diff --git a/docker/testbed/Dockerfile.scenarios b/docker/testbed/Dockerfile.scenarios
index 0b639e6e..9660d23e 100644
--- a/docker/testbed/Dockerfile.scenarios
+++ b/docker/testbed/Dockerfile.scenarios
@@ -4,4 +4,5 @@ ARG TESTBED_IMAGE
 FROM ${TESTBED_IMAGE}
 COPY runner.mjs /opt/openrig-testbed/runner.mjs
 COPY scenarios/ /opt/openrig-testbed/scenarios/
+COPY library/ /opt/openrig-testbed/library/
 CMD ["node", "/opt/openrig-testbed/runner.mjs", "healthy"]
diff --git a/packages/daemon/test/helpers/scenario-pipeline.ts b/packages/daemon/test/helpers/scenario-pipeline.ts
index 40013485..a8a70af4 100644
--- a/packages/daemon/test/helpers/scenario-pipeline.ts
+++ b/packages/daemon/test/helpers/scenario-pipeline.ts
@@ -215,8 +215,8 @@ export interface RunScenarioFileOptions {
   topologyKind?: "stub" | "real";
   /** Base environment for the hermetic scaffold (HOME/PATH/TERM). */
   baseEnv?: Record<string, string | undefined>;
-  /** Overrides forwarded to buildRealDeps (clock/sleep/appendRecord/defaults/normalizer). */
-  deps?: Partial<Pick<RealDepsOptions, "now" | "sleep" | "appendRecord" | "defaults" | "normalizer">>;
+  /** Overrides forwarded to buildRealDeps, including an explicit test fault controller. */
+  deps?: Partial<Pick<RealDepsOptions, "now" | "sleep" | "appendRecord" | "defaults" | "normalizer" | "seedRegression">>;
   /**
    * 51-04 opt-in: how the scenario-local daemon is stood up. ABSENT => host-mode,
    * byte-identical to pre-51-04 (`defaultHostDaemon` = spawnScenarioDaemon with rigBin).
diff --git a/packages/daemon/test/helpers/scenario-real-deps.ts b/packages/daemon/test/helpers/scenario-real-deps.ts
index a63d97ba..5b864132 100644
--- a/packages/daemon/test/helpers/scenario-real-deps.ts
+++ b/packages/daemon/test/helpers/scenario-real-deps.ts
@@ -17,7 +17,9 @@
  *   down          → rig down <rigName|rigId> --json --force
  *   daemon {op}   → the ScenarioDaemon lifecycle (sigterm | restart)
  *
- * restore/emit/mutate/policy/seed_regression have NO shipped runtime binding at v1
+ * seed_regression calls an explicitly supplied test fault controller. With no
+ * controller it fails loud; a declaration alone never counts as a seeded test.
+ * restore/emit/mutate/policy have NO shipped runtime binding at v1
  * (they ride 51-03 / A5 items 6-8) — the adapter FAILS LOUD with a named
  * UnboundActionError rather than fabricating a call (same floor as the FLAG-1
  * `proof` surface: unbound is never silently-skipped).
@@ -92,6 +94,10 @@ export interface RealDepsOptions {
   /** The mission scope reads audit (D3) — threaded from the scenario's
    *  env.scope_mission into `rig scope audit --mission <name> --json`. */
   scopeMission?: string;
+  /** Arm a named, scenario-local test fault (or explicitly record its healthy
+   * control). The paired harness owns injection timing and verifies the actual
+   * failing observation; this must never invoke a production `rig` command. */
+  seedRegression?: (regressionClass: string) => Promise<ActionResult>;
 }
 
 /** `rig up` is heavy (real tmux seat launch) — give it a generous ceiling. */
@@ -153,8 +159,17 @@ export function buildRealDeps(opts: RealDepsOptions): ScenarioRunnerDeps {
         if (op === "restart") { await daemon.restart(); return { code: 0, stdout: "", stderr: "" }; }
         return fail(`daemon: unknown op ${JSON.stringify(op)} (allowed: sigterm, restart)`);
       }
+      case "seed_regression": {
+        const regressionClass = payload && typeof payload === "object"
+          ? (payload as { class?: unknown }).class : undefined;
+        if (typeof regressionClass !== "string" || regressionClass.length === 0) {
+          return fail("seed_regression: a non-empty class is required");
+        }
+        if (!opts.seedRegression) throw new UnboundActionError(verb);
+        return opts.seedRegression(regressionClass);
+      }
       default:
-        // restore / emit / mutate / policy / seed_regression — no shipped binding at v1.
+        // restore / emit / mutate / policy — no shipped binding at v1.
         throw new UnboundActionError(verb);
     }
   };
diff --git a/packages/daemon/test/scenario-pipeline.test.ts b/packages/daemon/test/scenario-pipeline.test.ts
index 1e991c05..d50a49b0 100644
--- a/packages/daemon/test/scenario-pipeline.test.ts
+++ b/packages/daemon/test/scenario-pipeline.test.ts
@@ -33,6 +33,23 @@ function write(name: string, body: string): string {
 }
 
 describe("loadScenarioFile", () => {
+  it("threads the explicit seed controller through the pipeline without a live daemon", async () => {
+    const { runScenarioFile } = await import("./helpers/scenario-pipeline.js");
+    const p = write("seed.yaml", "scenario: seeded\ntopology: ./unused.yaml\nsteps:\n  - seed_regression: {class: baton-drop}\n");
+    const seedRegression = vi.fn(async () => ({ code: 0, stdout: "armed", stderr: "" }));
+    const result = await runScenarioFile(p, {
+      rigBin: "/not-executed",
+      deps: { seedRegression },
+      daemon: async scaffold => ({
+        port: 9, baseUrl: "http://127.0.0.1:9", readEnv: scaffold.env,
+        sigterm: async () => {}, restart: async () => {},
+        stop: async () => scaffold.cleanup(),
+      }),
+    });
+    expect(result).toEqual({ scenario: "seeded", verdict: "PASS" });
+    expect(seedRegression).toHaveBeenCalledExactlyOnceWith("baton-drop");
+  });
+
   it("parses a valid scenario and resolves topology relative to the scenario file", () => {
     const p = write("s.yaml", [
       "scenario: baton-survives",
diff --git a/packages/daemon/test/scenario-real-deps.test.ts b/packages/daemon/test/scenario-real-deps.test.ts
index 29b041a5..bbe9552d 100644
--- a/packages/daemon/test/scenario-real-deps.test.ts
+++ b/packages/daemon/test/scenario-real-deps.test.ts
@@ -97,6 +97,25 @@ describe("buildRealDeps runAction verb->rig map", () => {
     expect(deps.defaults.withinMs).toBeGreaterThan(0);
     expect(deps.defaults.pollIntervalMs).toBeGreaterThan(0);
   });
+
+  it("binds a named seed to the caller's fault controller and preserves its failure", async () => {
+    const result = { code: 1, stdout: "", stderr: "fault could not be armed" };
+    const seedRegression = vi.fn(async () => result);
+    const runRig = vi.fn(async () => ok());
+    const deps = buildRealDeps({ daemon: fakeDaemon(), rigBin: "/bin/rig", topologyPath: "/t.yaml", runRig, seedRegression });
+    expect(await deps.runAction("seed_regression", { class: "baton-drop" })).toBe(result);
+    expect(seedRegression).toHaveBeenCalledExactlyOnceWith("baton-drop");
+    expect(runRig).not.toHaveBeenCalled();
+  });
+
+  it("rejects a malformed seed before invoking the fault controller", async () => {
+    const seedRegression = vi.fn(async () => ok());
+    const deps = buildRealDeps({ daemon: fakeDaemon(), rigBin: "/bin/rig", topologyPath: "/t.yaml", seedRegression });
+    for (const payload of [undefined, {}, { class: "" }, { class: 42 }]) {
+      expect((await deps.runAction("seed_regression", payload)).code).toBe(1);
+    }
+    expect(seedRegression).not.toHaveBeenCalled();
+  });
 });
 
