RA-live: durable business logic in production — host drives the kernel service (LIVE)

Steps 1+2 of RA-live/TA-live, live-verified end-to-end on blog.rose-ash.com.

(1) DEPLOY: docker-compose.dev-sx-host.yml gains an sx_kernel service running next/kernel/serve.sh
(the durable-execution kernel), SX_HTTP_HOST=0.0.0.0 so the host container reaches it at
http://sx_kernel:8930.

(2) HOST AS CLIENT: lib/host/ra.sx gains a KERNEL runner — host/ra--make-kernel-runner drives the
kernel over HTTP (http-request, native primitive; returns {status headers body}). It advertises
{effect,branch,each,suspend}, so select-runner routes a durable DAG to it. host/blog.sx: the DAG
registry + runner fleet are now mutable (register-dag!/add-runner!); emit! records SUSPENSIONS in a
durable pending log; /flows shows suspended instances with a resume link (?resume=<id>) driving
host/ra--kernel-resume. serve.sh wires it: set kernel-base, add the kernel runner, register the
durable 'blog-digest' DAG, declare a DURABLE behavior on article (create→publish SYNC, update→
blog-digest DURABLE), add a 'category' field.

LIVE PROOF: editing a published newsletter article → Update → routes to the kernel runner → POST
/flow/start/newsletter → kernel SUSPENDS (instance 5, shown pending on /flows) → /flows?resume=5 →
host re-drives the kernel → DONE → digest-sent effect + pending cleared. Durable suspend/resume
across separate HTTP requests, on a deployed persistent kernel. urgent edits complete immediately
(digest). http-request works in the serving context. blog 217/217, full conformance green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docker-compose.dev-sx-host.yml

@@ -53,6 +53,29 @@ services:
       - default
     restart: unless-stopped
 
+  # The durable-execution KERNEL (next/kernel/host_kernel.erl) — a persistent next/ service holding
+  # flow_store across requests (RA-live substrate). The host reaches it at http://sx_kernel:8930 over
+  # the shared `default` network. SX_HTTP_HOST=0.0.0.0 so the bind is reachable cross-container.
+  sx_kernel:
+    image: registry.rose-ash.com:5000/sx_docs:latest
+    container_name: sx-dev-sx_kernel-1
+    entrypoint: ["bash", "/app/next/kernel/serve.sh"]
+    working_dir: /app
+    environment:
+      SX_PROJECT_DIR: /app
+      SX_SERVER: /app/bin/sx_server
+      KERNEL_PORT: "8930"
+      SX_HTTP_HOST: "0.0.0.0"
+      OCAMLRUNPARAM: "b"
+    volumes:
+      - ./spec:/app/spec:ro
+      - ./lib:/app/lib:ro
+      - ./next:/app/next:ro
+      - ./hosts/ocaml/_build/default/bin/sx_server.exe:/app/bin/sx_server:ro
+    networks:
+      - default
+    restart: unless-stopped
+
 networks:
   externalnet:
     external: true