diff --git a/packages/paperclip-runner/src/control-plane/acpx-controller-recovery.test.ts b/packages/paperclip-runner/src/control-plane/acpx-controller-recovery.test.ts
index 446322a0ec9..0f63269c5ee 100644
--- a/packages/paperclip-runner/src/control-plane/acpx-controller-recovery.test.ts
+++ b/packages/paperclip-runner/src/control-plane/acpx-controller-recovery.test.ts
@@ -8,6 +8,7 @@ import { resolve } from "node:path";
 import { fileURLToPath } from "node:url";
 import { beforeAll, expect, it, vi } from "vitest";
 import { DurablePrpControlPlane, decodeDurablePrpCheckpoint, type DurablePrpCheckpoint } from "./durable-prp-control-plane.js";
+import { copyOwnedNodeRuntime } from "../test-support/owned-node-runtime.js";
 import { GENERATED_ACPX_SIDECAR_PROTOCOL_VERSION } from "../drivers/acpx/generated-sidecar-contract.js";
 import { createCapabilityRunnerdCodexTransport } from "../live/runnerd-codex-transport.js";
 
@@ -66,6 +67,7 @@ function sidecarSource(root: string) {
 
 async function fixture() {
   const root = mkdtempSync(resolve(tmpdir(), "acpx-controller-recovery-"));
+  const { executable: nodeCommand } = await copyOwnedNodeRuntime(resolve(root, "node"));
   const stateDirectory = resolve(root, "control-plane");
   const script = resolve(root, "sidecar.cjs");
   writeFileSync(script, sidecarSource(root), { mode: 0o700 });
@@ -74,7 +76,7 @@ async function fixture() {
     agent: "claude", model: "scripted-model", acpxVersion: profiles.acpxVersion,
     agentServerPackage: profile.agentServerPackage, agentServerVersion: profile.agentServerVersion,
     agentRuntimePackage: profile.agentRuntimePackage, agentRuntimeVersion: profile.agentRuntimeVersion,
-    commandDigest: profile.commandDigest, sidecarCommand: process.execPath, sidecarArgs: [script],
+    commandDigest: profile.commandDigest, sidecarCommand: nodeCommand, sidecarArgs: [script],
     runtimeDirectory: runtime, normalizedSessionId: identity.normalizedSessionId, runId: identity.runId,
     cwd: root, instructions: "Do the supplied synthetic task.", permissionMode: "approve-reads", permissionModePinned: true,
     runtimeContext: null };
@@ -95,7 +97,7 @@ async function fixture() {
     "--run-id",identity.runId,"--session-id",identity.normalizedSessionId,"--turn-id",identity.turnId,"--item-id",identity.itemId,
     "--runner-version",expectedRunnerVersion,"--runner-digest",expectedRunnerDigest,"--max-runtime-ms","0",
     "--reconnect-grace-ms","15000","--reconnect-delay-ms","25","--acpx-launch-authority-digest","sha256:"+"d".repeat(64),
-    "--acpx-sidecar-command",process.execPath,"--acpx-sidecar-command-sha256",digest(process.execPath),
+    "--acpx-sidecar-command",nodeCommand,"--acpx-sidecar-command-sha256",digest(nodeCommand),
     "--acpx-sidecar-script",script,"--acpx-sidecar-script-sha256",digest(script)];
   const startedAt = new Date().toISOString();
   const child = spawn(binary,args,{env:{PATH:process.env.PATH,PAPERCLIP_RUNNER_BOOTSTRAP_TICKET:ticket},stdio:["ignore","ignore","pipe"],detached:true});
diff --git a/packages/paperclip-runner/src/drivers/acpx/native-distribution-integrity.test.ts b/packages/paperclip-runner/src/drivers/acpx/native-distribution-integrity.test.ts
index 438a3db12e3..397cd56a238 100644
--- a/packages/paperclip-runner/src/drivers/acpx/native-distribution-integrity.test.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/native-distribution-integrity.test.ts
@@ -8,6 +8,7 @@ import { tmpdir } from "node:os";
 import { dirname, join } from "node:path";
