format-sync

A procedure for keeping two implementations of the same data format in sync: one written in Rust and one in Node.js. It also requires conformance tests and a fixture, which is a saved example used for testing.

In plain words
What is it for?
Use it after changing entry fields, frontmatter parsing, slug creation, GitHub URL cleanup, duplicate detection, or category data, so the Rust and Node versions are updated and tested together.
Why use it?
It prevents the desktop app and MCP server from parsing or writing the same files differently after a format change.

Command for Claude Code

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 commands/nel-neru/libraium/format-sync
Clone the repo
git clone --depth 1 https://github.com/nel-neru/LibrAIum

Made for: Claude Code.

Per session 20 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 793 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original 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 $0.00020 $0.00793
Opus 5 $0.00010 $0.00396
Sonnet 5 $0.00004 $0.00159
Haiku 4.5 $0.00002 $0.00079

Measured yesterday against content hash 87a08a634cad, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

format-sync 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 yesterday.

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.

.claude/commands/format-sync.md · 43 lines

How it starts

The opening of the file, as written. The whole thing — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.

The LibrAIum data format is deliberately dual-implemented: the Rust core (desktop app) and the Node MCP server each parse, validate, and serialize the same files. After ANY change to the entry format, slugify, URL normalization, duplicate detection, or category master shape, run this synchronization procedure.

1. Identify what changed and mirror it

Walk this mapping and make the counterpart change on the other side:

Concern Rust Node
Frontmatter schema, field defaults (status: active, source: manual, stars: 0, optional-field omission) src-tauri/src/models.rs (EntryMeta) mcp-server/lib/store.js (parseEntry consumers, summarize defaults)
Frontmatter split/parse/serialize (BOM handling, --- fences, body trimming, trailing newline) src-tauri/src/frontmatter.rs mcp-server/lib/store.js (splitFrontmatter, parseEntry, serializeEntry)
slugify (allowed charset [a-z0-9-_.], /-, lowercase, trim -) src-tauri/src/store.rs (slugify) mcp-server/lib/store.js (slugify)
GitHub URL normalization (http/https/bare/git@ forms, .git, trailing /, /tree/...) src-tauri/src/store.rs (normalize_github_url) mcp-server/lib/store.js (normalizeGithubUrl)
Duplicate detection (case-insensitive full_name) and entry id (<category>/<slug>) src-tauri/src/store.rs (find_duplicate, list_entries) mcp-server/lib/store.js (findDuplicate, listEntries, saveNewEntry)

Both sides must accept, reject, and produce identical results. Where the change touches parsing, check the reject cases too (missing opening ---, unterminated frontmatter) — error behavior must match even if error text differs.

2. Add a fixture for the new shape

Add a fixture covering the new format shape to tests/fixtures/format/. Follow the naming pattern already used there (valid inputs that must round-trip, and invalid inputs both sides must reject). The conformance runner picks fixtures up automatically. Also extend the unit tests nearest the change (frontmatter::tests / store::tests in Rust) if the fixture alone can't express it.

Read the full file on GitHub · 43 lines

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. yesterday First seen · 43 lines · 20 tokens per session scan A 87a08a634cad

Subscribe to this mod's changes

format-sync is a command published in the GitHub repository nel-neru/LibrAIum (0 stars, last pushed 5d ago), licensed MIT. It adds 20 tokens to every session and 793 once invoked, about $0.0001 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 2026-08-31.