next: the real durable-execution KERNEL SERVICE (host_kernel) — RA-live substrate

Promotes the persistent-kernel spike into a real service. next/kernel/host_kernel.erl: boots
flow_store, registers named behavior flows (blog_digest), then blocks in http:listen so the
er-scheduler + gen_server stay alive across requests. Parameterised flow routes (paths matched by
byte prefix — binary =:= is buggy): GET /flow/start/<category> starts the flow with that category and
returns '<InstanceId>:<status>' (suspended|done); GET /flow/resume/<id> resumes that instance. Path
plumbing (starts_with / last_seg / field) is byte-level for portability.

next/kernel/serve.sh: the persistent service launcher (container entrypoint / local) — loads the
runtime + next/flow + the kernel, then host_kernel:start(); sleep infinity holds stdin so
the listener serves forever. next/tests/host_kernel.sh: drives it over HTTP — 4/4: newsletter →
instance 1 SUSPENDED, urgent → 2 DONE, draft → 3 DONE (skipped), resume 1 in a SEPARATE request →
DONE (durable state persists across requests). serve.sh launcher verified live (bind + start +
resume).

This is the RA-live substrate: a working durable-execution service the host drives over HTTP.
Remaining for RA-live: deploy it (a container/placement), point host/ra.sx's real-eval at it (POST
/flow instead of in-process erlang-eval-ast), route a durable binding to RA. TA-live adds inbox/
outbox routes on the same kernel.

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

next/tests/host_kernel.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+# next/tests/host_kernel.sh — the durable-execution kernel (host_kernel.erl) over HTTP.
+# Boots it as a background sx_server, then drives it with curl: category branching (newsletter →
+# suspend, urgent/draft → done), sequential instance ids, and RESUME of a suspended instance in a
+# SEPARATE request (durable state persists). This is the RA-live substrate.
+set -uo pipefail
+cd "$(git rev-parse --show-toplevel)"
+SX_SERVER="${SX_SERVER:-hosts/ocaml/_build/default/bin/sx_server.exe}"
+[ -x "$SX_SERVER" ] || SX_SERVER="/root/rose-ash/hosts/ocaml/_build/default/bin/sx_server.exe"
+PORT=51878
+PASS=0; FAIL=0
+EPOCH_FILE=$(mktemp); LOG_FILE=$(mktemp)
+cleanup() {
+  [ -n "${SXPID:-}" ] && { kill -KILL "$SXPID" 2>/dev/null || true; wait "$SXPID" 2>/dev/null || true; }
+  [ -n "${HOLDPID:-}" ] && { kill -KILL "$HOLDPID" 2>/dev/null || true; wait "$HOLDPID" 2>/dev/null || true; }
+  rm -f "$EPOCH_FILE" "$LOG_FILE"
+}
+trap cleanup EXIT
+
+cat > "$EPOCH_FILE" <<EPOCHS
+(epoch 1)
+(load "lib/erlang/tokenizer.sx")
+(load "lib/erlang/parser.sx")
+(load "lib/erlang/parser-core.sx")
+(load "lib/erlang/parser-expr.sx")
+(load "lib/erlang/parser-module.sx")
+(load "lib/erlang/transpile.sx")
+(load "lib/erlang/runtime.sx")
+(load "lib/erlang/vm/dispatcher.sx")
+(epoch 2)
+(eval "(er-load-gen-server!)")
+(eval "(get (erlang-load-module (file-read \"next/kernel/envelope.erl\")) :name)")
+(eval "(get (erlang-load-module (file-read \"next/flow/flow.erl\")) :name)")
+(eval "(get (erlang-load-module (file-read \"next/flow/flow_spec.erl\")) :name)")
+(eval "(get (erlang-load-module (file-read \"next/flow/flow_store.erl\")) :name)")
+(eval "(get (erlang-load-module (file-read \"next/flow/flows/blog_publish_digest.erl\")) :name)")
+(eval "(get (erlang-load-module (file-read \"next/kernel/host_kernel.erl\")) :name)")
+(epoch 3)
+(eval "(erlang-eval-ast \"host_kernel:start($PORT)\")")
+EPOCHS
+
+FIFO=$(mktemp -u); mkfifo "$FIFO"
+( cat "$EPOCH_FILE"; sleep 180 ) > "$FIFO" &
+HOLDPID=$!
+"$SX_SERVER" < "$FIFO" > "$LOG_FILE" 2>&1 &
+SXPID=$!
+rm -f "$FIFO"
+
+echo "── waiting for host_kernel to bind :$PORT ──"
+BOUND=""
+for i in $(seq 1 300); do
+  if (exec 3<>/dev/tcp/127.0.0.1/$PORT) 2>/dev/null; then BOUND=1; exec 3>&- 3<&-; echo "bound (iter $i)"; break; fi
+  sleep 1
+done
+if [ -z "$BOUND" ]; then echo "FAIL: never bound"; tail -25 "$LOG_FILE"; exit 1; fi
+
+ck() { local got; got=$(curl -s -m 8 "http://127.0.0.1:$PORT$1"); if echo "$got" | grep -q "$2"; then PASS=$((PASS+1)); echo "  ok  [$3] $1 → $got"; else FAIL=$((FAIL+1)); echo "  FAIL [$3] $1 → '$got' (want '$2')"; fi; }
+
+echo "── driving the kernel over HTTP ──"
+ck /flow/start/newsletter "1:suspended" "newsletter → instance 1, SUSPENDED (durable wait)"
+ck /flow/start/urgent     "2:done"      "urgent → instance 2, DONE (sync branch)"
+ck /flow/start/draft      "3:done"      "draft → instance 3, DONE (skipped)"
+ck /flow/resume/1         "resume:done" "resume instance 1 (SEPARATE request) → DONE (persisted)"
+
+echo "─────────────────────────────────────────────────────"
+echo "PASS=$PASS FAIL=$FAIL"
+[ "$FAIL" -eq 0 ] || { echo "--- kernel log tail ---"; tail -20 "$LOG_FILE"; }