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Agent skill

Trace

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

A skill your agent uses when debugging how a value or request reaches Elixir code, finding who calls a function, or planning a signature change.

MITAuto-check passedDevelopment

Install Trace

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

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

GitHub CLI
$ gh skill install oliver-kriska/claude-elixir-phoenix trace --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/plugins/elixir-phoenix/skills/trace .claude/skills/trace && 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
trace
GitHub stars
565
Token cost
~819 tokens
SKILL.md length
344 words
Files
4 (incl. references)
Skills in repo
105
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when debugging how a value or request reaches Elixir code, finding who calls a function, or planning a signature change.

  • Works in 5 steps: Always use mix xref callers first - It's… → Stop at entry points - Controllers,… → Track visited MFAs - Prevent infinite… → …
  • Debugging how a value
  • SKILL.md covers Iron Laws - Never Violate These, When to Build Call Tree (Use…, Quick Trace and Entry Points (Stop Here), plus 3 more sections
  • Calls claude

What it does

Trace is an agent skill from oliver-kriska/claude-elixir-phoenix. Use when debugging how a value or request reaches Elixir code, finding who calls a function, or planning a signature change. Builds the call tree with mix xref callers instead of reading files one by one.

Its SKILL.md is about 820 tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including reference files (for example `references/argument-extraction.md`, `references/entry-points.md` and `references/mix-xref-usage.md`).

It sits in Development, covering Debugging. 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

  • Debugging how a value
  • Request reaches Elixir code
  • Finding who calls a function
  • Planning a signature change

Example prompts

  • “/trace”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

  1. Always use mix xref callers first - It's authoritative; grep is fallback only
  2. Stop at entry points - Controllers, LiveView callbacks, Oban workers, GenServer callbacks
  3. Track visited MFAs - Prevent infinite loops from circular calls
  4. Extract argument patterns - Just knowing "who calls" isn't enough; HOW they call matters
  5. Max depth 10 - Deeper trees indicate architectural issues, not useful traces

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

    Shell commands in SKILL.md call:

    • claude

    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

Trace loads about 819 tokens when it runs, and up to ~4.8k if it reads all its reference files. Until then it costs about 53 tokens; SKILL.md has 344 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~53
When it runs · the whole SKILL.md, loaded when a task matches
~819
With references · SKILL.md plus every file in references/, read only if the agent opens them
~4.8k

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). 344 words, ~819 tokens.

Download SKILL.mdSave it as .claude/skills/trace/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.
name
trace
description
Use when debugging how a value or request reaches Elixir code, finding who calls a function, or planning a signature change. Builds the call tree with mix xref callers instead of reading files one by one.
effort
medium

Call Tracing

Build call trees showing how functions are reached from entry points.

Iron Laws - Never Violate These

  1. Always use mix xref callers first - It's authoritative; grep is fallback only
  2. Stop at entry points - Controllers, LiveView callbacks, Oban workers, GenServer callbacks
  3. Track visited MFAs - Prevent infinite loops from circular calls
  4. Extract argument patterns - Just knowing "who calls" isn't enough; HOW they call matters
  5. Max depth 10 - Deeper trees indicate architectural issues, not useful traces

When to Build Call Tree (Use Proactively)

ConditionWhy Call Tree Helps
Unexpected nil/value at runtimeTrace where the value originates
Bug can't reproduce locallySee all entry points that reach the code
Changing function signatureFind all callers and their argument patterns
Incomplete stack traceGet full path context
"Where does X come from?"Visual answer to data flow question

Quick Trace

Run the caller query first, then inspect another function in the chain as needed:

bash
mix xref callers MyApp.Accounts.update_user/2
mix xref callers MyApp.Accounts.get_user/1

Read the reported locations to see argument patterns.

