metreja-profiler

Metreja Profiler

A .NET profiler plugin for Claude Code — built for AI-driven performance and memory analysis. Tell Claude "find why this is slow" or "where am I wasting memory?" and it profiles, analyzes, and gives you an answer backed by real data. No detours, no GUIs.

"This endpoint takes 3 seconds, find out why" / "Check if the import service is leaking memory" — Claude handles session setup, profiling, and analysis automatically. Both slowness and wastefulness, one conversation.

What You Get

Install the plugin and Claude profiles as part of fixing the problem — not as a separate step. The skill activates automatically, runs the full measure-analyze-fix loop, and gives you actionable results:

You: "This endpoint takes 3 seconds, find out why"

Claude: Setting up profiling session...
        Running with profiler attached...
        Analyzing trace (42,381 events captured)...

        Top hotspots (by self time):
        ┌──────────────────────────────────┬───────┬────────────┬───────────┐
        │ Method                           │ Calls │ Self (ms)  │ Incl (ms) │
        ├──────────────────────────────────┼───────┼────────────┼───────────┤
        │ OrderService.ValidateInventory   │    47 │    1,842.3 │   2,104.1 │
        │ DbContext.SaveChangesInternal    │    12 │      891.7 │     891.7 │
        │ PricingEngine.CalculateDiscount  │   312 │      203.4 │     247.8 │
        └──────────────────────────────────┴───────┴────────────┴───────────┘

        ValidateInventory is your bottleneck — 1.8s of self time across
        47 calls. It queries inventory per-item instead of batching.
        Here's the fix...

Plugin Contents

Component	Name	Description
Skill	metreja-profiler	Structured .NET profiling workflow — auto-activates on performance, memory, and debugging questions

Installation

Prerequisites

Metreja CLI — the .NET global tool that does the actual profiling:

dotnet tool install -g Metreja

Add Marketplace

/plugin marketplace add kodroi/metreja-profiler-marketplace

Install Plugin

/plugin install metreja-profiler@metreja-profiler-marketplace

Capabilities

Finds the real bottleneck — Self-time analysis pinpoints the method that's actually slow, not the one that calls it.

Catches wastefulness — Excessive allocations, GC thrashing, memory pressure. See which types allocate the most and which methods trigger gen2 collections.

Traces call paths — Follow execution through your code, including async state machines resolved to their original method names.

Proves the fix worked — Diff two traces. See the numbers. No guessing whether your change helped.

Drills down iteratively — Start broad, then narrow to a specific namespace, class, or method. The agent handles the iterative investigation.

How It Works

The skill guides Claude through five phases:

1. Target analysis — Identifies the project and designs method filters based on your question
2. Session setup — Creates a profiling session with the metreja CLI, configuring filters, output paths, and event caps
3. Profiled execution — Runs your app with the native profiler DLL attached via .NET's COR_PROFILER mechanism
4. Analysis — Reads the captured NDJSON trace using hotspots, call tree, callers, and memory commands
5. Findings — Links trace data back to your source code with actionable fix suggestions

Example Prompts

What you say	What happens
"Profile this app and find the bottleneck"	Full performance scan with hotspot analysis
"Why is ProcessOrder slow?"	Targeted profiling with call tree drill-down
"Check for memory leaks in the import service"	GC + allocation analysis with track-memory enabled
"What exceptions are thrown during checkout?"	Execution trace with exception event filtering
"Compare performance before and after my fix"	Two profiling sessions + analyze-diff

CLI Quick Reference