diff --git a/acp-model/api/acp-model.api b/acp-model/api/acp-model.api
index c0b3301..cb8c88e 100644
--- a/acp-model/api/acp-model.api
+++ b/acp-model/api/acp-model.api
@@ -172,18 +172,16 @@ public abstract interface class com/agentclientprotocol/model/AcpWithSessionId {
 public final class com/agentclientprotocol/model/AgentCapabilities : com/agentclientprotocol/model/AcpCapabilities, com/agentclientprotocol/model/AcpWithMeta {
 	public static final field Companion Lcom/agentclientprotocol/model/AgentCapabilities$Companion;
 	public fun <init> ()V
-	public fun <init> (ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;)V
-	public synthetic fun <init> (ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public fun <init> (ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lkotlinx/serialization/json/JsonElement;)V
+	public synthetic fun <init> (ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public final fun component1 ()Z
 	public final fun component2 ()Lcom/agentclientprotocol/model/PromptCapabilities;
 	public final fun component3 ()Lcom/agentclientprotocol/model/McpCapabilities;
 	public final fun component4 ()Lcom/agentclientprotocol/model/SessionCapabilities;
-	public final fun component5 ()Lcom/agentclientprotocol/model/AuthCapabilities;
-	public final fun component6 ()Lkotlinx/serialization/json/JsonElement;
-	public final fun copy (ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;)Lcom/agentclientprotocol/model/AgentCapabilities;
-	public static synthetic fun copy$default (Lcom/agentclientprotocol/model/AgentCapabilities;ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lcom/agentclientprotocol/model/AgentCapabilities;
+	public final fun component5 ()Lkotlinx/serialization/json/JsonElement;
+	public final fun copy (ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lkotlinx/serialization/json/JsonElement;)Lcom/agentclientprotocol/model/AgentCapabilities;
+	public static synthetic fun copy$default (Lcom/agentclientprotocol/model/AgentCapabilities;ZLcom/agentclientprotocol/model/PromptCapabilities;Lcom/agentclientprotocol/model/McpCapabilities;Lcom/agentclientprotocol/model/SessionCapabilities;Lkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lcom/agentclientprotocol/model/AgentCapabilities;
 	public fun equals (Ljava/lang/Object;)Z
-	public final fun getAuth ()Lcom/agentclientprotocol/model/AuthCapabilities;
 	public final fun getLoadSession ()Z
 	public final fun getMcpCapabilities ()Lcom/agentclientprotocol/model/McpCapabilities;
 	public final fun getPromptCapabilities ()Lcom/agentclientprotocol/model/PromptCapabilities;
@@ -658,14 +656,16 @@ public final class com/agentclientprotocol/model/CancelRequestNotification$Compa
 public final class com/agentclientprotocol/model/ClientCapabilities : com/agentclientprotocol/model/AcpCapabilities, com/agentclientprotocol/model/AcpWithMeta {
 	public static final field Companion Lcom/agentclientprotocol/model/ClientCapabilities$Companion;
 	public fun <init> ()V
-	public fun <init> (Lcom/agentclientprotocol/model/FileSystemCapability;ZLkotlinx/serialization/json/JsonElement;)V
-	public synthetic fun <init> (Lcom/agentclientprotocol/model/FileSystemCapability;ZLkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public fun <init> (Lcom/agentclientprotocol/model/FileSystemCapability;ZLcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;)V
+	public synthetic fun <init> (Lcom/agentclientprotocol/model/FileSystemCapability;ZLcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public final fun component1 ()Lcom/agentclientprotocol/model/FileSystemCapability;
 	public final fun component2 ()Z
-	public final fun component3 ()Lkotlinx/serialization/json/JsonElement;
-	public final fun copy (Lcom/agentclientprotocol/model/FileSystemCapability;ZLkotlinx/serialization/json/JsonElement;)Lcom/agentclientprotocol/model/ClientCapabilities;
-	public static synthetic fun copy$default (Lcom/agentclientprotocol/model/ClientCapabilities;Lcom/agentclientprotocol/model/FileSystemCapability;ZLkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lcom/agentclientprotocol/model/ClientCapabilities;
+	public final fun component3 ()Lcom/agentclientprotocol/model/AuthCapabilities;
+	public final fun component4 ()Lkotlinx/serialization/json/JsonElement;
+	public final fun copy (Lcom/agentclientprotocol/model/FileSystemCapability;ZLcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;)Lcom/agentclientprotocol/model/ClientCapabilities;
+	public static synthetic fun copy$default (Lcom/agentclientprotocol/model/ClientCapabilities;Lcom/agentclientprotocol/model/FileSystemCapability;ZLcom/agentclientprotocol/model/AuthCapabilities;Lkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lcom/agentclientprotocol/model/ClientCapabilities;
 	public fun equals (Ljava/lang/Object;)Z
+	public final fun getAuth ()Lcom/agentclientprotocol/model/AuthCapabilities;
 	public final fun getFs ()Lcom/agentclientprotocol/model/FileSystemCapability;
 	public final fun getTerminal ()Z
 	public fun get_meta ()Lkotlinx/serialization/json/JsonElement;
diff --git a/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Capabilities.kt b/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Capabilities.kt
index a9473ac..3e1c77e 100644
--- a/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Capabilities.kt
+++ b/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Capabilities.kt
@@ -63,9 +63,12 @@ public data class AuthCapabilities(
  * See protocol docs: [Client Capabilities](https://agentclientprotocol.com/protocol/initialization#client-capabilities)
  */
 @Serializable
+@OptIn(UnstableApi::class)
 public data class ClientCapabilities(
     @EncodeDefault val fs: FileSystemCapability? = null,
     @EncodeDefault val terminal: Boolean = false,
+    @property:UnstableApi
+    @EncodeDefault val auth: AuthCapabilities? = null,
     override val _meta: JsonElement? = null
 ) : AcpCapabilities, AcpWithMeta
 
@@ -145,7 +148,5 @@ public data class AgentCapabilities(
     @EncodeDefault val promptCapabilities: PromptCapabilities = PromptCapabilities(),
     @EncodeDefault val mcpCapabilities: McpCapabilities = McpCapabilities(),
     @EncodeDefault val sessionCapabilities: SessionCapabilities = SessionCapabilities(),
-    @property:UnstableApi
-    @EncodeDefault val auth: AuthCapabilities? = null,
     override val _meta: JsonElement? = null
 ) : AcpCapabilities, AcpWithMeta
\ No newline at end of file
diff --git a/build.gradle.kts b/build.gradle.kts
index d05042f..4680d8d 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -7,7 +7,7 @@ plugins {
 private val buildNumber: String? = System.getenv("GITHUB_RUN_NUMBER")
 private val isReleasePublication = System.getenv("RELEASE_PUBLICATION")?.toBoolean() ?: false
 
-private val baseVersion = "0.16.4"
+private val baseVersion = "0.16.5"
 
 allprojects {
     group = "com.agentclientprotocol"