Agent Supply Chain Integrity

Generate and verify integrity manifests for AI agent plugins and tools. Detect tampering, enforce version pinning, and establish supply chain provenance.

Overview

Agent plugins and MCP servers have the same supply chain risks as npm packages or container images — except the ecosystem has no equivalent of npm provenance, Sigstore, or SLSA. This skill fills that gap.

Plugin Directory → Hash All Files (SHA-256) → Generate INTEGRITY.json
                                                    ↓
Later: Plugin Directory → Re-Hash Files → Compare Against INTEGRITY.json
                                                    ↓
                                          Match? VERIFIED : TAMPERED

When to Use

• Before promoting a plugin from development to production
• During code review of plugin PRs
• As a CI step to verify no files were modified after review
• When auditing third-party agent tools or MCP servers
• Building a plugin marketplace with integrity requirements

Pattern 1: Generate Integrity Manifest

Create a deterministic INTEGRITY.json with SHA-256 hashes of all plugin files.

import hashlib
import json
from datetime import datetime, timezone
from pathlib import Path

EXCLUDE_DIRS = {".git", "__pycache__", "node_modules", ".venv", ".pytest_cache"}
EXCLUDE_FILES = {".DS_Store", "Thumbs.db", "INTEGRITY.json"}

def hash_file(path: Path) -> str:
    """Compute SHA-256 hex digest of a file."""
    h = hashlib.sha256()
    with open(path, "rb") as f:
        for chunk in iter(lambda: f.read(8192), b""):
            h.update(chunk)
    return h.hexdigest()

def generate_manifest(plugin_dir: str) -> dict:
    """Generate an integrity manifest for a plugin directory."""
    root = Path(plugin_dir)
    files = {}

    for path in sorted(root.rglob("*")):
        if not path.is_file():
            continue
        if path.name in EXCLUDE_FILES:
            continue
        if any(part in EXCLUDE_DIRS for part in path.relative_to(root).parts):
            continue
        rel = path.relative_to(root).as_posix()
        files[rel] = hash_file(path)

    # Chain hash: SHA-256 of all file hashes concatenated in sorted order
    chain = hashlib.sha256()
    for key in sorted(files.keys()):
        chain.update(files[key].encode("ascii"))

    manifest = {
        "plugin_name": root.name,
        "generated_at": datetime.now(timezone.utc).isoformat(),
        "algorithm": "sha256",
        "file_count": len(files),
        "files": files,
        "manifest_hash": chain.hexdigest(),
    }
    return manifest

# Generate and save
manifest = generate_manifest("my-plugin/")
Path("my-plugin/INTEGRITY.json").write_text(
    json.dumps(manifest, indent=2) + "\n"
)
print(f"Generated manifest: {manifest['file_count']} files, "
      f"hash: {manifest['manifest_hash'][:16]}...")

Output (INTEGRITY.json):

{
  "plugin_name": "my-plugin",
  "generated_at": "2026-04-01T03:00:00+00:00",
  "algorithm": "sha256",
  "file_count": 12,
  "files": {
    ".claude-plugin/plugin.json": "a1b2c3d4...",
    "README.md": "e5f6a7b8...",
    "skills/search/SKILL.md": "c9d0e1f2...",
    "agency.json": "3a4b5c6d..."
  },
  "manifest_hash": "7e8f9a0b1c2d3e4f..."
}

Pattern 2: Verify Integrity

Check that current files match the manifest.

# Requires: hash_file() and generate_manifest() from Pattern 1 above
import json
from pathlib import Path

def verify_manifest(plugin_dir: str) -> tuple[bool, list[str]]:
    """Verify plugin files against INTEGRITY.json."""
    root = Path(plugin_dir)
    manifest_path = root / "INTEGRITY.json"

    if not manifest_path.exists():
        return False, ["INTEGRITY.json not found"]

    manifest = json.loads(manifest_path.read_text())
    recorded = manifest.get("files", {})
    errors = []

    # Check recorded files
    for rel_path, expected_hash in recorded.items():
        full = root / rel_path
        if not full.exists():
            errors.append(f"MISSING: {rel_path}")
            continue
        actual = hash_file(full)
        if actual != expected_hash:
            errors.append(f"MODIFIED: {rel_path}")

    # Check for new untracked files
    current = generate_manifest(plugin_dir)
    for rel_path in current["files"]:
        if rel_path not in recorded:
            errors.append(f"UNTRACKED: {rel_path}")

    return len(errors) == 0, errors

# Verify
passed, errors = verify_manifest("my-plugin/")
if passed:

…