Restore agent reasoning from event history

Author: benbrandt

src/ResponseItemHistoryFallback.ts

@@ -190,6 +190,8 @@ function createEventMsgUpdates(record: JsonRecord): UpdateSessionEvent[] | null
     switch (payload["type"]) {
         case "user_message":
             return createUserMessageEventUpdates(payload);
+        case "agent_reasoning":
+            return createAgentReasoningEventUpdates(payload);
         default:
             return [];
     }
@@ -210,6 +212,18 @@ function createUserMessageEventUpdates(payload: JsonRecord): UpdateSessionEvent[
     }));
 }
 
+function createAgentReasoningEventUpdates(payload: JsonRecord): UpdateSessionEvent[] {
+    const text = stringValue(payload["text"]);
+    if (text === null || text.length === 0) {
+        return [];
+    }
+
+    return [{
+        sessionUpdate: "agent_thought_chunk",
+        content: { type: "text", text },
+    }];
+}
+
 function imageBlocks(images: unknown): ContentBlock[] {
     if (!Array.isArray(images)) {
         return [];

src/__tests__/CodexACPAgent/load-session.test.ts

@@ -320,11 +320,19 @@ describe("CodexACPAgent - loadSession", () => {
                         content: [{ type: "input_text", text: "List the files" }],
                     },
                 },
+                {
+                    type: "event_msg",
+                    payload: {
+                        type: "agent_reasoning",
+                        text: "Need to inspect the directory.",
+                    },
+                },
                 {
                     type: "response_item",
                     payload: {
                         type: "reasoning",
-                        summary: [{ type: "summary_text", text: "Need to inspect the directory." }],
+                        summary: [],
+                        content: [],
                         encrypted_content: null,
                     },
                 },