diff --git a/cases/base-share/a-duplicated-base-in-the-recent-list.case.ts b/cases/base-share/a-duplicated-base-in-the-recent-list.case.ts
index d6e129e..de61cc5 100644
--- a/cases/base-share/a-duplicated-base-in-the-recent-list.case.ts
+++ b/cases/base-share/a-duplicated-base-in-the-recent-list.case.ts
@@ -11,6 +11,10 @@ export default defineBugCase({
   title: "A freshly duplicated base is in the recent list",
   runner: "duplicate-base-recent-list",
   timeoutMs: 240_000,
+  // Recent bases are user-global state. Another concurrent case may visit its
+  // own base after this copy and correctly move ahead of it, invalidating this
+  // checkpoint without reproducing T2571.
+  serial: true,
   bug: {
     issue: "T2571",
     status: "fixed",
diff --git a/e2e-lab.e2e-spec.ts b/e2e-lab.e2e-spec.ts
index ac89d15..93b3047 100644
--- a/e2e-lab.e2e-spec.ts
+++ b/e2e-lab.e2e-spec.ts
@@ -78,18 +78,22 @@ describe("e2e-lab bug regression runner (e2e)", () => {
   });
 
   for (const bugCase of bugCases) {
-    it.concurrent(
-      `observes ${bugCase.id} [${bugCase.bug.issue}]`,
-      { timeout: bugCase.timeoutMs },
-      async () => {
-        logPhase("case:start", { caseId: bugCase.id });
-        const caseStarted = performance.now();
-        await runBugCase(bugCase, { app, appUrl, cookie });
-        logPhase("case:done", {
-          caseId: bugCase.id,
-          caseMs: Math.round(performance.now() - caseStarted),
-        });
-      },
-    );
+    const name = `observes ${bugCase.id} [${bugCase.bug.issue}]`;
+    const options = { timeout: bugCase.timeoutMs };
+    const run = async () => {
+      logPhase("case:start", { caseId: bugCase.id });
+      const caseStarted = performance.now();
+      await runBugCase(bugCase, { app, appUrl, cookie });
+      logPhase("case:done", {
+        caseId: bugCase.id,
+        caseMs: Math.round(performance.now() - caseStarted),
+      });
+    };
+
+    if (bugCase.serial) {
+      it(name, options, run);
+    } else {
+      it.concurrent(name, options, run);
+    }
   }
 });
diff --git a/framework/types.ts b/framework/types.ts
index 972755e..58aad40 100644
--- a/framework/types.ts
+++ b/framework/types.ts
@@ -169,6 +169,12 @@ interface BugCaseBase {
   id: string;
   title: string;
   bug: BugRef;
+  /**
+   * Run without overlapping any concurrent case. Use only when the checkpoint
+   * intentionally observes user-global state that per-case bases cannot
+   * isolate (for example, the current user's recent-base ordering).
+   */
+  serial?: boolean;
   timeoutMs: number;
 }