coder · mafredri · Apr 20, 2026 · Apr 17, 2026 · Apr 17, 2026 · Apr 17, 2026
diff --git a/coderd/database/db2sdk/db2sdk.go b/coderd/database/db2sdk/db2sdk.go
@@ -1609,6 +1609,11 @@ func Chat(c database.Chat, diffStatus *database.ChatDiffStatus, files []database
 		parentChatID := c.ParentChatID.UUID
 		chat.ParentChatID = &parentChatID
 	}
+	// Always initialize Children to an empty slice so the JSON
+	// field serializes as [] rather than null. Root chats may
+	// later have children populated; child chats remain empty
+	// because nesting depth is capped at 1.
+	chat.Children = []codersdk.Chat{}
 	switch {
 	case c.RootChatID.Valid:
 		rootChatID := c.RootChatID.UUID
@@ -1756,19 +1761,21 @@ func ChatDebugStep(s database.ChatDebugStep) codersdk.ChatDebugStep {
 	}
 }
 
-// ChatRows converts a slice of database.GetChatsRow (which embeds
-// Chat plus HasUnread) to codersdk.Chat, looking up diff statuses
-// from the provided map. When diffStatusesByChatID is non-nil,
-// chats without an entry receive an empty DiffStatus.
-func ChatRows(rows []database.GetChatsRow, diffStatusesByChatID map[uuid.UUID]database.ChatDiffStatus) []codersdk.Chat {
-	result := make([]codersdk.Chat, len(rows))
-	for i, row := range rows {
-		diffStatus, ok := diffStatusesByChatID[row.Chat.ID]
+// ChildChatRows converts child chat rows to codersdk.Chat values,
+// resolving diff statuses from the shared map. When diffStatuses
+// is non-nil, children without an entry receive an empty DiffStatus.
+func ChildChatRows(
+	children []database.GetChildChatsByParentIDsRow,
+	diffStatuses map[uuid.UUID]database.ChatDiffStatus,
+) []codersdk.Chat {
+	result := make([]codersdk.Chat, len(children))
+	for i, row := range children {
+		diffStatus, ok := diffStatuses[row.Chat.ID]
 		if ok {
 			result[i] = Chat(row.Chat, &diffStatus, nil)
 		} else {
 			result[i] = Chat(row.Chat, nil, nil)
-			if diffStatusesByChatID != nil {
+			if diffStatuses != nil {
 				emptyDiffStatus := ChatDiffStatus(row.Chat.ID, nil)
 				result[i].DiffStatus = &emptyDiffStatus
 			}
@@ -1778,6 +1785,43 @@ func ChatRows(rows []database.GetChatsRow, diffStatusesByChatID map[uuid.UUID]da
 	return result
 }
 
+// ChatRowsWithChildren converts root chat rows and their child rows
+// into codersdk.Chat values with children embedded under each parent.
+// Both root and child diff statuses are resolved from the shared map.
+func ChatRowsWithChildren(
+	roots []database.GetChatsRow,
+	children []database.GetChildChatsByParentIDsRow,
+	diffStatuses map[uuid.UUID]database.ChatDiffStatus,
+) []codersdk.Chat {
+	// Group children by parent ID.
+	childrenByParent := make(map[uuid.UUID][]database.GetChildChatsByParentIDsRow, len(children))
+	for _, row := range children {
+		parentID := row.Chat.ParentChatID.UUID
+		childrenByParent[parentID] = append(childrenByParent[parentID], row)
+	}
+
+	result := make([]codersdk.Chat, len(roots))
+	for i, row := range roots {
+		diffStatus, ok := diffStatuses[row.Chat.ID]
+		if ok {
+			result[i] = Chat(row.Chat, &diffStatus, nil)
+		} else {
+			result[i] = Chat(row.Chat, nil, nil)
+			if diffStatuses != nil {
+				emptyDiffStatus := ChatDiffStatus(row.Chat.ID, nil)
+				result[i].DiffStatus = &emptyDiffStatus
+			}
+		}
+		result[i].HasUnread = row.HasUnread
+
+		// Embed child chats.
+		if childRows, ok := childrenByParent[row.Chat.ID]; ok {
+			result[i].Children = ChildChatRows(childRows, diffStatuses)
+		}
+	}
+	return result
+}
+
 // ChatDiffStatus converts a database.ChatDiffStatus to a
 // codersdk.ChatDiffStatus. When status is nil an empty value
 // containing only the chatID is returned.

