diff --git a/test/integration/coupled-pair-spike.test.ts b/test/integration/coupled-pair-spike.test.ts
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+/**
+ * SPIKE for novox/hq 04-ISSUES/066 — a partly applied declaration leaves a mixed state.
+ *
+ * The apply is deliberately not a transaction: every resource is attempted, every failure reported,
+ * and a failed gate stops what follows it (issue 011, ADR 0053). The question 066 asks is whether a
+ * pairing exists whose half-state is harmful. This bed makes one, on purpose, and RECORDS what the
+ * machine is observed doing in it — it is evidence for a decision, not a rule being enforced.
+ *
+ * The pair: a config file and a long-lived container that serves the file's content as it was when
+ * the container started, with a run-once gate between them that validates the file. First push:
+ * the file says "v1", the gate passes, the service serves v1. Second push: the file says "v2" and
+ * the gate is made to refuse it. The file is applied before the gate (declaration order), the gate
+ * fails, the service after it is left as it was — so the machine has v2 on disk and serves v1, and
+ * reports the push as failed. That is the mixed state. Whether it is harmful is what a person
+ * decides from this; whether a `together` grouping should exist is what the decision would say.
+ *
+ * When such a grouping lands, this bed is where it is proven: the assertions below flip.
+ */
+
+import { test, before, after } from "node:test";
+import assert from "node:assert/strict";
+import { existsSync, readFileSync } from "node:fs";
+import { loadScenario } from "../../src/declaration/parse.ts";
+import { raise } from "../../src/lifecycle/raise.ts";
+import { destroy, exec } from "../../src/lifecycle/operate.ts";
+import { hostBinaryPath, HOST_PATH } from "../../src/lifecycle/place.ts";
+import { labIsUsable, destroyAll, foundationBundle, onTheMachine } from "./harness.ts";
+import type { HeldImage } from "../../src/pinning.ts";
+
+const capability = await labIsUsable();
+const binary = hostBinaryPath();
+const bundle = process.env["MESH_LAB_BUNDLE"] ?? "";
+
+const skip = !capability.usable
+  ? `lab not usable: ${capability.why}`
+  : !binary || !existsSync(binary)
+    ? "MESH_LAB_HOST_BINARY is not set to a built mesh-host"
+    : !bundle || !existsSync(bundle)
+      ? "MESH_LAB_BUNDLE is not set to a foundation bundle (mesh-host examples/)"
+      : false;
+
+const SCENARIO = "schedule-tick"; // a bare node, as the tick bed uses
+const MACHINE = "anchor";
+
+let instanceId = "";
+/** The mesh's own images, as the machines hold them. */
+let held: HeldImage[] = [];
+
+function quote(s: string): string {
+  return `'${s.replaceAll("'", `'\\''`)}'`;
+}
+
+async function on(command: string, timeoutMs?: number): Promise<{ out: string; ok: boolean }> {
+  const { stdout } = await exec(instanceId, MACHINE, [
+    "sh", "-c", `exec 2>&1\n${command}\necho "__exit=$?"`,
+  ], timeoutMs);
+  const marker = stdout.lastIndexOf("__exit=");
+  if (marker < 0) return { out: stdout, ok: false };
+  return { out: stdout.slice(0, marker), ok: stdout.slice(marker + 7).trim() === "0" };
+}
+
+async function must(command: string, timeoutMs?: number): Promise<string> {
+  const { out, ok } = await on(command, timeoutMs);
+  if (!ok) throw new Error(`${MACHINE}: ${command}\n${out}`);
+  return out;
+}
+
+/** The control plane, a container on the node. */
+async function mesh(command: string, timeoutMs?: number): Promise<string> {
+  return must(`docker exec mesh-controller /mesh-controller ${command}`, timeoutMs);
+}
+
+/** The reference a manifest should carry, once this scenario has been raised. */
+/** What a manifest's image reference becomes on the machine — ours by ID, everything else as written. */
+function pinned(reference: string): string {
+  return onTheMachine(reference, held);
+}
+
+/** The foundation bundle: ours by the ID the machine holds, everything else upstream. */
+function bundleFor(images: HeldImage[]): string {
+  return foundationBundle(bundle, images);
+}
+
+function tokenFrom(said: string): string {
+  const found = said.split("\n").map((l) => l.trim()).find((l) => l.length > 100 && !l.includes(" "));
+  assert.ok(found, `no token in:\n${said}`);
+  return found;
+}
+
+/**
+ * How many lines the tick has written so far — tolerant of the run log not existing yet.
