Agent skill

Phx Perf

by oliver-kriska in oliver-kriska/claude-elixir-phoenix

A skill your agent uses when anything in a Phoenix app is slow, times out, or uses too much memory, even if the cause looks obvious.

MITAuto-check passedAI & LLM Engineering

Install Phx Perf

skills CLI

$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install oliver-kriska/claude-elixir-phoenix phx-perf --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .claude/skills && cp -r skills-src/targets/codex/skills/phx-perf .claude/skills/phx-perf && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "phx-perf" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf into .claude/skills/phx-perf/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-perf", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install oliver-kriska/claude-elixir-phoenix phx-perf --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .agents/skills && cp -r skills-src/targets/codex/skills/phx-perf .agents/skills/phx-perf && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "phx-perf" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf into .agents/skills/phx-perf/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-perf", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install oliver-kriska/claude-elixir-phoenix phx-perf --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/targets/codex/skills/phx-perf .cursor/skills/phx-perf && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "phx-perf" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf into .cursor/skills/phx-perf/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-perf", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/oliver-kriska/claude-elixir-phoenix.git --path targets/codex/skills/phx-perf

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install oliver-kriska/claude-elixir-phoenix phx-perf --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/targets/codex/skills/phx-perf .gemini/skills/phx-perf && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "phx-perf" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf into .gemini/skills/phx-perf/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-perf", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install oliver-kriska/claude-elixir-phoenix phx-perf

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .github/skills && cp -r skills-src/targets/codex/skills/phx-perf .github/skills/phx-perf && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "phx-perf" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf into .github/skills/phx-perf/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-perf", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install oliver-kriska/claude-elixir-phoenix phx-perf --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/targets/codex/skills/phx-perf .opencode/skills/phx-perf && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "phx-perf" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/phx-perf into .opencode/skills/phx-perf/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-perf", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: phx-perf
GitHub stars: 565
Token cost: ~963 tokens
SKILL.md length: 329 words
Files: 2 (incl. references)
Skills in repo: 109
Repo updated: Oct 5, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

A skill your agent uses when anything in a Phoenix app is slow, times out, or uses too much memory, even if the cause looks obvious.

Works in 5 steps: Identify Scope → Run Analysis Tracks → Prioritize Findings → …
Anything in a Phoenix app is slow
SKILL.md covers Usage, Arguments, Iron Laws and Workflow, plus 2 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Phx Perf is an agent skill from oliver-kriska/claude-elixir-phoenix. Use when anything in a Phoenix app is slow, times out, or uses too much memory, even if the cause looks obvious. Load…

Its SKILL.md is about 960 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/benchmarking.md`).

It sits in AI & LLM Engineering, covering LLM observability. It works with Elixir. The repository describes itself as: Claude Code plugin for Elixir/Phoenix/LiveView — 26 specialist agents, Iron Laws enforcement, and Tidewave MCP integration. Plan features with parallel research agents, execute… The licence is MIT.

When your agent uses it

Anything in a Phoenix app is slow
Uses too much memory
Even if the cause looks obvious

Example prompts

“/phx-perf”

Workflow steps

5 steps, taken from the step headings in SKILL.md.

Identify Scope
Run Analysis Tracks
Prioritize Findings
Present Top 5
Offer Next Steps

What it can do on your machine

Read from SKILL.md and the folder at commit 9767a82. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are bash and markdown).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Phx Perf loads about 963 tokens when it runs, and up to ~2.3k if it reads all its reference files. Until then it costs about 32 tokens; SKILL.md has 329 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~32
When it runs · the whole SKILL.md, loaded when a task matches: ~963
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~2.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from oliver-kriska/claude-elixir-phoenix at commit 9767a82, republished under its MIT licence (© oliver-kriska). 329 words, ~963 tokens.

Download SKILL.mdSave it as .claude/skills/phx-perf/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

name: phx-perf
description: Use when anything in a Phoenix app is slow, times out, or uses too much memory, even if the cause looks obvious. Load…

Performance Analysis

Analyze code for performance issues across Ecto, LiveView, and OTP layers. Prioritize findings by impact and effort.

Usage

$elixir-phoenix:phx-perf                           # Analyze full project
$elixir-phoenix:phx-perf lib/my_app/accounts.ex    # Analyze specific module
$elixir-phoenix:phx-perf --focus ecto              # Ecto queries only
$elixir-phoenix:phx-perf --focus liveview          # LiveView memory only
$elixir-phoenix:phx-perf --focus otp               # OTP bottlenecks only

Arguments

$ARGUMENTS = Optional module/context path and --focus flag.

Iron Laws

MEASURE BEFORE OPTIMIZING — Never optimize without evidence of a problem
DATABASE FIRST — 90% of Elixir performance issues are query-related
ONE CHANGE AT A TIME — Isolate optimizations to measure impact
NEVER benchmark in dev mode — Always use MIX_ENV=prod for performance measurements; dev mode includes code reloading, debug logging, and unoptimized compilation that invalidate results

Workflow

Step 1: Identify Scope

Check specific file if provided. Otherwise scan full project:

bash

# Find hot paths: contexts, LiveViews, workers
find lib/ -name "*.ex" | head -50

Step 2: Run Analysis Tracks

Spawn analysis agents in parallel based on focus:

Ecto Track (default or --focus ecto):

Spawn phx:elixir-reviewer with prompt: "Analyze for N+1 queries, missing preloads, unindexed queries, and inefficient patterns. Check: Repo.all in loops, Enum.map with Repo calls, missing preload, queries without indexes on WHERE/JOIN columns."

