diff --git a/changelog/unreleased/codex-stream-tool-name.md b/changelog/unreleased/codex-stream-tool-name.md
new file mode 100644
index 00000000..690cd1e6
--- /dev/null
+++ b/changelog/unreleased/codex-stream-tool-name.md
@@ -0,0 +1,7 @@
+### English
+
+- Codex streaming keeps the function name on tool calls: it is read from `response.output_item.added` instead of the argument events, which carry only the item id. Clients no longer receive a tool call whose `name` is empty, and a session that recorded one no longer has every later request rejected with `Invalid 'input[n].name': empty string`.
+
+### 中文
+
+- Codex 流式工具调用保留函数名：名字改从 `response.output_item.added` 的 item 读取，参数事件本身只带 item id。客户端不会再收到 `name` 为空的工具调用，之前记录过这种调用的会话也不会再被 `Invalid 'input[n].name': empty string` 整轮拒绝。
diff --git a/internal/providers/codex/sse.go b/internal/providers/codex/sse.go
index b8d43c25..c5549a33 100644
--- a/internal/providers/codex/sse.go
+++ b/internal/providers/codex/sse.go
@@ -197,13 +197,32 @@ func (c *streamConverter) handleEvent(event, payload string) {
 			c.emitReasoning(d)
 		}
 	case "response.output_item.added", "response.output_item.done":
+		// The tool name rides on the item; the argument events that follow
+		// carry only the item id. Record it here so the announced tool_call is
+		// never sent with an empty name: a client cannot dispatch a call whose
+		// name is empty, and replaying that empty name in history makes the
+		// upstream reject the whole request.
 		var item struct {
 			Type   string `json:"type"`
-			Status string `json:"status"`
+			ID     string `json:"id"`
+			CallID string `json:"call_id"`
+			Name   string `json:"name"`
 		}
 		if json.Unmarshal(obj["item"], &item) != nil {
 			return
 		}
+		if item.Type != "function_call" && item.Type != "custom_tool_call" {
+			return
+		}
+		var outputIndex int
+		_ = json.Unmarshal(obj["output_index"], &outputIndex)
+		call := c.toolCall(outputIndex, item.ID)
+		if item.Name != "" && call.name == "" {
+			call.name = item.Name
+		}
+		if item.CallID != "" {
+			call.id = item.CallID
+		}
 	case "response.function_call_arguments.delta":
 		var delta struct {
 			Delta       string `json:"delta"`
diff --git a/internal/providers/codex/sse_test.go b/internal/providers/codex/sse_test.go
new file mode 100644
index 00000000..cf10423a
--- /dev/null
+++ b/internal/providers/codex/sse_test.go
@@ -0,0 +1,86 @@
+package codex
+
+import (
+	"io"
+	"strings"
+	"testing"
+)
+
+// A Codex stream announces the tool name on response.output_item.added and then
+// sends the arguments in separate events that carry only the item id. The relay
+// must announce the tool call with that name: a client cannot dispatch a call
+// whose name is empty, and replaying the empty name in history makes the
+// upstream reject the request with "Invalid 'input[n].name': empty string".
+func TestRewriteStreamKeepsToolNameFromOutputItem(t *testing.T) {
+	sse := `event: response.output_item.added
+data: {"type":"response.output_item.added","output_index":0,"item":{"type":"function_call","id":"fc_1","call_id":"call_1","name":"get_weather","arguments":""}}
+
+event: response.function_call_arguments.delta
+data: {"type":"response.function_call_arguments.delta","output_index":0,"item_id":"fc_1","delta":"{\"city\":\"Tokyo\"}"}
+
+event: response.function_call_arguments.done
+data: {"type":"response.function_call_arguments.done","output_index":0,"item_id":"fc_1","arguments":"{\"city\":\"Tokyo\"}"}
+
+event: response.completed
+data: {"type":"response.completed","response":{"status":"completed","usage":{"input_tokens":10,"output_tokens":5}}}
+
+`
+
+	stream, err := rewriteStream(strings.NewReader(sse), "gpt-6.1-sol")
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := io.ReadAll(stream.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := string(body)
+
+	if !strings.Contains(out, `"name":"get_weather"`) {
+		t.Fatalf("tool call lost its name: %s", out)
+	}
+	if !strings.Contains(out, `"id":"call_1"`) {
+		t.Fatalf("tool call lost its call id: %s", out)
+	}
+	if !strings.Contains(out, `"arguments":"{\"city\":\"Tokyo\"}"`) {
+		t.Fatalf("tool call lost its arguments: %s", out)
+	}
+}
+
+// An item that is not a tool call must not consume a tool-call index or emit a
+// chunk, otherwise a reasoning item would shift every later call.
+func TestRewriteStreamIgnoresNonToolOutputItems(t *testing.T) {
+	sse := `event: response.output_item.added
+data: {"type":"response.output_item.added","output_index":0,"item":{"type":"reasoning","id":"rs_1","summary":[]}}
+
+event: response.output_item.added
+data: {"type":"response.output_item.added","output_index":1,"item":{"type":"function_call","id":"fc_2","call_id":"call_2","name":"read_file","arguments":""}}
+
+event: response.function_call_arguments.done
+data: {"type":"response.function_call_arguments.done","output_index":1,"item_id":"fc_2","arguments":"{\"path\":\"a.txt\"}"}
+
+event: response.completed
+data: {"type":"response.completed","response":{"status":"completed","usage":{"input_tokens":1,"output_tokens":1}}}
+
+`
+
+	stream, err := rewriteStream(strings.NewReader(sse), "gpt-6.1-sol")
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := io.ReadAll(stream.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := string(body)
+
+	if strings.Contains(out, `"name":"rs_1"`) || strings.Contains(out, `"name":""`) {
+		t.Fatalf("non-tool item leaked into tool_calls: %s", out)
+	}
+	if !strings.Contains(out, `"name":"read_file"`) {
+		t.Fatalf("tool call lost its name: %s", out)
+	}
+	if !strings.Contains(out, `"index":0`) {
+		t.Fatalf("tool call index should start at 0: %s", out)
+	}
+}