Adopt a third-party workload, and keep a mesh between runs

**The adoption.** Software nobody here wrote, taking its credentials the
way such software does — from its environment — and needing two
containers that reach each other by name. The first module that could
not have been declared this morning: it needs the network shape and it
needs a sealed value to reach a container's environment.

Its password is accepted rather than generated, which is the whole shape
of an adoption: a service that already exists keeps the credential it
already has. Asserted properly — a wrong password is refused by the same
database, so the passing case means something.

**The warm scenario.** A mesh kept between runs and returned to, which
turned twelve minutes of bootstrap into thirty seconds of restore. Off
unless asked for: a run that is meant to mean something raises from
nothing.

Its guard fired for real during this work, unprompted — a mesh-host
commit landed and it refused the stale base, naming both commits, rather
than passing tests against yesterday's binary. That is 04-ISSUES/005's
rule one level down.

Three things the guard learned the hard way and now handles: a snapshot
captures disk and not memory, so the host is restarted after a restore
and asserted to have come back; the stocked image digests are worked out
while raising and a restored instance never raises, so they are kept;
and comparing only the repositories this run can see clears the ones it
cannot, so both directions are compared.

The one real bug behind five failed attempts was in mesh-host and it
reported itself precisely: a network shape the language had and no host
implemented. Everything else was scaffolding of mine.

scenarios/two-nodes.yml

@@ -28,6 +28,10 @@ images:
   # what the mesh's registry is built from — the same chicken-and-egg the bootstrap has, resolved
   # the same way.
   - registry:2
+  # A real third-party workload, for adopting one the way the conversion will. Its database is
+  # the substrate's postgres image rather than its own: what is under test is the mesh delivering
+  # a module, not which postgres it delivers.
+  - ghcr.io/umami-software/umami:postgresql-latest
   # And the builder, because it is a module the mesh assigns rather than a program somebody
   # starts by hand — which is the only way its credential can be one the mesh delivered.
   - mesh-builder:development

src/cli.ts

@@ -30,6 +30,8 @@ const USAGE = `mesh-lab — raise a disposable mesh on one machine
   diagram <scenario.yml> [out.drawio]      draw what a scenario asks for
   diagram --live <instance> [out.drawio]   draw what is actually raised
 
+  warm                           the scenario kept between runs, and whether it still counts
+  warm cool                      destroy it and forget it
   suite [paths...] [--no-build]  rebuild the artifacts, run the end-to-end tests, leave a receipt
   last-run                       whether the last run still counts; non-zero when it does not
 
@@ -118,6 +120,39 @@ async function main(): Promise<void> {
       return;
     }
 
+    // A base state many tests start from, rather than each raising its own mesh.
+    //
+    // **The speed is the lesser half.** Tests that share one long-lived mesh accumulate each
+    // other's state, and a test that reads what the previous one left is a test that passes for
+    // the wrong reason — which has already happened here once. Returning to a named state between
+    // tests makes each of them independent.
+    case "warm": {
+      const { remembered, ready, cool } = await import("./warm.ts");
+      const what = rest[0] ?? "status";
+      if (what === "cool") {
+        const gone = await cool();
+        console.log(gone ? `destroyed ${gone}, and forgot it` : "nothing was being kept warm");
+        return;
+      }
+      const held = remembered();
+      if (!held) {
+        console.log("nothing is being kept warm.");
+        console.log("  a scenario is warmed by whatever brought it to a state worth keeping;");
+        console.log("  the integration suite does it when MESH_LAB_WARM is set.");
+        return;
+      }
+      console.log(`${held.instanceId} — ${held.scenario}, warmed ${held.at}`);
+      for (const [name, commit] of Object.entries(held.against)) {
+        console.log(`  ${name.padEnd(14)} ${commit}`);
+      }
+      const said = await ready(held.scenario);
+      console.log(said.use === "restore"
+        ? "\n  usable: it can be returned to"
+        : `\n  NOT usable: ${said.why}`);
+      if (said.use !== "restore") process.exitCode = 1;
+      return;
+    }
+
     case "base": {
       // `base build` exists because a sealed scenario cannot install a container runtime, and
       // the runtime has to come from somewhere with a network (novox/hq ADR 0006).