 describe("D2 — the unbound-verb message states WHY and names the v1 path", () => {
diff --git a/packages/test-system/README.md b/packages/test-system/README.md
index 7bd50666..c9cd7134 100644
--- a/packages/test-system/README.md
+++ b/packages/test-system/README.md
@@ -2,8 +2,9 @@
 
 The first PR automation increment is described in [ci/README.md](ci/README.md).
 It runs the existing daemon-restart baton fixture plus a fault control in the
-installed-package testbed. Hosted green/red execution is required before claiming
-that increment verified. The eleven authored scenarios below are a broader target;
+installed-package testbed, now alongside the library's queue-baton scenario and
+its explicit seed binding. Hosted green/red execution is required before claiming
+either verified. The eleven authored scenarios below are a broader target;
 they are not eleven admitted CI passes.
 
 ## Historical 51-03 seed contract — the ten (+ one)
@@ -42,6 +43,12 @@ scenario's `expect` legs MUST catch it. Acceptance per scenario = the PAIR: GREE
 shipped tip + RED on the seeded run whose runner diff (expected vs last-observed) names
 the class. A scenario that cannot be shown RED is not delivered.
 
+For executable seeds, place the step before the affected action and supply the
+pipeline's `deps.seedRegression` controller. It must arm a real local fault in the
+seeded run and explicitly record that fault as disabled in the healthy run. The
+paired harness verifies the injection receipt and the specific failed observation.
+The remaining historical markers after their assertions are not executable proofs.
+
 ## Run status honesty (authored before the runner exists)
 YAML authoring is cleared ahead of the 51-02 runner (dispatch authority). These files
 are the runner's acceptance targets; they are authored to the locked format and DO NOT
diff --git a/packages/test-system/ci/README.md b/packages/test-system/ci/README.md
index ebc2e679..468138da 100644
--- a/packages/test-system/ci/README.md
+++ b/packages/test-system/ci/README.md
@@ -32,7 +32,7 @@ fault is a storage-state reset, not a replay of a specific production bug.
 ## Isolation and evidence
 
 Use `bash scripts/run-pr-scenarios.sh` on a disposable GitHub Linux runner after
-`npm ci`. It refuses ordinary local invocation. Runtime is inside unprivileged,
+`npm ci`, or select a prepared remote executor as below. Runtime is inside unprivileged,
 network-disabled containers, with no host mounts, a read-only root, private
 writable `/tmp`, dropped capabilities and bounded memory/processes/time. Image
 construction uses network to retrieve the pinned base, Node and dependencies;
@@ -47,16 +47,70 @@ injection receipt. The pure `scripts/pr-scenarios.test.mjs` controls validate re
 admission only; they are
 **not** a substitute for the three actual container runs.
 
-## Remaining authored scenarios
+## Library scenario increment
 
-The eleven YAML scenarios in `../scenarios/` remain unchanged and **unadmitted**.
-All currently reach `seed_regression`, which `scenario-real-deps.ts` rejects as
-unbound. Several additionally require step-time `emit`, `policy`, `mutate`, or
-`restore`, and `kill-daemon-mid-handoff` still has its documented setup/observable
-gaps. The bounded daemon-restart fixture used here is not the original seat-resume
-scenario's full contract. Do not count this increment as eleven passing scenarios,
-strip their assertions, or convert unsupported actions into no-ops.
+The same job also runs `../scenarios/queue-baton-survives-restart.yaml` in three
+fresh containers: healthy, `baton-drop`, healthy again. It brings up the library's
+two-seat stub rig and asserts the exact `dev-qa@dev-pair-stub` claim after restart.
+The original fixture and its three controls remain unchanged.
+
+`seed_regression` now calls an explicit fault controller supplied through the
+pipeline. With no controller it still fails loudly. The library baton declares
+its seed **before** restart, not after the assertions; the controller records the
+healthy control or arms the stopped-DB mutation. Unknown classes, a missing seed,
+an injection failure, a surviving fault, or an unrelated failing observation fail
+the job. Assertions continue to use the shipped queue read, never a fake observer.
+
+The other ten library scenarios are **unadmitted**. Several need step-time `emit`,
+`policy`, `mutate`, or `restore`. Others have incomplete assertions or setup:
+clean-lifecycle has no post-down residue assertion, ps-scope neither brings up its
+second topology nor excludes extra rows, and the home/preseed and send/render
+scenarios need input behavior from the stub. `kill-daemon-mid-handoff` still has
+its documented setup/observable gaps. A callback binding does not fix these gaps.
+Do not count this increment as eleven passing scenarios or native seat-resume
+coverage. Container evidence for each selected case is required for admission.
 
