diff --git a/server/src/__tests__/heartbeat-orphaned-active-lease-sweep.test.ts b/server/src/__tests__/heartbeat-orphaned-active-lease-sweep.test.ts
index 6ff69f16f0a..5d5b65277e5 100644
--- a/server/src/__tests__/heartbeat-orphaned-active-lease-sweep.test.ts
+++ b/server/src/__tests__/heartbeat-orphaned-active-lease-sweep.test.ts
@@ -5,6 +5,7 @@ import {
   costEvents,
   agents,
   companies,
+  computers,
   createDb,
   environmentLeases,
   environments,
@@ -65,6 +66,7 @@ describeEmbeddedPostgres("heartbeat sweepOrphanedActiveLeases", () => {
     await db.delete(environmentLeases);
     await db.delete(costEvents);
     await db.delete(heartbeatRuns);
+    await db.delete(computers);
     await db.delete(environments);
     await db.delete(agents);
     await db.delete(companies);
@@ -98,7 +100,7 @@ describeEmbeddedPostgres("heartbeat sweepOrphanedActiveLeases", () => {
     await db.insert(environments).values({
       id: environmentId,
       companyId,
-      name: "Fake Sandbox",
+      name: `Fake Sandbox ${environmentId}`,
       driver: "sandbox",
       status: "active",
       config: { provider: "fake", image: "ubuntu:24.04" },
@@ -160,6 +162,104 @@ describeEmbeddedPostgres("heartbeat sweepOrphanedActiveLeases", () => {
 
   const oldEnough = () => new Date(Date.now() - 60 * 60 * 1000);
 
+  async function seedWarmComputerLease() {
+    const scope = await seedCompanyAgentAndEnvironment();
+    await db.update(environments).set({ driver: "computer" }).where(eq(environments.id, scope.environmentId));
+    const runId = await insertHeartbeatRun({ ...scope, status: "succeeded" });
+    const computerId = randomUUID(), ownerId = randomUUID();
+    const owner = { id: ownerId, generation: 1, kind: "runner", phase: "warm", agentId: scope.agentId,
+      runId, admittedAt: oldEnough().toISOString(), deadline: new Date(Date.now() + 300_000).toISOString(),
+      absoluteDeadline: null, retirementDeadline: null, process: { bootId: randomUUID(), unitName: "test", nonce: "test", launchGeneration: 1 } };
+    await db.insert(computers).values({ id: computerId, companyId: scope.companyId, environmentId: scope.environmentId,
+      provider: "boat", providerId: randomUUID(), ledger: { status: "attached", owners: [owner], placements: {}, action: null } });
+    const leaseId = await insertActiveLease({ ...scope, heartbeatRunId: runId, updatedAt: oldEnough(),
+      provider: "boat", providerLeaseId: ownerId });
+    await db.update(environmentLeases).set({ metadata: { driver: "computer", agentId: scope.agentId,
+      computerOwner: { computerId, ownerId, generation: 1 } } }).where(eq(environmentLeases.id, leaseId));
+    return { ...scope, runId, computerId, ownerId, leaseId, owner };
+  }
+
+  it("preserves an authoritative warm computer while successful-run instruction cleanup delays lease retention", async () => {
+    const fixture = await seedWarmComputerLease();
+    const destroyRunLease = vi.fn();
+    const heartbeat = heartbeatService(db, { environmentRuntime: { destroyRunLease } as unknown as HeartbeatEnvironmentRuntime });
+    expect(await heartbeat.sweepOrphanedActiveLeases({ backoffMs: 300_000 })).toEqual({ recovered: 0 });
+    await heartbeat.sweepPendingCleanupLeases({ backoffMs: 0 });
+    expect(destroyRunLease).not.toHaveBeenCalled();
+    expect(await leaseRow(fixture.leaseId)).toMatchObject({ status: "active", failureReason: null });
+    // The normal heartbeat can finish its delayed cleanup and retain the lease.
