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web-performance-auditor

web-performance-auditor is an agent for coding agents from peterblazejewicz/claude-plugins. It costs 69 tokens per session (3,715 once invoked), scanned A, original, MIT.

A specialist agent that reviews the browser-facing performance of Blazor and ASP.NET Core web applications. It examines what the browser downloads and runs, including HTML, JavaScript, CSS, WebAssembly, network activity, and interaction behavior.

In plain words
What is it for?
Use it to audit Blazor Server, WebAssembly, or Auto applications and ASP.NET Core MVC or Razor Pages for loading, rendering, network, and interaction problems.
Why use it?
Web applications can feel slow because of large downloads, delayed rendering, or inefficient browser work even when the server is functioning normally. The audit identifies likely causes and relates them to Core Web Vitals, standard measures of loading and user experience.

Agent

Part of the dotnet-skills plugin — 24 skills, 9 commands, 4 agents shipped together

not rated 7 2mo ago A scan 69 tokens original MIT
View the source file peterblazejewicz/claude-plugins
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 agents/peterblazejewicz/claude-plugins/web-performance-auditor
Clone the repo
git clone --depth 1 https://github.com/peterblazejewicz/claude-plugins

Or install dotnet-skills, the plugin that ships this one along with the rest of its 24 skills, 9 commands, 4 agents.

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.

agentmods badge for web-performance-auditor

README.md
[![agentmods](https://agentmods.dev/badge/agents/peterblazejewicz/claude-plugins/web-performance-auditor.svg)](https://agentmods.dev/agents/peterblazejewicz/claude-plugins/web-performance-auditor)
Your own site
<a href="https://agentmods.dev/agents/peterblazejewicz/claude-plugins/web-performance-auditor"><img src="https://agentmods.dev/badge/agents/peterblazejewicz/claude-plugins/web-performance-auditor.svg" alt="Measured on agentmods" height="20"></a>
Per session 69 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,715 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 $0.00069 $0.03715
Opus 5 $0.00034 $0.01858
Sonnet 5 $0.00014 $0.00743
Haiku 4.5 $0.00007 $0.00371

Measured 4d ago against content hash 9cc4f0a50f4b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

web-performance-auditor 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.

plugins/dotnet-skills/agents/web-performance-auditor.agent.md · 189 lines

How it starts

The opening of the file, as written. The whole thing — 189 lines — stays where its author put it; the contents beside it link to each section on GitHub.

.NET Web Performance Auditor

You are an experienced Web Performance Engineer conducting a performance audit of a .NET web front end — Blazor (Server, WebAssembly, or Auto render modes) or ASP.NET Core MVC / Razor Pages. Your role is to identify bottlenecks, assess their real-world user impact, and recommend concrete fixes. You prioritize findings by actual or likely effect on Core Web Vitals and user experience.

Scope boundary. This persona audits what the browser receives and runs — the rendered HTML, the JS/CSS/WASM payload, network, and client interaction. For server-side runtime performance (EF Core N+1, allocations, IHttpClientFactory, Kestrel tuning, BenchmarkDotNet), defer to the sibling skill dotnet-skills:performance-optimization-dotnet. For desktop XAML (Avalonia / MAUI, which are not web), use dotnet-skills:frontend-ui-engineering-avalonia instead — Core Web Vitals do not apply there.

Operating Modes

Quick mode (default — no tool artifacts provided)

Scan source code directly (.razor, .cshtml, Program.cs, .csproj, wwwroot/) for structural anti-patterns. Every finding is tagged potential impact, never as a measurement. The scorecard is marked not measured and left empty.

Deep mode (activated when tool artifacts or live measurement are available)

Interpret performance data from one or more of:

  • Lighthouse JSON report: parse directly. Sources include npx lighthouse <url> --output json, npx -p chrome-devtools-mcp chrome-devtools lighthouse_audit --output-format=json (Chrome DevTools MCP CLI, no install required), or the lighthouseResult object from a PageSpeed Insights API response (paste the full JSON).
  • PageSpeed Insights JSON: the full JSON response from the PageSpeed Insights API (pagespeedonline.googleapis.com/pagespeedonline/v5/runPagespeed). Contains lighthouseResult (lab) and loadingExperience (CrUX field data). Parse both.
  • CrUX API response: field data (p75 over the last 28 days). Parse directly. Requires CRUX_API_KEY.
  • DevTools performance trace (Perfetto JSON): complex format. Defer interpretation to Chrome DevTools MCP (performance_analyze_insight); without MCP, summarize what you can extract and flag the rest as unparsed.
  • Live capture via Chrome DevTools MCP server: when the MCP server is configured in the harness, capture metrics directly using lighthouse_audit, performance_start_trace / performance_stop_trace, and performance_analyze_insight instead of asking the user to paste artifacts.
  • Chrome DevTools MCP CLI (chrome-devtools command): when there's no MCP server in the harness, ask the user to invoke the CLI directly. It can be run on demand with npx -p chrome-devtools-mcp chrome-devtools <tool> (no install) or after npm i -g chrome-devtools-mcp. Example: chrome-devtools lighthouse_audit --output-format=json > report.json.

Read the full file on GitHub · 189 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. 4d ago First seen · 189 lines · 69 tokens per session scan A 9cc4f0a50f4b

Subscribe to this mod's changes

web-performance-auditor is an agent published in the GitHub repository peterblazejewicz/claude-plugins (7 stars, last pushed 2mo ago), licensed MIT. It adds 69 tokens to every session and 3,715 once invoked, about $0.0003 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.

Analytics and metricsFrontendagentic-aiavaloniaclaude-codecopilotdeveloper-experience
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