diff --git a/src/utils/messages.ts b/src/utils/messages.ts
index cc624abb2..067e0280d 100644
--- a/src/utils/messages.ts
+++ b/src/utils/messages.ts
@@ -753,6 +753,7 @@ export function normalizeMessages(messages: Message[]): NormalizedMessage[] {
   // and remains true for all subsequent messages in the normalization process.
   let isNewChain = false
   return messages.flatMap(message => {
+    if (!message) return [];
     switch (message.type) {
       case 'assistant': {
         const aMsg = message as AssistantMessage
@@ -776,7 +777,7 @@ export function normalizeMessages(messages: Message[]): NormalizedMessage[] {
             isVirtual: message.isVirtual,
             requestId: message.requestId,
             uuid,
-            error: message.error,
+            error: message?.error,
             isApiErrorMessage: message.isApiErrorMessage,
             advisorModel: message.advisorModel,
           } as NormalizedAssistantMessage
@@ -2376,6 +2377,7 @@ export function normalizeMessagesForAPI(
       },
     )
     .forEach(message => {
+      if (!message) return [];
       switch (message.type) {
         case 'system': {
           // local_command system messages need to be included as user messages
diff --git a/src/utils/messages/mappers.ts b/src/utils/messages/mappers.ts
index 8f2bff8b0..0290200fb 100644
--- a/src/utils/messages/mappers.ts
+++ b/src/utils/messages/mappers.ts
@@ -29,6 +29,7 @@ export function toInternalMessages(
   messages: readonly DeepImmutable<SDKMessage>[],
 ): Message[] {
   return messages.flatMap(message => {
+    if (!message) return [];
     switch (message.type) {
       case 'assistant':
         return [
@@ -127,6 +128,7 @@ export function fromSDKCompactMetadata(
 
 export function toSDKMessages(messages: Message[]): SDKMessage[] {
   return messages.flatMap((message): SDKMessage[] => {
+    if (!message) return [];
     switch (message.type) {
       case 'assistant':
         return [
@@ -138,7 +140,7 @@ export function toSDKMessages(messages: Message[]): SDKMessage[] {
             session_id: getSessionId(),
             parent_tool_use_id: null,
             uuid: message.uuid,
-            error: message.error,
+            error: message?.error,
           },
         ]
       case 'user':