+    await db.update(environmentLeases).set({ status: "retained" }).where(eq(environmentLeases.id, fixture.leaseId));
+    expect(await heartbeat.sweepOrphanedActiveLeases({ backoffMs: 0 })).toEqual({ recovered: 0 });
+  });
+
+  it.each(["expired", "retired", "foreign_run", "foreign_agent", "generation", "computer", "environment", "company", "provider_lease", "invalid_deadline", "missing_process", "invalid_process", "invalid_launch_generation"])(
+    "still recovers a computer lease without exact bounded warm authority: %s", async (kind) => {
+      const fixture = await seedWarmComputerLease();
+      const owner = { ...fixture.owner };
+      if (kind === "expired") owner.deadline = new Date(Date.now() - 60_000).toISOString();
+      if (kind === "retired") owner.phase = "retired";
+      if (kind === "foreign_run") owner.runId = randomUUID();
+      if (kind === "foreign_agent") owner.agentId = randomUUID();
+      if (kind === "generation") owner.generation += 1;
+      if (kind === "invalid_deadline") owner.deadline = "invalid";
+      if (kind === "missing_process") Object.assign(owner, { process: null });
+      if (kind === "invalid_process") owner.process = { ...owner.process, nonce: "" };
+      if (kind === "invalid_launch_generation") owner.process = { ...owner.process, launchGeneration: 0 };
+      await db.update(computers).set({ ledger: { status: "attached", owners: [owner] } }).where(eq(computers.id, fixture.computerId));
+      if (kind === "computer") await db.update(environmentLeases).set({ metadata: { driver: "computer", agentId: fixture.agentId,
+        computerOwner: { computerId: randomUUID(), ownerId: fixture.ownerId, generation: 1 } } }).where(eq(environmentLeases.id, fixture.leaseId));
+      if (kind === "provider_lease") await db.update(environmentLeases).set({ providerLeaseId: randomUUID() }).where(eq(environmentLeases.id, fixture.leaseId));
+      if (kind === "environment" || kind === "company") {
+        const foreign = await seedCompanyAgentAndEnvironment();
+        await db.update(computers).set(kind === "company" ? { companyId: foreign.companyId } : { environmentId: foreign.environmentId })
+          .where(eq(computers.id, fixture.computerId));
+      }
+      expect(await heartbeatService(db).sweepOrphanedActiveLeases({ backoffMs: 300_000 })).toEqual({ recovered: 1 });
+      expect(await leaseRow(fixture.leaseId)).toMatchObject({ status: "pending_cleanup", failureReason: "orphaned_active_lease_recovered" });
+    });
+
+  it("preserves a warm owner whose stopped process was relaunched within the same owner generation", async () => {
+    const fixture = await seedWarmComputerLease();
+    await db.update(computers).set({ ledger: { owners: [{ ...fixture.owner,
+      process: { ...fixture.owner.process, launchGeneration: 2 } }] } })
+      .where(eq(computers.id, fixture.computerId));
+    // Process launch generation is an independent counter, not an owner epoch.
+    expect(await heartbeatService(db).sweepOrphanedActiveLeases({ backoffMs: 300_000 })).toEqual({ recovered: 0 });
+  });
+
+  it("honors only the existing bounded warm shutdown grace", async () => {
+    const fixture = await seedWarmComputerLease();
+    await db.update(computers).set({ ledger: { owners: [{ ...fixture.owner, deadline: new Date(Date.now() - 10_000).toISOString() }] } })
+      .where(eq(computers.id, fixture.computerId));
+    expect(await heartbeatService(db).sweepOrphanedActiveLeases({ backoffMs: 300_000 })).toEqual({ recovered: 0 });
+  });
+
+  it("allows cleanup after the same warm reservation and shutdown grace expire", async () => {
+    const fixture = await seedWarmComputerLease();
+    const heartbeat = heartbeatService(db);
+    expect(await heartbeat.sweepOrphanedActiveLeases({ backoffMs: 0 })).toEqual({ recovered: 0 });
+    await db.update(computers).set({ ledger: { owners: [{ ...fixture.owner, deadline: new Date(Date.now() - 60_000).toISOString() }] } })
+      .where(eq(computers.id, fixture.computerId));
+    expect(await heartbeat.sweepOrphanedActiveLeases({ backoffMs: 0 })).toEqual({ recovered: 1 });
+  });
+
+  it("does not overwrite lease retention completed after the sweep selected its stale snapshot", async () => {
+    const fixture = await seedWarmComputerLease();
+    await db.update(computers).set({ ledger: { owners: [{ ...fixture.owner, phase: "retired" }] } })
+      .where(eq(computers.id, fixture.computerId));
+    const transaction = db.transaction.bind(db);
+    const intercept = vi.spyOn(db, "transaction").mockImplementationOnce(async (callback, config) => {
+      // Sweep has selected the old active row, but heartbeat finishes retention
+      // before the computer-row lock/cleanup claim. The status CAS must lose.