 import type { ChildProcess } from "node:child_process";
 import { afterEach, describe, expect, it, vi } from "vitest";
+import { copyOwnedNodeRuntime } from "../../test-support/owned-node-runtime.js";
 import { awaitVerifiedAcpxProviderExit, awaitVerifiedAcpxProviderOwnership, verifyNativeAcpxInstallation } from "./installation-integrity.js";
 import { createNativeAcpxDistributionSnapshot, readNativeAcpxDistributionEntries, parseNativeAcpxDistributionEntries, type NativeAcpxDistributionInput, type NativeAcpxDistributionEntry } from "./native-distribution-integrity.js";
 import { openCodexAcpxRuntime } from "./codex-runtime-adapter.js";
@@ -27,14 +28,10 @@ async function fixture(options: { node?: boolean; script?: string } = {}): Promi
   const root = await mkdtemp(join(tmpdir(), "native-acpx-test-")); roots.push(root);
   const entries: NativeAcpxDistributionEntry[] = [];
   if (options.node) {
-    await copyFile(process.execPath, join(root, "runtime")); await chmod(join(root, "runtime"), 0o700);
-    const bytes = await readFile(join(root, "runtime")); entries.push({ path: "runtime", sha256: hash(bytes), size: bytes.length, executable: true });
-    // Homebrew's test-host Node uses an @rpath libnode dylib. Include that
-    // dependency in this fixture's closure instead of relying on its old path.
-    const libraryRoot = join(dirname(process.execPath), "..", "lib");
-    for (const name of (await readdir(libraryRoot).catch(() => [] as string[])).filter(name => /^libnode\..*\.dylib$/.test(name))) {
-      await copyFile(join(libraryRoot, name), join(root, name)); await chmod(join(root, name), 0o600);
-      const library = await readFile(join(root, name)); entries.push({ path: name, sha256: hash(library), size: library.length, executable: false });
+    const { executable, libraries } = await copyOwnedNodeRuntime(root);
+    const bytes = await readFile(executable); entries.push({ path: "runtime", sha256: hash(bytes), size: bytes.length, executable: true });
+    for (const libraryPath of libraries) {
+      const library = await readFile(libraryPath); entries.push({ path: libraryPath.slice(root.length + 1), sha256: hash(library), size: library.length, executable: false });
     }
     const script = options.script ?? 'console.log("qualified-entry");';
     await writeFile(join(root, "entry.cjs"), script, { mode: 0o600 });
diff --git a/packages/paperclip-runner/src/test-support/owned-node-runtime.test.ts b/packages/paperclip-runner/src/test-support/owned-node-runtime.test.ts
new file mode 100644
index 00000000000..f99e6e3dafc
--- /dev/null
+++ b/packages/paperclip-runner/src/test-support/owned-node-runtime.test.ts
@@ -0,0 +1,55 @@
+import { chmod, lstat, mkdir, mkdtemp, readFile, rm, stat, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, expect, it } from "vitest";
+import { copyOwnedNodeRuntime } from "./owned-node-runtime.js";
+
+const roots: string[] = [];
+afterEach(async () => {
+  await Promise.all(roots.splice(0).map(root => rm(root, { recursive: true, force: true })));
+});
+
+it("copies writable host artifacts into an owned closure without changing the source", async () => {
+  const root = await mkdtemp(join(tmpdir(), "owned-node-test-")); roots.push(root);
+  const bin = join(root, "host", "bin"), lib = join(root, "host", "lib");
+  await mkdir(bin, { recursive: true }); await mkdir(lib);
+  const source = join(bin, "node"), library = join(lib, "libnode.137.dylib");
+  await writeFile(source, "synthetic Node artifact"); await chmod(source, 0o777);
