phx:trace
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.
npx skills add majiayu000/claude-skill-registry --skill call-tracing --agent claude-code
Same command for any agent — swap --agent for codex, cursor, copilot.
Weekly change comes from our own snapshots, not the repository page — it measures attention, not adoption.
# 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 | | Incomplete stack trace | Get full path context | | "Where does X come from?" | Visual answer to data flow question | ## Quick Trace Run `mix xref callers MyApp.Accounts.update_user/2` to find all callers. Then read the reported locations to see argument patterns. ## Entry Points (Stop Here) | Pattern
- Iron Laws - Never Violate These
- When to Build Call Tree (Use Proactively)
- Quick Trace
- Entry Points (Stop Here)
- Delegate to call-tracer Agent
- Output Location
- References
What does the phx:trace skill do?
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.
How do I install it?
Run `npx skills add majiayu000/claude-skill-registry --skill call-tracing --agent claude-code` — it drops the skill into your project so the agent can pick it up. Swap the --agent value for codex, cursor or copilot if you use one of those.
Where does this skill come from?
From majiayu000/claude-skill-registry, a repository with 534 stars. We read it straight from the repository tree rather than a submitted listing, so what you see here is what is actually published.
Is a popular skill a good skill?
Not necessarily. Stars measure attention, not adoption — a repository can trend for a week and be abandoned. That is why we show the weekly change from our own snapshots next to the total, instead of a single flattering number.