diff --git a/okta/models/by_duration_expiry.py b/okta/models/by_duration_expiry.py
index b7acd4fc..93a1d6d3 100644
--- a/okta/models/by_duration_expiry.py
+++ b/okta/models/by_duration_expiry.py
@@ -51,11 +51,11 @@ def value_validate_regular_expression(cls, value):
             return value
 
         if not re.match(
-            r"^P(?:$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?:\d)(\d+H)?(\d+M)?(\d+S)?)?$",
+            r"^P(?!$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?=\d)(\d+H)?(\d+M)?(\d+S)?)?$",
             value,
         ):
             raise ValueError(
-                r"must validate the regular expression /^P(?:$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?:\d)(\d+H)?(\d+M)?(\d+S)?)?$/"
+                r"must validate the regular expression /^P(?!$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?=\d)(\d+H)?(\d+M)?(\d+S)?)?$/"
             )
         return value
 
diff --git a/okta/models/grace_period_expiry.py b/okta/models/grace_period_expiry.py
index 89b40125..0912bc0d 100644
--- a/okta/models/grace_period_expiry.py
+++ b/okta/models/grace_period_expiry.py
@@ -130,6 +130,44 @@ def from_json(cls, json_str: str) -> Self:
         except (ValidationError, ValueError) as e:
             error_messages.append(str(e))
 
+        # If no match found and the data is a primitive value, retry by wrapping
+        # it into each oneOf schema's single-property structure. This handles API
+        # responses where a scalar is returned for a oneOf field whose schemas
+        # are single-property objects.
+        if match == 0:
+            try:
+                _parsed_value = json.loads(json_str)
+            except (json.JSONDecodeError, TypeError):
+                _parsed_value = None
+            if _parsed_value is not None and isinstance(
+                _parsed_value, (str, int, float, bool)
+            ):
+                _retry_error_messages = []
+                # retry ByDateTimeExpiry with wrapped primitive
+                try:
+                    _model_fields = list(ByDateTimeExpiry.model_fields.keys())
+                    if len(_model_fields) == 1:
+                        instance.actual_instance = ByDateTimeExpiry.model_validate(
+                            {_model_fields[0]: _parsed_value}
+                        )
+                        match += 1
+                except (ValidationError, ValueError) as e:
+                    _retry_error_messages.append(str(e))
+                # retry ByDurationExpiry with wrapped primitive
+                try:
+                    _model_fields = list(ByDurationExpiry.model_fields.keys())
+                    if len(_model_fields) == 1:
+                        instance.actual_instance = ByDurationExpiry.model_validate(
+                            {_model_fields[0]: _parsed_value}
+                        )
+                        match += 1
+                except (ValidationError, ValueError) as e:
+                    _retry_error_messages.append(str(e))
+                if match > 0:
+                    error_messages = _retry_error_messages
+                else:
+                    error_messages.extend(_retry_error_messages)
+
         if match > 1:
             # more than 1 match
             raise ValueError(
diff --git a/openapi/api.yaml b/openapi/api.yaml
index f6fd5499..629eb090 100644
--- a/openapi/api.yaml
+++ b/openapi/api.yaml
@@ -62100,7 +62100,7 @@ components:
         value:
           type: string
           description: A time duration in ISO 8601 duration format.
-          pattern: ^P(?:$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?:\d)(\d+H)?(\d+M)?(\d+S)?)?$
+          pattern: ^P(?!$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?=\d)(\d+H)?(\d+M)?(\d+S)?)?$
     CAPTCHAInstance:
       title: CAPTCHAInstance
       description: ''
@@ -65855,6 +65855,7 @@ components:
       type: object
       properties:
         expiry:
+          x-okta-primitive-fallback: true
           oneOf:
             - $ref: '#/components/schemas/ByDateTimeExpiry'
             - $ref: '#/components/schemas/ByDurationExpiry'
diff --git a/openapi/templates/model_oneof.mustache b/openapi/templates/model_oneof.mustache
index 3d281613..6f2152ad 100644
--- a/openapi/templates/model_oneof.mustache
+++ b/openapi/templates/model_oneof.mustache
@@ -167,6 +167,40 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
         {{/isContainer}}
         {{/composedSchemas.oneOf}}
 
+        {{#vendorExtensions.x-okta-primitive-fallback}}
+        # If no match found and the data is a primitive value, retry by wrapping
+        # it into each oneOf schema's single-property structure. This handles API
+        # responses where a scalar is returned for a oneOf field whose schemas
+        # are single-property objects.
+        if match == 0:
+            try:
+                _parsed_value = json.loads(json_str)
+            except (json.JSONDecodeError, TypeError):
+                _parsed_value = None
+            if _parsed_value is not None and isinstance(_parsed_value, (str, int, float, bool)):
+                _retry_error_messages = []
+                {{#composedSchemas.oneOf}}
+                {{^isContainer}}
+                {{^isPrimitiveType}}
+                {{! Only retry non-primitive, non-container schemas. Primitive oneOf
+                    schemas would have already matched during the initial attempt above. }}
+                # retry {{{dataType}}} with wrapped primitive
+                try:
+                    _model_fields = list({{{dataType}}}.model_fields.keys())
+                    if len(_model_fields) == 1:
+                        instance.actual_instance = {{{dataType}}}.model_validate({_model_fields[0]: _parsed_value})
+                        match += 1
+                except (ValidationError, ValueError) as e:
+                    _retry_error_messages.append(str(e))
+                {{/isPrimitiveType}}
+                {{/isContainer}}
+                {{/composedSchemas.oneOf}}
+                if match > 0:
+                    error_messages = _retry_error_messages
+                else:
+                    error_messages.extend(_retry_error_messages)
+        {{/vendorExtensions.x-okta-primitive-fallback}}
+
         if match > 1:
             # more than 1 match
             raise ValueError("Multiple matches found when deserializing the JSON string into {{{classname}}} with oneOf schemas: {{#oneOf}}{{{.}}}{{^-last}}, {{/-last}}{{/oneOf}}. Details: " + ", ".join(error_messages))