diff --git a/src/ian/services/reminder_runner.py b/src/ian/services/reminder_runner.py
index 15fe8e0..2bfd12d 100644
--- a/src/ian/services/reminder_runner.py
+++ b/src/ian/services/reminder_runner.py
@@ -89,17 +89,21 @@ def run_once(target_date: str | None = None, dry: bool = False):
     message = format_reminder_message(events)
     eprint(f"\n[Reminder] Message:\n{message}\n")
 
-    if dry:
-        eprint("[Reminder] DRY RUN — no messages sent.")
+    try:
         members = load_members()
         bound = get_valid_bound_members(members)
+    except Exception as e:
+        eprint(f"[Reminder] Failed to load member data: {e}")
+        send_log(f"```\n[REMINDER] FAILED to load member data: {e}\n```")
+        return
+
+    if dry:
+        eprint("[Reminder] DRY RUN — no messages sent.")
         eprint(f"[Reminder] Would notify {len(bound)} member(s):")
         for m in bound:
             eprint(f"  - {m['name']} (Discord)")
         return
 
-    members = load_members()
-    bound = get_valid_bound_members(members)
     eprint(f"[Reminder] Notifying {len(bound)} member(s)...")
 
     discord_ok, discord_fail = 0, 0
@@ -115,11 +119,15 @@ def run_once(target_date: str | None = None, dry: bool = False):
 
         if m["discord_id"]:
             eprint(f"  Sending Discord DM to {name}...")
-            if send_discord_dm(m["discord_id"], personal_message):
-                discord_ok += 1
-                eprint(f"  [Discord] {name} OK")
-            else:
+            try:
+                if send_discord_dm(m["discord_id"], personal_message):
+                    discord_ok += 1
+                    eprint(f"  [Discord] {name} OK")
+                else:
+                    discord_fail += 1
+            except Exception as e:
                 discord_fail += 1
+                eprint(f"  [Discord] {name} failed: {e}")
             time.sleep(0.5)
 
     event_titles = ", ".join(ev["title"] for ev in events)
diff --git a/tests/domain/test_reminders.py b/tests/domain/test_reminders.py
index 6b4b8fc..d4d528d 100644
--- a/tests/domain/test_reminders.py
+++ b/tests/domain/test_reminders.py
@@ -21,6 +21,7 @@
 from datetime import datetime, timedelta, timezone
 
 import pandas as pd
+import pytest
 
 from ian.domain.reminders import (
     clean_value,
@@ -170,6 +171,33 @@ def test_format_reminder_message_omits_empty_optional_event_fields():
     assert "講義:" not in message
 
