add agent_message_clear

impls agentclientprotocol/agent-client-protocol#465

Author: steve02081504

schema/schema.json

@@ -3091,6 +3091,17 @@
           "required": ["sessionUpdate"],
           "type": "object"
         },
+        {
+          "description": "Instructs the client to clear the accumulated streamed content for the current agent message. Subsequent agent_message_chunk updates append from empty. Enables non-monotonic streaming (e.g. reformatting, delegation, iterative refinement).",
+          "properties": {
+            "sessionUpdate": {
+              "const": "agent_message_clear",
+              "type": "string"
+            }
+          },
+          "required": ["sessionUpdate"],
+          "type": "object"
+        },
         {
           "allOf": [
             {

src/examples/client.ts

@@ -53,6 +53,10 @@ class ExampleClient implements acp.Client {
           console.log(`[${update.content.type}]`);
         }
         break;
+      case "agent_message_clear":
+        // Client should clear accumulated streamed content for current agent message.
+        console.log(`[${update.sessionUpdate}]`);
+        break;
       case "tool_call":
         console.log(`\n🔧 ${update.title} (${update.status})`);
         break;

src/schema/index.ts

@@ -18,6 +18,7 @@ export type {
   CancelRequestNotification,
   ClientCapabilities,
   ClientNotification,
+  ClientOptions,
   ClientRequest,
   ClientResponse,
   ConfigOptionUpdate,

src/schema/types.gen.ts

@@ -2434,6 +2434,9 @@ export type SessionUpdate =
   | (ContentChunk & {
       sessionUpdate: "agent_message_chunk";
     })
+  | {
+      sessionUpdate: "agent_message_clear";
+    }
   | (ContentChunk & {
       sessionUpdate: "agent_thought_chunk";
     })

src/schema/zod.gen.ts

@@ -1580,6 +1580,9 @@ export const zSessionUpdate = z.union([
       sessionUpdate: z.literal("agent_message_chunk"),
     }),
   ),
+  z.object({
+    sessionUpdate: z.literal("agent_message_clear"),
+  }),
   zContentChunk.and(
     z.object({
       sessionUpdate: z.literal("agent_thought_chunk"),