diff --git a/codex-rs/core/src/response_processing.rs b/codex-rs/core/src/response_processing.rs
index 458f82526ae..3e018a3ab10 100644
--- a/codex-rs/core/src/response_processing.rs
+++ b/codex-rs/core/src/response_processing.rs
@@ -60,7 +60,56 @@ pub(crate) async fn process_items(
         outputs_to_record.push(item);
     }
 
-    let all_items_to_record = [outputs_to_record, new_inputs_to_record].concat();
+    // Preserve correct ordering when an assistant message and a tool call/output
+    // happen in the same turn: any non-empty assistant content must precede the
+    // tool call object. This mirrors the upstream Responses ordering expectations
+    // and avoids sending `{role:"assistant", content:null, tool_calls:[...]}`
+    // before a `{role:"assistant", content:"..."}` message.
+    let mut all_items_to_record = [outputs_to_record, new_inputs_to_record].concat();
+
+    // Fix order: move the last assistant Message with non-empty text so it appears
+    // immediately before the first tool call object if needed.
+    // We only adjust relative order within the items collected this turn to avoid
+    // perturbing prior history.
+    if all_items_to_record.len() > 1 {
+        // Find indices relevant to reordering within this batch.
+        let first_tool_call_idx = all_items_to_record.iter().position(|it| {
+            matches!(
+                it,
+                codex_protocol::models::ResponseItem::FunctionCall { .. }
+                    | codex_protocol::models::ResponseItem::LocalShellCall { .. }
+                    | codex_protocol::models::ResponseItem::CustomToolCall { .. }
+            )
+        });
+        let last_assistant_nonempty_idx =
+            all_items_to_record
+                .iter()
+                .enumerate()
+                .rev()
+                .find_map(|(i, it)| match it {
+                    codex_protocol::models::ResponseItem::Message { role, content, .. }
+                        if role == "assistant" =>
+                    {
+                        let has_text = content.iter().any(|c| match c {
+                            codex_protocol::models::ContentItem::OutputText { text } => {
+                                !text.is_empty()
+                            }
+                            _ => false,
+                        });
+                        if has_text { Some(i) } else { None }
+                    }
+                    _ => None,
+                });
+
+        if let (Some(tool_idx), Some(msg_idx)) = (first_tool_call_idx, last_assistant_nonempty_idx)
+            && msg_idx > tool_idx
+        {
+            // Move the assistant message so it sits before the first tool call.
+            let msg = all_items_to_record.remove(msg_idx);
+            all_items_to_record.insert(tool_idx, msg);
+        }
+    }
+
     // Only attempt to take the lock if there is something to record.
     if !all_items_to_record.is_empty() {
         sess.record_conversation_items(turn_context, &all_items_to_record)
@@ -68,3 +117,83 @@ pub(crate) async fn process_items(
     }
     (responses, all_items_to_record)
 }
+
+#[cfg(test)]
+mod tests {
+    use pretty_assertions::assert_eq;
+
+    use super::process_items;
+    use crate::codex::ProcessedResponseItem;
+    use crate::codex::make_session_and_context;
+    use codex_protocol::models::ContentItem;
+    use codex_protocol::models::FunctionCallOutputPayload;
+    use codex_protocol::models::ResponseInputItem;
+    use codex_protocol::models::ResponseItem;
+
+    // When assistant produces non-empty content and then a tool call, ensure
+    // recorded items place assistant content before the tool call object.
+    // Without the ordering fix, this test fails because the tool call would
+    // appear before the assistant message in the recorded turn.
+    #[tokio::test]
+    async fn assistant_content_precedes_tool_call_in_recorded_turn() {
+        let (sess, turn_ctx) = make_session_and_context();
+
+        // Simulate streamed order: FunctionCall first (as forwarded immediately),
+        // then the final assistant Message content.
+        let call_id = "call_1".to_string();
+
+        let fn_call = ResponseItem::FunctionCall {
+            id: None,
+            name: "run".to_string(),
+            arguments: "{}".to_string(),
+            call_id: call_id.clone(),
+        };
+        let fn_output = ResponseInputItem::FunctionCallOutput {
+            call_id: call_id.clone(),
+            output: FunctionCallOutputPayload {
+                content: "THE TOOL CALL RESULT".to_string(),
+                success: Some(true),
+                ..Default::default()
+            },
+        };
+
+        let assistant_msg = ResponseItem::Message {
+            id: None,
+            role: "assistant".to_string(),
+            content: vec![ContentItem::OutputText {
+                text: "THE STRING CONTENT".to_string(),
+            }],
+        };
+
+        let processed = vec![
+            ProcessedResponseItem {
+                item: fn_call.clone(),
+                response: Some(fn_output.clone()),
+            },
+            ProcessedResponseItem {
+                item: assistant_msg.clone(),
+                response: None,
+            },
+        ];
+
+        let (_responses, recorded) = process_items(processed, &sess, &turn_ctx).await;
+
+        // Expected order:
+        // 1) assistant message content
+        // 2) tool call object
+        // 3) tool output (input for next turn)
+        let expected = vec![
+            assistant_msg,
+            fn_call,
+            ResponseItem::FunctionCallOutput {
+                call_id,
+                output: match fn_output {
+                    ResponseInputItem::FunctionCallOutput { output, .. } => output,
+                    _ => unreachable!("constructed above as FunctionCallOutput"),
+                },
+            },
+        ];
+
+        assert_eq!(expected, recorded);
+    }
+}