diff --git a/chat/templates/_delete_impact_modal.html b/chat/templates/_delete_impact_modal.html
new file mode 100644
index 0000000..e5bab40
--- /dev/null
+++ b/chat/templates/_delete_impact_modal.html
@@ -0,0 +1,34 @@
+{# T110.3: delete-impact modal partial.
+
+Rendered from :func:`chat.web.drawer.delete_preview` via a Jinja2
+TemplateResponse so HTML autoescape covers user-controllable fields
+(item.kind, item.description, notes) automatically — the prior
+f-string assembly required explicit html.escape() calls (T110.2)
+which become redundant under autoescape.
+
+Inputs:
+  ``chat_id`` — the URL chat id (used to build the confirm form action).
+  ``impact``  — an :class:`~chat.services.delete_impact.ImpactReport`.
+#}
+<div class="delete-impact-modal">
+  <h3>Delete event {{ impact.target_event_id }}?</h3>
+  <p>This will discard {{ impact.cascading|length }} events. Cascade:</p>
+  <ul class="delete-impact-cascade">
+    {% if impact.cascading %}
+      {% for item in impact.cascading %}
+        <li><strong>{{ item.kind }}</strong>: {{ item.description }}</li>
+      {% endfor %}
+    {% else %}
+      <li>none</li>
+    {% endif %}
+  </ul>
+  <ul class="delete-impact-notes">
+    {% for note in impact.notes %}
+      <li>{{ note }}</li>
+    {% endfor %}
+  </ul>
+  <form hx-post="/chats/{{ chat_id }}/drawer/turn/delete/{{ impact.target_event_id }}"
+        hx-target="#drawer" hx-swap="innerHTML">
+    <button type="submit">Confirm delete</button>
+  </form>
+</div>
diff --git a/chat/templates/_drawer.html b/chat/templates/_drawer.html
index 8cfdd5f..6bbfeeb 100644
--- a/chat/templates/_drawer.html
+++ b/chat/templates/_drawer.html
@@ -547,6 +547,25 @@
         </ul>
       </details>
     {% endif %}
+    {# T110.4: bulk significance re-rate. Move every memory in this chat
+       at level_from to level_to with one manual_edit event per row, so
+       the audit trail stays per-memory. #}
+    <details class="bulk-significance">
+      <summary>Bulk re-rate significance</summary>
+      <form class="inline-edit"
+            hx-post="/chats/{{ chat.id }}/drawer/memory/significance/bulk"
+            hx-target="#drawer" hx-swap="innerHTML">
+        <label>
+          From:
+          <input type="number" name="level_from" min="0" max="3" value="0" required>
+        </label>
+        <label>
+          To:
+          <input type="number" name="level_to" min="0" max="3" value="1" required>
+        </label>
+        <button type="submit">Re-rate all</button>
+      </form>
+    </details>
   </section>
 
   <section class="drawer-section">
diff --git a/chat/web/drawer.py b/chat/web/drawer.py
index 5396ae8..5f94957 100644
--- a/chat/web/drawer.py
+++ b/chat/web/drawer.py
@@ -411,6 +411,64 @@ async def edit_memory_significance(
     return await drawer(chat_id, request, conn)
 