 The existing CLI `run-scenarios.mjs` still accepts paths only; `--container` is
 refused. This job runs the helper *inside* the isolated image, so it does not depend
 on the host-to-container staging adapter's unsupported per-seat-script path.
+
+## Run one case before pushing
+
+Any developer or agent can use the same script with a prepared SSH Docker executor;
+there is no seat-owner or per-run approval requirement. Use a private checkout with
+the normal Node 22/24 development dependencies. Source build/pack runs on the client;
+Docker image construction and the scenario run at the selected daemon.
+
+```sh
+DOCKER_HOST=ssh://your-test-executor bash scripts/run-pr-scenarios.sh \
+  --remote --case library --mode healthy --out dist/scenario-check
+```
+
+Leave `DOCKER_CONTEXT` unset when selecting `DOCKER_HOST`, so a saved context cannot
+override the explicitly selected executor. This does not change Docker configuration.
+Use a fresh output directory for each retained run. Without `--mode` the selected
+case runs healthy / lost-baton / healthy. Without `--case` both cases run. CI keeps
+its existing six-run default. A single healthy run establishes only that leg; it is
+not the paired seeded-regression proof.
+
+The client can be macOS/arm64 while Docker is Linux/amd64: the build reads the
+**server** OS/architecture and passes the same platform to the image builds and
+containers. The Node deadline helper replaces GNU `timeout`, preserves the real
+exit status, returns 124 on deadline and escalates TERM to KILL after 15 seconds.
+All daemon work remains in the container. No local OpenRig daemon is touched.
+
+Build contexts are uploaded by Docker, not mounted from the client. Logs, actual
+exit-code files, container names/inspection, server platform, image identity and
+manifests are written in the client's `--out` directory. The image-load check still
+runs once before the selected scenario to detect a broken package/native install.
+It has a 120-second deadline, a recorded unique container name, actual exit/log
+and inspection receipts, and bounded named cleanup even on failure or timeout.
+Scenario runtime is 2 CPUs, 2GiB memory with no swap, 256 PIDs, network-none, non-root
+and a read-only root plus scratch tmpfs. A rootless executor must enforce its
+configured cgroup limits; its aggregate budget is an executor setting, not a
+claim made by successful source checks.
+
+The script removes only its named containers. If SSH becomes unavailable, it
+reports incomplete cleanup with the exact name for later reconciliation; no remote
+cleanup can be guaranteed through a broken connection. It never prunes shared
+images or other agents' containers.
diff --git a/packages/test-system/ci/result.mjs b/packages/test-system/ci/result.mjs
index 5532a9cd..038c00d4 100644
--- a/packages/test-system/ci/result.mjs
+++ b/packages/test-system/ci/result.mjs
@@ -2,14 +2,24 @@ import assert from 'node:assert/strict';
 
 export const RESULT_PREFIX = 'OPENRIG_SCENARIO_RESULT=';
 export const SCENARIO = 'queue-baton-survives-restart';
+export const CASES = {
+  fixture: { file: 'scenarios/scenario-02-baton.yaml', destination: 'dev-worker@scn-baton', failedStep: 3 },
+  library: { file: 'library/queue-baton-survives-restart.yaml', destination: 'dev-qa@dev-pair-stub', failedStep: 4, seed: 'baton-drop' },
+};
 
 // A failed start, bad command, timeout, or unrelated assertion is NOT a caught regression.
-export function verifyRun(mode, exitCode, report) {
+export function verifyRun(mode, exitCode, report, caseName = 'fixture') {
+  const selected = CASES[caseName];
+  assert.ok(selected, 'unknown scenario case');
+  assert.equal(report.caseName ?? 'fixture', caseName);
   assert.equal(report.mode, mode);
   assert.equal(report.result?.scenario, SCENARIO);
   assert.equal(report.error, undefined);
   assert.equal(report.records.length, 1);
   assert.deepEqual(report.records[0], report.result);
+  if (selected.seed) {
+    assert.deepEqual(report.seed, { class: selected.seed, enabled: mode !== 'healthy' });
+  }
   if (mode === 'healthy') {
     assert.equal(exitCode, 0);
     assert.equal(report.result.verdict, 'PASS');
@@ -21,13 +31,13 @@ export function verifyRun(mode, exitCode, report) {
     assert.equal(report.fault?.before, 'in-progress');
     assert.equal(report.fault?.after, 'pending');
     assert.equal(report.result.verdict, 'FAIL');
-    assert.equal(report.result.failedStep, 3); // the queue read AFTER restart
+    assert.equal(report.result.failedStep, selected.failedStep); // queue read AFTER restart
     const observation = report.result.observation;
     assert.equal(observation?.surface, 'queue');
     assert.ok(Array.isArray(observation.value));
     const baton = observation.value.filter(row => row?.qitemId === 'baton-1');
     assert.equal(baton.length, 1);
-    assert.equal(baton[0].destinationSession, 'dev-worker@scn-baton');
+    assert.equal(baton[0].destinationSession, selected.destination);
     assert.equal(baton[0].state, 'pending');
   }
 }
diff --git a/packages/test-system/ci/run.mjs b/packages/test-system/ci/run.mjs
index bcda8a7d..ed3ec548 100644
--- a/packages/test-system/ci/run.mjs
+++ b/packages/test-system/ci/run.mjs
@@ -7,7 +7,7 @@ import { createRequire } from 'node:module';
 import { networkInterfaces } from 'node:os';
 import { join } from 'node:path';
 import { defaultHostDaemon, runScenarioFile } from '../../daemon/test/helpers/scenario-pipeline.ts';
-import { RESULT_PREFIX } from './result.mjs';
+import { CASES, RESULT_PREFIX } from './result.mjs';
 
 assert.equal(process.platform, 'linux', 'container execution only');
 assert.notEqual(process.getuid(), 0, 'run as the unprivileged testbed user');
@@ -15,11 +15,14 @@ assert.ok(Object.values(networkInterfaces()).flat().every(address => address.int
   'requires --network none');
 const mode = process.argv[2];
 assert.ok(['healthy', 'lost-baton'].includes(mode), 'expected healthy or lost-baton');
+const caseName = process.argv[3] ?? 'fixture';
+const selected = CASES[caseName];
+assert.ok(selected, 'unknown scenario case');
 const rigBin = realpathSync('/usr/local/bin/rig');
-const scenario = '/opt/openrig-testbed/scenarios/scenario-02-baton.yaml';
+const scenario = join('/opt/openrig-testbed', selected.file);
 const records = [];
 const report = {
-  mode, records, fault: null,
+  mode, caseName, records, fault: null,
   scenarioSha256: createHash('sha256').update(readFileSync(scenario)).digest('hex'),
 };
 
