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 PlamenTSV/plamen --skill ensure-invariantsgit clone --depth 1 https://github.com/PlamenTSV/plamenWrote 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/plamentsv/plamen/ensure-invariants)<a href="https://agentmods.dev/skills/plamentsv/plamen/ensure-invariants"><img src="https://agentmods.dev/badge/skills/plamentsv/plamen/ensure-invariants/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/plamentsv/plamen/ensure-invariants"><img src="https://agentmods.dev/badge/skills/plamentsv/plamen/ensure-invariants.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00022 | $0.01555 |
| Opus 5 | $0.00011 | $0.00777 |
| Sonnet 5 | $0.00004 | $0.00311 |
| Haiku 4.5 | $0.00002 | $0.00155 |
Grade A, and why
ensure-invariants 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 11d 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 — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.
ENSURE_INVARIANTS Skill (DAML)
Trigger Pattern: Always required for DAML audits Inject Into: Breadth agents, depth-edge-case Finding prefix:
[DML-EI-N]Rules referenced: R10, R12, R14
A template's ensure clause is its creation precondition: a create whose ensure is False throws PreconditionFailed and the contract never exists. A missing or weak ensure lets an invalid contract enter the ACS (negative amount, empty party list, inconsistent fields), and every downstream choice then trusts the broken invariant. Separately, DAML Int/Decimal arithmetic THROWS on overflow rather than wrapping — so an arithmetic boundary is a liveness/brick bug (the choice aborts and becomes un-exercisable), not a silent-wrap value bug. The PoC for this class is a set of boundary-value Script () functions (min / 1 / negative / max / empty-list), Aptos-style.
1. Ensure-Clause Inventory
For every template, record its ensure and the invariants it should enforce:
| Template | ensure Expr |
Invariants It Should Enforce | Gap? |
|---|---|---|---|
{T} |
amount > 0.0 && obs /= [] / NONE |
amount positive, parties non-empty, fields consistent | [DML-EI-N] if invariant unguarded |
Critical patterns to flag:
- No
ensureat all on a template carrying an amount/balance/cap → a negative or zero amount contract is creatable ([ELEVATE:ENSURE_GAP]). - An
ensurethat guards some fields but not the security-critical one (e.g., checksamount > 0but notamount <= cap, or notmaintainer non-empty). - An invariant assumed by a choice (
this.amount > 0) that theensuredoes not actually establish.
DAML note: ensure runs on create only. A choice that recreates a successor re-runs the successor's ensure; if the successor template has a weaker ensure, the invariant degrades across the lifecycle.
2. Boundary Substitution
For each ensure-guarded and arithmetic-bearing field, substitute boundary values and trace the outcome:
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.
- 11d ago First seen · 92 lines · 22 tokens per session scan A 448c7a1a855f
ensure-invariants is a skill published in the GitHub repository PlamenTSV/plamen (295 stars, last pushed 3d ago), licensed MIT. It adds 22 tokens to every session and 1,555 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 2026-08-30.
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