Add update_plan code mode result (#15103)

It's empty!

codex-rs/core/src/tools/handlers/plan.rs

@@ -3,21 +3,52 @@ use crate::client_common::tools::ToolSpec;
 use crate::codex::Session;
 use crate::codex::TurnContext;
 use crate::function_tool::FunctionCallError;
-use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::ToolInvocation;
+use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;
 use crate::tools::registry::ToolHandler;
 use crate::tools::registry::ToolKind;
 use crate::tools::spec::JsonSchema;
 use async_trait::async_trait;
 use codex_protocol::config_types::ModeKind;
+use codex_protocol::models::FunctionCallOutputPayload;
+use codex_protocol::models::ResponseInputItem;
 use codex_protocol::plan_tool::UpdatePlanArgs;
 use codex_protocol::protocol::EventMsg;
+use serde_json::Value as JsonValue;
 use std::collections::BTreeMap;
 use std::sync::LazyLock;
 
 pub struct PlanHandler;
 
+pub struct PlanToolOutput;
+
+const PLAN_UPDATED_MESSAGE: &str = "Plan updated";
+
+impl ToolOutput for PlanToolOutput {
+    fn log_preview(&self) -> String {
+        PLAN_UPDATED_MESSAGE.to_string()
+    }
+
+    fn success_for_logging(&self) -> bool {
+        true
+    }
+
+    fn to_response_item(&self, call_id: &str, _payload: &ToolPayload) -> ResponseInputItem {
+        let mut output = FunctionCallOutputPayload::from_text(PLAN_UPDATED_MESSAGE.to_string());
+        output.success = Some(true);
+
+        ResponseInputItem::FunctionCallOutput {
+            call_id: call_id.to_string(),
+            output,
+        }
+    }
+
+    fn code_mode_result(&self, _payload: &ToolPayload) -> JsonValue {
+        JsonValue::Object(serde_json::Map::new())
+    }
+}
+
 pub static PLAN_TOOL: LazyLock<ToolSpec> = LazyLock::new(|| {
     let mut plan_item_props = BTreeMap::new();
     plan_item_props.insert("step".to_string(), JsonSchema::String { description: None });
@@ -64,7 +95,7 @@ At most one step can be in_progress at a time.
 
 #[async_trait]
 impl ToolHandler for PlanHandler {
-    type Output = FunctionToolOutput;
+    type Output = PlanToolOutput;
 
     fn kind(&self) -> ToolKind {
         ToolKind::Function
@@ -88,10 +119,9 @@ impl ToolHandler for PlanHandler {
             }
         };
 
-        let content =
-            handle_update_plan(session.as_ref(), turn.as_ref(), arguments, call_id).await?;
+        handle_update_plan(session.as_ref(), turn.as_ref(), arguments, call_id).await?;
 
-        Ok(FunctionToolOutput::from_text(content, Some(true)))
+        Ok(PlanToolOutput)
     }
 }