@@ -27,13 +30,23 @@ try {
   report.result = await runScenarioFile(scenario, {
     rigBin,
     baseEnv: { PATH: '/usr/local/bin:/usr/bin:/bin', TERM: 'xterm-256color' },
-    deps: { appendRecord: record => records.push(record) },
+    deps: {
+      appendRecord: record => records.push(record),
+      seedRegression: async regressionClass => {
+        assert.equal(regressionClass, selected.seed, 'unsupported regression class');
+        assert.equal(report.seed, undefined, 'seed must be armed exactly once');
+        report.seed = { class: regressionClass, enabled: mode !== 'healthy' };
+        return { code: 0, stdout: JSON.stringify(report.seed), stderr: '' };
+      },
+    },
     daemon: async (scaffold, options) => {
       const daemon = await defaultHostDaemon(scaffold, options);
       if (mode === 'healthy') return daemon;
       return {
         ...daemon,
         restart: async () => {
+          if (selected.seed) assert.deepEqual(report.seed, { class: selected.seed, enabled: true },
+            'the scenario must arm its fault before restart');
           await daemon.sigterm();
           await assert.rejects(fetch(`${daemon.baseUrl}/healthz`),
             error => error.cause?.code === 'ECONNREFUSED', 'daemon must be stopped before fault injection');
@@ -42,8 +55,9 @@ try {
           const Database = createRequire(rigBin)('better-sqlite3');
           const db = new Database(join(scaffold.stateDir, 'scenario.db'), { fileMustExist: true });
           try {
-            const before = db.prepare('SELECT state FROM queue_items WHERE qitem_id = ?').get('baton-1');
+            const before = db.prepare('SELECT state, destination_session FROM queue_items WHERE qitem_id = ?').get('baton-1');
             assert.equal(before?.state, 'in-progress');
+            assert.equal(before.destination_session, selected.destination);
             const { changes } = db.prepare("UPDATE queue_items SET state = 'pending' WHERE qitem_id = ? AND state = 'in-progress'").run('baton-1');
             assert.equal(changes, 1);
             report.fault = {
diff --git a/packages/test-system/scenarios/queue-baton-survives-restart.yaml b/packages/test-system/scenarios/queue-baton-survives-restart.yaml
index f14c8f80..9ff78811 100644
--- a/packages/test-system/scenarios/queue-baton-survives-restart.yaml
+++ b/packages/test-system/scenarios/queue-baton-survives-restart.yaml
@@ -33,6 +33,9 @@ steps:
         - qitemId: baton-1
           state: in-progress
           destinationSession: dev-qa@dev-pair-stub
+  # Arm the paired harness BEFORE the affected action. Healthy runs record a
+  # disabled fault; seeded runs reset this exact claim while the daemon is down.
+  - seed_regression: {class: baton-drop}
   - daemon: { op: restart }
   # the baton MUST survive the restart: same item, still in-progress, still owned
   - expect:
@@ -46,5 +49,4 @@ steps:
   #   expect { surface: pane, seat: qa, contains: "restored" }. The stub-runner at the
   #   current tip emits only READY/EXITED; the `restore` behavior that prints the
   #   "restored" pane marker is A5 items 6-8. Lights up when they land.
-  - seed_regression: {class: baton-drop}
   - down: {}
diff --git a/scripts/build-testbed-image.sh b/scripts/build-testbed-image.sh
index ee547a0f..10b3950b 100755
--- a/scripts/build-testbed-image.sh
+++ b/scripts/build-testbed-image.sh
@@ -13,10 +13,16 @@ STUB_ASSETS_LIST="${TESTBED_DIR}/stub-assets.list"
 OUT_DIR="${1:-${REPO_ROOT}/dist/testbed-image}"
 
 command -v docker >/dev/null 2>&1 || {
-  echo "[testbed] docker not found — run this build HOST-side (locus ruling), not in the VM seat" >&2
+  echo "[testbed] Docker client not found; select the prepared disposable executor" >&2
   exit 3
 }
 
+# Resolve the daemon's platform BEFORE building locally. A remote amd64 daemon
+# reached from an arm64 Mac needs amd64 Node; client uname is not the target.
+mkdir -p "${OUT_DIR}"
+TARGET_PLATFORM="$(node "${REPO_ROOT}/scripts/scenario-executor.mjs" platform "${OUT_DIR}/docker-server.json")"
+TARGETARCH="${TARGET_PLATFORM#linux/}"
+
 # --- identity from the tree: the image is built AT this git sha, so gitSha == openrigSha ---
 GIT_SHA="$(git -C "${REPO_ROOT}" rev-parse HEAD)"
 IMAGE_TAG="openrig-testbed:${GIT_SHA}"
@@ -31,7 +37,15 @@ NODE_VERSION="$(sed -n 's/^ARG NODE_VERSION=\([0-9][0-9.]*\).*/\1/p' "${TESTBED_
 
 # --- assemble a clean build context: Dockerfile + entrypoint + the openrig pack + staged stub assets ---
 CONTEXT="$(mktemp -d)"
-trap 'rm -rf "${CONTEXT}"' EXIT
+LOAD_CONTAINER=""
+cleanup() {
+  if [ -n "${LOAD_CONTAINER}" ]; then
+    node "${REPO_ROOT}/scripts/scenario-executor.mjs" timeout 30 docker rm -f "${LOAD_CONTAINER}" >/dev/null ||
+      echo "[testbed] cleanup incomplete; retained container name: ${LOAD_CONTAINER}" >&2
+  fi
+  rm -rf "${CONTEXT}"
+}
+trap cleanup EXIT
 cp "${TESTBED_DIR}/Dockerfile" "${TESTBED_DIR}/entrypoint.sh" "${CONTEXT}/"
 
 # OpenRig CLI from the TREE (never the npm registry). ASSEMBLE the publishable @openrig/cli first
@@ -57,18 +71,8 @@ STUB_FILES_JSON="$(node -e \
   'const fs=require("fs");const l=fs.readFileSync(process.argv[1],"utf8").split("\n").map(s=>s.replace(/#.*/,"").trim()).filter(Boolean);process.stdout.write(JSON.stringify(l))' \
   "${STUB_ASSETS_LIST}")"
 
