core: migrate standalone web search to extension-owned turn items (#31525)

## Description

This PR migrates standalone web search onto the extension-owned
turn-item path introduced in #31283.

Standalone web search now emits `ExtensionItem::WebSearch` through
generic `TurnItem::Extension`, while app-server still exposes the
existing typed `ThreadItem::WebSearch` JSON shape. Hosted Responses API
web search stays on core-owned `TurnItem::WebSearch`.

## What changed

- Added `web_search::WebSearchItem` and `WebSearchAction` to
`codex-extension-items` under the stable `web.search` kind.
- Collapsed `ExtensionTurnItem` to generic `{ item, legacy_events }` now
that no typed extension special cases remain.
- Kept the existing `WebSearchBegin` / `WebSearchEnd` compatibility
events and canonical-first ordering.
- Updated app-server projection/history and generated TypeScript; the
app-server JSON schema is unchanged.

codex-rs/app-server-protocol/src/protocol/thread_history.rs

@@ -21,7 +21,10 @@ use crate::protocol::v2::TurnError;
 use crate::protocol::v2::TurnItemsView;
 use crate::protocol::v2::TurnStatus;
 use crate::protocol::v2::UserInput;
+#[cfg(test)]
 use crate::protocol::v2::WebSearchAction;
+use crate::protocol::v2::WebSearchItem;
+use crate::protocol::v2::web_search_action_from_core;
 use codex_extension_items::image_generation::ImageGenerationItem;
 use codex_protocol::items::parse_hook_prompt_message;
 use codex_protocol::models::MessagePhase;
@@ -613,20 +616,20 @@ impl ThreadHistoryBuilder {
     }
 
     fn handle_web_search_begin(&mut self, payload: &WebSearchBeginEvent) {
-        let item = ThreadItem::WebSearch {
+        let item = ThreadItem::WebSearch(WebSearchItem {
             id: payload.call_id.clone(),
             query: String::new(),
             action: None,
-        };
+        });
         self.upsert_item_in_current_turn(item);
     }
 
     fn handle_web_search_end(&mut self, payload: &WebSearchEndEvent) {
-        let item = ThreadItem::WebSearch {
+        let item = ThreadItem::WebSearch(WebSearchItem {
             id: payload.call_id.clone(),
             query: payload.query.clone(),
-            action: Some(WebSearchAction::from(payload.action.clone())),
-        };
+            action: Some(web_search_action_from_core(payload.action.clone())),
+        });
         self.upsert_item_in_current_turn(item);
     }
 
@@ -2549,14 +2552,14 @@ mod tests {
         assert_eq!(turns[0].items.len(), 4);
         assert_eq!(
             turns[0].items[1],
-            ThreadItem::WebSearch {
+            ThreadItem::WebSearch(WebSearchItem {
                 id: "search-1".into(),
                 query: "codex".into(),
                 action: Some(WebSearchAction::Search {
                     query: Some("codex".into()),
                     queries: None,
                 }),
-            }
+            })
         );
         assert_eq!(
             turns[0].items[2],
@@ -3982,14 +3985,14 @@ mod tests {
             ThreadHistoryChangeSet {
                 changed_items: vec![ThreadHistoryItemChange {
                     turn_id: "rollout-0".into(),
-                    item: ThreadItem::WebSearch {
+                    item: ThreadItem::WebSearch(WebSearchItem {
                         id: "search-1".into(),
                         query: "codex".into(),
                         action: Some(WebSearchAction::Search {
                             query: Some("codex".into()),
                             queries: None,
                         }),
-                    },
+                    }),
                 }],
                 changed_turns: Vec::new(),
                 removed_turn_ids: Vec::new(),
@@ -4117,14 +4120,14 @@ mod tests {
             ThreadHistoryChangeSet {
                 changed_items: vec![ThreadHistoryItemChange {
                     turn_id: "rollout-0".into(),
-                    item: ThreadItem::WebSearch {
+                    item: ThreadItem::WebSearch(WebSearchItem {
                         id: "search-1".into(),
                         query: "codex".into(),
                         action: Some(WebSearchAction::Search {
                             query: Some("codex".into()),
                             queries: None,
                         }),
-                    },
+                    }),
                 }],
                 changed_turns: vec![ThreadHistoryTurnChange {
                     turn_id: "rollout-0".into(),