+ *
+ * The scheduled container appends one line per fire with `date >> /data/runs.log`, and the data
+ * directory is mounted from /var/lib/schedtest on the machine, so counting newlines there counts
+ * fires. `wc -l` on an absent file is an error, so a missing file reads as 0 rather than throwing —
+ * which is exactly the pre-first-fire state.
+ */
+async function tickLines(): Promise<number> {
+  const { out } = await on(`wc -l < /var/lib/schedtest/runs.log 2>/dev/null || echo 0`);
+  const n = Number.parseInt(out.trim(), 10);
+  return Number.isFinite(n) ? n : 0;
+}
+
+async function settled(withinMs = 600_000): Promise<void> {
+  const until = Date.now() + withinMs;
+  let last = "";
+  while (Date.now() < until) {
+    const asked = await on(`docker exec mesh-controller /mesh-controller status --json`);
+    if (asked.ok) {
+      try {
+        const state = JSON.parse(asked.out) as {
+          wrong: { node: string; outcome: string }[];
+          waiting: { node: string }[];
+          reported: { node: string; outcome: string; current: boolean }[];
+        };
+        const bad = state.wrong.find((w) => w.node === MACHINE);
+        if (bad) throw new Error(`${MACHINE} did not apply what it was sent: ${bad.outcome}\n${asked.out}`);
+        const word = state.reported.find((r) => r.node === MACHINE);
+        if (!state.waiting.some((w) => w.node === MACHINE) && word?.outcome === "applied" && word.current) return;
+        last = asked.out;
+      } catch (err) {
+        if (err instanceof Error && err.message.includes("did not apply")) throw err;
+        last = asked.out;
+      }
+    }
+    await new Promise((r) => setTimeout(r, 5000));
+  }
+  throw new Error(`${MACHINE} never caught up within ${Math.round(withinMs / 1000)}s. Last:\n${last}`);
+}
+
+before(async () => {
+  if (skip) return;
+
+  const raised = await raise(loadScenario(`scenarios/${SCENARIO}.yml`), {
+    onProgress: (m) => console.log(`raise: ${m}`),
+  });
+  instanceId = raised.instanceId;
+  held = raised.images;
+
+  // Raise the foundation — store, broker, control — from the bundle.
+  await must(`cat > /tmp/foundation.lock <<'MESHBUNDLE'\n${bundleFor(raised.images)}\nMESHBUNDLE`);
+  await must(`${HOST_PATH} apply /tmp/foundation.lock`, 600_000);
+  const up = await must(`docker ps --format '{{.Names}}'`);
+  for (const c of ["mesh-store", "mesh-broker", "mesh-controller"]) {
+    assert.match(up, new RegExp(c), `the foundation did not raise ${c}:\n${up}`);
+  }
+
+  // The node joins its own mesh, so it is a node the mesh can assign to, and start the host so it
+  // applies what it is pushed AND fires scheduled steps off its clock (the daemon holds one
+  // Scheduler for the life of the process — novox/hq ADR 0053).
