RustFS is an open-source distributed object storage system written in Rust that stores data and provides compatible interfaces for S3-based applications. It is intended for storage migrations, coexistence with systems such as MinIO and Ceph, data lakes, AI, and other big-data workloads.
Borrowing it
Nothing to install: this file belongs to rustfs/rustfs. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/rustfs/rustfs/main/.agents/skills/plugin-contract-guard/SKILL.mdgit clone --depth 1 https://github.com/rustfs/rustfsWrote 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/rustfs/rustfs/plugin-contract-guard)<a href="https://agentmods.dev/skills/rustfs/rustfs/plugin-contract-guard"><img src="https://agentmods.dev/badge/skills/rustfs/rustfs/plugin-contract-guard/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/rustfs/rustfs/plugin-contract-guard"><img src="https://agentmods.dev/badge/skills/rustfs/rustfs/plugin-contract-guard.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 | $0.00071 | $0.01018 |
| Opus 5.5 | $0.00028 | $0.00407 |
| Sonnet 5.5 | $0.00014 | $0.00204 |
| Haiku 4.5 | $0.00007 | $0.00102 |
Grade A, and why
plugin-contract-guard 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 1mo 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 — 84 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Plugin & Extension Contract Guard
The "plugin system" spans four surfaces that must stay consistent:
| Surface | Location |
|---|---|
| Manifests & registry | crates/targets/src/{manifest,plugin}.rs |
| Install/enable planning (control plane) | crates/targets/src/control_plane.rs |
| Extension schemas | crates/extension-schema/src/lib.rs, crates/targets/src/catalog/extension.rs |
| Admin API contract | rustfs/src/admin/plugin_contract.rs, handlers/{plugins_catalog,plugins_instances,extensions,target_descriptor}.rs |
Hard invariants (verify before merging)
-
Secrets have one source of truth. Secret config keys are declared only in the plugin manifest (
TargetPluginManifest.secret_fields,crates/targets/src/manifest.rs) and flow to admin viaAdminTargetSpec.secret_fields. Never add a hand-maintained per-service secret table in a handler; if redaction misses a field, fix the manifest. -
Redaction must round-trip. Instance GET responses replace secret values with
***redacted***(REDACTED_SECRET_VALUEinplugins_instances.rs). Instance PUT restores the stored secret when it receives that placeholder back (restore_redacted_secret_values). Any new read or write path for target config must keep both halves: redact on the way out, restore the placeholder on the way in. The placeholder literal must never be persisted. -
Fixtures never reach production responses.
example_external_webhook_plugin()(crates/targets/src/catalog/mod.rs) is a test/demo fixture for control-plane planning tests. Production catalog/extension handlers must not include it; regression tests (plugin_catalog_never_exposes_example_or_external_fixtures,extension_catalog_never_exposes_example_or_external_fixtures) enforce it. -
External plugin flow is planning-only and deny-by-default.
plan_external_target_plugin_actionreturns decisions, it executes nothing.TargetPluginExternalFlowGate::default()is fully closed andTargetPluginInstallPolicy::default().allowed_download_hostsis empty — keep it that way; tests opt in via explicit policies. Install validation requires https, an allowlisted host, a full 64-hex-char sha256 digest, signature and provenance URIs, and an artifact matching the hosttarget_triple.
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.
- 1mo ago Changed · -12 tokens per session a4d7340e5dc7
- 1mo ago First seen · 84 lines · 83 tokens per session scan A 1525c36d21a6
plugin-contract-guard is a skill published in the GitHub repository rustfs/rustfs (35,418 stars, last pushed today), licensed Apache-2.0. It adds 71 tokens to every session and 1,018 once invoked, about $0.0003 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 2026-08-30.
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