Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-learn-from-fixgit clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenixWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/oliver-kriska/claude-elixir-phoenix/phx-learn-from-fix)<a href="https://agentmods.dev/skills/oliver-kriska/claude-elixir-phoenix/phx-learn-from-fix"><img src="https://agentmods.dev/badge/skills/oliver-kriska/claude-elixir-phoenix/phx-learn-from-fix/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/oliver-kriska/claude-elixir-phoenix/phx-learn-from-fix"><img src="https://agentmods.dev/badge/skills/oliver-kriska/claude-elixir-phoenix/phx-learn-from-fix.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00049 | $0.01616 |
| Opus 5 | $0.00024 | $0.00808 |
| Sonnet 5 | $0.00010 | $0.00323 |
| Haiku 4.5 | $0.00005 | $0.00162 |
Grade A, and why
phx-learn-from-fix scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
94% identical to learn-from-fix — 26 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 180 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Learn From Fix
After fixing a bug or receiving a correction, capture the lesson to prevent future mistakes.
Usage
phx-learn-from-fix Fixed N+1 query in user listing - was missing preload
phx-learn-from-fix String vs atom key mismatch in params handling
phx-learn-from-fix LiveView assign_async needs render_async in tests
phx-learn-from-fix --library ical --scope personal ICal.to_ics output needs CRLF line endings
phx-learn-from-fix --library ical --scope project Use method: "PUBLISH" for calendar feeds
Workflow
Step 1: Verify the Lesson
Persist only one of:
- A completed fix verified by tests, reproduction, or user confirmation
- An explicit rule the user taught or asked to save
Stop without writing if neither condition is met.
Do not save a hypothesis, unverified workaround, investigation narrative, or
unsolved error. Use phx-compound for a detailed completed investigation.
Capture the root cause as a concise actionable rule, not the symptom.
Step 2: Select the Route
When both --library <package> and --scope personal|project are present,
use the Library Route. Require both flags; do not guess scope.
For the skill directory only, trim surrounding whitespace and lowercase the
package name. Preserve underscores when forming directory names
(phoenix_live_view becomes hex-phoenix_live_view).
Validate the normalized name against ^[a-z][a-z0-9_]+$. If it does not match,
ask for a valid Hex package identifier instead of replacing characters or
inventing a name. Use the trimmed original identifier, not the normalized
directory name, to look up mix.lock.
Without --library, use the General Correction Route.
Step 3: Check Existing Knowledge
Check if already documented:
- Grep project CLAUDE.md and
~/.claude/CLAUDE.mdfor the pattern keyword - Check auto-memory files for similar lessons
- For library lessons, inspect both
~/.claude/skills/hex-<package>/SKILL.mdand.claude/skills/hex-<package>/SKILL.md - Read
references/common-mistakes.md(READ-ONLY plugin reference — do NOT edit this file)
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 6d ago First seen · 180 lines · 49 tokens per session scan A f06291565acc
phx-learn-from-fix is a skill published in the GitHub repository oliver-kriska/claude-elixir-phoenix (542 stars, last pushed 4d ago), licensed MIT. It adds 49 tokens to every session and 1,616 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to learn-from-fix, differing in 26 lines, and is treated as a copy.
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