diff --git a/coderd/database/db2sdk/db2sdk_test.go b/coderd/database/db2sdk/db2sdk_test.go
@@ -856,7 +856,7 @@ func TestChat_AllFieldsPopulated(t *testing.T) {
 
 	v := reflect.ValueOf(got)
 	typ := v.Type()
-	// HasUnread is populated by ChatRows (which joins the
+	// HasUnread is populated by ChatRowsWithChildren (which joins the
 	// read-cursor query), not by Chat. Warnings is a transient
 	// field populated by handlers, not the converter. Both are
 	// expected to remain zero here.

diff --git a/coderd/database/dbauthz/dbauthz.go b/coderd/database/dbauthz/dbauthz.go
@@ -2944,6 +2944,14 @@ func (q *querier) GetChatsUpdatedAfter(ctx context.Context, updatedAfter time.Ti
 	return q.db.GetChatsUpdatedAfter(ctx, updatedAfter)
 }
 
+func (q *querier) GetChildChatsByParentIDs(ctx context.Context, arg database.GetChildChatsByParentIDsParams) ([]database.GetChildChatsByParentIDsRow, error) {
+	// Each child is independently authorized via post-filter.
+	// The handler calls this after GetChats already authorized
+	// the parent chats, but we still verify read access on
+	// every child row for defense in depth.
+	return fetchWithPostFilter(q.auth, policy.ActionRead, q.db.GetChildChatsByParentIDs)(ctx, arg)
+}
+
 func (q *querier) GetConnectionLogsOffset(ctx context.Context, arg database.GetConnectionLogsOffsetParams) ([]database.GetConnectionLogsOffsetRow, error) {
 	// Just like with the audit logs query, shortcut if the user is an owner.
 	err := q.authorizeContext(ctx, policy.ActionRead, rbac.ResourceConnectionLog)

diff --git a/coderd/database/dbauthz/dbauthz_test.go b/coderd/database/dbauthz/dbauthz_test.go
@@ -820,6 +820,27 @@ func (s *MethodTestSuite) TestChats() {
 		// No asserts here because SQLFilter.
 		check.Args(params).Asserts()
 	}))
+	s.Run("GetChildChatsByParentIDs", s.Mocked(func(dbm *dbmock.MockStore, faker *gofakeit.Faker, check *expects) {
+		parentA := testutil.Fake(s.T(), faker, database.Chat{})
+		parentB := testutil.Fake(s.T(), faker, database.Chat{})
+		childA := testutil.Fake(s.T(), faker, database.Chat{
+			ParentChatID: uuid.NullUUID{UUID: parentA.ID, Valid: true},
+		})
+		childB := testutil.Fake(s.T(), faker, database.Chat{
+			ParentChatID: uuid.NullUUID{UUID: parentB.ID, Valid: true},
+		})
+		parentIDs := []uuid.UUID{parentA.ID, parentB.ID}
+		params := database.GetChildChatsByParentIDsParams{
+			ParentIds: parentIDs,
+			Archived:  sql.NullBool{Bool: false, Valid: true},
+		}
+		rows := []database.GetChildChatsByParentIDsRow{
+			{Chat: childA},
+			{Chat: childB},
+		}
+		dbm.EXPECT().GetChildChatsByParentIDs(gomock.Any(), params).Return(rows, nil).AnyTimes()
+		check.Args(params).Asserts(childA, policy.ActionRead, childB, policy.ActionRead).Returns(rows)
+	}))
 	s.Run("GetAuthorizedChats", s.Mocked(func(dbm *dbmock.MockStore, _ *gofakeit.Faker, check *expects) {
 		params := database.GetChatsParams{}
 		dbm.EXPECT().GetAuthorizedChats(gomock.Any(), params, gomock.Any()).Return([]database.GetChatsRow{}, nil).AnyTimes()