-# --- resolve the target arch HOST-side and pass it EXPLICITLY (builder-agnostic: correct on the
-# legacy builder — which NEVER populates the automatic TARGETARCH build-arg — AND on BuildKit). Fail
-# CLOSED on an unknown arch rather than letting the Dockerfile silently default to amd64, which fetches
-# x64 Node into an arm64 image and dies with a Rosetta/ELF failure (exit 133).
-case "$(uname -m)" in
-  x86_64|amd64) TARGETARCH=amd64 ;;
-  arm64|aarch64) TARGETARCH=arm64 ;;
-  *) echo "[testbed] cannot resolve a supported TARGETARCH from 'uname -m'=$(uname -m); refusing to build (a silent amd64 default installs wrong-arch Node = exit 133)" >&2; exit 4 ;;
-esac
-
 # --- build (host-side) ---
-docker build \
+docker build --platform "${TARGET_PLATFORM}" \
   --build-arg BASE_IMAGE="${BASE_IMAGE}" \
   --build-arg NODE_VERSION="${NODE_VERSION}" \
   --build-arg OPENRIG_TARBALL=openrig.tgz \
@@ -92,7 +96,23 @@ echo "[testbed] effect proof: daemon LOAD inside the container (better-sqlite3 m
 # kernel, confirm readiness by hitting /healthz DIRECTLY (deterministic — no fixed sleep), then daemon
 # status; an EXIT trap stops the daemon so a failed assertion still tears down. A broken native install
 # fails `rig daemon start` here → set -e → non-zero → the build verb fails BEFORE the A/B pin.
-docker run --rm --network none --cap-drop ALL --security-opt no-new-privileges "${IMAGE_TAG}" bash -lc 'set -euo pipefail; trap "rig daemon stop >/dev/null 2>&1 || true" EXIT; rig --version; rig daemon start --no-kernel; curl -fsS http://127.0.0.1:7433/healthz; rig daemon status'
+LOAD_CONTAINER="openrig-testbed-load-$(node -p 'require("node:crypto").randomUUID()')"
+printf '%s\n' "${LOAD_CONTAINER}" > "${OUT_DIR}/image-load.container-name.txt"
+load_status=0
+node "${REPO_ROOT}/scripts/scenario-executor.mjs" timeout 120 docker run --name "${LOAD_CONTAINER}" \
+  --platform "${TARGET_PLATFORM}" --network none --cap-drop ALL --security-opt no-new-privileges \
+  --cpus 2 --memory 2g --memory-swap 2g --pids-limit 256 "${IMAGE_TAG}" bash -lc \
+  'set -euo pipefail; trap "rig daemon stop >/dev/null 2>&1 || true" EXIT; rig --version; rig daemon start --no-kernel; curl -fsS http://127.0.0.1:7433/healthz; rig daemon status' \
+  > "${OUT_DIR}/image-load.log" 2>&1 || load_status=$?
+printf '%s\n' "${load_status}" > "${OUT_DIR}/image-load.exit-code.txt"
+cat "${OUT_DIR}/image-load.log" >&2
+inspect_status=0
+node "${REPO_ROOT}/scripts/scenario-executor.mjs" timeout 30 docker inspect "${LOAD_CONTAINER}" \
+  > "${OUT_DIR}/image-load.container.json" || inspect_status=$?
+[ "${load_status}" -eq 0 ] || exit "${load_status}"
+[ "${inspect_status}" -eq 0 ] || exit "${inspect_status}"
+node "${REPO_ROOT}/scripts/scenario-executor.mjs" timeout 30 docker rm -f "${LOAD_CONTAINER}" >/dev/null
+LOAD_CONTAINER=""
 
 # --- emit the reproducible manifest + census receipt via the tested node orchestrator ---
 INPUTS="$(mktemp)"
diff --git a/scripts/build-testbed-image.test.mjs b/scripts/build-testbed-image.test.mjs
index 2cab63d8..e2ab92fe 100644
--- a/scripts/build-testbed-image.test.mjs
+++ b/scripts/build-testbed-image.test.mjs
@@ -1,6 +1,7 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { readFileSync } from "node:fs";
+import { readFileSync, writeFileSync, mkdirSync, copyFileSync, mkdtempSync, rmSync, existsSync } from "node:fs";
+import { spawnSync } from "node:child_process";
 import { fileURLToPath } from "node:url";
 import { dirname, join } from "node:path";
 
@@ -61,11 +62,13 @@ test("Q2 fix A: packs the ASSEMBLED @openrig/cli (has the `rig` bin), NEVER the
   assert.doesNotMatch(text, /cd\s+"?\$\{REPO_ROOT\}"?\s*&&\s*npm pack/, "must NOT pack the monorepo root");
 });
 
-test("Q2 fix B: resolves the target arch HOST-side + passes it explicitly, fail-CLOSED (never a silent amd64 default -> exit 133)", () => {
+test("resolves the target from the Docker server and passes both platform and arch", () => {
   const text = readScript();
-  assert.match(text, /uname -m/, "must resolve the host arch (uname -m) so the legacy builder gets a real TARGETARCH");
-  assert.match(text, /--build-arg\s+TARGETARCH=/, "must pass TARGETARCH explicitly (builder-agnostic)");
-  assert.match(text, /uname -m[\s\S]*?exit\s+[1-9]/, "must fail-closed (non-zero exit) on an unresolvable arch");
+  assert.match(text, /scenario-executor\.mjs.*platform/);
+  assert.match(text, /--build-arg\s+TARGETARCH=/);
+  assert.match(text, /docker build --platform/);
+  assert.match(text, /docker run --name/);
+  assert.doesNotMatch(text, /case.*uname -m/);
 });
 
