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 agentmods add instructions/jeyben/fixedformat4j/claude-mdgit clone --depth 1 https://github.com/jeyben/fixedformat4jWrote 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/instructions/jeyben/fixedformat4j/claude-md)<a href="https://agentmods.dev/instructions/jeyben/fixedformat4j/claude-md"><img src="https://agentmods.dev/badge/instructions/jeyben/fixedformat4j/claude-md.svg" alt="Measured on agentmods" 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 | $0.02452 | $0.02452 |
| Opus 5 | $0.01226 | $0.01226 |
| Sonnet 5 | $0.00490 | $0.00490 |
| Haiku 4.5 | $0.00245 | $0.00245 |
Grade A, and why
fixedformat4j CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
Java Version
Tests require Java 11. Set JAVA_HOME before running Maven:
# Temurin 11 (installed via brew install --cask temurin@11 or sdkman)
export JAVA_HOME=/Library/Java/JavaVirtualMachines/temurin-11.jdk/Contents/Home
# Or use java_home helper on macOS
export JAVA_HOME=$(/usr/libexec/java_home -v 11)
mvn test
Build and Test Commands
This is a Maven multi-module project. Run from the repo root:
# Build and install all modules
mvn install
# Run all tests
mvn test
# Run tests for the main library only
cd fixedformat4j && mvn test
# Run a single test class
mvn test -pl fixedformat4j -Dtest=TestBigDecimalFormatter
# Run a single test method
mvn test -pl fixedformat4j -Dtest=TestBigDecimalFormatter#testSomeMethod
Project Structure
Four Maven modules:
fixedformat4j/— the core library (main artifact)fixedformat4j-processor/— optional compile-time annotation processor (since 1.9.0); mirrors the statically decidable subset of the runtime validation via the mirror API. Any change toFieldValidator/PatternValidatorchecks must be mirrored in the processor'sFieldChecker/RecordValidator, and vice versa.fixedformat4j-micrometer/— optional Micrometer instrumentation module (since 1.9.0); decorator-based, no changes to the core artifact; never add Micrometer hooks to core.samples/— usage examples
Version synchronisation: none of the modules declare a <parent>. When bumping the project version, update the <version> element in every module pom.xml (fixedformat4j/pom.xml, fixedformat4j-processor/pom.xml, fixedformat4j-micrometer/pom.xml, samples/pom.xml) in addition to the root pom.xml.
Core production source is under fixedformat4j/src/main/java/com/ancientprogramming/fixedformat4j/.
Architecture
The library maps Java POJOs annotated with @Record and @Field to/from fixed-width flat-file strings.
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.
- 4d ago First seen · 138 lines · 2,452 tokens per session scan A 21badcbf1e08
fixedformat4j CLAUDE.md is an instructions file published in the GitHub repository jeyben/fixedformat4j (53 stars, last pushed 5d ago), licensed Apache-2.0. It adds 2,452 tokens to every session, about $0.0123 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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