Safe Pkgs

🚀 safe-pkgs

Conduct package safety checks for AI agents before installation. A Rust MCP server and CLI that provides allow/deny decisions, risk scoring, and audit logs.

Documentation · GitHub Action

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✨ Features

safe-pkgs checks package risk before dependency actions and returns one machine-enforceable decision.

Decision payload includes:

• allow: true or false
• risk: low | medium | high | critical
• reasons: human-readable findings
• evidence: structured findings (kind, stable id, severity, message, facts)
• metadata: package context (latest, publish date, downloads, advisories)
• fingerprints: deterministic hashes (config, policy)

📦 Installation

Install once

cargo install --path . --locked

Run MCP server

safe-pkgs serve

Run a one-off audit

safe-pkgs audit /path/to/project-or-lockfile
safe-pkgs audit /path/to/requirements.txt --registry pypi

Windows MCP hosts (Claude Desktop, etc.)

safe-pkgs-mcp.exe

💻 Usage Examples

No Subscription Required

safe-pkgs does not require a paid plan, hosted account, or API key for built-in checks.

• Runs locally as a Rust binary (MCP server or CLI).
• Uses public package/advisory endpoints by default:
  • npm registry + npm downloads API + npms popularity index
  • crates.io API
  • PyPI JSON API + pypistats + top-pypi index
  • OSV advisory API
• Stores cache and audit logs locally on your machine.

Registry and Check Support

Supported registries:

• npm (default)
• cargo (crates.io)
• pypi (Python packages)

View support map:

• Command: safe-pkgs support-map

Configuration

Global file

• ~/.config/safe-pkgs/config.toml

Project override

• .safe-pkgs.toml (merged on top of global)

Minimal example

min_version_age_days = 7
min_weekly_downloads = 50
max_risk = "medium"

[cache]
ttl_minutes = 30

[allowlist]
packages = ["my-internal-pkg"]

[denylist]
packages = ["event-stream@3.3.6"]

Full configuration schema

• docs/configuration-spec.md

MCP Config Example

macOS/Linux

{
  "servers": {
    "safe-pkgs": {
      "type": "stdio",
      "command": "/path/to/safe-pkgs",
      "args": ["serve"]
    }
  },
  "inputs": []
}

Windows (no console window)

{
  "servers": {
    "safe-pkgs": {
      "type": "stdio",
      "command": "safe-pkgs-mcp.exe"
    }
  },
  "inputs": []
}

Decision Output Example

{
  "allow": true,
  "risk": "low",
  "reasons": [
    "lodash@3.10.1 is 1 major version behind latest (4.17.21)"
  ],
  "evidence": [
    {
      "kind": "check",
      "id": "staleness.behind_latest",
      "severity": "low",
      "message": "lodash@3.10.1 is 1 major version behind latest (4.17.21)",
      "facts": {
        "package_name": "lodash",
        "resolved_version": "3.10.1",
        "latest_version": "4.17.21",
        "major_gap": 1
      }
    }
  ],
  "fingerprints": {
    "config": "c7d9f5b8b9a8f2a9f6b1f42f0e8e8c8a63f2b2ef8fdde1f3cd9ea4f5a2c08a0b",
    "policy": "fca103ee4fd5b86595a6a6e933f8a5f87db0ce087f80744dc1ea9cdbf58f7a6f"
  },
  "metadata": {
    "latest": "4.17.21",
    "requested": "3.10.1",
    "published": "2015-08-31T00:00:00Z",
    "weekly_downloads": 45000000
  }
}

Lockfile Audit Output Example (dependency_ancestry)

Input lockfile (package-lock.json)

{
  "name": "demo",
  "lockfileVersion": 2,
  "dependencies": {
    "react": {
      "version": "18.2.0",
      "dependencies": {
        "loose-envify": {
          "version": "1.4.0"
        }
      }
    }
  }
}