Entry Points (Stop Here)

PatternType
def mount/3, def handle_event/3LiveView
def index/2, def show/2, def create/2Controller
def perform(%Oban.Job{})Oban Worker
def handle_call/3, def handle_cast/2GenServer

Delegate to call-tracer Agent

For full recursive tree with argument extraction and parallel category tracing:

Determine the effective maximum nesting depth. Use an explicit positive-integer CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH value first; when it is unset, inspect claude --version (the default is 1 in 2.1.217–2.1.218 and 3 in 2.1.219+). If the version is unavailable, conservatively use 1. At depth 2+, delegate to the orchestrator below. At depth 1, keep orchestration in this main session: spawn the applicable controller, LiveView, worker, and internal tracing prompts directly, then merge their results. Never spawn an orchestrator that cannot delegate.

Agent(subagent_type: "phx:call-tracer", prompt: "Build call tree for MyApp.Accounts.update_user/2")

The call-tracer agent uses parallel subagents for each entry point category:

  • Controllers subagent (HTTP paths)
  • LiveView subagent (WebSocket paths)
  • Workers subagent (Background jobs)
  • Internal subagent (Cross-context calls)

Each gets a fresh context for deep exploration.

Output Location

.claude/plans/{slug}/research/call-tree-{function}.md

References

For detailed patterns:

  • ${CLAUDE_SKILL_DIR}/references/mix-xref-usage.md - Full mix xref commands and options
  • ${CLAUDE_SKILL_DIR}/references/entry-points.md - All Phoenix/OTP entry point patterns
  • ${CLAUDE_SKILL_DIR}/references/argument-extraction.md - AST parsing for argument patterns

© 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 plugins/elixir-phoenix/skills/trace of oliver-kriska/claude-elixir-phoenix.

  • SKILL.md
  • references/argument-extraction.md
  • references/entry-points.md
  • references/mix-xref-usage.md

Open the folder on GitHubat commit 9767a82

Compare with similar skills

Trace 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.

Trace compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Trace this skilloliver-kriska/claude-elixir-phoenix565—~819Automated safety check: PassMIT
Trellis Session Insightmindfold-ai/Trellis15k4 repos~1.7kAutomated safety check: PassAGPL-3.0
Native Data FetchingCherryHQ/cherry-studio-app4k6 repos~2.9kAutomated safety check: NotesMIT
Debugging Executionsn8n-io/n8n207k—~2.6kAutomated safety check: PassCustom licence
Aoti Debugpytorch/pytorch104k1 repos~1.7kAutomated safety check: PassCustom licence
Herdr Throwaway Reproductionherdrdev/herdr43k—~2.4kAutomated safety check: PassApache-2.0

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Works with

Categories

Questions about Trace

What does Trace do?

A skill your agent uses when debugging how a value or request reaches Elixir code, finding who calls a function, or planning a signature change. Trace is an agent skill from oliver-kriska/claude-elixir-phoenix. Use when debugging how a value or request reaches Elixir code, finding who calls a function, or planning a signature change.

When should I use Trace?

Trace fits situations like: debugging how a value; request reaches Elixir code; finding who calls a function; planning a signature change.

How do I install Trace in Claude Code?

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

How do I install Trace in Codex?

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

Can I use Trace 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 trace -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/trace, .gemini/skills/trace, .github/skills/trace and .opencode/skills/trace in your project.

What does Trace need to run?

Going by SKILL.md and its folder, Trace needs the command-line tools its instructions call (claude).

Does Trace 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 Trace 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 Trace use?

Trace 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 Trace use?

About 819 tokens (SKILL.md is roughly 3.3k 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 4k tokens, read only when the agent opens those files.

What are the alternatives to Trace?

Skills that share tags, products or a category with Trace: Trellis Session Insight (mindfold-ai/Trellis, 15k stars), Native Data Fetching (CherryHQ/cherry-studio-app, 4k stars), Debugging Executions (n8n-io/n8n, 207k stars) and Aoti Debug (pytorch/pytorch, 104k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Trace?

oliver-kriska (a GitHub user) maintains it in oliver-kriska/claude-elixir-phoenix, which has 565 GitHub stars. The repository holds 105 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.