diff --git a/surfsense_backend/alembic/versions/75_add_thread_id_to_chat_comments.py b/surfsense_backend/alembic/versions/75_add_thread_id_to_chat_comments.py
new file mode 100644
index 000000000..ceeb589f4
--- /dev/null
+++ b/surfsense_backend/alembic/versions/75_add_thread_id_to_chat_comments.py
@@ -0,0 +1,68 @@
+"""Add thread_id to chat_comments for denormalized Electric subscriptions
+
+This denormalization allows a single Electric SQL subscription per thread
+instead of one per message, significantly reducing connection overhead.
+
+Revision ID: 75
+Revises: 74
+"""
+
+from collections.abc import Sequence
+
+from alembic import op
+
+revision: str = "75"
+down_revision: str | None = "74"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Add thread_id column to chat_comments and backfill from messages."""
+    # Add the column (nullable initially for backfill)
+    op.execute(
+        """
+        ALTER TABLE chat_comments
+        ADD COLUMN IF NOT EXISTS thread_id INTEGER;
+        """
+    )
+
+    # Backfill thread_id from the related message
+    op.execute(
+        """
+        UPDATE chat_comments c
+        SET thread_id = m.thread_id
+        FROM new_chat_messages m
+        WHERE c.message_id = m.id
+        AND c.thread_id IS NULL;
+        """
+    )
+
+    # Make it NOT NULL after backfill
+    op.execute(
+        """
+        ALTER TABLE chat_comments
+        ALTER COLUMN thread_id SET NOT NULL;
+        """
+    )
+
+    # Add FK constraint
+    op.execute(
+        """
+        ALTER TABLE chat_comments
+        ADD CONSTRAINT fk_chat_comments_thread_id
+        FOREIGN KEY (thread_id) REFERENCES new_chat_threads(id) ON DELETE CASCADE;
+        """
+    )
+
+    # Add index for efficient Electric subscriptions by thread
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS idx_chat_comments_thread_id ON chat_comments(thread_id)"
+    )
+
+
+def downgrade() -> None:
+    """Remove thread_id column from chat_comments."""
+    op.execute("DROP INDEX IF EXISTS idx_chat_comments_thread_id")
+    op.execute("ALTER TABLE chat_comments DROP CONSTRAINT IF EXISTS fk_chat_comments_thread_id")
+    op.execute("ALTER TABLE chat_comments DROP COLUMN IF EXISTS thread_id")
diff --git a/surfsense_backend/app/db.py b/surfsense_backend/app/db.py
index 35b512c5e..181f78101 100644
--- a/surfsense_backend/app/db.py
+++ b/surfsense_backend/app/db.py
@@ -413,6 +413,13 @@ class ChatComment(BaseModel, TimestampMixin):
         nullable=False,
         index=True,
     )
+    # Denormalized thread_id for efficient Electric SQL subscriptions (one per thread)
+    thread_id = Column(
+        Integer,
+        ForeignKey("new_chat_threads.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
     parent_id = Column(
         Integer,
         ForeignKey("chat_comments.id", ondelete="CASCADE"),
@@ -436,6 +443,7 @@ class ChatComment(BaseModel, TimestampMixin):
 
     # Relationships
     message = relationship("NewChatMessage", back_populates="comments")
+    thread = relationship("NewChatThread")
     author = relationship("User")
     parent = relationship(
         "ChatComment", remote_side="ChatComment.id", backref="replies"
diff --git a/surfsense_backend/app/services/chat_comments_service.py b/surfsense_backend/app/services/chat_comments_service.py
index fa26bf6d5..7e07a56e6 100644
--- a/surfsense_backend/app/services/chat_comments_service.py
+++ b/surfsense_backend/app/services/chat_comments_service.py
@@ -281,8 +281,10 @@ async def create_comment(
             detail="You don't have permission to create comments in this search space",
         )
 
+    thread = message.thread
     comment = ChatComment(
         message_id=message_id,
+        thread_id=thread.id,  # Denormalized for efficient Electric subscriptions
         author_id=user.id,
         content=content,
     )
@@ -299,7 +301,6 @@ async def create_comment(
     user_names = await get_user_names_for_mentions(session, set(mentions_map.keys()))
 
     # Create notifications for mentioned users (excluding author)
-    thread = message.thread
     author_name = user.display_name or user.email
     content_preview = render_mentions(content, user_names)
     for mentioned_user_id, mention_id in mentions_map.items():
@@ -391,8 +392,10 @@ async def create_reply(
             detail="You don't have permission to create comments in this search space",
         )
 
+    thread = parent_comment.message.thread
     reply = ChatComment(
         message_id=parent_comment.message_id,
+        thread_id=thread.id,  # Denormalized for efficient Electric subscriptions
         parent_id=comment_id,
         author_id=user.id,
         content=content,
@@ -410,7 +413,6 @@ async def create_reply(
     user_names = await get_user_names_for_mentions(session, set(mentions_map.keys()))
 
     # Create notifications for mentioned users (excluding author)
-    thread = parent_comment.message.thread
     author_name = user.display_name or user.email
     content_preview = render_mentions(content, user_names)
     for mentioned_user_id, mention_id in mentions_map.items():