Audit output

{
  "allow": true,
  "risk": "low",
  "total": 2,
  "denied": 0,
  "packages": [
    {
      "name": "react",
      "requested": "18.2.0",
      "allow": true,
      "risk": "low",
      "reasons": [],
      "evidence": []
    },
    {
      "name": "loose-envify",
      "requested": "1.4.0",
      "allow": true,
      "risk": "low",
      "reasons": [],
      "evidence": [],
      "dependency_ancestry": {
        "paths": [
          { "ancestors": ["react"] }
        ]
      }
    }
  ],
  "fingerprints": {
    "config": "<sha256>",
    "policy": "<sha256>"
  }
}

paths[].ancestors lists only ancestors (root to immediate parent), excluding the package itself. For direct dependencies, dependency_ancestry is omitted.

evidence.id is stable and machine-oriented:

• Built-in checks: <check_id>.<reason_code> (example: staleness.behind_latest)
• Custom rules: custom_rule.<rule_id> (example: custom_rule.low-downloads)
• Policy/runtime items: explicit IDs (example: denylist.package, risk.medium_pair_escalation)

🔧 Technical Details

Trust and Security Posture

• Fail-closed behavior: check/runtime failures are surfaced and do not silently allow installs.
• Local audit trail: append-only audit log for decision review.
• Deterministic policy context: responses include policy_snapshot_version, config and policy fingerprints, and enabled check set.
• Local cache: SQLite cache keyed by policy fingerprint + package tuple with TTL expiry.

📚 Documentation

Disclaimer

safe-pkgs works as an MCP tool that AI agents can call before installing packages. However, we cannot guarantee that an AI agent will always choose to call this tool — agentic models that autonomously select tools may proceed with package installation without invoking check_package or check_lockfile first, depending on the model, prompt context, and system prompt configuration.

If your AI agent skipped safe-pkgs when it should have called it, please open an issue with the prompt and response so we can improve tool descriptions and usage guidance.

Roadmap

Now

• [ ] Dependency confusion defenses for internal/private package names
• [ ] Policy simulation mode (what-if) without enforcement
• [ ] Metrics/log schema for latency, cache hit ratio, and registry error rates
• [ ] Support remote audit storage backends
• [ ] Support remote config sources (GitHub repo, HTTP endpoint, etc.)
• [ ] Support for private registries

Next

• [ ] Policy waivers with expiry
• [ ] Package provenance checks (where ecosystem metadata supports it)
• [ ] Publisher trust signals (account age, maintainer churn, ownership changes)
• [ ] Performance/scale improvements (request coalescing + bounded concurrency for large lockfiles)

Later

• [ ] NVD advisory enrichment
• [ ] Optional Snyk advisory provider
• [ ] Socket.dev integration
• [ ] GitHub Actions integration for CI auditing
• [ ] Registry-driven MCP schema and docs generation (single source of truth)
• [ ] HTTP Streamable MCP server option
• [ ] More validated editor config examples
• [ ] Git hook integration for pre-commit checks

Development

cargo fmt --all -- --check
cargo clippy --all-targets -- -D warnings
cargo test

Coverage

Install

rustup component add llvm-tools-preview
cargo install cargo-llvm-cov

Summary

cargo llvm-cov --workspace --all-features --summary-only

HTML report

cargo llvm-cov --workspace --all-features --html

Report path

• target/llvm-cov/html/index.html

Local Docs

pip install zensical
zensical serve

Note: This project now uses Zensical instead of MkDocs. MkDocs 2.0 drops the plugin system and breaks backward compatibility with no migration path (announcement).

Deterministic Evaluation Clock (Optional)

Set SAFE_PKGS_EVALUATION_TIME to an RFC3339 timestamp to force a fixed policy evaluation time (useful for replay/debug runs):

SAFE_PKGS_EVALUATION_TIME=2026-01-01T00:00:00Z safe-pkgs audit /path/to/project

$env:SAFE_PKGS_EVALUATION_TIME = "2026-01-01T00:00:00Z"
safe-pkgs audit C:\path\to\project