 
+@router.post(
+    "/chats/{chat_id}/drawer/memory/significance/bulk",
+    response_class=HTMLResponse,
+)
+async def bulk_re_rate_significance(
+    chat_id: str,
+    request: Request,
+    level_from: int = Form(...),
+    level_to: int = Form(...),
+    conn=Depends(get_conn),
+):
+    """T110.4: bulk re-rate every memory in this chat at ``level_from``
+    to ``level_to``.
+
+    Fans out into one ``manual_edit`` event per matching memory rather
+    than a single bulk event so the §6.4 audit trail stays per-row —
+    each affected memory carries its own ``prior_value -> new_value``
+    snapshot, so an inverse edit can restore an individual row without
+    needing to inspect a bulk payload's member list. The drawer's
+    significance-distribution panel surfaces the new buckets on the
+    refreshed partial.
+
+    Both levels are clamped to 0..3 (matching ``edit_memory_significance``)
+    and a no-op (``level_from == level_to``) is rejected with 400 so a
+    misclick can't pad the event log with empty edits.
+    """
+    chat = get_chat(conn, chat_id)
+    if chat is None:
+        raise HTTPException(status_code=404, detail=f"chat not found: {chat_id}")
+
+    lf = max(0, min(3, int(level_from)))
+    lt = max(0, min(3, int(level_to)))
+    if lf == lt:
+        raise HTTPException(
+            status_code=400,
+            detail=f"level_from and level_to must differ (both = {lf})",
+        )
+
+    rows = conn.execute(
+        "SELECT id FROM memories WHERE chat_id = ? AND significance = ? "
+        "ORDER BY id ASC",
+        (chat_id, lf),
+    ).fetchall()
+    for row in rows:
+        memory_id = int(row[0])
+        append_and_apply(
+            conn,
+            kind="manual_edit",
+            payload={
+                "target_kind": "memory_significance",
+                "target_id": memory_id,
+                "prior_value": lf,
+                "new_value": lt,
+            },
+        )
+    return await drawer(chat_id, request, conn)
+
+
 @router.post(
     "/chats/{chat_id}/drawer/memory/{memory_id}/pin",
     response_class=HTMLResponse,
@@ -1234,28 +1292,18 @@ async def delete_preview(
 
     report = compute_delete_impact(conn, target_event_id=int(event_id))
 
-    # Build the modal HTML directly — the impact report is small and
-    # reusing the drawer template would require a fragment include just
-    # for this surface. Mirrors the rewind-preview style in
-    # :func:`chat.web.turns.rewind_preview`.
-    items_html = "".join(
-        f"<li><strong>{item.kind}</strong>: {item.description}</li>"
-        for item in report.cascading
+    # T110.3: render via the ``_delete_impact_modal.html`` Jinja partial
+    # so HTML autoescape covers user-controllable fields (item.kind,
+    # item.description, notes) automatically. The prior implementation
+    # built the modal HTML via raw f-string concatenation and required
+    # explicit ``html.escape()`` calls (T110.2) on each interpolated
+    # field; under autoescape those calls become redundant. Mirrors the
+    # rewind-preview style in :func:`chat.web.turns.rewind_preview`.
+    return TEMPLATES.TemplateResponse(
+        request,
+        "_delete_impact_modal.html",
+        {"chat_id": chat_id, "impact": report},
     )
-    notes_html = "".join(f"<li>{note}</li>" for note in report.notes)
-    body = (
-        "<div class='delete-impact-modal'>"
-        f"<h3>Delete event {report.target_event_id}?</h3>"
-        f"<p>This will discard {len(report.cascading)} events. Cascade:</p>"
-        f"<ul class='delete-impact-cascade'>{items_html or '<li>none</li>'}</ul>"
-        f"<ul class='delete-impact-notes'>{notes_html}</ul>"
-        f"<form hx-post='/chats/{chat_id}/drawer/turn/delete/{report.target_event_id}' "
-        "hx-target='#drawer' hx-swap='innerHTML'>"
-        "<button type='submit'>Confirm delete</button>"
-        "</form>"
-        "</div>"
-    )
-    return HTMLResponse(body)
 