src/warm.ts

@@ -0,0 +1,210 @@
+/**
+ * A scenario kept between runs, already brought to a state worth starting from.
+ *
+ * **Bootstrapping a mesh takes minutes and proves the same thing every time.** The tests worth
+ * iterating on are the ones after it — assigning a module, adopting a workload, watching something
+ * fail. A warm instance is raised once, brought to that state, snapshotted, and restored on every
+ * later run in seconds.
+ *
+ * **The danger is precisely the one 04-ISSUES/005 is about**, one level down: a mesh snapshotted
+ * against yesterday's binaries will pass today's tests and report green, and nothing about the
+ * result would say what it was actually run against. So a warm instance records the commits it was
+ * built from, and is refused — not silently rebuilt, refused — when they have moved.
+ *
+ * **Fresh stays the default.** This is for iterating. A run that is meant to mean something raises
+ * from nothing, because "it passes" must not quietly come to mean "it passes against a mesh
+ * somebody bootstrapped last week".
+ */
+
+import { readFileSync, writeFileSync, mkdirSync, rmSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { homedir } from "node:os";
+
+import { list, restore, snapshot, snapshots, destroy } from "./lifecycle/operate.ts";
+import type { Against } from "./lastrun.ts";
+import { whatWasTested } from "./lastrun.ts";
+
+/** The state a warm instance is kept at. One label, because a second is a state nobody named. */
+export const label = "warm";
+
+export interface Warm {
+  scenario: string;
+  instanceId: string;
+  /**
+   * The image references the scenario's registry serves, pinned by digest.
+   *
+   * Kept because they are worked out while raising and a restored instance never raises. Without
+   * them a warm run knows nothing about what it can pull, and every test naming an image fails
+   * for a reason that has nothing to do with what it was testing.
+   */
+  images: string[];
+  /** The commit each repository was at when this was brought to its state. */
+  against: Against;
+  at: string;
+}
+
+/** Where the record lives: XDG state, beside the run receipt, for the same reason. */
+export function recordPath(): string {
+  const state = process.env["XDG_STATE_HOME"] ?? join(homedir(), ".local", "state");
+  return join(state, "mesh-lab", "warm.json");
+}
+
+export function remember(warm: Warm): void {
+  const path = recordPath();
+  mkdirSync(dirname(path), { recursive: true });
+  writeFileSync(path, JSON.stringify(warm, null, 2) + "\n");
+}
+
+export function remembered(): Warm | null {
+  try {
+    return JSON.parse(readFileSync(recordPath(), "utf8")) as Warm;
+  } catch {
+    return null;
+  }
+}
+
+export function forget(): void {
+  rmSync(recordPath(), { force: true });
+}
+
+export type Verdict =
+  | { use: "restore"; instanceId: string }
+  | { use: "raise"; why: string };
+
+/**
+ * judge decides whether a remembered instance may be restored.
+ *
+ * **Every reason to refuse is a reason a test would otherwise pass while meaning nothing**, so
+ * each is named rather than collapsed into "not usable".
+ */
+export function judge(
+  warm: Warm | null,
+  scenario: string,
+  standing: string[],
+  hasSnapshot: boolean,
+  against: Against,
+): Verdict {
+  if (!warm) return { use: "raise", why: "nothing is being kept warm" };
+  if (warm.scenario !== scenario) {
+    return { use: "raise", why: `what is kept warm is ${warm.scenario}, and this is ${scenario}` };
+  }
+  if (!standing.includes(warm.instanceId)) {
+    return { use: "raise", why: `${warm.instanceId} is no longer standing` };
+  }
+  if (!hasSnapshot) {
+    return { use: "raise", why: `${warm.instanceId} has no ${label} snapshot to return to` };
+  }
+  // The check that keeps this honest. A mesh built from code that has since moved would pass
+  // today's tests against yesterday's binaries, and say nothing about it.