+      await db.update(environmentLeases).set({ status: "retained" }).where(eq(environmentLeases.id, fixture.leaseId));
+      return transaction(callback, config);
+    });
+    try {
+      expect(await heartbeatService(db).sweepOrphanedActiveLeases({ backoffMs: 0 })).toEqual({ recovered: 0 });
+      expect(await leaseRow(fixture.leaseId)).toMatchObject({ status: "retained", failureReason: null });
+    } finally { intercept.mockRestore(); }
+  });
+
   it.each([false, true])("releases an interrupted local run's bookkeeping lease (deleted environment: %s)", async (deletedEnvironment) => {
     const { companyId, agentId, environmentId } = await seedCompanyAgentAndEnvironment();
     await db.delete(environments).where(eq(environments.driver, "local"));
diff --git a/server/src/modules/computers/application/service.ts b/server/src/modules/computers/application/service.ts
index ba2ab0f2514..2aa863ea292 100644
--- a/server/src/modules/computers/application/service.ts
+++ b/server/src/modules/computers/application/service.ts
@@ -1,6 +1,7 @@
 import { randomUUID } from "node:crypto";
 import type { ComputerRepository, ComputerBackend } from "./ports.js";
 import {
+  COMPUTER_RETIREMENT_GRACE_MS as RETIREMENT_GRACE_MS,
   ComputerError,
   ComputerStopPendingError,
   assertAdmission,
@@ -25,8 +26,6 @@ class ComputerSessionBusyError extends ComputerError {
   }
 }
 
-// This is shutdown time only; admission and ordinary work stop at the warm deadline.
-const RETIREMENT_GRACE_MS = 30_000;
 const FILE_OPERATION_BUDGET_MS = 120_000;
 const FILE_OPERATION_SETTLEMENT_MS = 5000;
 type Scope = { companyId: string; environmentId: string };
diff --git a/server/src/modules/computers/domain/ledger.ts b/server/src/modules/computers/domain/ledger.ts
index eceef75e212..1d5f50bb86c 100644
--- a/server/src/modules/computers/domain/ledger.ts
+++ b/server/src/modules/computers/domain/ledger.ts
@@ -1,3 +1,6 @@
+/** Shutdown only; ordinary work remains fenced at the warm deadline. */
+export const COMPUTER_RETIREMENT_GRACE_MS = 30_000;
+
 export type OwnerRef = {
   computerId: string;
   ownerId: string;
diff --git a/server/src/services/heartbeat/recovery.ts b/server/src/services/heartbeat/recovery.ts
index a727f4ad5f4..95cd90b00ea 100644
--- a/server/src/services/heartbeat/recovery.ts
+++ b/server/src/services/heartbeat/recovery.ts
@@ -1,3 +1,4 @@
+import { COMPUTER_RETIREMENT_GRACE_MS } from "../../modules/computers/domain/ledger.js";
 import { preserveWorkspaceRestoreRecoveryMetadataSql } from "../legacy-workspace-restore-recovery.js";
 import { pendingNativeWorkspaceFinalizationCondition } from "../native-runtime/native-workspace-finalization-state.js";
 import { CHAT_COMPLETION_WAKE_REASON } from "../chat-completion-delivery.js";
@@ -30,6 +31,7 @@ import {
 import type { Db } from "@paperclipai/db";
 import {
   agents,
+  computers,
   environmentLeases,
   heartbeatRuns,
   issues,
@@ -1413,7 +1415,7 @@ export function createHeartbeatRecovery(db: Db, dependencies: HeartbeatRecoveryD
     const cutoff = new Date(Date.now() - opts.backoffMs);
 
     const rows = await db
-      .select({ lease: environmentLeases })
+      .select({ lease: environmentLeases, runAgentId: heartbeatRuns.agentId })
       .from(environmentLeases)
       .leftJoin(
         heartbeatRuns,
@@ -1435,7 +1437,7 @@ export function createHeartbeatRecovery(db: Db, dependencies: HeartbeatRecoveryD
       .limit(ORPHANED_ACTIVE_LEASE_SWEEP_PAGE_SIZE);
 
     let recovered = 0;
-    for (const { lease } of rows) {
+    for (const { lease, runAgentId } of rows) {
       // A provider resource id names one physical sandbox. A different lease
       // row can still hold that same resource in a live status, so this sweep
       // must not tear down a sandbox that a different lease still owns.
