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Agent skill

Phx Investigate

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

Investigate Elixir/Phoenix bugs root-cause first. An agent skill from oliver-kriska/claude-elixir-phoenix.

MITAuto-check passedAI & LLM Engineering

Install Phx Investigate

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

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

GitHub CLI
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-investigate --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/amp/skills/phx-investigate .claude/skills/phx-investigate && 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/

Facts

Skill name
phx-investigate
GitHub stars
565
Token cost
~1.1k tokens
SKILL.md length
556 words
Files
4 (incl. references)
Skills in repo
109
Repo updated
First seen
Licence
MIT

At a glance

Investigate Elixir/Phoenix bugs root-cause first. An agent skill from oliver-kriska/claude-elixir-phoenix.

  • Works in 7 steps: Consult Existing Evidence → Capture Runtime Context When Available → Run Sanity Checks → …
  • Tasks that involve LLM observability
  • SKILL.md covers Usage, Iron Laws, Workflow and References, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Phx Investigate is an agent skill from oliver-kriska/claude-elixir-phoenix. Investigate Elixir/Phoenix bugs root-cause first. Reproduce failures, cite evidence, and use optional Amp subagents only when useful.

Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including reference files (for example `references/debug-commands.md`, `references/error-patterns.md` and `references/investigation-template.md`).

It sits in AI & LLM Engineering, covering LLM observability, Root cause analysis and Subagents. 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

  • Tasks that involve LLM observability
  • Tasks that involve Root cause analysis
  • Tasks that involve Subagents

Example prompts

  • “/phx-investigate”

Workflow steps

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

  1. Consult Existing Evidence
  2. Capture Runtime Context When Available
  3. Run Sanity Checks
  4. Reproduce Before Fixing
  5. Check the Obvious
  6. Trace and Test the Hypothesis
  7. Report

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).

    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 Investigate loads about 1.1k tokens when it runs, and up to ~2.3k if it reads all its reference files. Until then it costs about 37 tokens; SKILL.md has 556 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~37
When it runs · the whole SKILL.md, loaded when a task matches
~1.1k
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). 556 words, ~1,134 tokens.

Download SKILL.mdSave it as .claude/skills/phx-investigate/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.
name
phx-investigate
description
Investigate Elixir/Phoenix bugs root-cause first. Reproduce failures, cite evidence, and use optional Amp subagents only when useful.

Investigate Bug

Investigate Elixir/Phoenix bugs root-cause first. Reproduce or establish the failing behavior before recommending a fix, and cite concrete paths and lines.

Usage

text
phx-investigate Users can't log in after password reset
phx-investigate FunctionClauseError in UserController.show
phx-investigate Complex auth bug --parallel

Treat the text after the skill name as the bug description. --parallel asks for independent investigation tracks when native Amp subagent tooling is available; it is an optimization, never a requirement.

Iron Laws

  1. Read the error literally first — extract the exception, message, failing assertion, and first relevant application frame before theorizing.
  2. Check the obvious before going deep — compile errors, missing migrations, atom/string mismatches, nil values, stale servers, and changeset errors explain many failures.
  3. Reproduce before proposing a fix — run the smallest relevant test or controlled command and record its output. If reproduction is impossible, state exactly what evidence establishes the failure instead.
  4. Confirm the root cause with evidence — distinguish the observed failure, the causal code path, and the proposed correction.
  5. Do not edit while investigating unless the user asks for a fix — the investigation result is evidence and a recommendation, not an implicit patch.

Workflow

1. Consult Existing Evidence

Search .claude/solutions/, recent diffs, tests, logs, and the literal error. Do not block if .claude/solutions/ does not exist.

2. Capture Runtime Context When Available

Tidewave is optional. If its tools are configured, use them for logs, source locations, safe queries, or hypothesis checks. Otherwise use repository files, mix commands, and local logs. Never fail or ask the user to install Tidewave merely to continue an investigation.

3. Run Sanity Checks

Choose focused checks that fit the report, such as:

bash
mix compile --warnings-as-errors
mix test test/path_test.exs --trace

Do not run migrations or other state-changing commands unless they are necessary, safe for the fixture, and authorized by the user.

