diff --git a/tests/runner-e2e/harness-env.ts b/tests/runner-e2e/harness-env.ts
index 3264ba7bfa..b8ac040e08 100644
--- a/tests/runner-e2e/harness-env.ts
+++ b/tests/runner-e2e/harness-env.ts
@@ -26,6 +26,21 @@ const AMBIENT_EXTERNAL_STATE_KEYS = [
 ] as const;
 const PROVIDER_SECRET_KEY = /^(?:OPENAI|ANTHROPIC|OPENROUTER|DAYTONA)(?:_|$)/;
 
+export function runnerE2EServerControlPaths(temporaryRoot: string) {
+  const controlDirectory = path.join(temporaryRoot, "control");
+  return {
+    controlDirectory,
+    restartRequestPath: path.join(
+      controlDirectory,
+      "server-restart.request.json",
+    ),
+    restartAcknowledgementPath: path.join(
+      controlDirectory,
+      "server-restart.ack.json",
+    ),
+  };
+}
+
 /**
  * Local native cells use the debug binary produced by build:runner-binaries.
  * Preserve an explicit override for release builds and developer workflows.
diff --git a/tests/runner-e2e/runner.spec.ts b/tests/runner-e2e/runner.spec.ts
index 5a0ad01cbe..b1fee74603 100644
--- a/tests/runner-e2e/runner.spec.ts
+++ b/tests/runner-e2e/runner.spec.ts
@@ -6,6 +6,7 @@ import { RunnerApi, pollUntil } from "./api.js";
 import { buildRuntimeUsage, summarizeExecutionBilling } from "./billing.js";
 import { runnerExecutionById } from "./catalog.js";
 import { classifyFailure } from "./failure-classifier.js";
+import { runnerE2EServerControlPaths } from "./harness-env.js";
 import { setupLiveFixtures, type LiveFixtureValues } from "./live-fixtures.js";
 import { evaluateMatcher, type MatcherResult } from "./matchers.js";
 import {
@@ -166,15 +167,11 @@ async function restartIsolatedPaperclipServer(input: {
   requestId: string;
   deadlineAt: number;
 }): Promise<void> {
-  const controlDirectory = path.join(privateRoot!, "control");
-  const requestPath = path.join(
+  const {
     controlDirectory,
-    "server-restart.request.json",
-  );
-  const acknowledgementPath = path.join(
-    controlDirectory,
-    "server-restart.ack.json",
-  );
+    restartRequestPath: requestPath,
+    restartAcknowledgementPath: acknowledgementPath,
+  } = runnerE2EServerControlPaths(temporaryRoot!);
   await mkdir(controlDirectory, { recursive: true });
   const temporaryRequestPath = `${requestPath}.${process.pid}.${input.requestId}.tmp`;
   await writeFile(
@@ -237,10 +234,11 @@ const executionIds = (() => {
 })();
 const executions = executionIds.map(runnerExecutionById);
 const attempt = Number(process.env.PAPERCLIP_RUNNER_E2E_ATTEMPT ?? "1");
+const temporaryRoot = process.env.PAPERCLIP_RUNNER_E2E_TEMP_ROOT;
 const privateRoot = process.env.PAPERCLIP_RUNNER_E2E_PRIVATE_DIR;
 const workspacePath = process.env.PAPERCLIP_RUNNER_E2E_WORKSPACE;
-if (!privateRoot || !workspacePath)
-  throw new Error("Runner E2E private/workspace paths are required");
+if (!temporaryRoot || !privateRoot || !workspacePath)
+  throw new Error("Runner E2E temporary/private/workspace paths are required");
 
 function record(value: unknown): Record<string, unknown> {
   return value && typeof value === "object" && !Array.isArray(value)
@@ -1424,8 +1422,7 @@ for (const execution of executions) {
           )?.[1] ??
           /Using fallback workspace "([^"]+)"/.exec(runLogContent)?.[1];
         const cwd = String(workspaceContext.cwd ?? fallbackWorkspace ?? "");
-        const isolatedRoot = process.env.PAPERCLIP_RUNNER_E2E_TEMP_ROOT ?? "";
-        if (!isolatedRoot || !cwd.startsWith(`${isolatedRoot}/`)) {
+        if (!cwd.startsWith(`${temporaryRoot}/`)) {
           invariantFailures.push(
             `local run workspace escaped the isolated root: ${cwd}`,
           );
diff --git a/tests/runner-e2e/server.ts b/tests/runner-e2e/server.ts
index bdf286b771..7de94a4874 100644
--- a/tests/runner-e2e/server.ts
+++ b/tests/runner-e2e/server.ts
@@ -5,6 +5,7 @@ import path from "node:path";
 import {
   assertIsolatedServerEnvironment,
   buildPaperclipServerEnvironment,
+  runnerE2EServerControlPaths,
 } from "./harness-env.js";
 
 function required(name: string) {
@@ -21,12 +22,11 @@ const port = required("PAPERCLIP_RUNNER_E2E_PORT");
 const repositoryRoot = path.resolve(import.meta.dirname, "../..");
 const tsxCli = path.join(repositoryRoot, "cli/node_modules/tsx/dist/cli.mjs");
 const paperclipCli = path.join(repositoryRoot, "cli/src/index.ts");
-const controlDirectory = path.join(temporaryRoot, "control");
-const restartRequestPath = path.join(
+const {
   controlDirectory,
-  "server-restart.request.json",
-);
-const restartAckPath = path.join(controlDirectory, "server-restart.ack.json");
+  restartRequestPath,
+  restartAcknowledgementPath: restartAckPath,
+} = runnerE2EServerControlPaths(temporaryRoot);
 const restartTimeoutMs = 180_000;
 const gracefulStopTimeoutMs = 30_000;
 const serverEnvironment = buildPaperclipServerEnvironment(process.env, {
diff --git a/tests/runner-e2e/support.test.ts b/tests/runner-e2e/support.test.ts
index 015a7c83c7..9bbcb7d643 100644
--- a/tests/runner-e2e/support.test.ts
+++ b/tests/runner-e2e/support.test.ts
@@ -11,6 +11,7 @@ import {
   assertIsolatedServerEnvironment,
   buildPaperclipServerEnvironment,
   resolvePaperclipRunnerBinaryForHarness,
+  runnerE2EServerControlPaths,
 } from "./harness-env.js";
 import { runnerExecutionById } from "./catalog.js";
 import { assertEmbeddedDatabaseIsolation } from "./instance-isolation.js";
@@ -354,6 +355,22 @@ describe("runner E2E failure policy", () => {
 });
 
 describe("runner E2E server isolation", () => {
+  it("shares restart control files beneath the isolated temporary root", () => {
+    expect(runnerE2EServerControlPaths("/tmp/cell")).toEqual({
+      controlDirectory: path.join("/tmp/cell", "control"),
+      restartRequestPath: path.join(
+        "/tmp/cell",
+        "control",
+        "server-restart.request.json",
+      ),
+      restartAcknowledgementPath: path.join(
+        "/tmp/cell",
+        "control",
+        "server-restart.ack.json",
+      ),
+    });
+  });
+
   it("strips database and paid-provider credentials from the Paperclip process", () => {
     const env = buildPaperclipServerEnvironment(
       {