LiveView Track (default or --focus liveview):

Spawn phx:elixir-reviewer with prompt: "Analyze LiveViews for memory issues: large assigns, missing streams for lists, assigns that grow unbounded, heavy handle_info processing, missing assign_async for slow ops."

OTP Track (only with --focus otp):

Spawn phx:otp-advisor with prompt: "Analyze for OTP bottlenecks: GenServer mailbox growth, synchronous calls in hot paths, missing Task.async for parallel work, ETS opportunities for read-heavy state."

Step 3: Prioritize Findings

Score each finding on a 2x2 matrix:

	Low Effort	High Effort
High Impact	DO FIRST	PLAN
Low Impact	QUICK WIN	SKIP

High impact = affects response time, memory per user, or query count. Low effort = single file change, no migration needed.

Step 4: Present Top 5

Present findings sorted by priority:

markdown

## Performance Analysis: {scope}

### 1. {Finding} — DO FIRST
**Impact**: {what improves}
**Location**: {file}:{line}
**Current**: {problematic pattern}
**Fix**: {optimized pattern}
**Estimated gain**: {e.g., "eliminates N+1, reduces queries from O(n) to O(1)"}

### 2. {Finding} — PLAN
...

Step 5: Offer Next Steps

Always end with actionable next steps — findings without follow-up get lost. Present options based on severity:

How would you like to proceed?

- `$elixir-phoenix:phx-plan` — Create a plan from these findings (recommended for 3+ fixes)
- `$elixir-phoenix:phx-quick` — Apply top priority fix directly (1-2 simple fixes)
- `$elixir-phoenix:phx-investigate` — Deep-dive into a specific finding

Tidewave Integration

If Tidewave MCP is available:

Use mcp__tidewave__project_eval to run Repo.query!("EXPLAIN ANALYZE ...") on suspicious queries
Use mcp__tidewave__project_eval to check Process.info(pid, :message_queue_len) for GenServer bottlenecks
Use mcp__tidewave__execute_sql_query to check missing indexes

References

references/benchmarking.md — Benchee patterns, profiling, flame graphs

Files

SKILL.md and 1 other file (references) in targets/codex/skills/phx-perf of oliver-kriska/claude-elixir-phoenix.

SKILL.md
references/benchmarking.md

Open the folder on GitHubat commit 9767a82

Compare with similar skills

Phx Perf next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Phx Perf compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Phx Perf this skilloliver-kriska/claude-elixir-phoenix	565	—	~963	Automated safety check: Pass	MIT	4 days ago
Elixir Architectmaxim-ist/elixir-architect	145	—	~7.6k	Automated safety check: Pass	MIT	10 mo ago
Phoenix Frameworkpodlove/radiator	136	—	~562	Automated safety check: Pass	MIT	15 days ago
Elixir Expertpass-agent/loomkin	181	1 repos	~796	Automated safety check: Pass	MIT	4 mo ago
Usage Rulesbradleygolden/claude-marketplace-elixir	176	—	~4.9k	Automated safety check: Notes	MIT	9 mo ago
Elixir Prodavila7/claude-code-templates	33k	8 repos	~486	Automated safety check: Pass	MIT	today

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Questions about Phx Perf

What does Phx Perf do?

A skill your agent uses when anything in a Phoenix app is slow, times out, or uses too much memory, even if the cause looks obvious. Phx Perf is an agent skill from oliver-kriska/claude-elixir-phoenix. Use when anything in a Phoenix app is slow, times out, or uses too much memory, even if the cause looks obvious.

When should I use Phx Perf?

Phx Perf fits situations like: anything in a Phoenix app is slow; uses too much memory; even if the cause looks obvious.

How do I install Phx Perf in Claude Code?

Run `npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a claude-code`. Or copy the skill folder (targets/codex/skills/phx-perf in oliver-kriska/claude-elixir-phoenix) into .claude/skills/phx-perf in your project. Claude Code loads it when a task matches its description.

How do I install Phx Perf in Codex?

Run `npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a codex`. Or copy the skill folder (targets/codex/skills/phx-perf in oliver-kriska/claude-elixir-phoenix) into .agents/skills/phx-perf in your project. Codex loads it when a task matches its description.

Can I use Phx Perf in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-perf -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/phx-perf, .gemini/skills/phx-perf, .github/skills/phx-perf and .opencode/skills/phx-perf in your project.

What does Phx Perf need to run?

SKILL.md names no scripts, command-line tools or credentials: Phx Perf is instructions for the agent only.

Does Phx Perf access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Phx Perf safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Phx Perf use?

Phx Perf is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Phx Perf use?

About 963 tokens (SKILL.md is roughly 3.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.3k tokens, read only when the agent opens those files.

What are the alternatives to Phx Perf?

Skills that share tags, products or a category with Phx Perf: Elixir Architect (maxim-ist/elixir-architect, 145 stars), Phoenix Framework (podlove/radiator, 136 stars), Elixir Expert (pass-agent/loomkin, 181 stars) and Usage Rules (bradleygolden/claude-marketplace-elixir, 176 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Phx Perf?

oliver-kriska (a GitHub user) maintains it in oliver-kriska/claude-elixir-phoenix, which has 565 GitHub stars. The repository holds 109 skills in this directory. The repository was last updated on October 5, 2026.

Source: oliver-kriska/claude-elixir-phoenix on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Phx Perf

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Performance Analysis

Usage

Arguments

Iron Laws

Workflow

Step 1: Identify Scope

Step 2: Run Analysis Tracks

Step 3: Prioritize Findings

Step 4: Present Top 5

Step 5: Offer Next Steps

Tidewave Integration

References

Files

Compare with similar skills

Similar skills

More from oliver-kriska/claude-elixir-phoenix

Related

Questions about Phx Perf