+  //
+  // **Both directions, because comparing only what is in front of you clears what is not.** The
+  // first version walked the current repositories alone, so running without the environment that
+  // names where they are compared nothing and reported the mesh usable — a warm instance built
+  // from code that had since moved, cleared by a check that had looked at neither. That is
+  // 04-ISSUES/005's rule again: a record that says nothing about something is not a record that
+  // clears it.
+  for (const name of new Set([...Object.keys(warm.against), ...Object.keys(against)])) {
+    const then = warm.against[name];
+    const now = against[name];
+    if (then === now) continue;
+    if (!now) {
+      return {
+        use: "raise",
+        why: `${name} was at ${then} when this was warmed, and nothing says where it is now — ` +
+          `so nothing can say whether it moved`,
+      };
+    }
+    return {
+      use: "raise",
+      why: `${name} was at ${then ?? "nothing recorded"} when this was warmed, ` +
+        `and is now at ${now}`,
+    };
+  }
+  return { use: "restore", instanceId: warm.instanceId };
+}
+
+/** What is standing right now, by instance. */
+export async function standingNow(): Promise<string[]> {
+  return (await list()).map((i) => i.instanceId);
+}
+
+/**
+ * ready returns an instance already at its warm state, or says why one must be raised.
+ *
+ * It never raises: raising needs a scenario, images and a bootstrap, and all of that belongs to
+ * whoever is using this rather than here.
+ */
+export async function ready(
+  scenario: string,
+  env: NodeJS.ProcessEnv = process.env,
+): Promise<Verdict> {
+  const warm = remembered();
+  const standing = await standingNow();
+  const has = warm ? (await snapshots(warm.instanceId)).includes(label) : false;
+  return judge(warm, scenario, standing, has, whatWasTested(env));
+}
+
+/** returnTo puts a warm instance back to its state, and says how long it took. */
+export async function returnTo(
+  instanceId: string,
+  log: (message: string) => void = () => {},
+): Promise<number> {
+  const { usableSeconds } = await restore(instanceId, label, 180, log);
+  return usableSeconds;
+}
+
+/**
+ * keep snapshots an instance as the state to come back to, and records what it was built from.
+ *
+ * Called once the caller has brought the scenario to whatever "ready to work" means for it.
+ */
+export async function keep(
+  scenario: string,
+  instanceId: string,
+  env: NodeJS.ProcessEnv = process.env,
+): Promise<Warm> {
+  await snapshot(instanceId, label);
+  const warm: Warm = {
+    scenario,
+    instanceId,
+    images: stockOf(instanceId),
+    against: whatWasTested(env),
+    at: new Date().toISOString(),
+  };
+  remember(warm);
+  return warm;
+}
+
+/** cool destroys what is being kept and forgets it. */
+export async function cool(): Promise<string | null> {
+  const warm = remembered();
+  forget();
+  if (!warm) return null;
+  if ((await standingNow()).includes(warm.instanceId)) {
+    await destroy(warm.instanceId);
+  }
+  return warm.instanceId;
+}
+
+/**
+ * What a raised scenario stocked, held until it is kept.
+ *
+ * Raising works the images out and snapshotting happens later, so this carries them between the
+ * two without the caller having to hold them.
+ */
+const stock = new Map<string, string[]>();
+
+export function rememberStock(instanceId: string, images: string[]): void {
+  stock.set(instanceId, images);
+}
+
+function stockOf(instanceId: string): string[] {
+  return stock.get(instanceId) ?? [];
+}
+
+/** What a restored instance's registry serves, from when it was warmed. */
+export function warmStock(instanceId: string): { images: string[] } {
+  const warm = remembered();
+  if (!warm || warm.instanceId !== instanceId) return { images: [] };
+  return { images: warm.images };
+}