 
 @router.post(
@@ -1278,7 +1326,19 @@ async def delete_turn(
 
     A snapshot is taken before truncation (inside ``execute_rewind``)
     so the user can recover via the snapshot index.
+
+    T110.1 guards ``event_id <= 0``: a stale tab or hand-crafted request
+    posting ``event_id=0`` would otherwise compute ``after_event_id=-1``
+    and silently truncate the entire log. ``id`` is auto-assigned by
+    SQLite starting at 1 so any caller's "real" id is always >= 1; a
+    zero or negative value can only mean a client bug, surfaced as 400.
     """
+    if int(event_id) <= 0:
+        raise HTTPException(
+            status_code=400,
+            detail=f"event_id must be a positive integer, got {event_id}",
+        )
+
     chat = get_chat(conn, chat_id)
     if chat is None:
         raise HTTPException(status_code=404, detail=f"chat not found: {chat_id}")
diff --git a/tests/test_drawer_phase4.py b/tests/test_drawer_phase4.py
index f94f266..be4d854 100644
--- a/tests/test_drawer_phase4.py
+++ b/tests/test_drawer_phase4.py
@@ -458,6 +458,183 @@ def test_t98_4_delete_invokes_rewind_and_drops_cascade(client, tmp_path):
             assert row is None, f"event {ev_id} should have been deleted"
 
