diff --git a/.changeset/unlucky-sloths-cough.md b/.changeset/unlucky-sloths-cough.md
new file mode 100644
index 0000000000000..ce42ebea33969
--- /dev/null
+++ b/.changeset/unlucky-sloths-cough.md
@@ -0,0 +1,6 @@
+---
+"@rocket.chat/meteor": patch
+"@rocket.chat/rest-typings": patch
+---
+
+Add OpenAPI support for the Rocket.Chat chat.getMessage API endpoints by migrating to a modern chained route definition syntax and utilizing shared AJV schemas for validation to enhance API documentation and ensure type safety through response validation.
diff --git a/apps/meteor/app/api/server/v1/chat.ts b/apps/meteor/app/api/server/v1/chat.ts
index f289960f4f411..84344d6be0379 100644
--- a/apps/meteor/app/api/server/v1/chat.ts
+++ b/apps/meteor/app/api/server/v1/chat.ts
@@ -10,7 +10,6 @@ import {
 	isChatGetThreadsListProps,
 	isChatDeleteProps,
 	isChatSyncMessagesProps,
-	isChatGetMessageProps,
 	isChatPostMessageProps,
 	isChatSearchProps,
 	isChatSendMessageProps,
@@ -144,33 +143,6 @@ API.v1.addRoute(
 	},
 );
 
-API.v1.addRoute(
-	'chat.getMessage',
-	{
-		authRequired: true,
-		validateParams: isChatGetMessageProps,
-	},
-	{
-		async get() {
-			if (!this.queryParams.msgId) {
-				return API.v1.failure('The "msgId" query parameter must be provided.');
-			}
-
-			const msg = await getSingleMessage(this.userId, this.queryParams.msgId);
-
-			if (!msg) {
-				return API.v1.failure();
-			}
-
-			const [message] = await normalizeMessagesForUser([msg], this.userId);
-
-			return API.v1.success({
-				message,
-			});
-		},
-	},
-);
-
 type ChatPinMessage = {
 	messageId: IMessage['_id'];
 };
@@ -179,6 +151,10 @@ type ChatUnpinMessage = {
 	messageId: IMessage['_id'];
 };
 
+type ChatGetMessage = {
+	msgId: IMessage['_id'];
+};
+
 const ChatPinMessageSchema = {
 	type: 'object',
 	properties: {
@@ -203,10 +179,24 @@ const ChatUnpinMessageSchema = {
 	additionalProperties: false,
 };
 
+const ChatGetMessageSchema = {
+	type: 'object',
+	properties: {
+		msgId: {
+			type: 'string',
+			minLength: 1,
+		},
+	},
+	required: ['msgId'],
+	additionalProperties: false,
+};
+
 const isChatPinMessageProps = ajv.compile<ChatPinMessage>(ChatPinMessageSchema);
 
 const isChatUnpinMessageProps = ajv.compile<ChatUnpinMessage>(ChatUnpinMessageSchema);
 
+const isChatGetMessageProps = ajv.compile<ChatGetMessage>(ChatGetMessageSchema);
+
 const chatEndpoints = API.v1
 	.post(
 		'chat.pinMessage',
@@ -346,6 +336,47 @@ const chatEndpoints = API.v1
 			const updatedMessage = await Messages.findOneById(msg._id);
 			const [message] = await normalizeMessagesForUser(updatedMessage ? [updatedMessage] : [], this.userId);
 
+			return API.v1.success({
+				message,
+			});
+		},
+	)
+	.get(
+		'chat.getMessage',
+		{
+			authRequired: true,
+			query: isChatGetMessageProps,
+			response: {
+				400: validateBadRequestErrorResponse,
+				401: validateUnauthorizedErrorResponse,
+				200: ajv.compile<{ message: IMessage }>({
+					type: 'object',
+					properties: {
+						message: { $ref: '#/components/schemas/IMessage' },
+						success: {
+							type: 'boolean',
+							enum: [true],
+						},
+					},
+					required: ['message', 'success'],
+					additionalProperties: false,
+				}),
+			},
+		},
+
+		async function action() {
+			if (!this.queryParams.msgId) {
+				return API.v1.failure('The "msgId" query parameter must be provided.');
+			}
+
+			const msg: IMessage | null = await getSingleMessage(this.userId, this.queryParams.msgId);
+
+			if (!msg) {
+				return API.v1.failure();
+			}
+
+			const [message]: IMessage[] = await normalizeMessagesForUser([msg], this.userId);
+
 			return API.v1.success({
 				message,
 			});
diff --git a/apps/meteor/app/lib/server/functions/updateMessage.ts b/apps/meteor/app/lib/server/functions/updateMessage.ts
index baf2628e73394..f5787cbce41b1 100644
--- a/apps/meteor/app/lib/server/functions/updateMessage.ts
+++ b/apps/meteor/app/lib/server/functions/updateMessage.ts
@@ -1,6 +1,7 @@
 import { AppEvents, Apps } from '@rocket.chat/apps';
 import { Message } from '@rocket.chat/core-services';
 import type { IMessage, IUser, AtLeast } from '@rocket.chat/core-typings';
+import type { Root } from '@rocket.chat/message-parser';
 import { Messages, Rooms } from '@rocket.chat/models';
 import { Meteor } from 'meteor/meteor';
 
@@ -74,6 +75,27 @@ export const updateMessage = async function (
 		delete editedMessage.md;
 	}
 
+	if (editedMessage.attachments != null) {
+		const attachments = Array.isArray(editedMessage.attachments) ? editedMessage.attachments : [editedMessage.attachments];
+
+		editedMessage.attachments = attachments.map((attachment) => {
+			let normalizedMd: Root;
+
+			if (Array.isArray(attachment.md)) {
+				normalizedMd = attachment.md;
+			} else if (attachment.md != null) {
+				normalizedMd = [attachment.md];
+			} else {
+				normalizedMd = [];
+			}
+
+			return {
+				...attachment,
+				md: normalizedMd,
+			};
+		});
+	}
+
 	// do not send $unset if not defined. Can cause exceptions in certain mongo versions.
 	await Messages.updateOne(
 		{ _id },
diff --git a/packages/rest-typings/src/v1/chat.ts b/packages/rest-typings/src/v1/chat.ts
index 71fd745d7f95c..1819a8745370a 100644
--- a/packages/rest-typings/src/v1/chat.ts
+++ b/packages/rest-typings/src/v1/chat.ts
@@ -115,24 +115,6 @@ const chatUnfollowMessageSchema = {
 
 export const isChatUnfollowMessageProps = ajv.compile<ChatUnfollowMessage>(chatUnfollowMessageSchema);
 
-type ChatGetMessage = {
-	msgId: IMessage['_id'];
-};
-
-const ChatGetMessageSchema = {
-	type: 'object',
-	properties: {
-		msgId: {
-			type: 'string',
-			minLength: 1,
-		},
-	},
-	required: ['msgId'],
-	additionalProperties: false,
-};
-
-export const isChatGetMessageProps = ajv.compile<ChatGetMessage>(ChatGetMessageSchema);
-
 type ChatStarMessage = {
 	messageId: IMessage['_id'];
 };
@@ -962,11 +944,6 @@ export type ChatEndpoints = {
 			message: IMessage;
 		};
 	};
-	'/v1/chat.getMessage': {
-		GET: (params: ChatGetMessage) => {
-			message: IMessage;
-		};
-	};
 	'/v1/chat.followMessage': {
 		POST: (params: ChatFollowMessage) => void;
 	};