fix: Emit plan contents in plan mode

src/CodexAcpServer.ts

@@ -1469,7 +1469,7 @@ export class CodexAcpServer {
             case "contextCompaction":
                 return [createCompletedContextCompactionUpdate(item)];
             case "plan":
-                return [this.createPlanUpdate(item)];
+                return [this.createPlanMessageUpdate(item)];
         }
     }
 
@@ -1520,16 +1520,14 @@ export class CodexAcpServer {
         };
     }
 
-    private createPlanUpdate(
+    private createPlanMessageUpdate(
         item: ThreadItem & { type: "plan" }
     ): UpdateSessionEvent {
-        return {
-            sessionUpdate: "agent_message_chunk",
-            content: {
-                type: "text",
-                text: `Plan:\n${item.text}`,
-            },
-        };
+        return createAgentTextMessageChunk(
+            item.text,
+            item.id,
+            createCodexMessagePhaseMeta("final_answer"),
+        );
     }
 
     private userInputToContentBlocks(input: UserInput): acp.ContentBlock[] {

src/CodexEventHandler.ts

@@ -19,6 +19,7 @@ import type {
     ItemStartedNotification,
     ThreadItem,
     ModelReroutedNotification,
+    PlanDeltaNotification,
     ReasoningSummaryPartAddedNotification,
     ReasoningSummaryTextDeltaNotification,
     ReasoningTextDeltaNotification,
@@ -76,6 +77,7 @@ export class CodexEventHandler {
     private readonly activeGuardianApprovalReviews = new Set<string>();
     private readonly activeImageGenerationItems = new Set<string>();
     private readonly emittedImageViewItems = new Set<string>();
+    private readonly planDeltaTextByItemId = new Map<string, string>();
     private readonly seenReasoningDeltaItemIds = new Set<string>();
     private readonly terminalCommandIds = new Set<string>();
     private readonly terminalCommandOutputIds = new Set<string>();
@@ -110,6 +112,8 @@ export class CodexEventHandler {
         switch (notification.method) {
             case "item/agentMessage/delta":
                 return await this.createTextEvent(notification.params);
+            case "item/plan/delta":
+                return this.createPlanDeltaEvent(notification.params);
             case "item/started":
                 return await this.createItemEvent(notification.params);
             case "item/completed":
@@ -223,7 +227,6 @@ export class CodexEventHandler {
             case "rawResponseItem/completed":
             case "rawResponse/completed":
             case "thread/started":
-            case "item/plan/delta":
             case "remoteControl/status/changed":
             case "app/list/updated":
             case "thread/settings/updated":
@@ -293,6 +296,15 @@ export class CodexEventHandler {
         return this.createAgentThoughtEvent(event.delta, event.itemId);
     }
 
+    private createPlanDeltaEvent(event: PlanDeltaNotification): UpdateSessionEvent | null {
+        if (event.delta.length === 0) {
+            return null;
+        }
+        const text = this.planDeltaTextByItemId.get(event.itemId) ?? "";
+        this.planDeltaTextByItemId.set(event.itemId, text + event.delta);
+        return null;
+    }
+
     private createReasoningSectionBreakEvent(event: ReasoningSummaryPartAddedNotification): UpdateSessionEvent {
         this.seenReasoningDeltaItemIds.add(event.itemId);
         return this.createAgentThoughtEvent("\n\n", event.itemId);
@@ -389,6 +401,11 @@ export class CodexEventHandler {
             case "agentMessage":
                 this.rememberAgentMessagePhase(event.item);
                 return null;
+            case "plan": {
+                const deltaText = this.planDeltaTextByItemId.get(event.item.id) ?? "";
+                this.planDeltaTextByItemId.delete(event.item.id);
+                return this.createCompletedPlanEvent(event.item, deltaText);
+            }
             case "exitedReviewMode":
                 return this.createExitedReviewModeEvent(event.item);
             case "contextCompaction":
@@ -404,7 +421,6 @@ export class CodexEventHandler {
             case "userMessage":
             case "hookPrompt":
             case "enteredReviewMode":
-            case "plan":
                 return null;
 
         }
@@ -423,6 +439,25 @@ export class CodexEventHandler {
         return this.createAgentThoughtEvent(text, item.id);
     }
 
+    private createCompletedPlanEvent(
+        item: ThreadItem & { type: "plan" },
+        deltaText: string,
+    ): UpdateSessionEvent | null {
+        const text = item.text.length > 0 ? item.text : deltaText;
+        if (text.length === 0) {
+            return null;
+        }
+        return this.createPlanTextEvent(text, item.id);
+    }
+
+    private createPlanTextEvent(text: string, messageId: string): UpdateSessionEvent {
+        return createAgentTextMessageChunk(
+            text,
+            messageId,
+            createCodexMessagePhaseMeta("final_answer"),
+        );
+    }
+
     private createExitedReviewModeEvent(item: ThreadItem & { type: "exitedReviewMode" }): UpdateSessionEvent | null {
         const text = item.review.trim();
         if (text.length === 0) {

src/__tests__/CodexACPAgent/data/load-session-response-item-history-fallback.json

@@ -151,9 +151,15 @@
       "sessionId": "session-legacy",
       "update": {
         "sessionUpdate": "agent_message_chunk",
+        "messageId": "item-plan-1",
         "content": {
           "type": "text",
-          "text": "Plan:\nInspect project files"
+          "text": "Inspect project files"
+        },
+        "_meta": {
+          "codex": {
+            "phase": "final_answer"
+          }
         }
       }
     }

src/__tests__/CodexACPAgent/data/plan-checklist-update.json

@@ -0,0 +1,23 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "plan",
+        "entries": [
+          {
+            "status": "completed",
+            "content": "Add the event mapping",
+            "priority": "medium"
+          },
+          {
+            "status": "in_progress",
+            "content": "Verify it in Zed",
+            "priority": "medium"
+          }
+        ]
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/data/plan-completed-fallback.json

@@ -0,0 +1,21 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "agent_message_chunk",
+        "messageId": "plan-2",
+        "content": {
+          "type": "text",
+          "text": "### Fallback plan\n\n1. Use the completed item."
+        },
+        "_meta": {
+          "codex": {
+            "phase": "final_answer"
+          }
+        }
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/data/plan-delta-fallback.json

@@ -0,0 +1,21 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "agent_message_chunk",
+        "messageId": "plan-2",
+        "content": {
+          "type": "text",
+          "text": "### Buffered plan\n\n1. Use the buffered fallback."
+        },
+        "_meta": {
+          "codex": {
+            "phase": "final_answer"
+          }
+        }
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/data/plan-deltas.json

@@ -0,0 +1,21 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "agent_message_chunk",
+        "messageId": "plan-1",
+        "content": {
+          "type": "text",
+          "text": "Completed text should not duplicate the streamed plan."
+        },
+        "_meta": {
+          "codex": {
+            "phase": "final_answer"
+          }
+        }
+      }
+    }
+  ]
+}