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 mix-compressiongit 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/mix-compression)<a href="https://agentmods.dev/skills/oliver-kriska/claude-elixir-phoenix/mix-compression"><img src="https://agentmods.dev/badge/skills/oliver-kriska/claude-elixir-phoenix/mix-compression/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/mix-compression"><img src="https://agentmods.dev/badge/skills/oliver-kriska/claude-elixir-phoenix/mix-compression.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00048 | $0.01076 |
| Opus 5 | $0.00024 | $0.00538 |
| Sonnet 5 | $0.00010 | $0.00215 |
| Haiku 4.5 | $0.00005 | $0.00108 |
Grade A, and why
mix-compression 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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 104 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mix Output Compression
Mix commands (mix test, mix credo, mix dialyzer, mix compile) emit
verbose, repetitive output that consumes context fast. This skill installs
rtk — a CLI proxy that filters tool output
before it lands in the transcript.
The filters short-circuit happy paths to a single line (mix test: all pass)
while preserving full failure blocks, compile errors, and stack traces. Net win:
5-15% per-session token reduction on mix-heavy workflows.
When to use
- Long sessions —
/phx:workor/phx:fullhitting context limits from mix output - Debugging loops —
/phx:investigateretryingmix compile/mix testrepeatedly - Dialyzer-heavy projects —
mix dialyzeroutput dominates the transcript
Iron Laws
- NEVER strip critical signals — compile errors (
** (CompileError),== Compilation error in), test failures (FAILURES,0 failures— preserved even on short-circuit), dialyzer warnings, and stack traces withfile:lineMUST pass through unchanged - Verify after install — run
rtk verify(orrtk verify --filter mix-test) to confirm the bundled test fixtures pass before declaring success - Never overwrite existing
.rtk/filters.toml— diff and merge instead
Workflow
Step 1: Detect rtk
which rtk && rtk --version
Read ${CLAUDE_SKILL_DIR}/references/install.md if rtk is missing — covers
homebrew install + shell hook setup.
Step 2: Seed .rtk/filters.toml
Reference filters live at ${CLAUDE_SKILL_DIR}/references/rtk-filters.toml. Six
production-tested filters covering:
mix-test— short-circuits all-pass, preserves failure blocks + compile errorsmix-credo— collapses clean runs, preserves violation blocksmix-dialyzer— drops PLT progress, keeps warnings + summarymix-deps-get— collapses unchanged package listsmix-ecto-migrate— strips compile prefix, short-circuits "already up"mix-compile— handles parallel worker prefixes (N>) and MIX_ENV
What ships with it
2 files 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.
- 5d ago First seen · 104 lines · 48 tokens per session scan A 9014ef278621
mix-compression is a skill published in the GitHub repository oliver-kriska/claude-elixir-phoenix (541 stars, last pushed 3d ago), licensed MIT. It adds 48 tokens to every session and 1,076 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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