diff --git a/services/graph/app/fsma_recall/models.py b/services/graph/app/fsma_recall/models.py
index 0f64b141b..88e380279 100644
--- a/services/graph/app/fsma_recall/models.py
+++ b/services/graph/app/fsma_recall/models.py
@@ -120,7 +120,10 @@ def sla_status(self) -> SLAStatus:
         sla_limit = 24 * 3600  # 24 hours in seconds
 
         if self.status == RecallStatus.COMPLETED:
-            if self.duration_seconds and self.duration_seconds <= sla_limit:
+            duration = self.duration_seconds
+            # 0 seconds is a valid (instant) completion, so compare against
+            # None rather than relying on truthiness.
+            if duration is not None and duration <= sla_limit:
                 return SLAStatus.MET
             return SLAStatus.BREACHED
 
diff --git a/services/graph/tests/test_recall_sla_zero_duration.py b/services/graph/tests/test_recall_sla_zero_duration.py
new file mode 100644
index 000000000..a1961b10a
--- /dev/null
+++ b/services/graph/tests/test_recall_sla_zero_duration.py
@@ -0,0 +1,59 @@
+"""Data-free tests for zero-second completed drills under 21 CFR 1.1455(c)(1).
+
+21 CFR 1.1455(c)(1) requires records within 24 hours of an FDA request.
+A drill completed in 0 seconds is well inside that limit and must be MET.
+The 24h (MET) and 24h + 1s (BREACHED) boundaries must not move.
+Timestamps only; no records, CSV rows or EPCIS documents.
+"""
+
+from __future__ import annotations
+
+from datetime import datetime, timedelta, timezone
+
+from services.graph.app.fsma_recall.models import (
+    RecallDrill,
+    RecallSeverity,
+    RecallStatus,
+    RecallType,
+    SLAStatus,
+)
+
+START = datetime(2026, 1, 1, tzinfo=timezone.utc)
+
+
+def _completed(elapsed: timedelta) -> RecallDrill:
+    return RecallDrill(
+        drill_id="",
+        tenant_id="",
+        created_at=START,
+        drill_type=list(RecallType)[0],
+        severity=list(RecallSeverity)[0],
+        status=RecallStatus.COMPLETED,
+        started_at=START,
+        completed_at=START + elapsed,
+    )
+
+
+def test_zero_second_completion_is_met():
+    """21 CFR 1.1455(c)(1): 0 s elapsed is within 24h, so MET (not BREACHED)."""
+    drill = _completed(timedelta(0))
+    assert drill.duration_seconds == 0
+    assert drill.sla_status == SLAStatus.MET
+
+
+def test_exactly_24h_still_met():
+    """21 CFR 1.1455(c)(1): exactly 24h remains MET."""
+    assert _completed(timedelta(hours=24)).sla_status == SLAStatus.MET
+
+
+def test_24h_plus_one_second_still_breached():
+    """21 CFR 1.1455(c)(1): 24h + 1s remains BREACHED."""
+    assert _completed(timedelta(hours=24, seconds=1)).sla_status == SLAStatus.BREACHED
+
+
+def test_completed_without_completed_at_uses_elapsed():
+    """21 CFR 1.1455(c)(1): a completed drill missing completed_at falls back to elapsed time."""
+    drill = _completed(timedelta(0))
+    drill.completed_at = None
+    drill.started_at = datetime.now(timezone.utc) - timedelta(hours=25)
+    assert drill.sla_status == SLAStatus.BREACHED