codex-rs/app-server-protocol/src/protocol/v2/item.rs

@@ -13,6 +13,8 @@ use crate::protocol::item_builders::convert_patch_changes;
 use codex_experimental_api_macros::ExperimentalApi;
 use codex_extension_items::ExtensionItem;
 pub use codex_extension_items::image_generation::ImageGenerationItem;
+pub use codex_extension_items::web_search::WebSearchAction;
+pub use codex_extension_items::web_search::WebSearchItem;
 use codex_protocol::approvals::GuardianAssessmentAction as CoreGuardianAssessmentAction;
 use codex_protocol::approvals::GuardianAssessmentDecisionSource as CoreGuardianAssessmentDecisionSource;
 use codex_protocol::approvals::GuardianCommandSource as CoreGuardianCommandSource;
@@ -358,13 +360,7 @@ pub enum ThreadItem {
         agent_thread_id: String,
         agent_path: String,
     },
-    #[serde(rename_all = "camelCase")]
-    #[ts(rename_all = "camelCase")]
-    WebSearch {
-        id: String,
-        query: String,
-        action: Option<WebSearchAction>,
-    },
+    WebSearch(WebSearchItem),
     #[serde(rename_all = "camelCase")]
     #[ts(rename_all = "camelCase")]
     ImageView {
@@ -432,12 +428,12 @@ impl ThreadItem {
             | ThreadItem::DynamicToolCall { id, .. }
             | ThreadItem::CollabAgentToolCall { id, .. }
             | ThreadItem::SubAgentActivity { id, .. }
-            | ThreadItem::WebSearch { id, .. }
             | ThreadItem::ImageView { id, .. }
             | ThreadItem::Sleep { id, .. }
             | ThreadItem::EnteredReviewMode { id, .. }
             | ThreadItem::ExitedReviewMode { id, .. }
             | ThreadItem::ContextCompaction { id, .. } => id,
+            ThreadItem::WebSearch(item) => &item.id,
             ThreadItem::ImageGeneration(item) => &item.id,
         }
     }
@@ -786,40 +782,20 @@ impl TryFrom<GuardianApprovalReviewAction> for CoreGuardianAssessmentAction {
     }
 }
 
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
-#[serde(tag = "type", rename_all = "camelCase")]
-#[ts(tag = "type", rename_all = "camelCase")]
-#[ts(export_to = "v2/")]
-pub enum WebSearchAction {
-    Search {
-        query: Option<String>,
-        queries: Option<Vec<String>>,
-    },
-    OpenPage {
-        url: Option<String>,
-    },
-    FindInPage {
-        url: Option<String>,
-        pattern: Option<String>,
-    },
-    #[serde(other)]
-    Other,
-}
-
-impl From<codex_protocol::models::WebSearchAction> for WebSearchAction {
-    fn from(value: codex_protocol::models::WebSearchAction) -> Self {
-        match value {
-            codex_protocol::models::WebSearchAction::Search { query, queries } => {
-                WebSearchAction::Search { query, queries }
-            }
-            codex_protocol::models::WebSearchAction::OpenPage { url } => {
-                WebSearchAction::OpenPage { url }
-            }
-            codex_protocol::models::WebSearchAction::FindInPage { url, pattern } => {
-                WebSearchAction::FindInPage { url, pattern }
-            }
-            codex_protocol::models::WebSearchAction::Other => WebSearchAction::Other,
+pub(crate) fn web_search_action_from_core(
+    value: codex_protocol::models::WebSearchAction,
+) -> WebSearchAction {
+    match value {
+        codex_protocol::models::WebSearchAction::Search { query, queries } => {
+            WebSearchAction::Search { query, queries }
         }
+        codex_protocol::models::WebSearchAction::OpenPage { url } => {
+            WebSearchAction::OpenPage { url }
+        }
+        codex_protocol::models::WebSearchAction::FindInPage { url, pattern } => {
+            WebSearchAction::FindInPage { url, pattern }
+        }
+        codex_protocol::models::WebSearchAction::Other => WebSearchAction::Other,
     }
 }
 
