write-compressor

Guidance for building custom compression encoders that produce data an existing decoder can read. Compression reduces file size, while an encoder creates the compressed data and a decoder restores it.

In plain words
What is it for?
Use it to implement or debug compatible compression encoders, including encoders using arithmetic coding.
Why use it?
It addresses the compatibility problems that arise when a new compressor must match an existing decompressor, especially for arithmetic coding.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/lazyfroglol/harness_engineering/write-compressor
Any agent
npx skills add lazyFrogLOL/Harness_Engineering --skill write-compressor
Clone the repo
git clone --depth 1 https://github.com/lazyFrogLOL/Harness_Engineering

Made for: Claude Code, Codex.

Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,449 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00064 $0.01449
Opus 5 $0.00032 $0.00724
Sonnet 5 $0.00013 $0.00290
Haiku 4.5 $0.00006 $0.00145

Measured 3d ago against content hash 6e13c97fd195, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

write-compressor 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 3d 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.

skills/write-compressor/SKILL.md · 193 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

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.

  1. 3d ago First seen · 193 lines · 64 tokens per session scan A 6e13c97fd195

Subscribe to this mod's changes

write-compressor is a skill published in the GitHub repository lazyFrogLOL/Harness_Engineering (126 stars, last pushed 3mo ago), with no licence file. It adds 64 tokens to every session and 1,449 once invoked, about $0.0003 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 2026-08-30.

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