Kastell Architecture

kastell-ops

Kastell CLI patterns, architecture, anti-patterns, and decision trees. Use automatically when working in Kastell codebase or when asked about Kastell server infrastructure, security audit, hardening, lock, provision, or provider management.

kastelldev/kastell·0installs60stars

SKILL.md

Full skill instructions

Kastell Architecture

Kastell is a CLI toolkit for provisioning, securing, and managing self-hosted servers. TypeScript, ESM, strict mode. 31 CLI commands, 13 MCP tools, 4 cloud providers (hetzner, digitalocean, vultr, linode), 2 platform adapters (coolify, dokploy).

Live Context

Version: !node -e "import('fs').then(f=>console.log(JSON.parse(f.readFileSync('package.json','utf8')).version)).catch(()=>console.log('unknown'))" Registered servers: !kastell list 2>/dev/null || echo "No servers registered"

Architecture File Map

src/
  commands/     # 31 thin CLI wrappers (parse args + delegate only)
  core/         # Business logic (ALL computation here)
  providers/    # Cloud API: hetzner, digitalocean, vultr, linode
  adapters/     # Platform abstraction: coolify, dokploy
    interface.ts  # PlatformAdapter contract
    factory.ts    # getAdapter(), detectPlatform(), resolvePlatform()
  mcp/
    server.ts     # 13 tool registrations
    tools/        # Handler files (Zod schema + handler per tool)
  utils/        # ssh, config, cloudInit, modeGuard, migration
  types/        # ServerMode, ServerRecord, Platform
  constants.ts  # PROVIDER_REGISTRY (single source of truth)
  index.ts      # CLI entry point

Layer Rules

Layer	Path	Responsibility	Rule
Commands	src/commands/	Parse CLI args, call core, display output	ZERO business logic
Core	src/core/	All business logic, orchestration	No UI/chalk/ora imports
Providers	src/providers/	Cloud API calls per provider	Implements cloud CRUD
Adapters	src/adapters/	Platform-specific ops (Coolify/Dokploy)	Via PlatformAdapter interface
MCP	src/mcp/	MCP server + tool handlers	Delegates to core
Utils	src/utils/	SSH, config, modeGuard, errorMapper	Shared infrastructure

Adapter Contract

Access adapters via getAdapter(platform) from src/adapters/factory.ts. Never import CoolifyAdapter or DokployAdapter directly in commands.

interface PlatformAdapter {
  readonly name: string;              // "coolify" | "dokploy"
  readonly port: number;              // 8000 (Coolify) | 3000 (Dokploy)
  readonly defaultLogService: string; // matches platform name
  readonly platformPorts: readonly number[]; // ports protected from firewall removal
  getCloudInit(serverName: string): string;
  healthCheck(ip: string, domain?: string): Promise<HealthResult>;
  createBackup(ip: string, serverName: string, provider: string): Promise<PlatformBackupResult>;
  getStatus(ip: string): Promise<PlatformStatusResult>;
  update(ip: string): Promise<UpdateResult>;
  restoreBackup?(ip, backupPath, manifest): Promise<PlatformRestoreResult>; // optional
}

Factory exports: getAdapter(platform), detectPlatform(ip), resolvePlatform(server)

Provider Registry

Provider	Env Key	Display Name
hetzner	HETZNER_TOKEN	Hetzner Cloud
digitalocean	DIGITALOCEAN_TOKEN	DigitalOcean
vultr	VULTR_TOKEN	Vultr
linode	LINODE_TOKEN	Linode (Akamai)

PROVIDER_REGISTRY in src/constants.ts is the single source of truth for providers.

What Do I Want to Add?

New CLI command

src/commands/<name>.ts — thin wrapper (parse + delegate, no logic)
src/core/<name>.ts — all business logic here
src/index.ts — register with program
src/__tests__/ — test core, not command

New audit check

src/core/audit/<category>/ — add to existing category
Update check catalog in src/core/audit/catalog.ts
No new command file needed — runs through kastell audit

New provider

src/providers/<name>.ts — implements base.ts contract
src/constants.ts — add to PROVIDER_REGISTRY
No adapter changes — providers handle cloud API only

New MCP tool

src/mcp/tools/server<Name>.ts — Zod schema + handler
src/mcp/server.ts — import + registerTool()
Annotations: readOnlyHint / destructiveHint / idempotentHint

Key Conventions

ESM project ("type": "module") — import, not require
KASTELL_SAFE_MODE + isSafeMode() = destructive operation guard
assertValidIp() before every SSH operation
sanitizedEnv for subprocess calls
sanitizeResponseData() whitelist approach for API error responses
Config dir: user home kastell/ directory (auto-migrated from legacy name)
PROVIDER_REGISTRY = single source of truth for providers
withProviderErrorHandling HOF for consistent provider error handling
describe.each with jest.resetAllMocks() (not clearAllMocks())

Scripts (Deterministic)

Run without LLM — deterministic analysis scripts:

# Parse audit JSON into 5 security domain summaries
kastell audit --server myserver --json > /tmp/audit.json
scripts/parse_audit.sh /tmp/audit.json

# Generate fleet-wide server score table
kastell fleet --json > /tmp/fleet.json
scripts/fleet_report.sh /tmp/fleet.json

# Compare audit check count vs test coverage
scripts/check_coverage.sh

Reference Files

31 CLI commands — see references/commands.md
13 MCP tools — see references/mcp-tools.md
Patterns and test templates — see references/patterns.md
Known pitfalls — see references/pitfalls.md

Install skill

Copy and run in your terminal

npx -y skills add https://github.com/kastelldev/kastell --skill kastell-ops

View on GitHub

kastell-plugin/skills/kastell-ops/SKILL.md