Fix 400 due to missing id parameter

Fixes issue #6700 which describes failures when search is enabled like
this:
```
■ unexpected status 400 Bad Request: {
  "error": {
    "message": "Missing required parameter: 'input[25].id'.",
    "type": "invalid_request_error",
    "param": "input[25].id",
    "code": "missing_required_parameter"
  }
}
```

This also fixes another issue I ran into after fixing the above issue:
```
■ unexpected status 400 Bad Request: {
  "error": {
    "message": "Invalid value: 'other'. Supported values are: 'search', 'open_page', and 'find_in_page'.",
    "type": "invalid_request_error",
    "param": "input[60].action.type",
    "code": "invalid_value"
  }
}
```

codex-rs/core/src/client.rs

@@ -263,7 +263,11 @@ impl ModelClient {
 
         let mut payload_json = serde_json::to_value(&payload)?;
         if azure_workaround {
-            attach_item_ids(&mut payload_json, &input_with_instructions);
+            attach_item_ids(
+                &mut payload_json,
+                &input_with_instructions,
+                &self.conversation_id,
+            );
         }
 
         let max_attempts = self.provider.request_max_retries();
@@ -607,7 +611,11 @@ struct ResponseCompletedOutputTokensDetails {
     reasoning_tokens: i64,
 }
 
-fn attach_item_ids(payload_json: &mut Value, original_items: &[ResponseItem]) {
+fn attach_item_ids(
+    payload_json: &mut Value,
+    original_items: &[ResponseItem],
+    conversation_id: &ConversationId,
+) {
     let Some(input_value) = payload_json.get_mut("input") else {
         return;
     };
@@ -615,25 +623,47 @@ fn attach_item_ids(payload_json: &mut Value, original_items: &[ResponseItem]) {
         return;
     };
 
-    for (value, item) in items.iter_mut().zip(original_items.iter()) {
-        if let ResponseItem::Reasoning { id, .. }
-        | ResponseItem::Message { id: Some(id), .. }
-        | ResponseItem::WebSearchCall { id: Some(id), .. }
-        | ResponseItem::FunctionCall { id: Some(id), .. }
-        | ResponseItem::LocalShellCall { id: Some(id), .. }
-        | ResponseItem::CustomToolCall { id: Some(id), .. } = item
-        {
-            if id.is_empty() {
-                continue;
-            }
-
-            if let Some(obj) = value.as_object_mut() {
-                obj.insert("id".to_string(), Value::String(id.clone()));
-            }
+    for (index, (value, item)) in items.iter_mut().zip(original_items.iter()).enumerate() {
+        if let Some(obj) = value.as_object_mut() {
+            let item_id = response_item_id(item)
+                .filter(|id| !id.is_empty())
+                .unwrap_or_else(|| format!("{conversation_id}-input-{index}"));
+            obj.insert("id".to_string(), Value::String(item_id));
         }
     }
 }
 
+fn response_item_id(item: &ResponseItem) -> Option<String> {
+    match item {
+        ResponseItem::Reasoning { id, .. } => (!id.is_empty()).then_some(id.clone()),
+        ResponseItem::Message { id, .. } => id.as_ref().filter(|v| !v.is_empty()).cloned(),
+        ResponseItem::WebSearchCall { id, .. } => id.as_ref().filter(|v| !v.is_empty()).cloned(),
+        ResponseItem::FunctionCall { id, call_id, .. } => id
+            .as_ref()
+            .filter(|v| !v.is_empty())
+            .cloned()
+            .or_else(|| (!call_id.is_empty()).then_some(call_id.clone())),
+        ResponseItem::LocalShellCall { id, call_id, .. } => id
+            .as_ref()
+            .filter(|v| !v.is_empty())
+            .cloned()
+            .or_else(|| call_id.as_ref().filter(|v| !v.is_empty()).cloned()),
+        ResponseItem::CustomToolCall { id, call_id, .. } => id
+            .as_ref()
+            .filter(|v| !v.is_empty())
+            .cloned()
+            .or_else(|| (!call_id.is_empty()).then_some(call_id.clone())),
+        ResponseItem::FunctionCallOutput { call_id, .. } => {
+            (!call_id.is_empty()).then_some(call_id.clone())
+        }
+        ResponseItem::CustomToolCallOutput { call_id, .. } => {
+            (!call_id.is_empty()).then_some(call_id.clone())
+        }
+        ResponseItem::GhostSnapshot { .. } => None,
+        ResponseItem::Other => None,
+    }
+}
+
 fn parse_rate_limit_snapshot(headers: &HeaderMap) -> Option<RateLimitSnapshot> {
     let primary = parse_rate_limit_window(
         headers,

