Load a conversation's history on the client

The conversation pages rendered their messages on the server, so a page
the back button restored from the back-forward cache showed an old
thread. The server now renders everything else (rail, header, composer)
and the history (active session, latest messages, active task) loads
from api/admin/bots/conversation-history once the page is on screen,
with a loading line under the header, and again on a pageshow restore.
Messages sent or pushed while it loads are merged with it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/pages/api/admin/bots/conversation-history.ts

@@ -0,0 +1,62 @@
+import userAuth from "@/src/functions/backend/auth/user-auth";
+import grabConversationHistory from "@/src/functions/backend/db/bot-sessions/grab-conversation-history";
+import { BotConversationRequestSchema } from "@/src/schemas/bot-schema";
+import type { ConversationHistoryPayload } from "@/src/types";
+import AppError from "@/src/utils/app-error";
+import parseWithSchema from "@/src/utils/parse-with-schema";
+import canManageCrew from "@/src/utils/rbac/can-manage-crew";
+import safeErrorMessage from "@/src/utils/safe-error-message";
+import type {
+    APIResponseObject,
+    BunextAPIRouteHandler,
+} from "@moduletrace/bunext/types";
+
+/**
+ * A conversation's history (`grabConversationHistory`: its active session,
+ * latest messages and the bot's active task there), which the
+ * conversation pages load once they are on screen instead of rendering it
+ * on the server, so a page restored by the back button never shows an
+ * old thread. When the user can't chat with the bot there any more,
+ * `redirect` says where the page goes instead: their bots, or the
+ * workspace (its settings for managers).
+ */
+export const handler: BunextAPIRouteHandler<
+    APIResponseObject<ConversationHistoryPayload>
+> = async ({ req, body }) => {
+    try {
+        if (req.method != "POST") {
+            throw new AppError(`Method not allowed`);
+        }
+
+        const { user, user_types } = await userAuth({ req });
+
+        if (!user?.logged_in_status || !user.id) {
+            return { success: false, msg: `Unauthorized`, logoutUser: true };
+        }
+
+        const { bot_id, workspace_id } = parseWithSchema({
+            schema: BotConversationRequestSchema,
+            data: body,
+        });
+
+        const history = await grabConversationHistory({
+            user_id: Number(user.id),
+            bot_id,
+            workspace_id,
+        });
+
+        if (!history) {
+            const redirect = !workspace_id
+                ? "/admin/bots"
+                : canManageCrew({ user_types })
+                  ? `/admin/settings/workspaces/${workspace_id}`
+                  : `/admin/workspaces/${workspace_id}`;
+
+            return { success: true, singleRes: { redirect } };
+        }
+
+        return { success: true, singleRes: { history } };
+    } catch (error: unknown) {
+        return { success: false, msg: safeErrorMessage({ error }) };
+    }
+};