 
+def test_delete_impact_modal_uses_jinja_partial(client, tmp_path):
+    """T110.3: the modal HTML is rendered from a Jinja partial
+    (`_delete_impact_modal.html`) rather than f-string concatenation in
+    Python. Verify the partial-rendered shape: the wrapping
+    ``delete-impact-modal`` div, the cascade list, and the confirm form.
+
+    The partial inherits Jinja2 autoescape so HTML safety follows
+    automatically — the explicit ``html.escape()`` calls from T110.2
+    become redundant once this lands.
+    """
+    db = tmp_path / "test.db"
+    _seed_chat(db)
+    user_id, _bot_id = _seed_turns(db)
+
+    response = client.get(
+        f"/chats/chat_bot_a/drawer/turn/delete-preview/{user_id}"
+    )
+    assert response.status_code == 200
+    body = response.text
+
+    # Markup shape that the partial produces. Double-quoted attributes
+    # signal Jinja rendering (the prior f-string used single quotes).
+    assert '<div class="delete-impact-modal">' in body
+    assert '<ul class="delete-impact-cascade">' in body
+    # The confirm form still posts to the same delete route.
+    assert f"/chats/chat_bot_a/drawer/turn/delete/{user_id}" in body
+    assert "Confirm delete" in body
+
+
+def test_delete_impact_modal_escapes_user_controllable_strings(client, tmp_path):
+    """T110.2: defense-in-depth — fields embedded in the modal HTML come
+    from event payloads (turn prose, scene timestamps, etc.) which are
+    ultimately user-controllable. Wrap them with ``html.escape`` so a
+    payload like ``<script>alert(1)</script>`` renders as inert text and
+    doesn't leak through into the rendered modal as actual markup.
+    """
+    db = tmp_path / "test.db"
+    _seed_chat(db)
+
+    # Seed a user_turn whose prose contains an HTML-script payload. The
+    # modal renders ``description = "turn N (you: <prose excerpt>)"`` so
+    # the prose flows verbatim into the cascade list <li>.
+    with open_db(db) as conn:
+        evil_id = append_and_apply(
+            conn,
+            kind="user_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "prose": "<script>alert('xss')</script>",
+                "segments": [],
+            },
+        )
+
+    response = client.get(
+        f"/chats/chat_bot_a/drawer/turn/delete-preview/{evil_id}"
+    )
+    assert response.status_code == 200
+    body = response.text
+
+    # Raw <script> must NOT survive into the rendered HTML. The escaped
+    # form (&lt;script&gt;) is what we want to see instead.
+    assert "<script>alert" not in body
+    assert "&lt;script&gt;alert" in body
+
+
+def test_bulk_significance_re_rate_emits_manual_edit_per_memory(client, tmp_path):
+    """T110.4: bulk significance re-rate fans out into one
+    ``manual_edit`` event per matching memory — preserving the per-row
+    audit trail (and reversibility) instead of collapsing everything
+    into a single bulk event.
+
+    Seed five memories at significance 0, bulk re-rate 0 -> 2, and
+    verify five new ``memory_significance`` ``manual_edit`` rows landed
+    AND every memory now sits at significance 2.
+    """
+    db = tmp_path / "test.db"
+    _seed_chat(db)
+
+    # Five memories at significance 0.
+    with open_db(db) as conn:
+        for i in range(5):
+            append_and_apply(
+                conn,
+                kind="memory_written",
+                payload={
+                    "owner_id": "bot_a",
+                    "chat_id": "chat_bot_a",
+                    "pov_summary": f"low-sig memory {i}",
+                    "witness_you": 1,
+                    "witness_host": 1,
+                    "witness_guest": 0,
+                    "significance": 0,
+                },
+            )
+        # Plus one memory at significance 1 to verify the re-rate is
+        # scoped to ``level_from`` and doesn't sweep the whole chat.
+        append_and_apply(
+            conn,
+            kind="memory_written",
+            payload={
+                "owner_id": "bot_a",
+                "chat_id": "chat_bot_a",
+                "pov_summary": "already-rated memory",
+                "witness_you": 1,
+                "witness_host": 1,
+                "witness_guest": 0,
+                "significance": 1,
+            },
+        )
+        prior_manual_edits = conn.execute(
+            "SELECT COUNT(*) FROM event_log WHERE kind = 'manual_edit'"
+        ).fetchone()[0]
+
+    response = client.post(
+        "/chats/chat_bot_a/drawer/memory/significance/bulk",
+        data={"level_from": "0", "level_to": "2"},
+    )
+    assert response.status_code == 200
+
+    with open_db(db) as conn:
+        # Five new manual_edit rows, one per matching memory.
+        new_manual_edits = conn.execute(
+            "SELECT COUNT(*) FROM event_log WHERE kind = 'manual_edit'"
+        ).fetchone()[0]
+        assert new_manual_edits - prior_manual_edits == 5
+
+        # Every emitted edit is a memory_significance edit with prior=0
+        # and new=2.
+        import json as _json
+
+        rows = conn.execute(
+            "SELECT payload_json FROM event_log "
+            "WHERE kind = 'manual_edit' "
+            "ORDER BY id DESC LIMIT 5"
+        ).fetchall()
+        for r in rows:
+            payload = _json.loads(r[0])
+            assert payload["target_kind"] == "memory_significance"
+            assert payload["prior_value"] == 0
+            assert payload["new_value"] == 2
+
+        # Projection caught up — five memories at sig=2, the untouched
+        # one stays at sig=1, none remain at sig=0.
+        dist = dict(
+            conn.execute(
+                "SELECT significance, COUNT(*) FROM memories "
+                "WHERE chat_id = 'chat_bot_a' GROUP BY significance"
+            ).fetchall()
+        )
+        assert dist.get(0, 0) == 0
+        assert dist.get(1, 0) == 1
+        assert dist.get(2, 0) == 5
+
+
+def test_delete_turn_with_event_id_zero_returns_400(client, tmp_path):
+    """T110.1: ``event_id <= 0`` is an obvious client error and must NOT
+    silently rewind the entire log via ``after_event_id = -1``. The route
+    rejects it with 400 so the audit trail stays intact.
+    """
+    db = tmp_path / "test.db"
+    _seed_chat(db)
+    _seed_turns(db)
+
+    # Sanity: events present before the bad request.
+    with open_db(db) as conn:
+        before = conn.execute("SELECT COUNT(*) FROM event_log").fetchone()[0]
+        assert before > 0
+
+    response = client.post("/chats/chat_bot_a/drawer/turn/delete/0")
+    assert response.status_code == 400
+
+    # And the log was NOT truncated.
+    with open_db(db) as conn:
+        after = conn.execute("SELECT COUNT(*) FROM event_log").fetchone()[0]
+        assert after == before
+
+
 # ---------------------------------------------------------------------------
 # T98.5 — remaining v1 edits (chat narrative anchor + weather).
 # ---------------------------------------------------------------------------