diff --git a/packages/paperclip-runner/devtools/issue-thread/index.html b/packages/paperclip-runner/devtools/issue-thread/index.html
index 8c344f1635e..ff5100b74d6 100644
--- a/packages/paperclip-runner/devtools/issue-thread/index.html
+++ b/packages/paperclip-runner/devtools/issue-thread/index.html
@@ -4,7 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover" />
     <meta name="color-scheme" content="dark" />
-    <title>🫧 Mock Paperclip · Issue thread</title>
+    <title>🧯 Mock Paperclip · Issue thread</title>
   </head>
   <body>
     <div id="root"></div>
diff --git a/packages/paperclip-runner/scripts/phase7-issue-thread-server.mjs b/packages/paperclip-runner/scripts/phase7-issue-thread-server.mjs
index c48b1446dd3..ea581d9450a 100644
--- a/packages/paperclip-runner/scripts/phase7-issue-thread-server.mjs
+++ b/packages/paperclip-runner/scripts/phase7-issue-thread-server.mjs
@@ -1,5 +1,5 @@
 import { createHash, randomBytes, timingSafeEqual } from "node:crypto";
-import { mkdtemp, rm } from "node:fs/promises";
+import { mkdir, mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { resolve } from "node:path";
 
@@ -120,8 +120,12 @@ function scratchRoot() {
   return process.env.PAPERCLIP_RUN_SCRATCH_DIR ?? process.env.PAPERCLIP_SCRATCH_DIR ?? tmpdir();
 }
 
-async function createWorkingDirectory(prefix = "phase7-issue-thread-") {
-  return mkdtemp(resolve(scratchRoot(), prefix));
+async function createWorkingDirectory(root, prefix = "phase7-issue-thread-") {
+  // Managed previews can outlive the heartbeat that launched them. Paperclip
+  // removes that heartbeat's scratch directory when the run ends, so ensure
+  // the inherited parent still exists before every later session is minted.
+  await mkdir(root, { recursive: true });
+  return mkdtemp(resolve(root, prefix));
 }
 
 /** Mock-only fixture seed. Identifiers use the reserved `MCK-` prefix (§1.3). */
@@ -171,6 +175,7 @@ class RouteError extends Error {
 
 export function createPhase7IssueThreadMiddleware(options = {}) {
   const load = options.loadRunner ?? loadRunner;
+  const workingDirectoryRoot = options.scratchRoot ?? scratchRoot();
   let bootstrap = null;
   let bindHost = options.bindHost ?? "127.0.0.1";
   /**
@@ -195,7 +200,8 @@ export function createPhase7IssueThreadMiddleware(options = {}) {
     bootstrap = (async () => {
       const runner = await load();
       runner.assertPhase4bLoopbackBindHost(bindHost);
-      const workingDirectory = options.workingDirectory ?? (await createWorkingDirectory());
+      const workingDirectory =
+        options.workingDirectory ?? (await createWorkingDirectory(workingDirectoryRoot));
       const service = new runner.Phase7LiveSessionService({
         store: new runner.InMemoryPhase7LiveSessionStore(),
         ...(options.transportFactory === undefined
@@ -322,7 +328,10 @@ export function createPhase7IssueThreadMiddleware(options = {}) {
     for (const stale of open.slice(0, Math.max(0, open.length - (MAX_CLEAN_ROOM_SESSIONS - 1)))) {
       await retire(service, stale.session.id, "clean-room capacity");
     }
-    const workingDirectory = await createWorkingDirectory("phase7-clean-room-");
+    const workingDirectory = await createWorkingDirectory(
+      workingDirectoryRoot,
+      "phase7-clean-room-",
+    );
     const { identity, input } = runner.createPhase7CleanRoomSessionInput({ workingDirectory });
     let session;
     try {
diff --git a/packages/paperclip-runner/src/phase7/clean-room-server.test.ts b/packages/paperclip-runner/src/phase7/clean-room-server.test.ts
index e4301021554..a00980da0b7 100644
--- a/packages/paperclip-runner/src/phase7/clean-room-server.test.ts
+++ b/packages/paperclip-runner/src/phase7/clean-room-server.test.ts
@@ -1,6 +1,9 @@
 import { once } from "node:events";
+import { mkdtemp, rm } from "node:fs/promises";
 import { createServer, type Server } from "node:http";
 import type { AddressInfo } from "node:net";
+import { tmpdir } from "node:os";
+import { resolve } from "node:path";
 
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
 
@@ -468,13 +471,16 @@ let server: Server;
 let origin: string;
 let middleware: Awaited<ReturnType<typeof createMiddleware>>;
 let providerState: FakeProviderState;
+let scratchParent: string;
+let scratchRoot: string;
 const requestedUrls: string[] = [];
 
-async function createMiddleware(state: FakeProviderState) {
+async function createMiddleware(state: FakeProviderState, root: string) {
   const module = await import("../../scripts/phase7-issue-thread-server.mjs");
   return module.createPhase7IssueThreadMiddleware({
     bindHost: "127.0.0.1",
     loadRunner: async () => await import("../index.js"),
+    scratchRoot: root,
     transportFactory: fakeTransportFactory(state),
   });
 }
@@ -520,6 +526,10 @@ async function status(path: string, body?: unknown, browser: Jar = jar): Promise
 
 beforeEach(async () => {
   requestedUrls.length = 0;
+  scratchParent = await mkdtemp(resolve(tmpdir(), "phase7-clean-room-server-test-"));
+  // Start with a missing child so the normal open path also proves that the
+  // middleware creates its configured scratch root.
+  scratchRoot = resolve(scratchParent, "run-scratch");
   jar = new Jar();
   providerState = {
     threadId: "codex-thread-clean-room",
@@ -529,7 +539,7 @@ beforeEach(async () => {
     gate: new Gate(),
     diagnostic: null,
   };
-  middleware = await createMiddleware(providerState);
+  middleware = await createMiddleware(providerState, scratchRoot);
   server = createServer((request, response) => {
     void middleware(request, response, () => {
       response.statusCode = 404;
@@ -545,6 +555,7 @@ afterEach(async () => {
   await middleware.close();
   server.close();
   await once(server, "close");
+  await rm(scratchParent, { recursive: true, force: true });
 });
 
 describe("Phase 7 clean-room chat server", () => {
@@ -570,6 +581,21 @@ describe("Phase 7 clean-room chat server", () => {
     expect(opened.view.evidence.traceability).toEqual([]);
   });
 
+  it("recreates a removed run scratch root before starting a later chat", async () => {
+    const opened = await call("/api/phase7/ui/cleanroom/session");
+
+    // Managed services survive the heartbeat that launched them, while the
+    // harness removes this run-owned parent as soon as that heartbeat exits.
+    await rm(scratchRoot, { recursive: true, force: true });
+
+    const fresh = await call("/api/phase7/ui/cleanroom/session", {
+      sessionId: opened.sessionId,
+    });
+    expect(fresh.sessionId).not.toBe(opened.sessionId);
+    expect(fresh.identity.token).not.toBe(opened.identity.token);
+    expect(fresh.view.composer.state).toBe("ready");
+  });
+
   it("publishes the real-API block as an inspectable record", async () => {
     const opened = await call("/api/phase7/ui/cleanroom/session");
     const guard = opened.view.evidence.control_plane.find((record) =>