Webhook ingress: the swappable public-reachability seam that lets a loopback-bound Ryu Core receive third-party webhooks (Composio triggers, per-workflow webhooks). Owns the four ingress backends (managed RyuRelay outbound SSE push, Tailscale Funnel, cloudflared quick tunnel, BYO own-relay), the path-routed inbound dispatcher with fail-closed HMAC re-verification, replay-window + delivery dedup, and the ingress-URL registry. An extracted Core capability crate — in-process default (no IPC on any hot path); the kernel couplings (composio verify/run, workflow-secret lookup, mesh funnel, auth token, data dir) are inverted through the WebhookIngressHost trait so this crate has ZERO dependency on apps/core. Public webhook ROUTES stay kernel-ingress in Core and forward into this engine (program §5).