test/integration/mesh.test.ts

@@ -26,6 +26,10 @@ import { hostBinaryPath, HOST_PATH } from "../../src/lifecycle/place.ts";
 import { labIsUsable, destroyAll } from "./harness.ts";
 import { incus } from "../../src/incus/client.ts";
 import { machineName } from "../../src/lifecycle/names.ts";
+import { ready, returnTo, keep, rememberStock, warmStock } from "../../src/warm.ts";
+
+/** Whether this run keeps its mesh for the next one. Off unless asked for. */
+const warming = process.env["MESH_LAB_WARM"] === "1";
 
 const capability = await labIsUsable();
 const binary = hostBinaryPath();
@@ -128,6 +132,44 @@ function tokenFrom(said: string): string {
 
 before(async () => {
   if (skip) return;
+
+  // A mesh kept between runs, when one is being kept and still counts.
+  //
+  // **Bootstrapping proves the same thing every time**, and the tests worth iterating on are the
+  // ones after it. Off by default: a run that is meant to mean something raises from nothing,
+  // because "it passes" must not come to mean "it passes against a mesh somebody bootstrapped
+  // last week".
+  if (warming) {
+    const said = await ready(SCENARIO);
+    if (said.use === "restore") {
+      instanceId = said.instanceId;
+      const seconds = await returnTo(instanceId);
+      stocked = warmStock(instanceId).images;
+
+      // **A snapshot captures disk, not memory.** Restoring reboots the machine, so everything
+      // this suite started by hand is gone — the host most of all. Without it the mesh looks
+      // perfectly healthy from the control plane's side: a module is assigned, a declaration is
+      // sent and recorded, and nothing on the machine is listening to apply it. That is exactly
+      // how this was first met, and it cost an hour to see.
+      //
+      // The real answer is a host started by init, which is what the design says it is anyway
+      // (novox/hq 05-the-node-host: a root service, installed as a package). Until the lab places
+      // it that way, the warm path restarts what it knows it started.
+      for (const machine of ["anchor", "laptop"]) {
+        await must(machine, `pgrep -x mesh-host >/dev/null || ` +
+          `(nohup ${HOST_PATH} run > /var/log/mesh-host.log 2>&1 & sleep 3)`);
+      }
+      const running = await on("anchor", `pgrep -x mesh-host >/dev/null && echo yes || echo no`);
+      assert.equal(running.out.trim(), "yes",
+        "the host did not come back after a restore, so nothing would apply anything");
+
+      console.log(`warm: returned ${instanceId} to its state in ${seconds.toFixed(1)}s, ` +
+        `and started the host again`);
+      return;
+    }
+    console.log(`warm: raising fresh — ${said.why}`);
+  }
+
   const raised = await raise(loadScenario(`scenarios/${SCENARIO}.yml`), {});
   instanceId = raised.instanceId;
 
@@ -153,9 +195,20 @@ before(async () => {
         `MESH_WORKSPACE=/var/lib/mesh-builder ` +
         `nohup /usr/local/bin/mesh-builder > /var/log/mesh-builder.log 2>&1 & sleep 3`);
   }
+  if (warming) {
+    // Snapshotted only now, with everything up: a state worth returning to is the one after the
+    // part nobody wants to repeat.
+    await rememberStock(instanceId, stocked);
+    const warm = await keep(SCENARIO, instanceId);
+    console.log(`warm: ${warm.instanceId} kept, against ` +
+      Object.entries(warm.against).map(([n, c]) => `${n} ${c}`).join(", "));
+  }
 }, { timeout: 1_800_000 });
 
