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 roedyrustam/vibes-plug --skill formal-spec-z3-verifiergit clone --depth 1 https://github.com/roedyrustam/vibes-plugWrote 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/roedyrustam/vibes-plug/formal-spec-z3-verifier)<a href="https://agentmods.dev/skills/roedyrustam/vibes-plug/formal-spec-z3-verifier"><img src="https://agentmods.dev/badge/skills/roedyrustam/vibes-plug/formal-spec-z3-verifier/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/roedyrustam/vibes-plug/formal-spec-z3-verifier"><img src="https://agentmods.dev/badge/skills/roedyrustam/vibes-plug/formal-spec-z3-verifier.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00104 | $0.02567 |
| Opus 5.5 | $0.00042 | $0.01027 |
| Sonnet 5.5 | $0.00021 | $0.00513 |
| Haiku 4.5 | $0.00010 | $0.00257 |
Grade A, and why
formal-spec-z3-verifier 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 7d 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 — 214 lines — stays where its author put it; the contents beside it link to each section on GitHub.
formal-spec-z3-verifier — vibes-plug Skill
English
Orchestration & Integration
Connects and orchestrates with brainstorming, zero-to-prod-orchestrator, saas-billing, doku-payment-gateway, authentication-identity-expert, and database-orm-expert to mathematically prove software invariants, state transitions, and authorization policies using formal SMT solvers before writing production code.
Description
Production guide for applying formal methods, mathematical specifications, and SMT (Satisfiability Modulo Theories) solvers (Z3, Dafny, TLA+) to mission-critical software systems. Proves zero-invariant violation across double-entry ledger bookkeeping, billing subscription state machines, multi-tenant isolation boundaries, and cryptographic key lifecycle models.
Trigger Conditions
Activate this skill when:
- Designing financial ledgers, wallets, or payment gateway state transition graphs.
- Verifying complex RBAC/ABAC permission rules to guarantee that privilege escalation is mathematically impossible.
- Modeling concurrent or distributed state machines where race conditions could cause state desynchronization.
- Formulating formal invariant specifications prior to backend ORM and database schema generation.
Core Concepts & Patterns
1. Invariant Specification Matrix
| System Domain | Mathematical Invariant | Solver Check |
|---|---|---|
| Double-Entry FinTech Ledger | $\sum \text{Debits} - \sum \text{Credits} = 0 \land \forall a, \text{balance}(a) \ge 0$ | Prove balance preservation across all concurrent transactions |
| SaaS Billing State Machine | $\text{State} \in { \text{Trial}, \text{Active}, \text{PastDue}, \text{Canceled} }$ with strict monotonic transitions | Prove unreachable illegal transition (e.g. Canceled $\to$ Active without Payment) |
| Multi-Tenant Authorization | $\forall r \in \text{Resources}, \text{TenantId}(r) = \text{Session}(\text{TenantId})$ | Prove satisfiability of data leakage equals $\emptyset$ |
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.
- 7d ago Changed 23210e39b4ca
- 12d ago First seen · 214 lines · 104 tokens per session scan A a21220bccb77
formal-spec-z3-verifier is a skill published in the GitHub repository roedyrustam/vibes-plug (75 stars, last pushed 2d ago), licensed MIT. It adds 104 tokens to every session and 2,567 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-10-04.
Other skills, from other repositories
test-driven-development
Drives development with tests using the red-green-refactor loop. Use when implementing any logic, fixing any bug, or changing any behavior. Use when you need to prove that code works, when a bug report arrives, or when you're about to modify existing functionality. Use when asked to add tests to a function, fix a bug…
browser-testing-with-devtools
Tests in real browsers via Chrome DevTools MCP. Use when building or debugging anything that runs in a browser. Use when you need to inspect the DOM, capture console errors, analyze network requests, profile performance, or verify visual output with real runtime data. Requires the chrome-devtools MCP server to be…
spec-driven-eval
Scores how completely an implementation fulfills a PRD/spec, case by case, and produces a single comparable final grade. Invoke only when explicitly named (e.g. run spec-driven-eval); do not auto-trigger. Use when benchmarking spec-driven implementations, grading acceptance criteria, evaluating whether a feature was…
tlc-implement
Implement a work already planned: extracts a checklist, builds it, and proves every check with an independent verifier. Use when the user says "extract a checklist", "build this ticket", "implement this spec", or "tlc-implement". Do NOT use when nobody has decided what to build, or to design the work.
tlc-spec-lean
Spec-driven feature work that freezes obligations instead of the plan: one human-reviewed plan with EARS criteria, path, entities, interface and one-way doors, then proof-backed checks, then build, then an independent Verifier. Use when the user says "tlc-spec-lean", "plan feature", "specify feature", "write the…
playwright-skill
Complete browser automation with Playwright. Auto-detects dev servers, writes clean test scripts to /tmp. Test pages, fill forms, take screenshots, check responsive design, validate UX, test login flows, check links, automate any browser task. Use when user wants to test websites, automate browser interactions…