fix: preserve extra_content (thought_signature) for Gemini multi-turn

codex-rs/codex-api/src/requests/chat.rs

@@ -202,19 +202,25 @@ impl<'a> ChatRequestBuilder<'a> {
                     name,
                     arguments,
                     call_id,
+                    extra_content,
                     ..
                 } => {
+                    let mut tool_call_obj = json!({
+                        "id": call_id,
+                        "type": "function",
+                        "function": {
+                            "name": name,
+                            "arguments": arguments,
+                        }
+                    });
+                    // Include extra_content (e.g., Gemini's thought_signature) if present
+                    if let Some(extra) = extra_content {
+                        tool_call_obj["extra_content"] = extra.clone();
+                    }
                     let mut msg = json!({
                         "role": "assistant",
                         "content": null,
-                        "tool_calls": [{
-                            "id": call_id,
-                            "type": "function",
-                            "function": {
-                                "name": name,
-                                "arguments": arguments,
-                            }
-                        }]
+                        "tool_calls": [tool_call_obj]
                     });
                     if let Some(reasoning) = reasoning_by_anchor_index.get(&idx)
                         && let Some(obj) = msg.as_object_mut()

codex-rs/codex-api/src/sse/chat.rs

@@ -43,6 +43,7 @@ pub async fn process_chat_sse<S>(
     struct ToolCallState {
         name: Option<String>,
         arguments: String,
+        extra_content: Option<serde_json::Value>,
     }
 
     let mut tool_calls: HashMap<String, ToolCallState> = HashMap::new();
@@ -171,6 +172,11 @@ pub async fn process_chat_sse<S>(
                                 call_state.arguments.push_str(arguments);
                             }
                         }
+
+                        // Capture extra_content (e.g., Gemini's thought_signature)
+                        if let Some(extra) = tool_call.get("extra_content") {
+                            call_state.extra_content = Some(extra.clone());
+                        }
                     }
                 }
             }
@@ -231,6 +237,7 @@ pub async fn process_chat_sse<S>(
                         name: state.name.unwrap_or_default(),
                         arguments: state.arguments,
                         call_id: call_id.clone(),
+                        extra_content: state.extra_content,
                     };
                     let _ = tx_event.send(Ok(ResponseEvent::OutputItemDone(item))).await;
                 }

codex-rs/core/src/context_manager/history_tests.rs

@@ -163,6 +163,7 @@ fn remove_first_item_removes_matching_output_for_function_call() {
             name: "do_it".to_string(),
             arguments: "{}".to_string(),
             call_id: "call-1".to_string(),
+            extra_content: None,
         },
         ResponseItem::FunctionCallOutput {
             call_id: "call-1".to_string(),
@@ -192,6 +193,7 @@ fn remove_first_item_removes_matching_call_for_output() {
             name: "do_it".to_string(),
             arguments: "{}".to_string(),
             call_id: "call-2".to_string(),
+            extra_content: None,
         },
     ];
     let mut h = create_history_with_items(items);
@@ -471,6 +473,7 @@ fn normalize_adds_missing_output_for_function_call() {
         name: "do_it".to_string(),
         arguments: "{}".to_string(),
         call_id: "call-x".to_string(),
+        extra_content: None,
     }];
     let mut h = create_history_with_items(items);
 
@@ -484,6 +487,7 @@ fn normalize_adds_missing_output_for_function_call() {
                 name: "do_it".to_string(),
                 arguments: "{}".to_string(),
                 call_id: "call-x".to_string(),
+                extra_content: None,
             },
             ResponseItem::FunctionCallOutput {
                 call_id: "call-x".to_string(),
@@ -614,6 +618,7 @@ fn normalize_mixed_inserts_and_removals() {
             name: "f1".to_string(),
             arguments: "{}".to_string(),
             call_id: "c1".to_string(),
+            extra_content: None,
         },
         // Orphan output that should be removed
         ResponseItem::FunctionCallOutput {
@@ -657,6 +662,7 @@ fn normalize_mixed_inserts_and_removals() {
                 name: "f1".to_string(),
                 arguments: "{}".to_string(),
                 call_id: "c1".to_string(),
+                extra_content: None,
             },
             ResponseItem::FunctionCallOutput {
                 call_id: "c1".to_string(),
@@ -709,6 +715,7 @@ fn normalize_adds_missing_output_for_function_call_panics_in_debug() {
         name: "do_it".to_string(),
         arguments: "{}".to_string(),
         call_id: "call-x".to_string(),
+        extra_content: None,
     }];
     let mut h = create_history_with_items(items);
     h.normalize_history();
@@ -786,6 +793,7 @@ fn normalize_mixed_inserts_and_removals_panics_in_debug() {
             name: "f1".to_string(),
             arguments: "{}".to_string(),
             call_id: "c1".to_string(),
+            extra_content: None,
         },
         ResponseItem::FunctionCallOutput {
             call_id: "c2".to_string(),

codex-rs/core/src/conversation_manager.rs

@@ -306,6 +306,7 @@ mod tests {
                 name: "tool".to_string(),
                 arguments: "{}".to_string(),
                 call_id: "c1".to_string(),
+                extra_content: None,
             },
             assistant_msg("a4"),
         ];

codex-rs/core/tests/chat_completions_payload.rs

@@ -159,6 +159,7 @@ fn function_call() -> ResponseItem {
         name: "f".to_string(),
         arguments: "{}".to_string(),
         call_id: "c1".to_string(),
+        extra_content: None,
     }
 }
 

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

@@ -1073,6 +1073,7 @@ async fn azure_responses_request_includes_store_and_reasoning_ids() {
         name: "do_thing".into(),
         arguments: "{}".into(),
         call_id: "function-call-id".into(),
+        extra_content: None,
     });
     prompt.input.push(ResponseItem::LocalShellCall {
         id: Some("local-shell-id".into()),

codex-rs/protocol/src/models.rs

@@ -85,6 +85,11 @@ pub enum ResponseItem {
         // Chat Completions + Responses API behavior.
         arguments: String,
         call_id: String,
+        /// Provider-specific metadata (e.g., Gemini's `thought_signature`).
+        /// This field is captured from SSE responses and must be echoed back
+        /// in subsequent requests for multi-turn tool calling to work correctly.
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        extra_content: Option<serde_json::Value>,
     },
     // NOTE: The input schema for `function_call_output` objects that clients send to the
     // OpenAI /v1/responses endpoint is NOT the same shape as the objects the server returns on the