diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
index ed459d5a86e..0639d27c6fb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
@@ -849,7 +849,7 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
                         ).trim();
                         return "multipart/form-data".equals(mediaType)
                                 || "application/x-www-form-urlencoded".equals(mediaType)
-                                || (mediaType.startsWith("application/") && mediaType.endsWith("json"));
+                                || (mediaType.startsWith("application/") && (mediaType.endsWith("json") || mediaType.endsWith("octet-stream")));
                     };
                     operation.consumes = operation.consumes == null ? null : operation.consumes.stream()
                             .filter(isSerializable)
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache
index ea711753abd..650703ba5e5 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache
@@ -86,6 +86,7 @@ import com.squareup.moshi.adapter
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -214,8 +215,15 @@ import com.squareup.moshi.adapter
                 }
             {{/jvm-okhttp4}}
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+            {{#jvm-okhttp3}}
+                RequestBody.create(MediaType.parse(OctetMediaType), content)
+            {{/jvm-okhttp3}}
+            {{#jvm-okhttp4}}
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            {{/jvm-okhttp4}}
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     {{#moshi}}
@@ -247,16 +255,19 @@ import com.squareup.moshi.adapter
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 {{#moshi}}Serializer.moshi.adapter<T>().fromJson(bodyContent){{/moshi}}{{!
                 }}{{#gson}}Serializer.gson.fromJson(bodyContent, (object: TypeToken<T>(){}).getType()){{/gson}}{{!
                 }}{{#jackson}}Serializer.jacksonObjectMapper.readValue(bodyContent, object: TypeReference<T>() {}){{/jackson}}{{!
                 }}{{#kotlinx_serialization}}Serializer.kotlinxSerializationJson.decodeFromString<T>(bodyContent){{/kotlinx_serialization}}
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 047c68d10ce..81cbdad3ec3 100644
--- a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -35,6 +35,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -109,8 +110,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                     )
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                RequestBody.create(MediaType.parse(OctetMediaType), content)
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -130,13 +133,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-default-values-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-default-values-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 047c68d10ce..81cbdad3ec3 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-default-values-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -35,6 +35,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -109,8 +110,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                     )
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                RequestBody.create(MediaType.parse(OctetMediaType), content)
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -130,13 +133,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 0f1ca0fcb9c..a01ca44bbbb 100644
--- a/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String? = JsonMediaType): T? {
@@ -131,13 +134,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.gson.fromJson(bodyContent, (object: TypeToken<T>(){}).getType())
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 5eb13189410..45b072f8278 100644
--- a/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String? = JsonMediaType): T? {
@@ -131,13 +134,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.jacksonObjectMapper.readValue(bodyContent, object: TypeReference<T>() {})
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 235c92379b5..5f684f2428a 100644
--- a/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -40,6 +40,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -113,8 +114,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String? = JsonMediaType): T? {
@@ -137,13 +140,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.kotlinxSerializationJson.decodeFromString<T>(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 67676016c1f..77aa25ca806 100644
--- a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -114,8 +115,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String? = JsonMediaType): T? {
@@ -134,13 +137,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.gson.fromJson(bodyContent, (object: TypeToken<T>(){}).getType())
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 81f05a77af3..5b2c0ad376a 100644
--- a/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 81f05a77af3..5b2c0ad376a 100644
--- a/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index ea4b7b65935..8e899898f01 100644
--- a/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 16c2bf9bc65..e8f2e7bb489 100644
--- a/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ internal open class ApiClient(val baseUrl: String, val client: OkHttpClient = de
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ internal open class ApiClient(val baseUrl: String, val client: OkHttpClient = de
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ internal open class ApiClient(val baseUrl: String, val client: OkHttpClient = de
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 81f05a77af3..5b2c0ad376a 100644
--- a/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 34db45767ad..0f1fae4e64a 100644
--- a/samples/client/petstore/kotlin-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -35,6 +35,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -109,8 +110,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                     )
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                RequestBody.create(MediaType.parse(OctetMediaType), content)
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -130,13 +133,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 81f05a77af3..5b2c0ad376a 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 2592a3baad3..7a9960d7e1f 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 6459e6aff54..00e451fa20e 100644
--- a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -39,6 +39,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -112,8 +113,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String? = JsonMediaType): T? {
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.kotlinxSerializationJson.decodeFromString<T>(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 81f05a77af3..5b2c0ad376a 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -38,6 +38,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         protected const val FormDataMediaType = "multipart/form-data"
         protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
         protected const val XmlMediaType = "application/xml"
+        protected const val OctetMediaType = "application/octet-stream"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -111,8 +112,10 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            mediaType == OctetMediaType && content is ByteArray ->
+                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -132,13 +135,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }
             return tempFile as T
         }
-        val bodyContent = body.string()
-        if (bodyContent.isEmpty()) {
-            return null
-        }
+
         return when {
-            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+            mediaType == null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) -> {
+                val bodyContent = body.string()
+                if (bodyContent.isEmpty()) {
+                    return null
+                }
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            }
+            mediaType == OctetMediaType -> body.bytes() as? T
             else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
         }
     }