diff --git a/test/integration/mesh.test.ts b/test/integration/mesh.test.ts
index 0a1102e..1d682ab 100644
--- a/test/integration/mesh.test.ts
+++ b/test/integration/mesh.test.ts
@@ -1017,3 +1017,62 @@ test("model access is answered by a record, and the key the mesh took is one it
     assert.equal(held.out.trim(), "0", `the key is in the open in ${where}`);
   }
 });
+
+test("a new commit reaches a machine that is already running the old one", {
+  skip: skip || (!builder ? "set MESH_LAB_BUILDER to a built mesh-builder" : false),
+  timeout: 900_000,
+}, async () => {
+  // novox/hq ADR 0010 names the real risk of replacing a pipeline with a comparison: losing the
+  // question "did my change go out?". This is that question, end to end — a commit, a build, a
+  // catalogue, and a machine that ends up running what the source says.
+  const repo = "/var/lib/mesh/builder/repositories/delivered";
+  const write = async (what: string) =>
+    await must("anchor", `mkdir -p ${repo} && printf %s '{"module":"delivered","version":"1",` +
+      `"resources":[{"id":"marker","type":"file","path":"/etc/delivered",` +
+      `"content":"${what}","mode":"0644"}]}' > ${repo}/module.json`);
+
+  await write("first");
+  await must("anchor", `cd ${repo} && git init -q . && git add -A && ` +
+    `git -c user.email=lab -c user.name=lab commit -qm first`);
+  await mesh(`build ${repo} --wait 300s`, 420_000);
+  await mesh("assign laptop delivered");
+  await mesh("push laptop");
+  await new Promise((r) => setTimeout(r, 15_000));
+  assert.equal((await must("laptop", `cat /etc/delivered`)).trim(), "first");
+
+  // Nothing has moved, so nothing is behind — and it says so rather than doing nothing quietly.
+  assert.match(await mesh("build --behind"), /every module the mesh holds is what its source last had/);
+
+  // Now the source moves.
+  await write("second");
+  await must("anchor", `cd ${repo} && git add -A && ` +
+    `git -c user.email=lab -c user.name=lab commit -qm second`);
+  const moved = (await must("anchor", `cd ${repo} && git rev-parse HEAD`)).trim();
+  await mesh(`module moved delivered ${moved}`);
+
+  // The mesh says which module is behind, and by how much, before anything is built.
+  const behind = await mesh("status");
+  assert.match(behind, /delivered/, `status does not name the module that moved:\n${behind}`);
+  assert.match(behind, /build --behind/, `status does not say how to catch up:\n${behind}`);
+
+  // The loop, in one command: everything behind its source is built and recorded.
+  const built = await mesh("build --behind --wait 300s", 420_000);
+  assert.match(built, /delivered/, built);
+
+  // The machine is still running the old one until it is told — the mesh changing its mind is
+  // not the same as a machine acting on it, and collapsing the two is how a mesh reports success
+  // for something that has not happened.
+  assert.equal((await must("laptop", `cat /etc/delivered`)).trim(), "first",
+    "the machine changed before anything was sent to it");
+
+  await mesh("push laptop");
+  await new Promise((r) => setTimeout(r, 15_000));
+  assert.equal((await must("laptop", `cat /etc/delivered`)).trim(), "second",
+    "the machine is still running what the source no longer says");
+
+  // And it is no longer out of date, which is the half that makes the answer trustworthy: a
+  // status that says "behind" for ever is one nobody reads.
+  const after = await mesh("status");
+  assert.doesNotMatch(after, /delivered.*<.*[0-9a-f]{8}/,
+    `the module is still reported as behind after catching up:\n${after}`);
+});