 test("Q2 fix B: the Dockerfile fails CLOSED on an empty TARGETARCH (no silent amd64 default)", () => {
@@ -109,3 +112,55 @@ test("Q2 rider (effect proof): the build verb LOADS the daemon inside the contai
   assert.match(text, /rig daemon start --no-kernel/, "must LOAD the daemon (better-sqlite3 binds) via the operator-corrected start, not merely check rig exists");
   assert.match(text, /\/healthz/, "must confirm readiness deterministically via /healthz (operator correction — no fixed sleep)");
 });
+
+test("image-load success, failure and deadline all retain status and remove only the named container", () => {
+  const root = mkdtempSync(join(process.cwd(), ".testbed-load-"));
+  try {
+    for (const p of ["scripts", "docker/testbed", "packages/cli", "bin"]) mkdirSync(join(root, p), { recursive: true });
+    copyFileSync(SCRIPT, join(root, "scripts/build-testbed-image.sh"));
+    copyFileSync(join(HERE, "scenario-executor.mjs"), join(root, "scripts/scenario-executor.mjs"));
+    writeFileSync(join(root, "scripts/build-package.sh"), "#!/bin/sh\nexit 0\n");
+    writeFileSync(join(root, "scripts/testbed-build-inputs.mjs"), "export const readBaseImage = () => ({ref:'fixture@sha256:abc'});\n");
+    writeFileSync(join(root, "scripts/testbed-emit-manifest.mjs"), "import fs from 'node:fs';fs.writeFileSync(process.argv[3]+'/manifest.json','{}');\n");
+    writeFileSync(join(root, "docker/testbed/Dockerfile"), "ARG NODE_VERSION=22.22.1\n");
+    for (const p of ["docker/testbed/entrypoint.sh", "docker/testbed/base-image", "docker/testbed/stub-assets.list"]) writeFileSync(join(root, p), "");
+    writeFileSync(join(root, "bin/git"), "#!/bin/sh\nprintf 'fake-source\\n'\n", { mode: 0o755 });
+    writeFileSync(join(root, "bin/npm"), "#!/bin/sh\ntouch fixture.tgz\nprintf 'fixture.tgz\\n'\n", { mode: 0o755 });
+    writeFileSync(join(root, "bin/mktemp"), '#!/bin/sh\nexec /usr/bin/mktemp "$@" "$HOME/tmp.XXXXXXXX"\n', { mode: 0o755 });
+    // Use the real deadline helper with a short test deadline. No Docker daemon,
+    // build, package install or network is involved; the marker models a remote
+    // container surviving the client process until an explicit named removal.
+    writeFileSync(join(root, "bin/node"), `#!${process.execPath}
+import {spawnSync} from 'node:child_process';const args=process.argv.slice(2);
+if(args[1]==='timeout')args[2]='0.4';
+const p=spawnSync(${JSON.stringify(process.execPath)},args,{stdio:'inherit'});process.exit(p.status??1);
+`, { mode: 0o755 });
+    writeFileSync(join(root, "bin/docker"), `#!${process.execPath}
+import fs from 'node:fs';const args=process.argv.slice(2);const marker=process.env.FAKE_CONTAINER;
+if(args[0]==='version')console.log(JSON.stringify({Os:'linux',Arch:'amd64'}));
+else if(args[0]==='build'){}
+else if(args[0]==='run'){
+  const at=args.indexOf('--name');if(at<0)process.exit(9);
+  fs.writeFileSync(marker,args[at+1]);
+  if(process.env.LOAD_CASE==='timeout')setInterval(()=>{},1000);
+  else process.exit(process.env.LOAD_CASE==='failure'?7:0);
+}else if(args[0]==='inspect')console.log('[]');
+else if(args[0]==='rm'){
+  if(fs.readFileSync(marker,'utf8')!==args.at(-1))process.exit(8);
+  fs.unlinkSync(marker);
+}else process.exit(8);
+`, { mode: 0o755 });
+    for (const [mode, status] of [["success", 0], ["failure", 7], ["timeout", 124]]) {
+      const out = join(root, mode), marker = join(root, "container");
+      const run = spawnSync("/bin/bash", [join(root, "scripts/build-testbed-image.sh"), out], {
+        env: { PATH: `${join(root, "bin")}:/usr/bin:/bin`, HOME: root, TMPDIR: root, LOAD_CASE: mode, FAKE_CONTAINER: marker },
+        encoding: "utf8", timeout: 8000,
+      });
+      assert.equal(run.status, status, `${mode}: ${run.stderr}`);
+      assert.equal(Number(readFileSync(join(out, "image-load.exit-code.txt"), "utf8")), status);
+      assert.match(readFileSync(join(out, "image-load.container-name.txt"), "utf8"), /^openrig-testbed-load-/);
+      assert.equal(existsSync(marker), false, `${mode}: container must be removed even after timeout`);
+      assert.equal(existsSync(join(out, "manifest.json")), status === 0);
+    }
+  } finally { rmSync(root, { recursive: true, force: true }); }
+});
diff --git a/scripts/pr-scenarios.test.mjs b/scripts/pr-scenarios.test.mjs
index 88505de4..7679f200 100644
--- a/scripts/pr-scenarios.test.mjs
+++ b/scripts/pr-scenarios.test.mjs
@@ -19,6 +19,24 @@ test('accepts a healthy run and a specifically observed post-restart lost baton'
   verifyRun('healthy', 0, green);
   verifyRun('lost-baton', 1, red);
 });
+test('library admission requires its own seed, failing step, and exact destination', () => {
+  const libraryGreen = { ...green, caseName: 'library', seed: { class: 'baton-drop', enabled: false } };
+  const result = {
+    ...red.result, failedStep: 4,
+    observation: { surface: 'queue', value: [
+      { qitemId: 'baton-1', state: 'pending', destinationSession: 'dev-qa@dev-pair-stub' },
+    ] },
+  };
+  const libraryRed = { ...report('lost-baton', result, red.fault), caseName: 'library', seed: { class: 'baton-drop', enabled: true } };
+  verifyRun('healthy', 0, libraryGreen, 'library');
+  verifyRun('lost-baton', 1, libraryRed, 'library');
+  for (const seed of [undefined, { class: 'typo', enabled: true }, { class: 'baton-drop', enabled: false }]) {
+    assert.throws(() => verifyRun('lost-baton', 1, { ...libraryRed, seed }, 'library'));
+  }
+  assert.throws(() => verifyRun('healthy', 0, libraryGreen));
+  assert.throws(() => verifyRun('lost-baton', 1, { ...libraryRed, result: red.result, records: [red.result] }, 'library'));
+  assert.throws(() => verifyRun('healthy', 0, green, 'unknown'));
+});
 test('rejects a surviving mutant and a failure before the seeded boundary', () => {
   assert.throws(() => verifyRun('lost-baton', 0, { ...green, mode: 'lost-baton' }));
   assert.throws(() => verifyRun('lost-baton', 1, report('lost-baton', {
diff --git a/scripts/run-pr-scenarios.sh b/scripts/run-pr-scenarios.sh
index 17e9c058..05667ebf 100644
--- a/scripts/run-pr-scenarios.sh
+++ b/scripts/run-pr-scenarios.sh
@@ -1,12 +1,36 @@
 #!/usr/bin/env bash
-# Hosted Linux only. All daemon/seat work runs inside the existing testbed.
+# All daemon/seat work runs inside the existing disposable testbed.
+# Default: GitHub CI. --remote: explicitly selected SSH Docker executor.
 set -euo pipefail
 REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
 cd "$REPO_ROOT"
-test "${GITHUB_ACTIONS:-}" = true || { echo 'Use a disposable GitHub runner, not a working host' >&2; exit 2; }
-test "$(uname -s)" = Linux
+REMOTE=false
+CASES=(fixture library)
+MODES=(healthy lost-baton healthy)
 OUT="$REPO_ROOT/dist/pr-scenarios"
+while [ "$#" -gt 0 ]; do
+  case "$1" in
+    --remote) REMOTE=true; shift ;;
+    --case)
+      case "${2:-}" in fixture|library) CASES=("$2");; *) echo 'Expected --case fixture|library' >&2; exit 2;; esac
+      shift 2 ;;
+    --mode)
+      case "${2:-}" in healthy|lost-baton) MODES=("$2");; *) echo 'Expected --mode healthy|lost-baton' >&2; exit 2;; esac
+      shift 2 ;;
+    --out) test -n "${2:-}" || exit 2; OUT="$2"; shift 2 ;;
+    *) echo "Unknown argument: $1" >&2; exit 2 ;;
+  esac
+done
+if "$REMOTE"; then
+  case "${DOCKER_HOST:-}" in ssh://?*) ;; *) echo '--remote requires explicit DOCKER_HOST=ssh://...' >&2; exit 2;; esac
+  test -z "${DOCKER_CONTEXT:-}" || { echo 'Unset DOCKER_CONTEXT so it cannot override the selected DOCKER_HOST' >&2; exit 2; }
+else
+  test "${GITHUB_ACTIONS:-}" = true || { echo 'Use GitHub CI or --remote with the prepared disposable SSH executor' >&2; exit 2; }
+  test "$(uname -s)" = Linux
+fi
 mkdir -p "$OUT"
+OUT="$(cd "$OUT" && pwd -P)"
+TARGET_PLATFORM="$(node scripts/scenario-executor.mjs platform "$OUT/docker-server.json")"
 