diff --git a/coderd/database/dbmetrics/querymetrics.go b/coderd/database/dbmetrics/querymetrics.go
diff --git a/coderd/database/dbmock/dbmock.go b/coderd/database/dbmock/dbmock.go
diff --git a/coderd/database/modelmethods.go b/coderd/database/modelmethods.go
@@ -182,6 +182,10 @@ func (r GetChatsRow) RBACObject() rbac.Object {
 	return r.Chat.RBACObject()
 }
 
+func (r GetChildChatsByParentIDsRow) RBACObject() rbac.Object {
+	return r.Chat.RBACObject()
+}
+
 func (c ChatFile) RBACObject() rbac.Object {
 	return rbac.ResourceChat.WithID(c.ID).WithOwner(c.OwnerID.String()).InOrg(c.OrganizationID)
 }

diff --git a/coderd/database/querier.go b/coderd/database/querier.go
diff --git a/coderd/database/queries.sql.go b/coderd/database/queries.sql.go
diff --git a/coderd/database/queries/chats.sql b/coderd/database/queries/chats.sql
@@ -373,6 +373,11 @@ WHERE
         WHEN sqlc.narg('label_filter')::jsonb IS NOT NULL THEN chats.labels @> sqlc.narg('label_filter')::jsonb
         ELSE true
     END
+    -- Paginate over root chats only. Children are fetched
+    -- separately via GetChildChatsByParentIDs and embedded under
+    -- each parent. Other callers that need the full set should
+    -- use a narrower query (e.g. GetChatsByWorkspaceIDs).
+    AND chats.parent_chat_id IS NULL
     -- Authorize Filter clause will be injected below in GetAuthorizedChats
     -- @authorize_filter
 ORDER BY
@@ -390,6 +395,45 @@ LIMIT
     -- Default to 50 to prevent accidental excessively large queries.
     COALESCE(NULLIF(@limit_opt :: int, 0), 50);
 
+-- name: GetChildChatsByParentIDs :many
+-- Fetches child chats for the given parent IDs. Used by the list
+-- handler and singular getChat to embed children under each root
+-- chat response.
+--
+-- The archived narg is three-state: NULL returns every child,
+-- true returns archived children only, false returns active
+-- children only. Callers pass the archive state that matches the
+-- parent list they are rendering, so sidebar views never surface
+-- children whose archive state differs from the parent.
+--
+-- The archive invariant (parent archived implies child archived)
+-- is enforced at write time, not here: ArchiveChatByID cascades
+-- through root_chat_id, patchChat allows individual child
+-- archive, and chatd.UnarchiveChildChatAtomic rejects unarchive
+-- of a child while the parent is archived. A stale read during a
+-- concurrent cascade can momentarily return an archive-state
+-- mismatch; the caller's next refetch converges.
+SELECT
+    sqlc.embed(chats),
+    EXISTS (
+        SELECT 1 FROM chat_messages cm
+        WHERE cm.chat_id = chats.id
+            AND cm.role = 'assistant'
+            AND cm.deleted = false
+            AND cm.id > COALESCE(chats.last_read_message_id, 0)
+    ) AS has_unread
+FROM
+    chats
+WHERE
+    chats.parent_chat_id = ANY(@parent_ids :: uuid[])
+    AND CASE
+        WHEN sqlc.narg('archived') :: boolean IS NULL THEN true
+        ELSE chats.archived = sqlc.narg('archived') :: boolean
+    END
+ORDER BY
+    chats.created_at ASC,
+    chats.id ASC;
+
 -- name: InsertChat :one
 INSERT INTO chats (
     organization_id,