diff --git a/server/src/__tests__/environment-runtime.test.ts b/server/src/__tests__/environment-runtime.test.ts
index 34c9b18aa09..4446aee2771 100644
--- a/server/src/__tests__/environment-runtime.test.ts
+++ b/server/src/__tests__/environment-runtime.test.ts
@@ -5534,6 +5534,29 @@ describeEmbeddedPostgres("environmentRuntimeService", () => {
     });
   });
 
+  it("destroys a retained restore-source sandbox (retain_on_failure) when its environment is deleted", async () => {
+    const { pluginId, runId, reusableLease } = await seedReusablePluginSandboxLease();
+    await db.update(heartbeatRuns).set({ status: "failed" }).where(eq(heartbeatRuns.id, runId));
+    // A failed run's sandbox kept, stopped, as a workspace-restore source.
+    await db.update(environmentLeases).set({ leasePolicy: "retain_on_failure", status: "released", cleanupStatus: "success",
+      releasedAt: new Date() }).where(eq(environmentLeases.id, reusableLease.id));
+    expect(await environmentService(db).getDeleteBlastRadius(reusableLease.environmentId!))
+      .toMatchObject({ reusableSandboxLeaseCount: 1, canDelete: false });
+    const workerManager = {
+      isRunning: vi.fn((id: string) => id === pluginId),
+      call: vi.fn(async (_pluginId: string, method: string) => {
+        if (method === "environmentDestroyLease") return { providerLeaseId: reusableLease.providerLeaseId, state: "destroyed" };
+        throw new Error(`Unexpected plugin method: ${method}`);
+      }),
+      getWorker: vi.fn(() => ({ supportedMethods: ["environmentResumeLease", "environmentReleaseLease", "environmentDestroyLease"] })),
+    } as unknown as PluginWorkerManager;
+    const result = await environmentRuntimeService(db, { pluginWorkerManager: workerManager })
+      .destroyReusableSandboxLeasesForEnvironment({ environmentId: reusableLease.environmentId!, failureReason: "environment_deleted" });
+    expect(result).toEqual({ destroyed: 1, failed: 0, skippedLiveRun: 0 });
+    await expect(environmentService(db).getLeaseById(reusableLease.id)).resolves.toMatchObject({
+      status: "expired", failureReason: "environment_deleted", cleanupStatus: "success" });
+  });
+
   it("destroys a failed reusable sandbox after successful release before deleting its environment", async () => {
     const { pluginId, companyId, runId, environment, reusableLease } = await seedReusablePluginSandboxLease();
     const workerManager = {
diff --git a/server/src/services/environment-runtime.ts b/server/src/services/environment-runtime.ts
index 2a9895ece08..02d108cf25a 100644
--- a/server/src/services/environment-runtime.ts
+++ b/server/src/services/environment-runtime.ts
@@ -4321,7 +4321,10 @@ export function environmentRuntimeService(
         .where(
           and(
             eq(environmentLeases.environmentId, input.environmentId),
-            eq(environmentLeases.leasePolicy, "reuse_by_environment"),
+            // Reusable sandboxes, and retain-on-failure sandboxes kept stopped as
+            // workspace-restore sources: both outlive their run, so a deleted
+            // environment must tear them down or they are orphaned.
+            inArray(environmentLeases.leasePolicy, ["reuse_by_environment", "retain_on_failure"]),
             // A failed run may have stopped its reusable sandbox without
             // destroying it; that provider handle still needs scoped teardown.
             inArray(environmentLeases.status, ["active", "released", "retained", "failed"]),
@@ -4360,7 +4363,8 @@ export function environmentRuntimeService(
           skippedLiveRun += 1;
           continue;
         }
-        const lease = await destroyClaimedSandboxLease({ environment, leaseRow, failureReason });
+        const lease = await destroyClaimedSandboxLease({ environment, leaseRow, failureReason, anyLeasePolicy: true,
+          scopeCondition: and(inArray(environmentLeases.leasePolicy, ["reuse_by_environment", "retain_on_failure"])) });
         if (!lease) {
           // Lost to a racing resume or a concurrent terminal transition — the
           // lease is no longer ours to destroy.
diff --git a/server/src/services/environments.ts b/server/src/services/environments.ts
index 72590988116..b7f57490c4e 100644
--- a/server/src/services/environments.ts
+++ b/server/src/services/environments.ts
@@ -1427,7 +1427,9 @@ export function environmentService(db: Db) {
           .where(
             and(
               eq(environmentLeases.environmentId, id),
-              eq(environmentLeases.leasePolicy, "reuse_by_environment"),
+              // A kept sandbox outlives its run: a reusable one for the next turn,
+              // and a retain-on-failure one as a workspace-restore source.
+              inArray(environmentLeases.leasePolicy, ["reuse_by_environment", "retain_on_failure"]),
               inArray(environmentLeases.status, ["active", "released", "retained", "failed"]),
             ),
           ),