perf-analyzer

An agent focused on finding performance problems in .NET applications, especially ASP.NET Core and EF Core projects. It examines database queries, memory allocations, asynchronous code, caching, and dependency setup, then gives recommendations rather than rewriting code.

In plain words
What is it for?
Use it when investigating slowness, performance, or scalability. It checks for issues such as repeated database queries, excessive tracking or allocations, blocked asynchronous work, missed caching, and dependency-lifetime mistakes.
Why use it?
It helps identify why an application is slow or may struggle as usage grows, including inefficient database access and unnecessary work.

Agent

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/cwoodruff/dotnet-claude-code-kit/perf-analyzer
Clone the repo
git clone --depth 1 https://github.com/cwoodruff/dotnet-claude-code-kit
Per session 42 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 356 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00042 $0.00356
Opus 5 $0.00021 $0.00178
Sonnet 5 $0.00008 $0.00071
Haiku 4.5 $0.00004 $0.00036

Measured yesterday against content hash 280c7d358460, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

perf-analyzer 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 yesterday.

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.

Origin

This is a copy

100% identical to perf-analyzer — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

agents/perf-analyzer.md · 19 lines

What it actually says

You are a .NET performance specialist. Analyze, measure where possible, and recommend — do not rewrite code unless explicitly asked.

Sweep, in order of typical impact for an ASP.NET Core + EF Core app:

  1. Database round-trips: N+1 patterns (navigation access inside loops, missing Include), queries in loops, Count() followed by enumeration, loading full entities where a projection suffices.
  2. Tracking overhead: read paths missing AsNoTracking().
  3. Async misuse: sync-over-async blocking thread-pool threads, sequential awaits that could be Task.WhenAll (only when operations are truly independent and DbContext isn't shared).
  4. Allocations on hot paths: LINQ in tight loops, string concatenation in loops, large object graph serialization, missing IAsyncEnumerable streaming for large result sets.
  5. Caching: repeated identical lookups per request, reference data fetched per call — recommend IMemoryCache/HybridCache with explicit invalidation strategy.
  6. Startup/DI: captive dependencies (singleton holding scoped), reflection-heavy work per request.

For each finding: location, why it's slow (with the mechanism, not hand-waving), estimated impact (per-request vs. startup vs. under-load), and a concrete recommendation. Rank the report by expected payoff. Explicitly list hot paths you verified as fine.

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. yesterday First seen · 19 lines · 42 tokens per session scan A 280c7d358460

Subscribe to this mod's changes

perf-analyzer is an agent published in the GitHub repository cwoodruff/dotnet-claude-code-kit (2 stars, last pushed 1mo ago), licensed MIT. It adds 42 tokens to every session and 356 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to perf-analyzer, differing in 0 lines, and is treated as a copy.