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Why “Exoskeleton”?

Sendy is a solid, proven email marketing tool — 50K+ licenses sold, reliable SES integration, simple interface. But its API is 7 legacy POST endpoints. No webhooks. No analytics API. No CLI. No AI. No health monitoring. SendyKit doesn’t replace Sendy. It wraps around it. Like an exoskeleton augments a human body — same body, dramatically expanded capabilities:

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How It Works Technically

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Database Layer

SendyKit reads Sendy’s existing tables (campaigns, subscribers, lists, links, login, apps) via read-only queries. It never writes to Sendy’s core tables. SendyKit creates its own tables with the sendykit_ prefix:
  • sendykit_migrations — migration tracking
  • sendykit_feature_flags — runtime feature toggles
  • sendykit_webhooks — webhook endpoint configuration
  • sendykit_proxy_settings — proxy and transport settings
  • sendykit_analytics_events — enriched event tracking
  • sendykit_doctor_reports — health check results
  • sendykit_audit_log — mutation audit trail
  • sendykit_tenants — multi-tenant SaaS
  • sendykit_payments — payment verification

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Proxy Layer

The Sendy admin UI is served through SendyKit’s reverse proxy. This allows:
  • CSS injection (dark mode, mobile responsive, design system)
  • Sidebar navigation (SendyKit pages appear in Sendy’s nav)
  • Payment interception (Stripe replaces PayPal)
  • Brand switching (unified dropdown)
Sendy’s PHP code is never modified. The proxy intercepts HTTP responses and injects CSS/JS before serving to the browser.

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Safe Migrations

Every database migration is:
  1. Versioned — v001_foundation.sql through v007_billing.sql
  2. Non-destructive — Never ALTERs Sendy tables. Only CREATEs sendykit_* tables.
  3. Tracked — sendykit_migrations table records which migrations have run
  4. Idempotent — Safe to run multiple times
  5. Reversible — Can DROP all sendykit_* tables to fully uninstall

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Fail-Safe Design

If SendyKit stops running:
  • Sendy continues working exactly as before
  • All campaigns continue sending
  • All subscriber management continues
  • The only things lost are SendyKit-specific features (API, CLI, admin pages)
This is the key advantage of the exoskeleton model: zero risk to the existing system.