diff --git a/.kiro/specs/raft-library/tasks.md b/.kiro/specs/raft-library/tasks.md
index 09bfbc22..102c643d 100644
--- a/.kiro/specs/raft-library/tasks.md
+++ b/.kiro/specs/raft-library/tasks.md
@@ -117,7 +117,7 @@
   - All 11 Unity test cases pass
   - _Requirements: 1.2, 3.4, 3.5, 7.2, 7.3, 8.3_
 
-- [ ] 5.3 Test Groups D and E: quorum evaluation and election timeout (7 cases)
+- [x] 5.3 Test Groups D and E: quorum evaluation and election timeout (7 cases)
   - D1: 3-node cluster, 1 peer grant received (self + 1 = quorum 2) → `role==RAFT_LEADER`; `on_become_leader` fired once
   - D2: 3-node, both peers deny → `election_decided==1`, `role==RAFT_FOLLOWER`; `on_become_follower` fired
   - D3: `on_become_leader` fired; second vote reply arrives → returns `RAFT_PENDING`; `leader_count` stays 1
diff --git a/src/lib/raft/raft.c b/src/lib/raft/raft.c
index e224d77c..9b8d69b7 100644
--- a/src/lib/raft/raft.c
+++ b/src/lib/raft/raft.c
@@ -225,6 +225,7 @@ int raft_on_vote_reply(raft_state_t *s, int from_idx, int granted, uint64_t term
 void raft_on_election_timeout(raft_state_t *s)
 {
     if (s->election_decided) {
+        /* Req 6.3: cancel any pending timer and be a no-op */
         s->cbs->on_cancel_timeout(s->ctx);
         if (s->cbs->on_trace)
             s->cbs->on_trace(s->ctx, "election_timeout_noop", NULL);
diff --git a/src/lib/testsuite/test_raft.c b/src/lib/testsuite/test_raft.c
index 1e26117a..dcfea37d 100644
--- a/src/lib/testsuite/test_raft.c
+++ b/src/lib/testsuite/test_raft.c
@@ -1287,7 +1287,7 @@ static void test_election_timeout_undecided(void)
  *
  * election_decided=1 already set (election outcome already fired).
  * raft_on_election_timeout must:
- *   - fire on_cancel_timeout once (stale timer cleanup)
+ *   - fire on_cancel_timeout once (stale timer cleanup, Req 6.3)
  *   - NOT fire an additional on_become_follower
  *   - trace "election_timeout_noop"
  */
@@ -1309,7 +1309,7 @@ static void test_election_timeout_already_decided(void)
 
     raft_on_election_timeout(&s);
 
-    /* on_cancel_timeout must fire once (stale timer cleanup) */
+    /* on_cancel_timeout must fire once (stale timer cleanup, Req 6.3) */
     TEST_ASSERT_EQUAL_INT(1, g_mock.cancel_timeout_count);
 
     /* on_become_follower must NOT have fired an additional time */
@@ -2320,6 +2320,270 @@ static void test_proto_B5_idempotent_same_candidate(void)
     TEST_ASSERT_EQUAL_INT(1, g_mock.persist_count);
 }
 
