diff --git a/scripts/run-vitest-stable.mjs b/scripts/run-vitest-stable.mjs
index 3abc0ad62e3..f0404fae69b 100644
--- a/scripts/run-vitest-stable.mjs
+++ b/scripts/run-vitest-stable.mjs
@@ -320,6 +320,8 @@ function runVitest(args, label, testShard = null) {
   const env = {
     ...process.env,
     NODE_ENV: "test",
+    PAPERCLIP_TEST_HOST_HOME: process.env.PAPERCLIP_TEST_HOST_HOME
+      ?? (process.env.PAPERCLIP_HOME?.trim() || path.join(os.homedir(), ".paperclip")),
     PAPERCLIP_HOME: path.join(testRoot, "h"),
     // Config discovery otherwise prefers the checkout's .paperclip/config.json
     // over PAPERCLIP_HOME, importing preview scheduling policy into unit tests.
diff --git a/server/src/__tests__/setup-supertest.ts b/server/src/__tests__/setup-supertest.ts
index 0fa086fe29b..9c7db2179d4 100644
--- a/server/src/__tests__/setup-supertest.ts
+++ b/server/src/__tests__/setup-supertest.ts
@@ -21,6 +21,9 @@ type SupertestTestConstructor = {
   };
 };
 
+// Keep the original home available only for read-only host port-lease checks.
+process.env.PAPERCLIP_TEST_HOST_HOME ??= process.env.PAPERCLIP_HOME?.trim() || path.join(os.homedir(), ".paperclip");
+
 // Receipt-spool recovery must never scan a developer's instance during tests.
 const paperclipTestHome = fs.mkdtempSync(path.join(os.tmpdir(), "paperclip-vitest-home-"));
 process.env.PAPERCLIP_HOME = paperclipTestHome;
diff --git a/server/src/__tests__/workspace-runtime-exposure-reservation.test.ts b/server/src/__tests__/workspace-runtime-exposure-reservation.test.ts
index 08615ec352e..ff08db371ff 100644
--- a/server/src/__tests__/workspace-runtime-exposure-reservation.test.ts
+++ b/server/src/__tests__/workspace-runtime-exposure-reservation.test.ts
@@ -101,7 +101,9 @@ let NEXT_HMR_PORT: number;
  * must be read before that happens. Mirrors the default in
  * `resolvePaperclipHomeDir`.
  */
-const REAL_PAPERCLIP_HOME = process.env.PAPERCLIP_HOME?.trim() || path.join(os.homedir(), ".paperclip");
+const REAL_PAPERCLIP_HOME = process.env.PAPERCLIP_TEST_HOST_HOME?.trim()
+  || process.env.PAPERCLIP_HOME?.trim()
+  || path.join(os.homedir(), ".paperclip");
 
 /**
  * Every port a local Paperclip instance's on-disk service registry currently