fix: sort child chats newest-first and prepend on creation (#24524)

GetChildChatsByParentIDs sorted created_at ASC, but the cache
helper appended new children to the end. On refetch the API and
cache agreed on oldest-first, putting the just-created child at
the bottom. Users expect newest first, matching the root-chat
sidebar convention.

- SQL: change child sort to created_at DESC, id DESC.
- Cache: prepend instead of append in addChildToParentInCache
  (renamed from appendChildToParentInCache to avoid leaking
  position semantics).
- Test: update ordering assertion to expect newest-first.

Refs #24404

coderd/database/queries.sql.go

@@ -6881,8 +6881,8 @@ WHERE
         ELSE chats.archived = $2 :: boolean
     END
 ORDER BY
-    chats.created_at ASC,
-    chats.id ASC
+    chats.created_at DESC,
+    chats.id DESC
 `
 
 type GetChildChatsByParentIDsParams struct {

coderd/database/queries/chats.sql

@@ -418,8 +418,8 @@ WHERE
         ELSE chats.archived = sqlc.narg('archived') :: boolean
     END
 ORDER BY
-    chats.created_at ASC,
-    chats.id ASC;
+    chats.created_at DESC,
+    chats.id DESC;
 
 -- name: InsertChat :one
 INSERT INTO chats (

coderd/exp_chats_test.go

@@ -1333,10 +1333,10 @@ func TestListChats(t *testing.T) {
 		}
 		require.Len(t, parent.Children, 2, "parent should embed 2 children")
 
-		// Children should be ordered by created_at ASC.
+		// Children are ordered by created_at DESC (newest first).
 		childIDs := []uuid.UUID{parent.Children[0].ID, parent.Children[1].ID}
-		require.Equal(t, child1.ID, childIDs[0])
-		require.Equal(t, child2.ID, childIDs[1])
+		require.Equal(t, child2.ID, childIDs[0])
+		require.Equal(t, child1.ID, childIDs[1])
 
 		// Verify each child has correct parent/root references.
 		for _, child := range parent.Children {

site/src/api/queries/chats.test.ts

@@ -4,7 +4,7 @@ import { API } from "#/api/api";
 import type * as TypesGen from "#/api/typesGenerated";
 import { buildOptimisticEditedMessage } from "./chatMessageEdits";
 import {
-	appendChildToParentInCache,
+	addChildToParentInCache,
 	archiveChat,
 	cancelChatListRefetches,
 	chatCostSummary,
@@ -1703,8 +1703,8 @@ describe("mutation onMutate cancels pagination fetches", () => {
 	});
 });
 
-describe("appendChildToParentInCache", () => {
-	it("appends the child to the matching parent's children array", () => {
+describe("addChildToParentInCache", () => {
+	it("prepends new child to the parent's children array", () => {
 		const queryClient = createTestQueryClient();
 		const parent = makeChat("parent-1");
 		seedInfiniteChats(queryClient, [parent]);
@@ -1713,7 +1713,7 @@ describe("appendChildToParentInCache", () => {
 			parent_chat_id: "parent-1",
 			root_chat_id: "parent-1",
 		});
-		appendChildToParentInCache(queryClient, child, "parent-1");
+		addChildToParentInCache(queryClient, child, "parent-1");
 
 		const result = readInfiniteChats(queryClient);
 		expect(result).toHaveLength(1);
@@ -1730,7 +1730,7 @@ describe("appendChildToParentInCache", () => {
 			parent_chat_id: "missing-parent",
 			root_chat_id: "missing-parent",
 		});
-		appendChildToParentInCache(queryClient, child, "missing-parent");
+		addChildToParentInCache(queryClient, child, "missing-parent");
 
 		const result = readInfiniteChats(queryClient);
 		expect(result).toHaveLength(1);
@@ -1747,7 +1747,7 @@ describe("appendChildToParentInCache", () => {
 		const parent = makeChat("parent-1", { children: [existingChild] });
 		seedInfiniteChats(queryClient, [parent]);
 
-		appendChildToParentInCache(queryClient, existingChild, "parent-1");
+		addChildToParentInCache(queryClient, existingChild, "parent-1");
 
 		const result = readInfiniteChats(queryClient);
 		expect(result?.[0].children).toHaveLength(1);

site/src/api/queries/chats.ts

@@ -103,11 +103,11 @@ export const readInfiniteChatsCache = (
 };
 
 /**
- * Appends a child chat to its parent's `children` array across all
+ * Adds a child chat to its parent's `children` array across all
  * infinite chat query caches. If the parent is not in any loaded page,
  * the child is silently dropped (it will appear when the parent loads).
  */
-export const appendChildToParentInCache = (
+export const addChildToParentInCache = (
 	queryClient: QueryClient,
 	child: TypesGen.Chat,
 	parentId: string,
@@ -119,7 +119,7 @@ export const appendChildToParentInCache = (
 			// Avoid duplicates.
 			if (c.children?.some((ch) => ch.id === child.id)) return c;
 			changed = true;
-			return { ...c, children: [...(c.children ?? []), child] };
+			return { ...c, children: [child, ...(c.children ?? [])] };
 		});
 		return changed ? next : chats;
 	});

site/src/pages/AgentsPage/AgentsPage.tsx

@@ -10,7 +10,7 @@ import { toast } from "sonner";
 import { API, watchChats } from "#/api/api";
 import { getErrorMessage } from "#/api/errors";
 import {
-	appendChildToParentInCache,
+	addChildToParentInCache,
 	archiveChat,
 	cancelChatListRefetches,
 	chatDiffContentsKey,
@@ -567,10 +567,10 @@ const AgentsPage: FC = () => {
 					// chat into every loaded page.
 					if (chatEvent.kind === "created") {
 						if (updatedChat.parent_chat_id) {
-							// Child chat: append to its parent's children
+							// Child chat: add to its parent's children
 							// array. If the parent is not in any loaded
 							// page, the child is silently dropped.
-							appendChildToParentInCache(
+							addChildToParentInCache(
 								queryClient,
 								updatedChat,
 								updatedChat.parent_chat_id,