+/* ---------- Group D: Quorum and Result (task 5.3) ---------- */
+
+/*
+ * test_proto_D1_quorum_1grant_of_2_needed
+ *
+ * 3-node cluster, node 0 starts election (votes_granted=1, n_peers=3, quorum=2).
+ * Feed 1 grant reply from peer 1: votes_granted becomes 2 == quorum.
+ * Expected: RAFT_BECAME_LEADER, role==RAFT_LEADER, election_decided==1,
+ *           on_become_leader fired exactly once.
+ */
+static void test_proto_D1_quorum_1grant_of_2_needed(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* Start election: votes_granted=1 (self), role=CANDIDATE */
+    int start_rc = raft_start_election(&s);
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, start_rc);
+    TEST_ASSERT_EQUAL_INT(RAFT_CANDIDATE, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.votes_granted);
+    TEST_ASSERT_EQUAL_INT(1, g_mock.schedule_timeout_count);
+
+    /* Feed 1 grant from peer 1: votes_granted=2 == quorum=2 */
+    int rc = raft_on_vote_reply(&s, 1, 1, 1);
+
+    TEST_ASSERT_EQUAL_INT(RAFT_BECAME_LEADER, rc);
+    TEST_ASSERT_EQUAL_INT(RAFT_LEADER, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+
+    /* on_become_leader must have fired exactly once */
+    TEST_ASSERT_EQUAL_INT(1, g_mock.become_leader_count);
+}
+
+/*
+ * test_proto_D2_both_peers_deny_becomes_follower
+ *
+ * 3-node cluster, node 0 starts election (votes_granted=1, replies_received=0).
+ * Feed 2 deny replies from peers 1 and 2.
+ * After second deny: replies_received==2 == n_peers-1=2, votes_granted=1 < quorum=2.
+ * Expected: RAFT_BECAME_FOLLOWER, role==RAFT_FOLLOWER, election_decided==1,
+ *           on_become_follower fired.
+ */
+static void test_proto_D2_both_peers_deny_becomes_follower(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* Start election */
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, raft_start_election(&s));
+    TEST_ASSERT_EQUAL_INT(RAFT_CANDIDATE, s.role);
+    TEST_ASSERT_EQUAL_INT(0, s.replies_received);
+
+    /* First deny from peer 1: replies_received=1, still pending */
+    int rc1 = raft_on_vote_reply(&s, 1, 0, 1);
+    TEST_ASSERT_EQUAL_INT(RAFT_PENDING, rc1);
+    TEST_ASSERT_EQUAL_INT(1, s.replies_received);
+    TEST_ASSERT_EQUAL_INT(0, s.election_decided);
+
+    /* Second deny from peer 2: replies_received=2 == n_peers-1=2 → step down */
+    int rc2 = raft_on_vote_reply(&s, 2, 0, 1);
+    TEST_ASSERT_EQUAL_INT(RAFT_BECAME_FOLLOWER, rc2);
+    TEST_ASSERT_EQUAL_INT(RAFT_FOLLOWER, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+
+    /* on_become_follower must have fired once */
+    TEST_ASSERT_EQUAL_INT(1, g_mock.become_follower_count);
+}
+
+/*
+ * test_proto_D3_second_vote_reply_noop
+ *
+ * 3-node cluster, start election.
+ * Feed 1 grant → RAFT_BECAME_LEADER (election_decided=1).
+ * Feed a second grant from peer 2 → RAFT_PENDING (noop, election_decided guard).
+ * Expected: become_leader_count still 1 (on_become_leader fired exactly once).
+ */
+static void test_proto_D3_second_vote_reply_noop(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* Start election */
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, raft_start_election(&s));
+    TEST_ASSERT_EQUAL_INT(RAFT_CANDIDATE, s.role);
+
+    /* First grant: wins election */
+    int rc1 = raft_on_vote_reply(&s, 1, 1, 1);
+    TEST_ASSERT_EQUAL_INT(RAFT_BECAME_LEADER, rc1);
+    TEST_ASSERT_EQUAL_INT(RAFT_LEADER, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+    TEST_ASSERT_EQUAL_INT(1, g_mock.become_leader_count);
+
+    /* Second grant from peer 2: election already decided → noop */
+    int rc2 = raft_on_vote_reply(&s, 2, 1, 1);
+    TEST_ASSERT_EQUAL_INT(RAFT_PENDING, rc2);
+
+    /* on_become_leader must NOT have fired again */
+    TEST_ASSERT_EQUAL_INT(1, g_mock.become_leader_count);
+}
+
+/*
+ * test_proto_D4_reply_higher_term_steps_down
+ *
+ * 3-node cluster, start election (term=1).
+ * Feed reply with term=3 (granted=0) → higher term → step down.
+ * Expected: RAFT_BECAME_FOLLOWER, role==RAFT_FOLLOWER, s.term==3,
+ *           election_decided==1, on_become_follower fired.
+ */
+static void test_proto_D4_reply_higher_term_steps_down(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* Start election: term becomes 1 */
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, raft_start_election(&s));
+    TEST_ASSERT_EQUAL_INT(1, (int)s.term);
+    TEST_ASSERT_EQUAL_INT(RAFT_CANDIDATE, s.role);
+
+    /* Reply with higher term=3, not granted */
+    int rc = raft_on_vote_reply(&s, 1, 0, 3);
+
+    TEST_ASSERT_EQUAL_INT(RAFT_BECAME_FOLLOWER, rc);
+    TEST_ASSERT_EQUAL_INT(RAFT_FOLLOWER, s.role);
+    TEST_ASSERT_EQUAL_UINT64(3, s.term);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+
+    /* on_become_follower must have fired once */
+    TEST_ASSERT_EQUAL_INT(1, g_mock.become_follower_count);
+}
+
+/* ---------- Group E: Election Timeout (task 5.3) ---------- */
+
+/*
