diff --git a/core/database.py b/core/database.py
index 5c33422..8a88b28 100644
--- a/core/database.py
+++ b/core/database.py
@@ -1485,6 +1485,10 @@ class CalendarEvent(TimestampMixin, Base):
     importance  = Column(String, default="normal")    # low | normal | high | critical
     event_type  = Column(String, nullable=True)        # work | personal | health | travel | meal | social | admin | other
     last_pinged = Column(DateTime, nullable=True)      # last time the assistant pinged about this event
+    # "caldav" = pulled from a CalDAV server (so the sync may prune it when it
+    # vanishes upstream). NULL/local = created locally (agent, email triage, or
+    # a UI event whose write-back failed) and must NOT be pruned by the sync.
+    origin      = Column(String, nullable=True, index=True)
 
     calendar = relationship("CalendarCal", back_populates="events")
 
@@ -1617,6 +1621,7 @@ def init_db():
     _migrate_seed_email_account()
     _migrate_add_calendar_metadata()
     _migrate_add_calendar_is_utc()
+    _migrate_add_calendar_origin()
     _migrate_encrypt_email_passwords()
     _migrate_encrypt_signatures()
     _migrate_encrypt_endpoint_keys()
@@ -1759,6 +1764,28 @@ def _migrate_add_calendar_is_utc():
         logging.getLogger(__name__).warning(f"is_utc migration failed: {e}")
 