 
-def test_seconds_until_next_run_returns_next_future_target():
-    now = datetime(2026, 3, 7, 20, 0, tzinfo=timezone(timedelta(hours=8)))
-    assert seconds_until_next_run(now, hour=19, minute=0) == 23 * 60 * 60
+def test_format_reminder_message_includes_slides_when_present():
+    message = format_reminder_message(
+        [_event(slides="https://slides.example/course")]
+    )
+
+    assert "講義: https://slides.example/course" in message
+
+
+@pytest.mark.parametrize(
+    ("hour", "minute", "second", "expected"),
+    [
+        pytest.param(18, 59, 30, 30, id="before-target"),
+        pytest.param(19, 0, 0, 24 * 60 * 60, id="exact-target"),
+        pytest.param(20, 0, 0, 23 * 60 * 60, id="after-target"),
+    ],
+)
+def test_seconds_until_next_run_handles_target_boundaries(
+    hour, minute, second, expected
+):
+    now = datetime(
+        2026,
+        3,
+        7,
+        hour,
+        minute,
+        second,
+        tzinfo=timezone(timedelta(hours=8)),
+    )
+
+    assert seconds_until_next_run(now, hour=19, minute=0) == expected
diff --git a/tests/services/test_reminder_runner.py b/tests/services/test_reminder_runner.py
new file mode 100644
index 0000000..65b06b2
--- /dev/null
+++ b/tests/services/test_reminder_runner.py
@@ -0,0 +1,287 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# Copyright (c) 2026 NTU AI Club
+#
+# This file is part of Ian, an open-source AI agent framework developed
+# and maintained by NTU AI Club.
+#
+# Ian is licensed under the GNU General Public License, either version 3
+# of the License, or (at your option) any later version.
+#
+# Ian is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ian. If not, see <https://www.gnu.org/licenses/>.
+#
+
+from datetime import datetime, timezone, timedelta
+
+import pandas as pd
+import pytest
+
+from ian.services import reminder_runner
+
+
+TARGET_DATE = "2026/07/12"
+EVENTS = [
+    {
+        "title": "Agent Evaluation",
+        "time": "19:00",
+    }
+]
+MESSAGE = "Hi! 明天 NTUAI 有 Agent Evaluation"
+
+
+def _stub_event_flow(monkeypatch, bound):
+    monkeypatch.setattr(reminder_runner, "fetch_course_data", pd.DataFrame)
+    monkeypatch.setattr(reminder_runner, "find_events_on_date", lambda *_: EVENTS)
+    monkeypatch.setattr(reminder_runner, "format_reminder_message", lambda *_: MESSAGE)
+    monkeypatch.setattr(reminder_runner, "load_members", list)
+    monkeypatch.setattr(reminder_runner, "get_valid_bound_members", lambda *_: bound)
+
+
+def test_run_once_logs_fetch_failure_without_loading_members(monkeypatch):
+    logs = []
+
+    def fail_fetch():
+        raise RuntimeError("sheet unavailable")
+
+    monkeypatch.setattr(reminder_runner, "fetch_course_data", fail_fetch)
+    monkeypatch.setattr(
+        reminder_runner,
+        "load_members",
+        lambda: (_ for _ in ()).throw(AssertionError("members should not be loaded")),
+    )
+    monkeypatch.setattr(reminder_runner, "send_discord_dm", lambda *_: False)
+    monkeypatch.setattr(reminder_runner, "send_log", logs.append)
+    monkeypatch.setattr(reminder_runner.time, "sleep", lambda *_: None)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+    assert logs == [
+        "```\n[REMINDER] FAILED to fetch course data: sheet unavailable\n```"
+    ]
+
+
+def test_run_once_with_no_events_does_not_load_members_or_send_messages(monkeypatch):
+    monkeypatch.setattr(reminder_runner, "fetch_course_data", pd.DataFrame)
+    monkeypatch.setattr(
+        reminder_runner,
+        "load_members",
+        lambda: (_ for _ in ()).throw(AssertionError("members should not be loaded")),
+    )
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_discord_dm",
+        lambda *_: (_ for _ in ()).throw(AssertionError("DM should not be sent")),
+    )
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_log",
+        lambda *_: (_ for _ in ()).throw(AssertionError("log should not be sent")),
+    )
+    monkeypatch.setattr(reminder_runner.time, "sleep", lambda *_: None)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+
+def test_run_once_dry_run_lists_recipients_without_sending_messages(
+    monkeypatch, capsys
+):
+    members = [{"name": "Alice"}, {"name": "Bob"}]
+    bound = [
+        {"name": "Alice", "email": "alice@example.test", "discord_id": "discord-1"},
+        {"name": "Bob", "email": "bob@example.test", "discord_id": "discord-2"},
+    ]
+
+    monkeypatch.setattr(reminder_runner, "fetch_course_data", pd.DataFrame)
+    monkeypatch.setattr(reminder_runner, "find_events_on_date", lambda *_: EVENTS)
+    monkeypatch.setattr(reminder_runner, "format_reminder_message", lambda *_: MESSAGE)
+    monkeypatch.setattr(reminder_runner, "load_members", lambda: members)
+    monkeypatch.setattr(reminder_runner, "get_valid_bound_members", lambda value: bound)
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_discord_dm",
+        lambda *_: (_ for _ in ()).throw(AssertionError("DM should not be sent")),
+    )
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_log",
+        lambda *_: (_ for _ in ()).throw(AssertionError("log should not be sent")),
+    )
+    monkeypatch.setattr(reminder_runner.time, "sleep", lambda *_: None)
+
+    reminder_runner.run_once(target_date=TARGET_DATE, dry=True)
+
+    captured = capsys.readouterr()
+    assert "Would notify 2 member(s)" in captured.err
+    assert "Alice (Discord)" in captured.err
+    assert "Bob (Discord)" in captured.err
+
+
+def test_run_once_sends_personalized_messages_and_reports_counts(monkeypatch):