 after(async () => {
+  // A kept instance survives on purpose, and `mesh-lab warm cool` is how it goes away. Everything
+  // else is destroyed, because an instance nobody meant to keep is one nobody will remember.
+  if (warming) return;
   if (instanceId) await destroy(instanceId);
   await destroyAll(`${SCENARIO}-`);
 }, { timeout: 600_000 });
@@ -774,16 +827,16 @@ test("rotating a credential moves both ends, and the old one stops working", {
   // holding a matching string proves they agree; only an authentication proves they are right.
   const store = "/var/lib/mesh/postgres";
   await must("anchor", `printf %s '{"module":"realstore","version":"1",` +
-    `"provides":[{"name":"realpostgres-database","scope":"mesh"}],` +
+    `"provides":[{"name":"real-postgres-database","scope":"mesh"}],` +
     `"capabilities":["container-runtime"],` +
-    `"serves":{"realpostgres-database":{"port":5433}},` +
+    `"serves":{"real-postgres-database":{"port":5433}},` +
     `"own-secrets":{"superuser":"${store}/superuser"},` +
-    `"grants":{"realpostgres-database":"${store}/grants"},` +
+    `"grants":{"real-postgres-database":"${store}/grants"},` +
     // Both halves. `grants` is where each consumer's sealed password lands; `receives` is the
     // manifest saying who asked and for what. Without the second the provisioner finds a
     // directory of unexplained secrets and says nothing has been granted — which is true, and
     // reads exactly like a credential that was never delivered.
-    `"receives":{"realpostgres-database":"${store}/grants/mesh.json"},` +
+    `"receives":{"real-postgres-database":"${store}/grants/mesh.json"},` +
     `"listens":[{"port":5433,"from":"mesh","why":"a database the mesh provisions"}],` +
     `"resources":[` +
     `{"id":"state","type":"directory","path":"${store}","mode":"0755"},` +
@@ -801,9 +854,9 @@ test("rotating a credential moves both ends, and the old one stops working", {
     `"MESH_PROVISION_POSTGRES":"postgres://postgres@127.0.0.1:5433/postgres?sslmode=disable"}}]}' ` +
     `> /tmp/realstore.json`);
   await must("anchor", `printf %s '{"module":"realapp","version":"1",` +
-    `"requires":["realpostgres-database"],"contributes":{"realpostgres-database":{"name":"realapp"}},` +
+    `"requires":["real-postgres-database"],"contributes":{"real-postgres-database":{"name":"realapp"}},` +
-    `"binds":{"realpostgres-database":"/etc/realapp/where.json"},` +
+    `"binds":{"real-postgres-database":"/etc/realapp/where.json"},` +
-    `"secrets":{"realpostgres-database":"/etc/realapp/password"},` +
+    `"secrets":{"real-postgres-database":"/etc/realapp/password"},` +
     `"resources":[{"id":"dir","type":"directory","path":"/etc/realapp","mode":"0755"}]}' ` +
     `> /tmp/realapp.json`);
   for (const f of ["realstore", "realapp"]) {
@@ -856,7 +909,7 @@ test("rotating a credential moves both ends, and the old one stops working", {
 
