diff --git a/rein_aharness/claim_loop.py b/rein_aharness/claim_loop.py
index eefeeed..0d04921 100644
--- a/rein_aharness/claim_loop.py
+++ b/rein_aharness/claim_loop.py
@@ -179,6 +179,23 @@ def process_one(
     finally:
         hb.stop()
 
+    if hb.monitor.lost:
+        loss = hb.monitor.evidence
+        assert loss is not None
+        return ProcessResult(
+            claimed=True,
+            run_id=run.id,
+            approach=approach,
+            ok=False,
+            reason=f"lease lost ({loss.error_type})",
+            detail={
+                "lease_loss": {
+                    "error_type": loss.error_type,
+                    "observed_at": loss.observed_at,
+                }
+            },
+        )
+
     payload = {
         "approach": ar.approach,
         "ok": ar.ok,
@@ -277,6 +294,23 @@ def _process_profiled_run(
     finally:
         hb.stop()
 
+    if hb.monitor.lost:
+        loss = hb.monitor.evidence
+        assert loss is not None
+        return ProcessResult(
+            claimed=True,
+            run_id=run.id,
+            approach=GLAS_APPROACH,
+            ok=False,
+            reason=f"lease lost ({loss.error_type})",
+            detail={
+                "lease_loss": {
+                    "error_type": loss.error_type,
+                    "observed_at": loss.observed_at,
+                }
+            },
+        )
+
     evidence = gateway_result["evidence"]
     ok = gateway_result["ok"]
     reason = str(evidence.get("error") or evidence.get("outcome") or "Glas execution failed")
diff --git a/tests/test_claim_loop.py b/tests/test_claim_loop.py
index 91fb880..0e1b689 100644
--- a/tests/test_claim_loop.py
+++ b/tests/test_claim_loop.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from unittest.mock import MagicMock, patch
+import time
 
 from rein_aharness.approaches import ApproachResult, APPROACH_FI_RESEARCH_BRIEF
 from rein_aharness.claim_loop import process_one, poll_peek
@@ -105,6 +106,35 @@ def test_process_one_failure_reopens() -> None:
     assert client.fail.call_args.kwargs["reopen"] is True
 
 
+def test_process_one_refuses_close_after_lease_loss() -> None:
+    client = MagicMock(spec=ActivityCoreOpsClient)
+    client.config = OpsRunConfig(worker_id="w", lease_seconds=90)
+    client.claim.return_value = [_claimed_run()]
+    client.heartbeat.side_effect = OpsRunError("lease rejected")
+    ar = ApproachResult(
+        ok=True,
+        approach=APPROACH_FI_RESEARCH_BRIEF,
+        result={"path": "briefs/x.md"},
+        reason="ok",
+    )
+
+    def slow_execute(*_args, **_kwargs):
+        time.sleep(0.05)
+        return ar
+
+    with (
+        patch("rein_aharness.claim_loop._heartbeat_interval", return_value=0.01),
+        patch("rein_aharness.claim_loop.execute_approach", side_effect=slow_execute),
+    ):
+        result = process_one(client)
+
+    assert result.ok is False
+    assert result.reason.startswith("lease lost")
+    assert "lease_loss" in result.detail
+    client.complete.assert_not_called()
+    client.fail.assert_not_called()
+
+
 def test_poll_peek() -> None:
     client = MagicMock(spec=ActivityCoreOpsClient)
     client.list_open.return_value = [_claimed_run()]
diff --git a/workplans/HARNESS-WP-0003-governed-runtime-integrity.md b/workplans/HARNESS-WP-0003-governed-runtime-integrity.md
index 389049f..fc9ed11 100644
--- a/workplans/HARNESS-WP-0003-governed-runtime-integrity.md
+++ b/workplans/HARNESS-WP-0003-governed-runtime-integrity.md
@@ -201,7 +201,10 @@ evidence instead of raw provider exception text. This establishes the signal
 needed by execution and acceptance boundaries without pretending that adapters
 can already cancel in-flight work. Remaining work is to classify Activity Core
 responses, connect cancellation at each adapter boundary, and refuse result
-acceptance/close after loss.
+acceptance/close after loss. The claim loop now implements that last refusal for
+normal and successful profiled executions: a lost lease returns bounded loss
+evidence and skips Activity Core completion/failure calls, leaving reconciliation
+to the owner of the expired lease.
 
 ## Verify accepted commits and reconcile metrics/reporting