Add default serializer for AvailableCommandInput without discriminator

acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/SessionUpdate.kt

@@ -13,6 +13,9 @@ import kotlinx.serialization.json.JsonElement
  * Input specification for a command.
  *
  * Specifies how the agent should collect input for this command.
+ *
+ * Note: Default deserializer for this sealed class is configured in [com.agentclientprotocol.rpc.ACPJson]
+ * to fall back to [Unstructured] when no type discriminator is present.
  */
 @Serializable
 @JsonClassDiscriminator(TYPE_DISCRIMINATOR)

acp-model/src/commonMain/kotlin/com/agentclientprotocol/rpc/JsonRpc.kt

@@ -2,6 +2,7 @@
 
 package com.agentclientprotocol.rpc
 
+import com.agentclientprotocol.model.AvailableCommandInput
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.Serializable
@@ -16,6 +17,8 @@ import kotlinx.serialization.json.JsonDecoder
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.modules.SerializersModule
+import kotlinx.serialization.modules.polymorphic
 import kotlin.jvm.JvmInline
 
 /**
@@ -170,13 +173,21 @@ public enum class JsonRpcErrorCode(public val code: Int, public val message: Str
     RESOURCE_NOT_FOUND(-32002, "Resource not found")
 }
 
+private val acpSerializersModule = SerializersModule {
+    polymorphic(AvailableCommandInput::class) {
+        subclass(AvailableCommandInput.Unstructured::class, AvailableCommandInput.Unstructured.serializer())
+        defaultDeserializer { AvailableCommandInput.Unstructured.serializer() }
+    }
+}
+
 @OptIn(ExperimentalSerializationApi::class)
 public val ACPJson: Json by lazy {
     Json {
         ignoreUnknownKeys = true
         encodeDefaults = true
         isLenient = true
         explicitNulls = false
+        serializersModule = acpSerializersModule
     }
 }
 

acp-model/src/commonTest/kotlin/com/agentclientprotocol/model/EmbeddedResourceResourceTest.kt → acp-model/src/commonTest/kotlin/com/agentclientprotocol/model/SerializationTests.kt

@@ -5,7 +5,7 @@ import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 
-class EmbeddedResourceResourceTest {
+class SerializationTests {
 
     @Test
     fun `decodes resource content without discriminator`() {
@@ -50,4 +50,53 @@ class EmbeddedResourceResourceTest {
         assertEquals("application/octet-stream", resource.mimeType)
         assertEquals("file:///tmp/data.bin", resource.uri)
     }
+
+    @Test
+    fun `decodes AvailableCommandInput without discriminator defaults to Unstructured`() {
+        val payload = """
+            {
+              "hint": "optional custom review instructions"
+            }
+        """.trimIndent()
+
+        val input = ACPJson.decodeFromString(AvailableCommandInput.serializer(), payload)
+
+        assertTrue(input is AvailableCommandInput.Unstructured)
+        assertEquals("optional custom review instructions", input.hint)
+    }
+
+    @Test
+    fun `decodes AvailableCommandInput with explicit discriminator`() {
+        val payload = """
+            {
+              "type": "unstructured",
+              "hint": "enter your query"
+            }
+        """.trimIndent()
+
+        val input = ACPJson.decodeFromString(AvailableCommandInput.serializer(), payload)
+
+        assertTrue(input is AvailableCommandInput.Unstructured)
+        assertEquals("enter your query", input.hint)
+    }
+
+    @Test
+    fun `decodes AvailableCommand with input without discriminator`() {
+        val payload = """
+            {
+              "name": "review",
+              "description": "Review code",
+              "input": {
+                "hint": "optional custom review instructions"
+              }
+            }
+        """.trimIndent()
+
+        val command = ACPJson.decodeFromString(AvailableCommand.serializer(), payload)
+
+        assertEquals("review", command.name)
+        assertEquals("Review code", command.description)
+        assertTrue(command.input is AvailableCommandInput.Unstructured)
+        assertEquals("optional custom review instructions", command.input.hint)
+    }
 }

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 = "0.10.1"
+private val baseVersion = "0.10.2"
 
 allprojects {
     group = "com.agentclientprotocol"