fizz-check

fizz-check is a skill for Claude Code, Codex from fizzbee-io/fizzbee. It costs 45 tokens per session (2,479 once invoked), scanned A, original, Apache-2.0.

A guide for running FizzBee, a tool that checks a system specification by exploring its possible states and actions. It covers exhaustive checking, random simulation, guided traces, and reading the results.

In plain words
What is it for?
Use it to run a .fizz file, simulate random behavior, replay an action sequence, extend a trace, change initial settings, choose a search strategy, and inspect output.
Why use it?
It provides the commands and options needed to verify a specification or quickly explore one possible behavior. Reproducible seeds and guided traces make specific runs easier to repeat.

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/fizzbee-io/fizzbee/fizz-check
Any agent
npx skills add fizzbee-io/fizzbee --skill fizz-check
Clone the repo
git clone --depth 1 https://github.com/fizzbee-io/fizzbee

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for fizz-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/fizzbee-io/fizzbee/fizz-check.svg)](https://agentmods.dev/skills/fizzbee-io/fizzbee/fizz-check)
Your own site
<a href="https://agentmods.dev/skills/fizzbee-io/fizzbee/fizz-check"><img src="https://agentmods.dev/badge/skills/fizzbee-io/fizzbee/fizz-check.svg" alt="Measured on agentmods" height="20"></a>
Per session 45 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,479 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 $0.00045 $0.02479
Opus 5 $0.00023 $0.01239
Sonnet 5 $0.00009 $0.00496
Haiku 4.5 $0.00005 $0.00248

Measured 4d ago against content hash 1233fafbdfa3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fizz-check 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.

.claude/skills/fizz-check/SKILL.md · 247 lines

How it starts

The opening of the file, as written. The whole thing — 247 lines — stays where its author put it; the contents beside it link to each section on GitHub.

FizzBee Model Checker

Installation

brew tap fizzbee-io/fizzbee && brew install fizzbee

Running

fizz spec.fizz                       # full model checking (exhaustive)
fizz -x --max_runs 1 --seed 42 spec.fizz   # simulation (single random path)

Note: fizz is the installed binary. If building from source, use ./fizz (wrapper script in the repo root).


All Flags

Flag Default Description
-x / --simulation off Simulation mode: single random path, fast
--seed N 0 Random seed for reproducible simulation / random exploration
--max_runs N 0 (unlimited) Number of simulation runs (simulation mode only)
--exploration_strategy bfs State exploration: bfs, dfs, or random (model checking)
--trace "line1\nline2" Guided trace: follow specific action sequence
--trace-file FILE Load guided trace from file
--trace-extend N 0 After trace, explore N more steps (shows enabled actions)
--preinit-hook "STMT" Override constants before Init runs
--preinit-hook-file FILE Load preinit hook from .cfg file
--output-dir DIR auto-timestamped Where to write output
--no-copy-ast off Don't copy AST to output dir
--experimental_processed_queue off EXPERIMENTAL: queue holds processed yield-points instead of unprocessed action-starts. Dedupes successors before they enter the queue → smaller peak queue memory (~10× on BFS, ~3× on DFS). State space and assertion outcomes unchanged under BFS. Under DFS / Random with max_actions set, exploration order differs and may visit a different subset within the bound — see Gotchas.

Understanding Output

Model checking specs/counter.json
StateSpaceOptions: options:{max_actions:100 max_concurrent_actions:2}
Nodes: 12, queued: 0, elapsed: 2.1ms
Valid Nodes: 12  Unique states: 8
IsLive: true
PASSED: Model checker completed successfully
  • Nodes: total graph nodes explored
  • Valid Nodes: nodes that passed all safety assertions
  • Unique states: distinct system states (after symmetry reduction)
  • IsLive: liveness assertions passed
  • PASSED / FAILED: overall result

Read the full file on GitHub · 247 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. 4d ago First seen · 247 lines · 45 tokens per session scan A 1233fafbdfa3

Subscribe to this mod's changes

fizz-check is a skill published in the GitHub repository fizzbee-io/fizzbee (347 stars, last pushed 9d ago), licensed Apache-2.0. It adds 45 tokens to every session and 2,479 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 2026-08-30.

Related

Other skills, from other repositories

tla-check

Write and iteratively refine executable TLA+ specs (.tla) and TLC model configs (.cfg) from natural-language system designs; run TLC model checking; summarize pass/fail and counterexamples with explicit assumptions and bounds. Use when asked to design or validate a protocol/state machine, create or edit .tla/.cfg…

younes-io/agent-skills · 79 tokens

tla-proof

Write and iteratively refine TLA+ theorem proofs in .tla modules with TLAPS (tlapm); run proof checks and summarize proved vs failed/omitted obligations with explicit assumptions and trust boundaries. Use when asked to create or fix THEOREM or PROOF blocks, diagnose TLAPS failures, strengthen inductive invariants…

younes-io/agent-skills · 87 tokens

vera-language

Write programs in the Vera programming language. Use when asked to write, edit, debug, or review Vera code (.vera files). Vera is a statically typed, purely functional language with algebraic effects, mandatory contracts, and typed slot references (@T.n) instead of variable names.

aallan/vera · 61 tokens

propagate

Generate tests from Allium specifications. Use when the user wants to propagate tests, generate test files from a spec, write tests for a specification, create property-based tests, produce state machine tests, check test coverage against spec obligations, or understand what tests a specification requires.

juxt/allium · 57 tokens

allium

Give your AI agents something more useful than a prompt. Velocity through clarity.

juxt/allium · 18 tokens

elicit

Run a structured discovery session to build an Allium specification through conversation. Use when the user wants to create a new spec from scratch, elicit or gather requirements, capture domain behaviour, specify a feature or system, define what a system should do, or is describing functionality and needs help…

juxt/allium · 66 tokens