codex-rs/core/src/event_mapping.rs

@@ -8,7 +8,6 @@ use codex_protocol::models::ContentItem;
 use codex_protocol::models::ReasoningItemContent;
 use codex_protocol::models::ReasoningItemReasoningSummary;
 use codex_protocol::models::ResponseItem;
-use codex_protocol::models::WebSearchAction;
 use codex_protocol::user_input::UserInput;
 use tracing::warn;
 use uuid::Uuid;
@@ -111,14 +110,17 @@ pub fn parse_turn_item(item: &ResponseItem) -> Option<TurnItem> {
                 raw_content,
             }))
         }
-        ResponseItem::WebSearchCall {
-            id,
-            action: WebSearchAction::Search { query },
-            ..
-        } => Some(TurnItem::WebSearch(WebSearchItem {
-            id: id.clone().unwrap_or_default(),
-            query: query.clone(),
-        })),
+        ResponseItem::WebSearchCall { id, action, .. } => {
+            if action.is_search()
+                && let Some(query) = action.query()
+            {
+                return Some(TurnItem::WebSearch(WebSearchItem {
+                    id: id.clone().unwrap_or_default(),
+                    query: query.to_string(),
+                }));
+            }
+            None
+        }
         _ => None,
     }
 }
@@ -305,9 +307,7 @@ mod tests {
         let item = ResponseItem::WebSearchCall {
             id: Some("ws_1".to_string()),
             status: Some("completed".to_string()),
-            action: WebSearchAction::Search {
-                query: "weather".to_string(),
-            },
+            action: WebSearchAction::search("weather"),
         };
 
         let turn_item = parse_turn_item(&item).expect("expected web search turn item");

codex-rs/core/tests/suite/client.rs

@@ -991,9 +991,7 @@ async fn azure_responses_request_includes_store_and_reasoning_ids() {
     prompt.input.push(ResponseItem::WebSearchCall {
         id: Some("web-search-id".into()),
         status: Some("completed".into()),
-        action: WebSearchAction::Search {
-            query: "weather".into(),
-        },
+        action: WebSearchAction::search("weather"),
     });
     prompt.input.push(ResponseItem::FunctionCall {
         id: Some("function-id".into()),
@@ -1020,6 +1018,13 @@ async fn azure_responses_request_includes_store_and_reasoning_ids() {
         name: "custom_tool".into(),
         input: "{}".into(),
     });
+    prompt.input.push(ResponseItem::Message {
+        id: None,
+        role: "user".into(),
+        content: vec![ContentItem::InputText {
+            text: "follow up question".into(),
+        }],
+    });
 
     let mut stream = client
         .stream(&prompt)
@@ -1043,13 +1048,18 @@ async fn azure_responses_request_includes_store_and_reasoning_ids() {
 
     assert_eq!(body["store"], serde_json::Value::Bool(true));
     assert_eq!(body["stream"], serde_json::Value::Bool(true));
-    assert_eq!(body["input"].as_array().map(Vec::len), Some(6));
+    assert_eq!(body["input"].as_array().map(Vec::len), Some(7));
     assert_eq!(body["input"][0]["id"].as_str(), Some("reasoning-id"));
     assert_eq!(body["input"][1]["id"].as_str(), Some("message-id"));
     assert_eq!(body["input"][2]["id"].as_str(), Some("web-search-id"));
     assert_eq!(body["input"][3]["id"].as_str(), Some("function-id"));
     assert_eq!(body["input"][4]["id"].as_str(), Some("local-shell-id"));
     assert_eq!(body["input"][5]["id"].as_str(), Some("custom-tool-id"));
+    let expected_user_id = format!("{conversation_id}-input-6");
+    assert_eq!(
+        body["input"][6]["id"].as_str(),
+        Some(expected_user_id.as_str())
+    );
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]

codex-rs/protocol/src/models.rs

@@ -8,6 +8,8 @@ use serde::Deserialize;
 use serde::Deserializer;
 use serde::Serialize;
 use serde::ser::Serializer;
+use serde_json::Value;
+use serde_json::json;
 use ts_rs::TS;
 
 use crate::user_input::UserInput;
@@ -120,7 +122,7 @@ pub enum ResponseItem {
     //   "action": {"type":"search","query":"weather: San Francisco, CA"}
     // }
     WebSearchCall {
-        #[serde(default, skip_serializing)]
+        #[serde(default, skip_serializing_if = "Option::is_none")]
         #[ts(skip)]
         id: Option<String>,
         #[serde(default, skip_serializing_if = "Option::is_none")]
@@ -211,13 +213,37 @@ pub struct LocalShellExecAction {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, JsonSchema, TS)]
-#[serde(tag = "type", rename_all = "snake_case")]
-pub enum WebSearchAction {
-    Search {
-        query: String,
-    },
-    #[serde(other)]
-    Other,
+#[serde(transparent)]
+#[ts(type = "Record<string, unknown>")]
+pub struct WebSearchAction(Value);
+
+impl WebSearchAction {
+    pub fn search(query: impl Into<String>) -> Self {
+        Self(json!({
+            "type": "search",
+            "query": query.into(),
+        }))
+    }
+
+    fn as_object(&self) -> Option<&serde_json::Map<String, Value>> {
+        self.0.as_object()
+    }
+
+    pub fn action_type(&self) -> Option<&str> {
+        self.as_object()
+            .and_then(|map| map.get("type"))
+            .and_then(Value::as_str)
+    }
+
+    pub fn is_search(&self) -> bool {
+        matches!(self.action_type(), Some("search"))
+    }
+
+    pub fn query(&self) -> Option<&str> {
+        self.as_object()
+            .and_then(|map| map.get("query"))
+            .and_then(Value::as_str)
+    }
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, JsonSchema, TS)]
@@ -703,4 +729,17 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn web_search_call_serializes_id() -> Result<()> {
+        let item = ResponseItem::WebSearchCall {
+            id: Some("search-1".into()),
+            status: Some("completed".into()),
+            action: WebSearchAction::search("weather"),
+        };
+
+        let json = serde_json::to_value(&item)?;
+        assert_eq!(json.get("id").and_then(|v| v.as_str()), Some("search-1"));
+        Ok(())
+    }
 }