How do I install the Phx Trace skill?

Run npx skillmds@latest add oliver-kriska/phx-trace in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Phx Trace safe to use?

This skill has not completed SkillMD's automated safety review yet. Capability flags: docs only. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Phx Trace?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Phx Trace free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Phx Trace?

oliver-kriska (@oliver-kriska) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Phx Trace by oliver-kriska — Agent Skill

Name: Phx Trace
Rating: 4.5 (4 reviews)
Author: oliver-kriska

File contents

Call Tracing

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

Iron Laws - Never Violate These

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

When to Build Call Tree (Use Proactively)

Condition	Why Call Tree Helps
Unexpected nil/value at runtime	Trace where the value originates
Bug can't reproduce locally	See all entry points that reach the code
Changing function signature	Find all callers and their argument patterns
Incomplete stack trace	Get 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:

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)

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

Full Recursive Trace

Trace controller, LiveView, worker, and internal entry-point categories in this session, starting each category with mix xref callers. Native generic workers may handle independent categories in parallel when the runtime provides them, but the same-session sequential path is fully supported and must produce the same call tree. Do not require a named custom agent or Claude-specific spawn configuration.

Output Location

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

References

For detailed patterns:

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

---name: phx-tracedescription: Trace Elixir call trees from entry points via mix xref. Use when debugging data flow, planning signature changes…---# Call TracingBuild call trees showing how functions are reached from entry points.## Iron Laws - Never Violate These1. **Always use `mix xref callers` first** - It's authoritative; grep is fallback only2. **Stop at entry points** - Controllers, LiveView callbacks, Oban workers, GenServer callbacks3. **Track visited MFAs** - Prevent infinite loops from circular calls4. **Extract argument patterns** - Just knowing "who calls" isn't enough; HOW they call matters5. **Max depth 10** - Deeper trees indicate architectural issues, not useful traces## When to Build Call Tree (Use Proactively)| Condition | Why Call Tree Helps ||-----------|---------------------|| Unexpected nil/value at runtime | Trace where the value originates || Bug can't reproduce locally | See all entry points that reach the code || Changing function signature | Find all callers and their argument patterns || Incomplete stack trace | Get full path context || "Where does X come from?" | Visual answer to data flow question |## Quick TraceRun the caller query first, then inspect another function in the chain as needed:```bashmix xref callers MyApp.Accounts.update_user/2mix xref callers MyApp.Accounts.get_user/1```Read the reported locations to see argument patterns.## Entry Points (Stop Here)| Pattern | Type ||---------|------|| `def mount/3`, `def handle_event/3` | LiveView || `def index/2`, `def show/2`, `def create/2` | Controller || `def perform(%Oban.Job{})` | Oban Worker || `def handle_call/3`, `def handle_cast/2` | GenServer |## Full Recursive TraceTrace controller, LiveView, worker, and internal entry-point categories in thissession, starting each category with `mix xref callers`. Native generic workersmay handle independent categories in parallel when the runtime provides them,but the same-session sequential path is fully supported and must produce thesame call tree. Do not require a named custom agent or Claude-specific spawnconfiguration.## Output Location`.claude/plans/{slug}/research/call-tree-{function}.md`## ReferencesFor detailed patterns:- `references/mix-xref-usage.md` - Full mix xref commands and options- `references/entry-points.md` - All Phoenix/OTP entry point patterns- `references/argument-extraction.md` - AST parsing for argument patterns

Frequently asked questions

Phx Trace