4. Reproduce Before Fixing

Capture the exact command, failure, and relevant output. Read references/error-patterns.md, then inspect only the code needed to trace the failure from entry point to cause.

5. Check the Obvious

Check saved files, atom/string keys, preload state, pattern matches, nil values, return values, server restarts, and changeset errors. For silent LiveView form failures, inspect {:error, changeset} and rendered validation errors before JS.

Show full SKILL.md (213 more words)Show less
6. Trace and Test the Hypothesis

Use targeted searches, source reads, tests, or non-mutating diagnostics. Only add temporary source diagnostics if the user explicitly authorizes edits, and remove them before reporting. Cite path:line evidence for both the failing behavior and the causal code.

If native Amp subagents are available and the bug genuinely spans independent areas, delegate read-only tracks by concern. Otherwise perform the same tracks sequentially in this session. Do not require named custom agents.

7. Report

Use references/investigation-template.md. Include:

  • reproduction or evidence establishing the failure;
  • root cause, not merely the symptom;
  • relevant paths and lines;
  • confidence and any unverified assumptions;
  • the smallest safe fix or next diagnostic step.

Route follow-up work with phx-quick, phx-plan, or phx-compound when appropriate. Do not invoke another skill unless the user asks you to continue.

References

  • references/error-patterns.md — common errors and checklist
  • references/investigation-template.md — output format
  • references/debug-commands.md — debug commands and common fixes

Amp native parallel investigation

For a non-trivial failure with independent reproduction, root-cause, impact, and fix-strategy questions, call elixir_phoenix_parallel_investigate once. Its four local child threads are enforced read-only (Read and finder only). Reconcile their output in this parent thread and verify every claimed evidence path before editing. If the tool is unavailable or a child fails, run only the missing track sequentially. Simple failures should stay sequential.

© oliver-kriska, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 3 other files (references) in targets/amp/skills/phx-investigate of oliver-kriska/claude-elixir-phoenix.

  • SKILL.md
  • references/debug-commands.md
  • references/error-patterns.md
  • references/investigation-template.md

Open the folder on GitHubat commit 9767a82

Compare with similar skills

Phx Investigate 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 Investigate compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Phx Investigate this skilloliver-kriska/claude-elixir-phoenix565—~1.1kAutomated safety check: PassMIT
Datadog Query Recipeslangfuse/langfuse36k—~824Automated safety check: PassCustom licence
Ash Frameworkpodlove/radiator136—~2.1kAutomated safety check: PassMIT
Sentry Elixir SDKgetsentry/sentry-for-ai268—~3.5kAutomated safety check: PassApache-2.0
Elixirstreamband/hydra-srt147—~804Automated safety check: PassApache-2.0
Change CleanupSimon-Initiative/oli-torus119—~3.7kAutomated safety check: PassMIT

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Works with

Categories

Questions about Phx Investigate

What does Phx Investigate do?

Investigate Elixir/Phoenix bugs root-cause first. An agent skill from oliver-kriska/claude-elixir-phoenix. Phx Investigate is an agent skill from oliver-kriska/claude-elixir-phoenix. Investigate Elixir/Phoenix bugs root-cause first.

When should I use Phx Investigate?

Phx Investigate fits situations like: tasks that involve LLM observability; tasks that involve Root cause analysis; tasks that involve Subagents.

How do I install Phx Investigate in Claude Code?

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

How do I install Phx Investigate in Codex?

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

Can I use Phx Investigate 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-investigate -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-investigate, .gemini/skills/phx-investigate, .github/skills/phx-investigate and .opencode/skills/phx-investigate in your project.

What does Phx Investigate need to run?

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

Does Phx Investigate 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 Investigate 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 Investigate use?

Phx Investigate 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 Investigate use?

About 1.1k tokens (SKILL.md is roughly 4.5k 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 1.1k tokens, read only when the agent opens those files.

What are the alternatives to Phx Investigate?

Skills that share tags, products or a category with Phx Investigate: Datadog Query Recipes (langfuse/langfuse, 36k stars), Ash Framework (podlove/radiator, 136 stars), Sentry Elixir SDK (getsentry/sentry-for-ai, 268 stars) and Elixir (streamband/hydra-srt, 147 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Phx Investigate?

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.