 
+def _migrate_add_calendar_origin():
+    """Add `origin` to calendar_events so the CalDAV sync can tell server-pulled
+    rows (prunable when they vanish upstream) from locally-created ones (agent /
+    email triage / failed write-back), which must never be pruned. Idempotent."""
+    import sqlite3
+    db_path = DATABASE_URL.replace("sqlite:///", "")
+    if not os.path.exists(db_path):
+        return
+    try:
+        conn = sqlite3.connect(db_path)
+        cursor = conn.execute("PRAGMA table_info(calendar_events)")
+        columns = [row[1] for row in cursor.fetchall()]
+        if columns and "origin" not in columns:
+            conn.execute("ALTER TABLE calendar_events ADD COLUMN origin TEXT")
+            conn.execute("CREATE INDEX IF NOT EXISTS ix_calendar_events_origin ON calendar_events(origin)")
+            conn.commit()
+            logging.getLogger(__name__).info("Migrated: added 'origin' column to calendar_events")
+        conn.close()
+    except Exception as e:
+        logging.getLogger(__name__).warning(f"calendar_events.origin migration failed: {e}")
+
+
 def _migrate_add_calendar_metadata():
     """Add importance/event_type/last_pinged columns to calendar_events table."""
     import sqlite3
diff --git a/src/caldav_sync.py b/src/caldav_sync.py
index 10ca51c..663c0bd 100644
--- a/src/caldav_sync.py
+++ b/src/caldav_sync.py
@@ -265,6 +265,7 @@ def _sync_blocking(owner: str, url: str, username: str, password: str) -> dict:
                             existing.all_day = all_day
                             existing.is_utc = row_is_utc
                             existing.rrule = rrule
+                            existing.origin = "caldav"
                         else:
                             new_ev = CalendarEvent(
                                 uid=uid_val,
@@ -277,6 +278,7 @@ def _sync_blocking(owner: str, url: str, username: str, password: str) -> dict:
                                 all_day=all_day,
                                 is_utc=row_is_utc,
                                 rrule=rrule,
+                                origin="caldav",
                             )
                             db.add(new_ev)
                             pending[uid_val] = new_ev
@@ -286,8 +288,13 @@ def _sync_blocking(owner: str, url: str, username: str, password: str) -> dict:
                 # Prune locally-cached CalDAV events that vanished
                 # upstream (only within our sync window — events outside
                 # the window aren't in `objs`, so we'd false-delete them).
+                # Only rows we previously pulled from the server (origin=="caldav")
+                # are prunable; locally-created events (agent / email triage / a
+                # UI event whose write-back failed) carry origin NULL and must
+                # never be deleted just because the server didn't return them.
                 stale = db.query(CalendarEvent).filter(
                     CalendarEvent.calendar_id == local_cal.id,
+                    CalendarEvent.origin == "caldav",
                     CalendarEvent.dtstart >= start,
                     CalendarEvent.dtstart <= end,
                     ~CalendarEvent.uid.in_(seen_uids) if seen_uids else CalendarEvent.uid.isnot(None),
diff --git a/tests/test_caldav_sync_prune_local_events.py b/tests/test_caldav_sync_prune_local_events.py
new file mode 100644
index 0000000..e332655
--- /dev/null
+++ b/tests/test_caldav_sync_prune_local_events.py
@@ -0,0 +1,101 @@
+"""CalDAV sync must not prune locally-created events (#2704).
+
+The prune step in `_sync_blocking` deletes events in the synced calendar+window
+whose UID the server didn't just return, to propagate upstream deletions. But
+`CalendarEvent` had no way to distinguish a server-pulled row from a locally
+created one (agent / email triage / a UI event whose write-back failed), so it
+also deleted events that were never on the server — silent data loss.
+
+The fix adds an `origin` column and gates the prune on `origin == "caldav"`.
+This test replicates the exact prune query against an in-memory DB (the prune is
+pure DB logic; `_sync_blocking` itself needs a live CalDAV client) and asserts a
+local-origin event survives while a server-origin one with a vanished UID does
+not.
+"""
+import tempfile
+from datetime import datetime, timedelta
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import NullPool
+
+import core.database as cdb
+from core.database import CalendarEvent, CalendarCal
+
+_TMPDB = tempfile.NamedTemporaryFile(suffix=".db", delete=False)
+_ENGINE = create_engine(
+    f"sqlite:///{_TMPDB.name}",
+    connect_args={"check_same_thread": False},
+    poolclass=NullPool,
+)
+cdb.Base.metadata.create_all(_ENGINE)
+_TS = sessionmaker(bind=_ENGINE, autoflush=False, autocommit=False)
+
+_NOW = datetime(2026, 6, 4, 12, 0)
+_START = _NOW - timedelta(days=90)
+_END = _NOW + timedelta(days=365)
+
+
+def _prune(db, calendar_id, seen_uids):
+    """The exact prune filter from src/caldav_sync.py (post-fix)."""
+    stale = db.query(CalendarEvent).filter(
+        CalendarEvent.calendar_id == calendar_id,
+        CalendarEvent.origin == "caldav",
+        CalendarEvent.dtstart >= _START,
+        CalendarEvent.dtstart <= _END,
+        ~CalendarEvent.uid.in_(seen_uids) if seen_uids else CalendarEvent.uid.isnot(None),
+    ).all()
+    for ev in stale:
+        db.delete(ev)
+    db.commit()
+    return len(stale)
+
+
+def _seed():
+    db = _TS()
+    try:
+        db.query(CalendarEvent).delete()
+        db.query(CalendarCal).delete()
+        db.add(CalendarCal(id="cal1", owner="alice", name="Work", source="caldav"))
+        # A server-synced event whose UID is NO LONGER returned (deleted upstream).
+        db.add(CalendarEvent(
+            uid="server-gone@svc", calendar_id="cal1", summary="Old server event",
+            dtstart=_NOW + timedelta(days=1), dtend=_NOW + timedelta(days=1, hours=1),
+            origin="caldav",
+        ))
+        # A locally-created event (agent / triage / failed write-back) — origin NULL.
+        db.add(CalendarEvent(
+            uid="local-uuid", calendar_id="cal1", summary="Dentist",
+            dtstart=_NOW + timedelta(days=2), dtend=_NOW + timedelta(days=2, hours=1),
+            origin=None,
+        ))
+        db.commit()
+    finally:
+        db.close()
+
+
+def test_local_event_survives_prune():
+    _seed()
+    db = _TS()
+    try:
+        # Server returned nothing (both UIDs absent from seen_uids).
+        deleted = _prune(db, "cal1", seen_uids={"some-other-uid"})
+        # Only the server-origin, now-vanished event is pruned.
+        assert deleted == 1
+        assert db.query(CalendarEvent).filter_by(uid="local-uuid").first() is not None
+        assert db.query(CalendarEvent).filter_by(uid="server-gone@svc").first() is None
+    finally:
+        db.close()
+
+
+def test_synced_event_still_returned_is_kept():
+    _seed()
+    db = _TS()
+    try:
+        # The server still returns the synced event → it must be kept.
+        deleted = _prune(db, "cal1", seen_uids={"server-gone@svc"})
+        assert deleted == 0
+        assert db.query(CalendarEvent).filter_by(uid="server-gone@svc").first() is not None
+        assert db.query(CalendarEvent).filter_by(uid="local-uuid").first() is not None
+    finally:
+        db.close()