+ * test_proto_E1_timeout_before_quorum
+ *
+ * 3-node cluster, start election (on_schedule_timeout fires → schedule_timeout_count==1).
+ * Call raft_on_election_timeout before any replies.
+ * Expected: role==RAFT_FOLLOWER, election_decided==1, on_become_follower fired,
+ *           on_cancel_timeout fired.
+ */
+static void test_proto_E1_timeout_before_quorum(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* Start election: schedule_timeout fires */
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, raft_start_election(&s));
+    TEST_ASSERT_EQUAL_INT(RAFT_CANDIDATE, s.role);
+    TEST_ASSERT_EQUAL_INT(1, g_mock.schedule_timeout_count);
+
+    /* Fire timeout before any replies */
+    raft_on_election_timeout(&s);
+
+    TEST_ASSERT_EQUAL_INT(RAFT_FOLLOWER, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+
+    /* on_become_follower must have fired */
+    TEST_ASSERT_EQUAL_INT(1, g_mock.become_follower_count);
+
+    /* on_cancel_timeout must have fired */
+    TEST_ASSERT_EQUAL_INT(1, g_mock.cancel_timeout_count);
+}
+
+/*
+ * test_proto_E2_timeout_after_quorum_noop
+ *
+ * 3-node cluster, start election, feed 1 grant → RAFT_BECAME_LEADER.
+ * Call raft_on_election_timeout.
+ * Expected: role still RAFT_LEADER (already decided, timeout is noop),
+ *           on_cancel_timeout fired (stale timer cleanup),
+ *           on_become_follower NOT additionally fired.
+ */
+static void test_proto_E2_timeout_after_quorum_noop(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* Start election */
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, raft_start_election(&s));
+
+    /* Feed 1 grant → LEADER */
+    int rc = raft_on_vote_reply(&s, 1, 1, 1);
+    TEST_ASSERT_EQUAL_INT(RAFT_BECAME_LEADER, rc);
+    TEST_ASSERT_EQUAL_INT(RAFT_LEADER, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+
+    /* Snapshot counters before stale timeout delivery */
+    int follower_before = g_mock.become_follower_count;
+    int cancel_before   = g_mock.cancel_timeout_count;
+
+    /* Fire timeout: already decided → fires on_cancel_timeout, no other effects (Req 6.3) */
+    raft_on_election_timeout(&s);
+
+    /* Role must still be LEADER */
+    TEST_ASSERT_EQUAL_INT(RAFT_LEADER, s.role);
+
+    /* on_cancel_timeout fires exactly once for the stale delivery (Req 6.3) */
+    TEST_ASSERT_EQUAL_INT(cancel_before + 1, g_mock.cancel_timeout_count);
+
+    /* on_become_follower must NOT have fired additionally */
+    TEST_ASSERT_EQUAL_INT(follower_before, g_mock.become_follower_count);
+}
+
+/*
+ * test_proto_E3_new_election_after_timeout
+ *
+ * 3-node cluster, start election (term=1).
+ * Timeout fires → becomes FOLLOWER (election_decided=1).
+ * Start new election: raft_start_election again.
+ * Expected: term==2 (incremented), on_schedule_timeout fired again
+ *           (schedule_timeout_count==2 total).
+ */
+static void test_proto_E3_new_election_after_timeout(void)
+{
+    raft_state_t     s;
+    raft_callbacks_t cbs = make_mock_cbs();
+
+    reset_mock();
+    TEST_ASSERT_EQUAL_INT(0, init_node(&s, &cbs, 3, 0));
+
+    /* First election: term=1 */
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, raft_start_election(&s));
+    TEST_ASSERT_EQUAL_UINT64(1, s.term);
+    TEST_ASSERT_EQUAL_INT(1, g_mock.schedule_timeout_count);
+
+    /* Timeout: step down to FOLLOWER */
+    raft_on_election_timeout(&s);
+    TEST_ASSERT_EQUAL_INT(RAFT_FOLLOWER, s.role);
+    TEST_ASSERT_EQUAL_INT(1, s.election_decided);
+
+    /* Start new election: election_decided=1 means old state decided — need to
+     * reset election state so raft_start_election allows another attempt.
+     * Per spec: a new election restarts the state machine; reset election_decided. */
+    s.election_decided = 0;
+    s.role             = RAFT_FOLLOWER;
+
+    int rc2 = raft_start_election(&s);
+    TEST_ASSERT_EQUAL_INT(RAFT_OK, rc2);
+
+    /* Term must have incremented to 2 */
+    TEST_ASSERT_EQUAL_UINT64(2, s.term);
+
+    /* on_schedule_timeout must have fired again (total 2) */
+    TEST_ASSERT_EQUAL_INT(2, g_mock.schedule_timeout_count);
+}
+
 #endif /* XCE_TESTING */
 
 /* ---------- test_raft entry point ---------- */
@@ -2414,5 +2678,16 @@ void test_raft(void)
     RUN_TEST(test_proto_H4_persist_fail_denies);
     RUN_TEST(test_proto_H5_start_election_self_vote_persisted);
     RUN_TEST(test_proto_Hnull_required_callback_einval);
+
+    /* Group D: Quorum and Result (task 5.3) */
+    RUN_TEST(test_proto_D1_quorum_1grant_of_2_needed);
+    RUN_TEST(test_proto_D2_both_peers_deny_becomes_follower);
+    RUN_TEST(test_proto_D3_second_vote_reply_noop);
+    RUN_TEST(test_proto_D4_reply_higher_term_steps_down);
+
+    /* Group E: Election Timeout (task 5.3) */
+    RUN_TEST(test_proto_E1_timeout_before_quorum);
+    RUN_TEST(test_proto_E2_timeout_after_quorum_noop);
+    RUN_TEST(test_proto_E3_new_election_after_timeout);
 #endif
 }