+  await writeFile(library, "synthetic library"); await chmod(library, 0o666);
+  await writeFile(join(lib, "unrelated.dylib"), "not in the Node closure");
+  const sourceMode = (await stat(source)).mode, libraryMode = (await stat(library)).mode;
+
+  const owned = await copyOwnedNodeRuntime(join(root, "owned"), source);
+
+  expect(owned.libraries).toEqual([join(root, "owned", "libnode.137.dylib")]);
+  expect(await readFile(owned.executable)).toEqual(await readFile(source));
+  expect(await readFile(owned.libraries[0]!)).toEqual(await readFile(library));
+  expect((await lstat(owned.executable)).isSymbolicLink()).toBe(false);
+  if (process.platform !== "win32") {
+    expect((await stat(owned.executable)).mode & 0o777).toBe(0o700);
+    expect((await stat(owned.libraries[0]!)).mode & 0o777).toBe(0o600);
+  }
+  expect((await stat(source)).mode).toBe(sourceMode);
+  expect((await stat(library)).mode).toBe(libraryMode);
+});
+
+it("copies the real host Node bytes without executing the runtime", async () => {
+  const root = await mkdtemp(join(tmpdir(), "owned-node-test-")); roots.push(root);
+  const owned = await copyOwnedNodeRuntime(root);
+  expect((await readFile(owned.executable)).equals(await readFile(process.execPath))).toBe(true);
+  expect((await lstat(owned.executable)).isFile()).toBe(true);
+  if (process.platform !== "win32") expect((await stat(owned.executable)).mode & 0o022).toBe(0);
+});
+
+it("rejects a broken adjacent library directory instead of returning an incomplete closure", async () => {
+  const root = await mkdtemp(join(tmpdir(), "owned-node-test-")); roots.push(root);
+  const bin = join(root, "host", "bin"), lib = join(root, "host", "lib");
+  await mkdir(bin, { recursive: true });
+  const source = join(bin, "node");
+  await writeFile(source, "synthetic Node artifact");
+  await writeFile(lib, "a file cannot be the library directory");
+  await expect(copyOwnedNodeRuntime(join(root, "owned"), source)).rejects.toMatchObject({
+    message: `Cannot read Node fixture libraries at ${lib}`,
+    cause: { code: "ENOTDIR" },
+  });
+});
diff --git a/packages/paperclip-runner/src/test-support/owned-node-runtime.ts b/packages/paperclip-runner/src/test-support/owned-node-runtime.ts
new file mode 100644
index 00000000000..2575061f1f8
--- /dev/null
+++ b/packages/paperclip-runner/src/test-support/owned-node-runtime.ts
@@ -0,0 +1,24 @@
+import { chmod, copyFile, mkdir, readdir } from "node:fs/promises";
+import { dirname, join } from "node:path";
+
+/** Copy the test host Node closure without changing its shared executable. */
+export async function copyOwnedNodeRuntime(directory: string, source = process.execPath) {
+  await mkdir(directory, { recursive: true });
+  const executable = join(directory, "runtime");
+  await copyFile(source, executable);
+  await chmod(executable, 0o700);
+  // Homebrew Node resolves its libnode dylib next to the relocated executable.
+  const libraryRoot = join(dirname(source), "..", "lib");
+  const libraries: string[] = [];
+  const names = await readdir(libraryRoot).catch((error: NodeJS.ErrnoException) => {
+    if (error.code === "ENOENT") return [] as string[];
+    throw new Error(`Cannot read Node fixture libraries at ${libraryRoot}`, { cause: error });
+  });
+  for (const name of names.filter(name => /^libnode\..*\.dylib$/.test(name))) {
+    const library = join(directory, name);
+    await copyFile(join(libraryRoot, name), library);
+    await chmod(library, 0o600);
+    libraries.push(library);
+  }
+  return { executable, libraries };
+}