diff --git a/src/Socket/chats.ts b/src/Socket/chats.ts
index cd1a0ac5..45336f5e 100644
--- a/src/Socket/chats.ts
+++ b/src/Socket/chats.ts
@@ -41,7 +41,7 @@ import {
 	newLTHashState,
 	processSyncAction
 } from '../Utils'
-import { makeMutex } from '../Utils/make-mutex'
+import { makeMutex, makeKeyedMutex } from '../Utils/make-mutex'
 import processMessage from '../Utils/process-message'
 import { buildTcTokenFromJid } from '../Utils/tc-token-utils'
 import {
@@ -74,8 +74,8 @@ export const makeChatsSocket = (config: SocketConfig) => {
 
 	let syncState: SyncState = SyncState.Connecting
 
-	/** this mutex ensures that messages are processed in order */
-	const messageMutex = makeMutex()
+	/** this mutex ensures that messages from the same chat are processed in order, while allowing parallel processing of messages from different chats */
+	const messageMutex = makeKeyedMutex()
 
 	/** this mutex ensures that receipts are processed in order */
 	const receiptMutex = makeMutex()
diff --git a/src/Socket/messages-recv.ts b/src/Socket/messages-recv.ts
index f7038bbd..d499a88c 100644
--- a/src/Socket/messages-recv.ts
+++ b/src/Socket/messages-recv.ts
@@ -1265,8 +1265,24 @@ export const makeMessagesRecvSocket = (config: SocketConfig) => {
 			)
 		}
 
+		// CRITICAL: Normalize JIDs BEFORE acquiring mutex to ensure messages from the same
+		// chat (arriving with different JID formats - LID vs PN) use the SAME mutex key.
+		// This prevents parallel processing of messages from the same conversation which
+		// would break message ordering guarantees.
+		// Addresses Copilot/Codex PR #75 critical review: JID normalization vulnerability
+		await normalizeMessageJids(msg, signalRepository, logger)
+
 		try {
-			await messageMutex.mutex(async () => {
+			// Use KeyedMutex with NORMALIZED remoteJid for parallel processing across different chats
+			// while maintaining sequential order within the same chat
+			// Fallback chain: remoteJid (normalized) > msg.key.id (unique) > 'unknown' (serializes all)
+			let mutexKey = msg.key.remoteJid
+			if (!mutexKey) {
+				logger.warn({ msgId: msg.key.id, fromMe: msg.key.fromMe }, 'Missing remoteJid after normalization, using msg.key.id as fallback')
+				mutexKey = msg.key.id || 'unknown'
+			}
+
+			await messageMutex.mutex(mutexKey, async () => {
 				await decrypt()
 				// message failed to decrypt
 				if (msg.messageStubType === proto.WebMessageInfo.StubType.CIPHERTEXT && msg.category !== 'peer') {
@@ -1480,7 +1496,8 @@ export const makeMessagesRecvSocket = (config: SocketConfig) => {
 					}
 				}
 
-				await normalizeMessageJids(msg, signalRepository, logger)
+				// JID normalization moved BEFORE mutex acquisition (line 1273) to prevent race conditions
+				// cleanMessage still runs inside mutex to ensure atomic message processing
 				cleanMessage(msg, authState.creds.me!.id, authState.creds.me!.lid!)
 
 				await upsertMessage(msg, node.attrs.offline ? 'append' : 'notify')
diff --git a/src/Socket/messages-send.ts b/src/Socket/messages-send.ts
index 58339125..fd8e3c59 100644
--- a/src/Socket/messages-send.ts
+++ b/src/Socket/messages-send.ts
@@ -1639,7 +1639,12 @@ export const makeMessagesSocket = (config: SocketConfig) => {
 			// Emit own event for album root if configured
 			if (config.emitOwnEvents) {
 				process.nextTick(async () => {
-					await messageMutex.mutex(() => upsertMessage(albumRootMsg, 'append'))
+					let mutexKey = albumRootMsg.key.remoteJid
+					if (!mutexKey) {
+						logger.warn({ msgId: albumRootMsg.key.id }, 'Missing remoteJid in albumRootMsg, using msg.key.id as fallback')
+						mutexKey = albumRootMsg.key.id || 'unknown'
+					}
+					await messageMutex.mutex(mutexKey, () => upsertMessage(albumRootMsg, 'append'))
 				})
 			}
 
@@ -1732,7 +1737,12 @@ export const makeMessagesSocket = (config: SocketConfig) => {
 						// Emit own event if configured
 						if (config.emitOwnEvents) {
 							process.nextTick(async () => {
-								await messageMutex.mutex(() => upsertMessage(mediaMsg, 'append'))
+								let mutexKey = mediaMsg.key.remoteJid
+								if (!mutexKey) {
+									logger.warn({ msgId: mediaMsg.key.id }, 'Missing remoteJid in mediaMsg, using msg.key.id as fallback')
+									mutexKey = mediaMsg.key.id || 'unknown'
+								}
+								await messageMutex.mutex(mutexKey, () => upsertMessage(mediaMsg, 'append'))
 							})
 						}
 
@@ -1931,7 +1941,12 @@ export const makeMessagesSocket = (config: SocketConfig) => {
 				})
 				if (config.emitOwnEvents) {
 					process.nextTick(async () => {
-						await messageMutex.mutex(() => upsertMessage(fullMsg, 'append'))
+						let mutexKey = fullMsg.key.remoteJid
+						if (!mutexKey) {
+							logger.warn({ msgId: fullMsg.key.id }, 'Missing remoteJid in fullMsg, using msg.key.id as fallback')
+							mutexKey = fullMsg.key.id || 'unknown'
+						}
+						await messageMutex.mutex(mutexKey, () => upsertMessage(fullMsg, 'append'))
 					})
 				}