   // Now rotate. One command: the record changes AND both ends are sent, because leaving the
   // sending to a later command is the fault above, exactly.
-  const said = await mesh("rotate realdatabase", 180_000);
+  const said = await mesh("rotate real-postgres-database", 180_000);
   assert.match(said, /anchor/, `rotation did not touch the provider:\n${said}`);
   assert.match(said, /laptop/, `rotation did not touch the consumer:\n${said}`);
   await new Promise((r) => setTimeout(r, 25_000));
@@ -1486,3 +1539,122 @@ test("a service is reached by a name under the machine it runs on", {
   }
   await mesh("push");
 });
+
+// A real third-party workload, adopted the way the conversion will adopt one.
+//
+// **Everything before this used modules written to exercise the mesh.** This one is software
+// nobody here wrote, taking its credentials the way such software does — from its environment —
+// and needing two containers that reach each other by name. It is the first module that could not
+// have been declared before today: it needs the `network` shape, and it needs a sealed value to
+// reach a container's environment.
+//
+// Its database password is **accepted rather than generated**, which is the whole shape of an
+// adoption: a service that already exists keeps the credential it already has, because minting a
+// new one is how a running application stops being able to reach its own database.
+test("a third-party workload is adopted, with the credential it already had", {
+  skip, timeout: 900_000,
+}, async () => {
+  const password = "the-password-it-already-had";
+
+  await must("anchor", `printf %s ${quote(JSON.stringify({
+    module: "umami",
+    version: "1",
+    capabilities: ["container-runtime"],
+    "own-secrets": {
+      database: "/var/lib/umami/database.env",
+      app: "/var/lib/umami/app.env",
+    },
+    listens: [{ port: 1212, protocol: "tcp", from: "mesh", why: "the analytics page" }],
+    resources: [
+      { id: "state", type: "directory", path: "/var/lib/umami", mode: "0700" },
+      // The two containers must reach each other by name, which is what this shape is for.
+      { id: "net", type: "network", name: "umami" },
+      {
+        id: "db", type: "container", name: "umami-db",
+        image: pinned("postgres"),
+        network: "umami",
+        env: { POSTGRES_DB: "umami", POSTGRES_USER: "umami" },
+        "env-file": ["/var/lib/umami/database.env"],
+      },
+      {
+        id: "app", type: "container", name: "umami",
+        image: pinned("ghcr.io/umami-software/umami"),
+        network: "umami",
+        env: { DATABASE_TYPE: "postgresql" },
+        "env-file": ["/var/lib/umami/app.env"],
+        ports: ["1212:3000"],
+      },
+    ],
+  }))} > /umami.json`);
+  await must("anchor", `docker cp /umami.json mesh-control:/umami.json`);
+  await mesh("module add /umami.json");
+
+  // **Accepted, not generated.** The value is what the database already answers to; the mesh
+  // seals it and cannot read it again. Given whole, as the environment lines the containers read.
+  await must("anchor",
+    `printf %s ${quote(`POSTGRES_PASSWORD=${password}`)} | ` +
+    `docker exec -i mesh-control /mesh-control secret accept anchor umami database --from -`);
+  await must("anchor",
+    `printf %s ${quote(
+      `DATABASE_URL=postgresql://umami:${password}@umami-db:5432/umami`)} | ` +
+    `docker exec -i mesh-control /mesh-control secret accept anchor umami app --from -`);
+
+  await mesh("assign anchor umami");
+  await mesh("push anchor", 300_000);
+
+  // Both containers, and the network they share.
+  let up = false;
+  for (let i = 0; i < 60 && !up; i++) {
+    const running = await on("anchor", `docker ps --format '{{.Names}}'`);
+    up = running.out.includes("umami-db") && running.out.includes("umami");
+    if (!up) await new Promise((r) => setTimeout(r, 5000));
+  }
+  if (!up) {
+    // Everything that could say why, gathered before asserting. "It did not start" is the one
+    // thing already known; what is wanted is whether the mesh sent it, whether the host refused
+    // it, and what the runtime said when it tried.
+    const said = await mesh("status");
+    const containers = await on("anchor", `docker ps -a --format '{{.Names}} {{.Status}}'`);
+    const applied = await on("anchor",
+      `${HOST_PATH} owned 2>&1 | head -30 || echo "the host could not say what it owns"`);
+    const files = await on("anchor", `ls -la /var/lib/umami/ 2>&1; ` +
+      `for f in /var/lib/umami/*.env; do echo "-- $f"; wc -c "$f"; done 2>&1`);
+    const tried = await on("anchor",
+      `docker inspect umami-db --format '{{.State.Status}} {{.State.Error}}' 2>&1; ` +
+      `docker logs umami-db 2>&1 | tail -15`);
+    assert.fail(
+      `the workload never started.\n\n` +
+      `── what the mesh thinks:\n${said}\n` +
+      `── containers:\n${containers.out}\n` +
+      `── what the host owns:\n${applied.out}\n` +
+      `── what the mesh wrote:\n${files.out}\n` +
+      `── the database container:\n${tried.out}\n`);
+  }
+
+  // The environment file the mesh sealed is on the machine and readable only by root.
+  const mode = await must("anchor", `stat -c %a /var/lib/umami/database.env`);
+  assert.equal(mode.trim(), "600", "a file holding a credential is readable by more than root");
+
+  // **The assertion that matters: the credential works.** Not that a file arrived — that the
+  // database the mesh started answers to the password the mesh was given rather than one it made.
+  let connected = { out: "", ok: false };
+  for (let i = 0; i < 40 && !connected.ok; i++) {
+    connected = await on("anchor",
+      `docker exec umami-db psql -U umami -d umami -qAt -c 'select 1'`);
+    if (!connected.ok) await new Promise((r) => setTimeout(r, 3000));
+  }
+  assert.ok(connected.ok, `the database never came up:\n${connected.out}`);
+
+  const wrong = await on("anchor",
+    `docker run --rm --network umami -e PGPASSWORD=not-the-password ${pinned("postgres")} ` +
+    `psql -h umami-db -U umami -d umami -qAt -c 'select 1'`);
+  assert.ok(!wrong.ok,
+    "the database accepted a password nobody gave it, so this proves nothing about the one that was");
+
+  // And the two containers reach each other by name over the module's own network.
+  const reached = await must("anchor",
+    `docker run --rm --network umami ${pinned("postgres")} ` +
+    `sh -c 'getent hosts umami-db || echo unreachable'`);
+  assert.doesNotMatch(reached, /unreachable/,
+    "a container could not reach the other by name, so the module's network did nothing");
+});