 # build-testbed-image performs the stock package build, clean target install,
 # and daemon-load effect proof, then records the image inputs. It never pushes.
@@ -17,41 +41,49 @@ IMAGE="openrig-pr-scenarios:$SHA"
 CONTEXT="$(mktemp -d)"
 CONTAINER=""
 cleanup() {
-  if [ -n "$CONTAINER" ]; then docker rm -f "$CONTAINER" >/dev/null; fi
+  if [ -n "$CONTAINER" ]; then
+    node scripts/scenario-executor.mjs timeout 30 docker rm -f "$CONTAINER" >/dev/null || echo "Cleanup incomplete; retained container name: $CONTAINER" >&2
+  fi
   rm -rf "$CONTEXT"
 }
 trap cleanup EXIT
 cp docker/testbed/Dockerfile.scenarios "$CONTEXT/Dockerfile"
 cp -R packages/daemon/test/fixtures/scenarios "$CONTEXT/scenarios"
+cp -R packages/test-system/scenarios "$CONTEXT/library"
 # esbuild already ships in the lockfile through tsx. Bundle the existing helper
 # closure (including YAML) so the container needs no source tree or dev install.
 node_modules/.bin/esbuild packages/test-system/ci/run.mjs --bundle --platform=node \
   --format=esm --banner:js='import { createRequire as nodeRequire } from "node:module"; const require = nodeRequire(import.meta.url);' \
   --outfile="$CONTEXT/runner.mjs" --metafile="$OUT/runner-inputs.json"
-docker build --network none --build-arg TESTBED_IMAGE="$BASE" -t "$IMAGE" "$CONTEXT"
+docker build --network none --platform "$TARGET_PLATFORM" --build-arg TESTBED_IMAGE="$BASE" -t "$IMAGE" "$CONTEXT"
 docker image inspect "$IMAGE" > "$OUT/image-inspect.json"
 
