diff --git a/src/lib/conversation-state.ts b/src/lib/conversation-state.ts
index 13963877f..32702408f 100644
--- a/src/lib/conversation-state.ts
+++ b/src/lib/conversation-state.ts
@@ -89,7 +89,7 @@ export function updateState<TTools extends readonly Tool[] = readonly Tool[]>(
  */
 export function appendToMessages(
   current: models.InputsUnion,
-  newItems: models.BaseInputsUnion[]
+  newItems: models.InputsUnion1[]
 ): models.InputsUnion {
   const currentArray = normalizeInputToArray(current);
   return [...currentArray, ...newItems];
diff --git a/src/lib/model-result.ts b/src/lib/model-result.ts
index e1382aaba..77c811c9e 100644
--- a/src/lib/model-result.ts
+++ b/src/lib/model-result.ts
@@ -444,7 +444,7 @@ export class ModelResult<
     await this.saveStateSafely({
       messages: appendToMessages(
         this.currentState.messages,
-        outputItems as models.BaseInputsUnion[]
+        outputItems as models.InputsUnion1[]
       ),
       previousResponseId: response.id,
     });
@@ -845,7 +845,7 @@ export class ModelResult<
     turnNumber: number
   ): Promise<models.OpenResponsesResult> {
     const originalInput = this.resolvedRequest?.input;
-    const normalizedOriginalInput: models.BaseInputsUnion[] =
+    const normalizedOriginalInput: models.InputsUnion1[] =
       Array.isArray(originalInput)
         ? originalInput
         : originalInput
@@ -854,9 +854,9 @@ export class ModelResult<
 
     const newInput: models.InputsUnion = [
       ...normalizedOriginalInput,
-      ...(Array.isArray(currentResponse.output)
+      ...((Array.isArray(currentResponse.output)
         ? currentResponse.output
-        : [currentResponse.output]),
+        : [currentResponse.output]) as models.InputsUnion1[]),
       ...toolResults,
     ];
 
@@ -1047,7 +1047,7 @@ export class ModelResult<
           const inputArray = Array.isArray(newInput) ? newInput : [newInput];
           baseRequest = {
             ...baseRequest,
-            input: appendToMessages(this.currentState.messages, inputArray as models.BaseInputsUnion[]),
+            input: appendToMessages(this.currentState.messages, inputArray as models.InputsUnion1[]),
           };
         } else {
           baseRequest = {
diff --git a/src/lib/turn-context.ts b/src/lib/turn-context.ts
index 58a412940..b8cf83b43 100644
--- a/src/lib/turn-context.ts
+++ b/src/lib/turn-context.ts
@@ -67,7 +67,7 @@ export function buildTurnContext(
  */
 export function normalizeInputToArray(
   input: models.InputsUnion
-): Array<models.BaseInputsUnion> {
+): Array<models.InputsUnion1> {
   if (typeof input === 'string') {
     // Construct object with all required fields - type is optional
     const message: models.EasyInputMessage = {