diff --git a/client/src/api/invocations.ts b/client/src/api/invocations.ts
index 00817980ab40..467267fe19f1 100644
--- a/client/src/api/invocations.ts
+++ b/client/src/api/invocations.ts
@@ -8,7 +8,7 @@ export type WorkflowInvocationElementView = components["schemas"]["WorkflowInvoc
 export type WorkflowInvocationCollectionView = components["schemas"]["WorkflowInvocationCollectionView"];
 export type InvocationJobsSummary = components["schemas"]["InvocationJobsResponse"];
 export type InvocationStep = components["schemas"]["InvocationStep"];
-export type InvocationMessage = components["schemas"]["WorkflowInvocationElementView"]["messages"][0];
+export type InvocationMessage = components["schemas"]["InvocationMessageResponseUnion"];
 
 export type StepJobSummary =
     | components["schemas"]["InvocationStepJobsResponseStepModel"]
diff --git a/client/src/api/schema/schema.ts b/client/src/api/schema/schema.ts
index fce5294b4509..65e445bc357e 100644
--- a/client/src/api/schema/schema.ts
+++ b/client/src/api/schema/schema.ts
@@ -8049,6 +8049,18 @@ export interface components {
                 [key: string]: number | undefined;
             };
         };
+        InvocationMessageResponseUnion:
+            | components["schemas"]["InvocationCancellationReviewFailedResponse"]
+            | components["schemas"]["InvocationCancellationHistoryDeletedResponse"]
+            | components["schemas"]["InvocationCancellationUserRequestResponse"]
+            | components["schemas"]["InvocationFailureDatasetFailedResponse"]
+            | components["schemas"]["InvocationFailureCollectionFailedResponse"]
+            | components["schemas"]["InvocationFailureJobFailedResponse"]
+            | components["schemas"]["InvocationFailureOutputNotFoundResponse"]
+            | components["schemas"]["InvocationFailureExpressionEvaluationFailedResponse"]
+            | components["schemas"]["InvocationFailureWhenNotBooleanResponse"]
+            | components["schemas"]["InvocationUnexpectedFailureResponse"]
+            | components["schemas"]["InvocationEvaluationWarningWorkflowOutputNotFoundResponse"];
         /** InvocationOutput */
         InvocationOutput: {
             /**
@@ -13316,19 +13328,7 @@ export interface components {
              * Messages
              * @description A list of messages about why the invocation did not succeed.
              */
-            messages: (
-                | components["schemas"]["InvocationCancellationReviewFailedResponse"]
-                | components["schemas"]["InvocationCancellationHistoryDeletedResponse"]
-                | components["schemas"]["InvocationCancellationUserRequestResponse"]
-                | components["schemas"]["InvocationFailureDatasetFailedResponse"]
-                | components["schemas"]["InvocationFailureCollectionFailedResponse"]
-                | components["schemas"]["InvocationFailureJobFailedResponse"]
-                | components["schemas"]["InvocationFailureOutputNotFoundResponse"]
-                | components["schemas"]["InvocationFailureExpressionEvaluationFailedResponse"]
-                | components["schemas"]["InvocationFailureWhenNotBooleanResponse"]
-                | components["schemas"]["InvocationUnexpectedFailureResponse"]
-                | components["schemas"]["InvocationEvaluationWarningWorkflowOutputNotFoundResponse"]
-            )[];
+            messages: components["schemas"]["InvocationMessageResponseUnion"][];
             /**
              * Model class
              * @description The name of the database model class.
diff --git a/lib/galaxy/schema/invocation.py b/lib/galaxy/schema/invocation.py
index 1d433fa5584a..4d5ce80548e8 100644
--- a/lib/galaxy/schema/invocation.py
+++ b/lib/galaxy/schema/invocation.py
@@ -20,6 +20,7 @@
 from typing_extensions import (
     Annotated,
     Literal,
+    TypeAliasType,
 )
 
 from galaxy.schema import schema
@@ -253,7 +254,7 @@ class GenericInvocationEvaluationWarningWorkflowOutputNotFound(
     EncodedDatabaseIdField
 ]
 
-InvocationMessageResponseUnion = Annotated[
+_InvocationMessageResponseUnion = Annotated[
     Union[
         InvocationCancellationReviewFailedResponseModel,
         InvocationCancellationHistoryDeletedResponseModel,
@@ -270,6 +271,8 @@ class GenericInvocationEvaluationWarningWorkflowOutputNotFound(
     Field(discriminator="reason"),
 ]
 
+InvocationMessageResponseUnion = TypeAliasType("InvocationMessageResponseUnion", _InvocationMessageResponseUnion)
+
 
 class InvocationMessageResponseModel(RootModel):
     root: InvocationMessageResponseUnion