@@ -1470,19 +1472,59 @@ export function createHeartbeatRecovery(db: Db, dependencies: HeartbeatRecoveryD
       // pending_cleanup sweep can accept the same row in this same tick. A
       // fresh timestamp here would push the row inside that sweep's own
       // backoff window and delay the teardown by one full tick.
-      const flipped = await db
+      const sameLease = and(
+          eq(environmentLeases.id, lease.id),
+          eq(environmentLeases.status, "active"),
+          // A completed heartbeat may retain or replace its bookkeeping while
+          // this sweep waits for the computer serialization boundary.
+          eq(environmentLeases.companyId, lease.companyId),
+          lease.environmentId ? eq(environmentLeases.environmentId, lease.environmentId) : isNull(environmentLeases.environmentId),
+          lease.heartbeatRunId ? eq(environmentLeases.heartbeatRunId, lease.heartbeatRunId) : isNull(environmentLeases.heartbeatRunId),
+          lease.metadata === null ? isNull(environmentLeases.metadata) : eq(environmentLeases.metadata, lease.metadata),
+          lease.provider === null ? isNull(environmentLeases.provider) : eq(environmentLeases.provider, lease.provider),
+          lease.providerLeaseId === null ? isNull(environmentLeases.providerLeaseId) : eq(environmentLeases.providerLeaseId, lease.providerLeaseId),
+        );
+      const claim = (query: Pick<Db, "update">) => query
         .update(environmentLeases)
-        .set({
-          status: "pending_cleanup",
-          failureReason: "orphaned_active_lease_recovered",
-        })
-        .where(
-          and(
-            eq(environmentLeases.id, lease.id),
-            eq(environmentLeases.status, "active"),
-          ),
-        )
+        .set({ status: "pending_cleanup", failureReason: "orphaned_active_lease_recovered" })
+        .where(sameLease)
         .returning({ id: environmentLeases.id });
+      const binding = parseObject(lease.metadata?.computerOwner);
+      const flipped = lease.provider === "boat" && lease.metadata?.driver === "computer"
+        ? await db.transaction(async (tx) => {
+          const [computer] = typeof binding.computerId === "string" && lease.environmentId
+            ? await tx.select().from(computers).where(and(
+              eq(sql`${computers.id}::text`, binding.computerId),
+              eq(computers.companyId, lease.companyId),
+              eq(computers.environmentId, lease.environmentId),
+              eq(computers.provider, "boat"),
+            )).for("update") : [];
+          const owner = Array.isArray(computer?.ledger.owners)
+            ? computer.ledger.owners.map(parseObject).find((value) =>
+              value.id === binding.ownerId && value.id === lease.providerLeaseId &&
+              Number.isSafeInteger(binding.generation) && Number(binding.generation) > 0 &&
+              value.generation === binding.generation && value.kind === "runner" &&
+              value.runId === lease.heartbeatRunId && runAgentId !== null &&
+              value.agentId === runAgentId && value.agentId === lease.metadata?.agentId)
+            : undefined;
+          const process = parseObject(owner?.process);
+          const processBound = [process.bootId, process.unitName, process.nonce]
+            .every((value) => typeof value === "string" && value.length > 0) &&
+            Number.isSafeInteger(process.launchGeneration) && Number(process.launchGeneration) > 0;
+          const deadline = typeof owner?.deadline === "string" ? Date.parse(owner.deadline) : NaN;
+          if (owner?.phase === "warm" && processBound && Number.isFinite(deadline) &&
+              deadline + COMPUTER_RETIREMENT_GRACE_MS > Date.now()) {
+            // Native completion retains the durable owner before heartbeat's
+            // later instruction cleanup can mark the lease retained. A terminal
+            // run is not permission to kill this bounded warm process. Keep it
+            // out of the page until a later sweep; expired/mismatched owners
+            // still follow the ordinary orphan cleanup path.
+            await tx.update(environmentLeases).set({ updatedAt: new Date() })
+              .where(sameLease);
+            return [];
+          }
+          return claim(tx);
+        }) : await claim(db);
       if (flipped.length > 0) recovered += 1;
     }