@@ -921,11 +897,11 @@ impl From<CoreTurnItem> for ThreadItem {
                 agent_thread_id: activity.agent_thread_id.to_string(),
                 agent_path: String::from(activity.agent_path),
             },
-            CoreTurnItem::WebSearch(search) => ThreadItem::WebSearch {
+            CoreTurnItem::WebSearch(search) => ThreadItem::WebSearch(WebSearchItem {
                 id: search.id,
                 query: search.query,
-                action: Some(WebSearchAction::from(search.action)),
-            },
+                action: Some(web_search_action_from_core(search.action)),
+            }),
             CoreTurnItem::ImageView(image) => ThreadItem::ImageView {
                 id: image.id,
                 path: image.path.into(),
@@ -936,6 +912,7 @@ impl From<CoreTurnItem> for ThreadItem {
             },
             CoreTurnItem::Extension(extension) => match extension {
                 ExtensionItem::ImageGeneration(item) => ThreadItem::ImageGeneration(item),
+                ExtensionItem::WebSearch(item) => ThreadItem::WebSearch(item),
             },
             CoreTurnItem::ImageGeneration(image) => {
                 ThreadItem::ImageGeneration(ImageGenerationItem {

codex-rs/app-server-protocol/src/protocol/v2/tests.rs

@@ -19,7 +19,7 @@ use codex_protocol::items::ReasoningItem;
 use codex_protocol::items::SubAgentActivityItem;
 use codex_protocol::items::TurnItem;
 use codex_protocol::items::UserMessageItem;
-use codex_protocol::items::WebSearchItem;
+use codex_protocol::items::WebSearchItem as CoreWebSearchItem;
 use codex_protocol::mcp::CallToolResult;
 use codex_protocol::mcp::McpServerInfo;
 use codex_protocol::memory_citation::MemoryCitation as CoreMemoryCitation;
@@ -2770,7 +2770,7 @@ fn core_turn_item_into_thread_item_converts_supported_variants() {
         }
     );
 
-    let search_item = TurnItem::WebSearch(WebSearchItem {
+    let search_item = TurnItem::WebSearch(CoreWebSearchItem {
         id: "search-1".to_string(),
         query: "docs".to_string(),
         action: CoreWebSearchAction::Search {
@@ -2779,16 +2779,24 @@ fn core_turn_item_into_thread_item_converts_supported_variants() {
         },
     });
 
+    let expected_search_item = WebSearchItem {
+        id: "search-1".to_string(),
+        query: "docs".to_string(),
+        action: Some(WebSearchAction::Search {
+            query: Some("docs".to_string()),
+            queries: None,
+        }),
+    };
+
     assert_eq!(
         ThreadItem::from(search_item),
-        ThreadItem::WebSearch {
-            id: "search-1".to_string(),
-            query: "docs".to_string(),
-            action: Some(WebSearchAction::Search {
-                query: Some("docs".to_string()),
-                queries: None,
-            }),
-        }
+        ThreadItem::WebSearch(expected_search_item.clone())
+    );
+    assert_eq!(
+        ThreadItem::from(TurnItem::Extension(
+            codex_extension_items::ExtensionItem::WebSearch(expected_search_item.clone()),
+        )),
+        ThreadItem::WebSearch(expected_search_item)
     );
 
     let image_view_item = TurnItem::ImageView(ImageViewItem {