Trace Elixir call trees from entry points via mix xref.
Trace Elixir call trees from entry points via mix xref. Use when debugging data flow, planning signature changes, or understanding how a bug reaches code.This is the skill's description: the text your AI reads to decide when the skill applies.
elixir-call-tracing/SKILL.md
---
name: phx:trace
description: Trace Elixir call trees from entry points via mix xref. Use when debugging data flow, planning signature changes, or understanding how a bug reaches code.
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)
| 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 |… load the full skill through Skill Me