diff --git a/acp-model/api/acp-model.api b/acp-model/api/acp-model.api
index 903379f..a429652 100644
--- a/acp-model/api/acp-model.api
+++ b/acp-model/api/acp-model.api
@@ -3765,15 +3765,17 @@ public final class com/agentclientprotocol/model/ToolCallContent$Content$Compani
 
 public final class com/agentclientprotocol/model/ToolCallContent$Diff : com/agentclientprotocol/model/ToolCallContent, com/agentclientprotocol/model/AcpWithMeta {
 	public static final field Companion Lcom/agentclientprotocol/model/ToolCallContent$Diff$Companion;
-	public fun <init> (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lkotlinx/serialization/json/JsonElement;)V
-	public synthetic fun <init> (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public fun <init> (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;ZLkotlinx/serialization/json/JsonElement;)V
+	public synthetic fun <init> (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;ZLkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public final fun component1 ()Ljava/lang/String;
 	public final fun component2 ()Ljava/lang/String;
 	public final fun component3 ()Ljava/lang/String;
-	public final fun component4 ()Lkotlinx/serialization/json/JsonElement;
-	public final fun copy (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lkotlinx/serialization/json/JsonElement;)Lcom/agentclientprotocol/model/ToolCallContent$Diff;
-	public static synthetic fun copy$default (Lcom/agentclientprotocol/model/ToolCallContent$Diff;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lcom/agentclientprotocol/model/ToolCallContent$Diff;
+	public final fun component4 ()Z
+	public final fun component5 ()Lkotlinx/serialization/json/JsonElement;
+	public final fun copy (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;ZLkotlinx/serialization/json/JsonElement;)Lcom/agentclientprotocol/model/ToolCallContent$Diff;
+	public static synthetic fun copy$default (Lcom/agentclientprotocol/model/ToolCallContent$Diff;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;ZLkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lcom/agentclientprotocol/model/ToolCallContent$Diff;
 	public fun equals (Ljava/lang/Object;)Z
+	public final fun getDeleted ()Z
 	public final fun getNewText ()Ljava/lang/String;
 	public final fun getOldText ()Ljava/lang/String;
 	public final fun getPath ()Ljava/lang/String;
diff --git a/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/ToolCall.kt b/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/ToolCall.kt
index 5b2a9c4..30899ad 100644
--- a/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/ToolCall.kt
+++ b/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/ToolCall.kt
@@ -86,6 +86,7 @@ public sealed class ToolCallContent {
         val path: String,
         val newText: String,
         val oldText: String? = null,
+        val deleted: Boolean = false,
         override val _meta: JsonElement? = null
     ) : ToolCallContent(), AcpWithMeta
 
diff --git a/acp-model/src/commonTest/kotlin/com/agentclientprotocol/model/SerializationTests.kt b/acp-model/src/commonTest/kotlin/com/agentclientprotocol/model/SerializationTests.kt
index f5c00ed..b2c80eb 100644
--- a/acp-model/src/commonTest/kotlin/com/agentclientprotocol/model/SerializationTests.kt
+++ b/acp-model/src/commonTest/kotlin/com/agentclientprotocol/model/SerializationTests.kt
@@ -3,6 +3,7 @@ package com.agentclientprotocol.model
 import com.agentclientprotocol.rpc.ACPJson
 import kotlin.test.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertFalse
 import kotlin.test.assertTrue
 
 class SerializationTests {
@@ -140,4 +141,60 @@ class SerializationTests {
         assertEquals(500000L, update.size)
         assertEquals(null, update.cost)
     }
-}
+
+    @Test
+    fun `decodes diff without deleted flag defaulting to false`() {
+        val payload = """
+            {
+              "type": "diff",
+              "path": "/home/user/project/src/main.kt",
+              "oldText": "fun main() {}",
+              "newText": ""
+            }
+        """.trimIndent()
+
+        val content = ACPJson.decodeFromString(ToolCallContent.serializer(), payload)
+
+        assertTrue(content is ToolCallContent.Diff)
+        assertEquals("/home/user/project/src/main.kt", content.path)
+        assertEquals("fun main() {}", content.oldText)
+        assertEquals("", content.newText)
+        assertFalse(content.deleted)
+    }
+
+    @Test
+    fun `decodes diff with deleted true`() {
+        val payload = """
+            {
+              "type": "diff",
+              "path": "/home/user/project/src/main.kt",
+              "oldText": "fun main() {}",
+              "newText": "",
+              "deleted": true
+            }
+        """.trimIndent()
+
+        val content = ACPJson.decodeFromString(ToolCallContent.serializer(), payload)
+
+        assertTrue(content is ToolCallContent.Diff)
+        assertTrue(content.deleted)
+    }
+
+    @Test
+    fun `decodes diff with deleted false`() {
+        val payload = """
+            {
+              "type": "diff",
+              "path": "/home/user/project/src/main.kt",
+              "oldText": "fun main() {}",
+              "newText": "",
+              "deleted": false
+            }
+        """.trimIndent()
+
+        val content = ACPJson.decodeFromString(ToolCallContent.serializer(), payload)
+
+        assertTrue(content is ToolCallContent.Diff)
+        assertFalse(content.deleted)
+    }
+}
\ No newline at end of file