+    bound = [
+        {
+            "name": "王 小明",
+            "email": "member+test@example.test",
+            "discord_id": "discord-success",
+        },
+        {
+            "name": "Failed Member",
+            "email": "failed@example.test",
+            "discord_id": "discord-failure",
+        },
+    ]
+    dm_calls = []
+    log_calls = []
+    sleep_calls = []
+
+    def send_dm(discord_id, message):
+        dm_calls.append((discord_id, message))
+        return discord_id == "discord-success"
+
+    _stub_event_flow(monkeypatch, bound)
+    monkeypatch.setattr(reminder_runner, "send_discord_dm", send_dm)
+    monkeypatch.setattr(reminder_runner, "send_log", log_calls.append)
+    monkeypatch.setattr(reminder_runner.time, "sleep", sleep_calls.append)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+    assert dm_calls == [
+        (
+            "discord-success",
+            f"{MESSAGE}\n\n簽到碼連結：https://watsonshih.github.io/QuickRecord/"
+            "user.html?name=%E7%8E%8B%20%E5%B0%8F%E6%98%8E&id=member%2Btest%40example.test",
+        ),
+        (
+            "discord-failure",
+            f"{MESSAGE}\n\n簽到碼連結：https://watsonshih.github.io/QuickRecord/"
+            "user.html?name=Failed%20Member&id=failed%40example.test",
+        ),
+    ]
+    assert sleep_calls == [0.5, 0.5]
+    assert len(log_calls) == 1
+    assert f"Events on {TARGET_DATE}: Agent Evaluation" in log_calls[0]
+    assert "Discord: 1 sent, 1 failed" in log_calls[0]
+    assert "Total members notified: 1" in log_calls[0]
+
+
+def test_run_once_logs_member_load_failure_without_sending_messages(monkeypatch):
+    logs = []
+
+    monkeypatch.setattr(reminder_runner, "fetch_course_data", pd.DataFrame)
+    monkeypatch.setattr(reminder_runner, "find_events_on_date", lambda *_: EVENTS)
+    monkeypatch.setattr(reminder_runner, "format_reminder_message", lambda *_: MESSAGE)
+    monkeypatch.setattr(
+        reminder_runner,
+        "load_members",
+        lambda: (_ for _ in ()).throw(ValueError("invalid member JSON")),
+    )
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_discord_dm",
+        lambda *_: (_ for _ in ()).throw(AssertionError("DM should not be sent")),
+    )
+    monkeypatch.setattr(reminder_runner, "send_log", logs.append)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+    assert logs == [
+        "```\n[REMINDER] FAILED to load member data: invalid member JSON\n```"
+    ]
+
+
+def test_run_once_continues_after_one_dm_raises(monkeypatch):
+    bound = [
+        {"name": "Alice", "email": "alice@example.test", "discord_id": "bad"},
+        {"name": "Bob", "email": "bob@example.test", "discord_id": "good"},
+    ]
+    attempted = []
+    logs = []
+
+    def send_dm(discord_id, _message):
+        attempted.append(discord_id)
+        if discord_id == "bad":
+            raise TimeoutError("Discord timeout")
+        return True
+
+    _stub_event_flow(monkeypatch, bound)
+    monkeypatch.setattr(reminder_runner, "send_discord_dm", send_dm)
+    monkeypatch.setattr(reminder_runner, "send_log", logs.append)
+    monkeypatch.setattr(reminder_runner.time, "sleep", lambda *_: None)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+    assert attempted == ["bad", "good"]
+    assert "Discord: 1 sent, 1 failed" in logs[0]
+
+
+def test_run_once_with_no_recipients_reports_zero_counts(monkeypatch):
+    logs = []
+
+    _stub_event_flow(monkeypatch, [])
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_discord_dm",
+        lambda *_: (_ for _ in ()).throw(AssertionError("DM should not be sent")),
+    )
+    monkeypatch.setattr(reminder_runner, "send_log", logs.append)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+    assert "Discord: 0 sent, 0 failed" in logs[0]
+    assert "Total members notified: 0" in logs[0]
+
+
+@pytest.mark.parametrize(
+    ("name", "email"),
+    [
+        pytest.param("Alice", "", id="missing-email"),
+        pytest.param("", "alice@example.test", id="missing-name"),
+        pytest.param("", "", id="missing-name-and-email"),
+    ],
+)
+def test_run_once_omits_checkin_link_without_complete_identity(
+    monkeypatch, name, email
+):
+    bound = [{"name": name, "email": email, "discord_id": "discord-1"}]
+    messages = []
+
+    _stub_event_flow(monkeypatch, bound)
+    monkeypatch.setattr(
+        reminder_runner,
+        "send_discord_dm",
+        lambda _discord_id, message: messages.append(message) or True,
+    )
+    monkeypatch.setattr(reminder_runner, "send_log", lambda *_: None)
+    monkeypatch.setattr(reminder_runner.time, "sleep", lambda *_: None)
+
+    reminder_runner.run_once(target_date=TARGET_DATE)
+
+    assert messages == [MESSAGE]
+
+
+def test_run_once_uses_taipei_tomorrow_when_target_date_is_omitted(monkeypatch):
+    checked_dates = []
+
+    class FixedDateTime(datetime):
+        @classmethod
+        def now(cls, tz=None):
+            return cls(2026, 12, 31, 23, 30, tzinfo=timezone(timedelta(hours=8)))
+
+    monkeypatch.setattr(reminder_runner, "datetime", FixedDateTime)
+    monkeypatch.setattr(reminder_runner, "fetch_course_data", pd.DataFrame)
+    monkeypatch.setattr(
+        reminder_runner,
+        "find_events_on_date",
+        lambda _df, target_date: checked_dates.append(target_date) or [],
+    )
+    monkeypatch.setattr(reminder_runner, "send_log", lambda *_: None)
+
+    reminder_runner.run_once()
+
+    assert checked_dates == ["2027/01/01"]