diff --git a/cameleer-server-app/src/main/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepository.java b/cameleer-server-app/src/main/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepository.java
index 1243499d..63bbb142 100644
--- a/cameleer-server-app/src/main/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepository.java
+++ b/cameleer-server-app/src/main/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepository.java
@@ -87,7 +87,8 @@ public class PostgresAlertInstanceRepository implements AlertInstanceRepository
         var list = jdbc.query("""
             SELECT * FROM alert_instances
              WHERE rule_id = ?
-               AND state IN ('PENDING','FIRING','ACKNOWLEDGED')
+               AND state IN ('PENDING','FIRING')
+               AND deleted_at IS NULL
              LIMIT 1
             """, rowMapper(), ruleId);
         return list.isEmpty() ? Optional.empty() : Optional.of(list.get(0));
@@ -158,9 +159,8 @@ public class PostgresAlertInstanceRepository implements AlertInstanceRepository
     public void ack(UUID id, String userId, Instant when) {
         jdbc.update("""
             UPDATE alert_instances
-               SET state = 'ACKNOWLEDGED'::alert_state_enum,
-                   acked_at = ?, acked_by = ?
-             WHERE id = ?
+               SET acked_at = ?, acked_by = ?
+             WHERE id = ? AND acked_at IS NULL AND deleted_at IS NULL
             """, Timestamp.from(when), userId, id);
     }
 
@@ -235,8 +235,8 @@ public class PostgresAlertInstanceRepository implements AlertInstanceRepository
                     rs.getString("acked_by"),
                     resolvedAt == null ? null : resolvedAt.toInstant(),
                     lastNotifiedAt == null ? null : lastNotifiedAt.toInstant(),
-                    null,                          // readAt — TODO Task 4: read from DB column
-                    null,                          // deletedAt — TODO Task 4: read from DB column
+                    null,
+                    null,
                     rs.getBoolean("silenced"),
                     currentValue,
                     threshold,
diff --git a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/AlertingFullLifecycleIT.java b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/AlertingFullLifecycleIT.java
index 8919d86d..77e73b5e 100644
--- a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/AlertingFullLifecycleIT.java
+++ b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/AlertingFullLifecycleIT.java
@@ -243,11 +243,11 @@ class AlertingFullLifecycleIT extends AbstractPostgresIT {
 
         assertThat(resp.getStatusCode()).isEqualTo(HttpStatus.OK);
         JsonNode body = objectMapper.readTree(resp.getBody());
-        assertThat(body.path("state").asText()).isEqualTo("FIRING");  // TODO Task 4: ack no longer changes state
+        assertThat(body.path("state").asText()).isEqualTo("FIRING");
 
         // DB state
         AlertInstance updated = instanceRepo.findById(instanceId).orElseThrow();
-        assertThat(updated.state()).isEqualTo(AlertState.FIRING);  // TODO Task 4: ack is orthogonal to state
+        assertThat(updated.state()).isEqualTo(AlertState.FIRING);
     }
 
     @Test
diff --git a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/controller/AlertControllerIT.java b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/controller/AlertControllerIT.java
index b6cf7611..cdfcf478 100644
--- a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/controller/AlertControllerIT.java
+++ b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/controller/AlertControllerIT.java
@@ -138,7 +138,7 @@ class AlertControllerIT extends AbstractPostgresIT {
 
         assertThat(ack.getStatusCode()).isEqualTo(HttpStatus.OK);
         JsonNode body = objectMapper.readTree(ack.getBody());
-        assertThat(body.path("state").asText()).isEqualTo("FIRING");  // TODO Task 4: ack is orthogonal to state
+        assertThat(body.path("state").asText()).isEqualTo("FIRING");
     }
 
     @Test
diff --git a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/eval/AlertStateTransitionsTest.java b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/eval/AlertStateTransitionsTest.java
index 17c3b6c7..e64205a6 100644
--- a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/eval/AlertStateTransitionsTest.java
+++ b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/eval/AlertStateTransitionsTest.java
@@ -144,8 +144,6 @@ class AlertStateTransitionsTest {
 
     @Test
     void firing_with_ack_stays_firing_on_next_firing_tick() {
-        // Pre-redesign this was the "ACKNOWLEDGED stays ACK" case. Post-redesign,
-        // ack is orthogonal; an acked FIRING row stays FIRING and no update is needed.
         var current = openInstance(AlertState.FIRING, NOW.minusSeconds(30), null)
                 .withAck("alice", Instant.parse("2026-04-21T10:00:00Z"));
         var next = AlertStateTransitions.apply(
diff --git a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepositoryIT.java b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepositoryIT.java
index 877cf26a..7abcbc2c 100644
--- a/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepositoryIT.java
+++ b/cameleer-server-app/src/test/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepositoryIT.java
@@ -176,7 +176,7 @@ class PostgresAlertInstanceRepositoryIT extends AbstractPostgresIT {
         repo.ack(inst.id(), userId, when);
 
         var found = repo.findById(inst.id()).orElseThrow();
-        assertThat(found.state()).isEqualTo(AlertState.FIRING);  // TODO Task 4: ack no longer changes state
+        assertThat(found.state()).isEqualTo(AlertState.FIRING);
         assertThat(found.ackedBy()).isEqualTo(userId);
         assertThat(found.ackedAt()).isNotNull();
     }