diff --git a/workspace-server/internal/handlers/delegation_ledger_integration_test.go b/workspace-server/internal/handlers/delegation_ledger_integration_test.go
index 44b510a0..c493bcb8 100644
--- a/workspace-server/internal/handlers/delegation_ledger_integration_test.go
+++ b/workspace-server/internal/handlers/delegation_ledger_integration_test.go
@@ -201,6 +201,121 @@ func TestIntegration_FailedTransitionCapturesErrorDetail(t *testing.T) {
 	}
 }
 
+// TestIntegration_Sweeper_DeadlineExceededIsMarkedFailed — real-Postgres
+// gate for the RFC #2829 PR-3 stuck-task sweeper. Inserts a row with a
+// past deadline, runs Sweep, asserts the row is now `failed` with
+// `deadline exceeded by sweeper` in error_detail.
+//
+// sqlmock unit tests pinned the SQL fired but couldn't observe the
+// real ON CONFLICT / index-scan behavior on the partial inflight
+// index. Real Postgres catches:
+//   - deadline timestamp comparison is correct under tz boundaries
+//   - the partial index actually serves the WHERE clause
+//   - SetStatus's terminal forward-only protection holds across the
+//     sweep + concurrent-write race
+func TestIntegration_Sweeper_DeadlineExceededIsMarkedFailed(t *testing.T) {
+	conn := integrationDB(t)
+	t.Setenv("DELEGATION_LEDGER_WRITE", "1")
+
+	id := "integ-sweeper-deadline-1"
+	caller := "11111111-1111-1111-1111-111111111111"
+	callee := "22222222-2222-2222-2222-222222222222"
+
+	// Insert + transition to dispatched (otherwise queued→failed is
+	// allowed but doesn't exercise the in-flight scan accurately).
+	recordLedgerInsert(context.Background(), caller, callee, id, "task", "")
+	recordLedgerStatus(context.Background(), id, "dispatched", "", "")
+
+	// Force the deadline into the past — Insert defaults to now+6h, so
+	// we override.
+	if _, err := conn.ExecContext(context.Background(),
+		`UPDATE delegations SET deadline = now() - interval '1 minute', last_heartbeat = now() WHERE delegation_id = $1`, id,
+	); err != nil {
+		t.Fatalf("backdate deadline: %v", err)
+	}
+
+	res := NewDelegationSweeper(nil, nil).Sweep(context.Background())
+	if res.DeadlineFailures != 1 {
+		t.Errorf("expected 1 deadline failure, got %+v", res)
+	}
+	status, _, errDet := readLedgerRow(t, conn, id)
+	if status != "failed" {
+		t.Errorf("status: want failed, got %q", status)
+	}
+	if errDet != "deadline exceeded by sweeper" {
+		t.Errorf("error_detail: %q", errDet)
+	}
+}
+
+// TestIntegration_Sweeper_StaleHeartbeatIsMarkedStuck — heartbeat
+// staleness path. Insert + dispatch + backdate last_heartbeat past the
+// 10× threshold; Sweep should mark the row stuck.
+func TestIntegration_Sweeper_StaleHeartbeatIsMarkedStuck(t *testing.T) {
+	conn := integrationDB(t)
+	t.Setenv("DELEGATION_LEDGER_WRITE", "1")
+	// Tighten threshold so the test is deterministic + fast.
+	t.Setenv("DELEGATION_STUCK_THRESHOLD_S", "10")
+
+	id := "integ-sweeper-stuck-1"
+	caller := "11111111-1111-1111-1111-111111111111"
+	callee := "22222222-2222-2222-2222-222222222222"
+
+	recordLedgerInsert(context.Background(), caller, callee, id, "task", "")
+	recordLedgerStatus(context.Background(), id, "dispatched", "", "")
+	recordLedgerStatus(context.Background(), id, "in_progress", "", "")
+
+	// Backdate last_heartbeat past the 10s threshold; deadline still in
+	// future so deadline check shouldn't fire.
+	if _, err := conn.ExecContext(context.Background(),
+		`UPDATE delegations SET last_heartbeat = now() - interval '60 seconds' WHERE delegation_id = $1`, id,
+	); err != nil {
+		t.Fatalf("backdate heartbeat: %v", err)
+	}
+
+	res := NewDelegationSweeper(nil, nil).Sweep(context.Background())
+	if res.StuckMarked != 1 {
+		t.Errorf("expected 1 stuck mark, got %+v", res)
+	}
+	status, _, errDet := readLedgerRow(t, conn, id)
+	if status != "stuck" {
+		t.Errorf("status: want stuck, got %q", status)
+	}
+	if errDet == "" {
+		t.Errorf("error_detail should mention 'no heartbeat for Xs'; got empty")
+	}
+}
+
+// TestIntegration_Sweeper_HealthyRowsNotTouched — sanity: rows with a
+// fresh heartbeat AND a future deadline are left alone. Confirms the
+// partial inflight index scan + per-row branching don't false-positive
+// against well-behaved delegations.
+func TestIntegration_Sweeper_HealthyRowsNotTouched(t *testing.T) {
+	conn := integrationDB(t)
+	t.Setenv("DELEGATION_LEDGER_WRITE", "1")
+
+	id := "integ-sweeper-healthy-1"
+	caller := "11111111-1111-1111-1111-111111111111"
+	callee := "22222222-2222-2222-2222-222222222222"
+
+	recordLedgerInsert(context.Background(), caller, callee, id, "task", "")
+	recordLedgerStatus(context.Background(), id, "dispatched", "", "")
+	// Fresh heartbeat = now()
+	if _, err := conn.ExecContext(context.Background(),
+		`UPDATE delegations SET last_heartbeat = now() WHERE delegation_id = $1`, id,
+	); err != nil {
+		t.Fatalf("set heartbeat: %v", err)
+	}
+
+	res := NewDelegationSweeper(nil, nil).Sweep(context.Background())
+	if res.DeadlineFailures != 0 || res.StuckMarked != 0 {
+		t.Errorf("healthy row touched; result: %+v", res)
+	}
+	status, _, _ := readLedgerRow(t, conn, id)
+	if status != "dispatched" {
+		t.Errorf("status changed unexpectedly: %q", status)
+	}
+}
+
 // TestIntegration_FullLifecycle_QueuedToDispatchedToCompleted — pins the
 // happy-path lifecycle. INSERT lands the row at queued; SetStatus moves
 // it through dispatched and into completed with preview. After the