 attempt=0
-for mode in healthy lost-baton healthy; do
+for scenario in "${CASES[@]}"; do
+for mode in "${MODES[@]}"; do
   attempt=$((attempt + 1))
   status=0
-  LOG="$OUT/$attempt-$mode.log"
+  LOG="$OUT/$attempt-$scenario-$mode.log"
   CONTAINER="openrig-pr-${SHA:0:12}-$attempt-$$"
+  printf '%s\n' "$CONTAINER" > "$OUT/$attempt-$scenario-$mode.container-name.txt"
   # Fresh writable scratch only. No mounts, host networking, credentials or Docker
   # socket; the container is non-root, resource bounded and removed even on failure.
-  timeout --signal=TERM --kill-after=15s 300s docker run --name "$CONTAINER" --network none \
+  node scripts/scenario-executor.mjs timeout 300 docker run --name "$CONTAINER" --platform "$TARGET_PLATFORM" --network none \
     --read-only --tmpfs /tmp:rw,exec,nosuid,nodev,size=512m,mode=1777 \
     --cap-drop ALL --security-opt no-new-privileges --pids-limit 256 \
-    --memory 2g --cpus 2 "$IMAGE" node /opt/openrig-testbed/runner.mjs "$mode" \
+    --memory 2g --memory-swap 2g --cpus 2 "$IMAGE" node /opt/openrig-testbed/runner.mjs "$mode" "$scenario" \
     > "$LOG" 2>&1 || status=$?
+  printf '%s\n' "$status" > "$OUT/$attempt-$scenario-$mode.exit-code.txt"
   cat "$LOG"
-  docker rm -f "$CONTAINER" >/dev/null
+  node scripts/scenario-executor.mjs timeout 30 docker inspect "$CONTAINER" > "$OUT/$attempt-$scenario-$mode.container.json"
+  node scripts/scenario-executor.mjs timeout 30 docker rm -f "$CONTAINER" >/dev/null
   CONTAINER=""
-  node --input-type=module - "$mode" "$status" "$LOG" <<'JS'
+  node --input-type=module - "$mode" "$status" "$LOG" "$scenario" <<'JS'
 import { readFileSync } from 'node:fs';
 import { readReport, verifyRun } from './packages/test-system/ci/result.mjs';
-const [mode, status, log] = process.argv.slice(2);
-verifyRun(mode, Number(status), readReport(readFileSync(log, 'utf8')));
-console.log(`${mode}: ${mode === 'healthy' ? 'healthy scenario passed' : 'seeded durability regression caught at the expected assertion'}`);
+const [mode, status, log, scenario] = process.argv.slice(2);
+verifyRun(mode, Number(status), readReport(readFileSync(log, 'utf8')), scenario);
+console.log(`${scenario}/${mode}: ${mode === 'healthy' ? 'healthy scenario passed' : 'seeded durability regression caught at the expected assertion'}`);
 JS
 done
+done
diff --git a/scripts/scenario-executor.mjs b/scripts/scenario-executor.mjs
new file mode 100644
index 00000000..c410b8f5
--- /dev/null
+++ b/scripts/scenario-executor.mjs
@@ -0,0 +1,75 @@
+// Client-side helpers for the existing scenario scripts; never runs a daemon.
+import { spawn, spawnSync } from 'node:child_process';
+import { writeFileSync } from 'node:fs';
+import { constants } from 'node:os';
+import { resolve } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+export function dockerPlatform(server) {
+  if (server?.Os !== 'linux' || !['amd64', 'arm64'].includes(server?.Arch)) {
+    throw new Error(`Unsupported Docker server: ${server?.Os}/${server?.Arch}`);
+  }
+  return `linux/${server.Arch}`;
+}
+
+export async function runWithDeadline(argv, { timeoutMs, killAfterMs = 15000 }) {
+  if (!argv.length || !Number.isFinite(timeoutMs) || timeoutMs <= 0 || killAfterMs <= 0) {
+    throw new Error('Command and positive finite deadline required');
+  }
+  return new Promise(resolveResult => {
+    const child = spawn(argv[0], argv.slice(1), { stdio: 'inherit', detached: true });
+    let forced, escalation, finished = false;
+    const signalChild = signal => {
+      if (!child.pid) return;
+      try { process.kill(-child.pid, signal); } catch (error) {
+        if (error.code !== 'ESRCH') throw error;
+      }
+    };
+    const terminate = code => {
+      if (forced !== undefined) return;
+      forced = code;
+      signalChild('SIGTERM');
+      escalation = setTimeout(() => signalChild('SIGKILL'), killAfterMs);
+    };
+    const timeout = setTimeout(() => terminate(124), timeoutMs);
+    const interrupt = () => terminate(130);
+    const shutdown = () => terminate(143);
+    process.once('SIGINT', interrupt);
+    process.once('SIGTERM', shutdown);
+    const finish = code => {
+      if (finished) return;
+      finished = true;
+      if (forced !== undefined) signalChild('SIGKILL');
+      clearTimeout(timeout); clearTimeout(escalation);
+      process.removeListener('SIGINT', interrupt);
+      process.removeListener('SIGTERM', shutdown);
+      resolveResult(forced ?? code);
+    };
+    child.once('error', error => {
+      console.error(`Cannot run ${argv[0]}: ${error.message}`);
+      finish(127);
+    });
+    child.once('close', (code, signal) => finish(code ?? (128 + (constants.signals[signal] ?? 0))));
+  });
+}
+
+if (process.argv[1] && resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
+  try {
+    const [operation, ...args] = process.argv.slice(2);
+    if (operation === 'platform') {
+      const version = spawnSync('docker', ['version', '--format', '{{json .Server}}'], { encoding: 'utf8', timeout: 30000 });
+      if (version.error || version.status !== 0) throw new Error(version.error?.message ?? version.stderr);
+      const server = JSON.parse(version.stdout);
+      const platform = dockerPlatform(server);
+      if (args[0]) writeFileSync(args[0], JSON.stringify({ platform, server }, null, 2) + '\n');
+      console.log(platform);
+    } else if (operation === 'timeout') {
+      process.exitCode = await runWithDeadline(args.slice(1), { timeoutMs: Number(args[0]) * 1000 });
+    } else {
+      throw new Error('Expected platform [receipt-path] or timeout <seconds> <command> [args...]');
+    }
+  } catch (error) {
+    console.error(error.message);
+    process.exitCode = 2;
+  }
+}
diff --git a/scripts/scenario-executor.test.mjs b/scripts/scenario-executor.test.mjs
new file mode 100644
index 00000000..869ed451
--- /dev/null
+++ b/scripts/scenario-executor.test.mjs
@@ -0,0 +1,60 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { dockerPlatform, runWithDeadline } from './scenario-executor.mjs';
+import { mkdtempSync, writeFileSync, readFileSync, rmSync } from 'node:fs';
+import { join, resolve } from 'node:path';
+import { spawnSync } from 'node:child_process';
+
+test('target follows the Docker server, not this client platform', () => {
+  assert.equal(dockerPlatform({ Os: 'linux', Arch: 'amd64' }), 'linux/amd64');
+  assert.equal(dockerPlatform({ Os: 'linux', Arch: 'arm64' }), 'linux/arm64');
+  for (const server of [undefined, {}, { Os: 'darwin', Arch: 'arm64' }, { Os: 'linux', Arch: 'mips' }]) {
+    assert.throws(() => dockerPlatform(server), /Unsupported Docker server/);
+  }
+});
+test('deadline wrapper preserves actual successful and nonzero exits', async () => {
+  assert.equal(await runWithDeadline([process.execPath, '-e', 'process.exit(0)'], { timeoutMs: 3000 }), 0);
+  assert.equal(await runWithDeadline([process.execPath, '-e', 'process.exit(7)'], { timeoutMs: 3000 }), 7);
+});
+test('deadline expires even when the child ignores TERM', async () => {
+  const start = Date.now();
+  const status = await runWithDeadline([process.execPath, '-e', "process.on('SIGTERM',()=>{});setInterval(()=>{},1000)"], { timeoutMs: 300, killAfterMs: 100 });
+  assert.equal(status, 124);
+  assert.ok(Date.now() - start < 3000);
+});
+test('a missing executable and an invalid deadline cannot report success', async () => {
+  assert.equal(await runWithDeadline(['/nonexistent/openrig-test-program'], { timeoutMs: 1000 }), 127);
+  await assert.rejects(runWithDeadline([process.execPath], { timeoutMs: 0 }), /positive/);
+});
+
+test('the platform CLI queries a fake remote server and writes its actual receipt', () => {
+  const root = mkdtempSync(join(process.cwd(), '.scenario-platform-'));
+  try {
+    const server = { Os: 'linux', Arch: 'amd64', Version: 'test-only' };
+    writeFileSync(join(root, 'docker'), `#!/bin/sh
+printf '%s\\n' '${JSON.stringify(server)}'
+`, { mode: 0o755 });
+    const receipt = join(root, 'server.json');
+    const run = spawnSync(process.execPath, [resolve('scripts/scenario-executor.mjs'), 'platform', receipt], {
+      env: { ...process.env, PATH: root + ':/usr/bin:/bin', DOCKER_HOST: 'ssh://fixture.invalid' }, encoding: 'utf8',
+    });
+    assert.equal(run.status, 0, run.stderr);
+    assert.equal(run.stdout.trim(), 'linux/amd64');
+    assert.deepEqual(JSON.parse(readFileSync(receipt, 'utf8')), { platform: 'linux/amd64', server });
+  } finally { rmSync(root, { recursive: true, force: true }); }
+});
+test('ordinary invocation and ambiguous remote selection refuse before any build', () => {
+  const script = resolve('scripts/run-pr-scenarios.sh');
+  for (const [args, extra, message] of [
+    [[], {}, /Use GitHub CI or --remote/],
+    [['--remote'], {}, /requires explicit DOCKER_HOST/],
+    [['--remote'], { DOCKER_HOST: 'ssh://fixture.invalid', DOCKER_CONTEXT: 'other' }, /Unset DOCKER_CONTEXT/],
+    [['--remote', '--case', 'typo'], {}, /Expected --case/],
+    [['--remote', '--mode', 'typo'], {}, /Expected --mode/],
+  ]) {
+    const env = { ...process.env, GITHUB_ACTIONS: '', DOCKER_HOST: '', DOCKER_CONTEXT: '', ...extra };
+    const run = spawnSync('/bin/bash', [script, ...args], { env, encoding: 'utf8', timeout: 3000 });
+    assert.equal(run.status, 2, run.stderr);
+    assert.match(run.stderr, message);
+  }
+});