test/warm.test.ts

@@ -0,0 +1,61 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { judge, type Warm } from "../src/warm.ts";
+
+const at = "2026-08-31T20:00:00Z";
+const built = { "mesh-lab": "aaa", "mesh-host": "bbb", "mesh-control": "ccc" };
+const warm = (over: Partial<Warm> = {}): Warm =>
+  ({ scenario: "two-nodes", instanceId: "mlab-two-nodes-1", images: [], against: built, at, ...over });
+
+// The check this exists for: a mesh warmed against code that has since moved would pass today's
+// tests against yesterday's binaries, and the result would say nothing about it.
+//
+// Same fault as novox/hq 04-ISSUES/005, one level down — a green result standing for a run
+// against something other than what is in front of you.
+test("a warm mesh built from code that has moved is refused", () => {
+  const said = judge(warm(), "two-nodes", ["mlab-two-nodes-1"], true,
+    { ...built, "mesh-host": "moved" });
+  assert.equal(said.use, "raise");
+  assert.match(said.use === "raise" ? said.why : "", /mesh-host was at bbb.*now at moved/);
+});
+
+test("a warm mesh built from the same code is used", () => {
+  const said = judge(warm(), "two-nodes", ["mlab-two-nodes-1"], true, built);
+  assert.equal(said.use, "restore");
+});
+
+// Each refusal is named, because each is a different thing being wrong.
+test("every reason to raise instead says which reason it was", () => {
+  const cases: [string, ReturnType<typeof judge>][] = [
+    ["nothing kept", judge(null, "two-nodes", [], true, built)],
+    ["another scenario", judge(warm({ scenario: "first-node" }), "two-nodes",
+      ["mlab-two-nodes-1"], true, built)],
+    ["not standing", judge(warm(), "two-nodes", [], true, built)],
+    ["no snapshot", judge(warm(), "two-nodes", ["mlab-two-nodes-1"], false, built)],
+  ];
+  for (const [what, said] of cases) {
+    assert.equal(said.use, "raise", what);
+    assert.ok(said.use === "raise" && said.why.length > 10,
+      `${what} was refused without saying why: ${JSON.stringify(said)}`);
+  }
+});
+
+// A repository the warm record never accounted for is a difference, not a match.
+test("a repository that was not recorded when it was warmed is refused", () => {
+  const said = judge(warm({ against: { "mesh-lab": "aaa" } }), "two-nodes",
+    ["mlab-two-nodes-1"], true, built);
+  assert.equal(said.use, "raise");
+});
+
+// A repository the current run cannot see is not a repository that agrees.
+//
+// **Found by testing the guard rather than trusting it.** The first version walked only the
+// repositories the current environment names, so running without that environment compared
+// nothing and called a stale mesh usable. The mesh had genuinely moved; the check had looked at
+// neither side.
+test("a repository this run cannot locate is refused, not passed over", () => {
+  const said = judge(warm(), "two-nodes", ["mlab-two-nodes-1"], true, { "mesh-lab": "aaa" });
+  assert.equal(said.use, "raise");
+  assert.match(said.use === "raise" ? said.why : "",
+    /nothing says where it is now|so nothing can say whether it moved/);
+});