: navigate the same loopback URL with the Playwright browser, screenshot the surface you changed, read the frame, and embed it in chat. Don't hand over a preview and call the change verified.

Example

Read the full file on GitHub · 62 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. 3d ago First seen · 62 lines · 79 tokens per session scan A c159d3a622cd

Subscribe to this mod's changes

web-preview is a skill published in the GitHub repository kirodotdev/KiroCrew (3,532 stars, last pushed yesterday), licensed Apache-2.0. It adds 79 tokens to every session and 682 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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