+  await mesh(`node add ${MACHINE}`);
+  const token = tokenFrom(await mesh(`token issue --node ${MACHINE}`));
+  await must(`${HOST_PATH} enrol --token ${quote(token)}`);
+  await must(`nohup ${HOST_PATH} run > /var/log/mesh-host.log 2>&1 & sleep 3`);
+}, { timeout: 1_800_000 });
+
+after(async () => {
+  if (instanceId) await destroy(instanceId);
+  await destroyAll(`${SCENARIO}-`);
+}, { timeout: 600_000 });
+
+function coupled(content: string, gateAccepts: boolean): string {
+  return JSON.stringify({
+    module: "coupled", version: "1",
+    resources: [
+      { id: "state", type: "directory", path: "/var/lib/coupled", mode: "0755" },
+      { id: "config", type: "file", path: "/var/lib/coupled/config", mode: "0644", content: content + "\n" },
+      // The gate: validates the file. Made to pass or fail from the manifest, which is the whole
+      // point — a real validator refusing a real bad config is exactly this shape.
+      {
+        id: "validate", type: "container", name: "coupled-validate", image: pinned("alpine"), "run-once": true,
+        volumes: ["/var/lib/coupled:/data:ro"],
+        args: ["sh", "-c", gateAccepts ? "test -s /data/config" : "echo 'config refused by the validator' >&2; exit 1"],
+      },
+      // The service: reads the file ONCE at start and serves that for its life, the way most
+      // servers read their configuration.
+      {
+        id: "service", type: "container", name: "coupled-service", image: pinned("alpine"), network: "host",
+        volumes: ["/var/lib/coupled:/data:ro"],
+        args: ["sh", "-c", "v=$(cat /data/config); while true; do printf 'HTTP/1.1 200 OK\\r\\nContent-Length: %s\\r\\n\\r\\n%s' \"${#v}\" \"$v\" | nc -l -p 8099; done"],
+        "restart-on": ["config"],
+      },
+    ],
+  });
+}
+
+async function served(): Promise<string> {
+  return (await on(`curl -s --max-time 3 http://127.0.0.1:8099/ || true`)).out.trim();
+}
+
+test("a coupled pair half-applied: the file moved, the gate refused, the service serves the old file — the machine is observed in the mixed state", {
+  skip, timeout: 900_000,
+}, async () => {
+  await must(`printf %s ${quote(coupled("v1", true))} > /tmp/coupled.json && docker cp /tmp/coupled.json mesh-controller:/coupled.json`);
+  await mesh("module add /coupled.json");
+  await mesh(`assign ${MACHINE} coupled`);
+  await mesh(`push ${MACHINE}`);
+  await settled();
+  let first = "";
+  for (let i = 0; i < 20 && first !== "v1"; i++) {
+    first = await served();
+    if (first !== "v1") await new Promise((r) => setTimeout(r, 2000));
+  }
+  assert.equal(first, "v1", "the service does not serve the first config");
+
+  // The change: a new file the validator refuses. Registered again under the same name so the
+  // mesh sends a new declaration; the file is applied, the gate fails, the service stays.
+  await must(`printf %s ${quote(coupled("v2", false))} > /tmp/coupled.json && docker cp /tmp/coupled.json mesh-controller:/coupled.json`);
+  await mesh("module add /coupled.json");
+  const pushed = await on(`docker exec mesh-controller /mesh-controller push ${MACHINE}`);
+  // The push is sent; what the machine did with it is read from its report.
+  let report = "";
+  for (let i = 0; i < 30; i++) {
+    const asked = await on(`docker exec mesh-controller /mesh-controller status --json`);
+    report = asked.out;
+    if (/"outcome":\s*"failed"/.test(report)) break;
+    await new Promise((r) => setTimeout(r, 3000));
+  }
+  assert.match(report, /"outcome":\s*"failed"/, `the machine did not report a failed apply:\n${pushed.out}\n${report}`);
+
+  // THE OBSERVATION. The file on disk is the new one; the service still serves the old one.
+  const onDisk = (await must(`cat /var/lib/coupled/config`)).trim();
+  const answered = await served();
+  assert.equal(onDisk, "v2", "the file was not applied before the gate");
+  assert.equal(answered, "v1", `the service was restarted onto a config the validator refused: ${answered}`);
+  console.log(`OBSERVED: config on disk = ${onDisk}, service serves = ${answered}, report = failed — the mixed state of novox/hq 04-ISSUES/066`);
+});