diff --git a/changelog.d/fixes/12370-responses-function-call-name.md b/changelog.d/fixes/12370-responses-function-call-name.md
new file mode 100644
index 0000000000..231a2a78af
--- /dev/null
+++ b/changelog.d/fixes/12370-responses-function-call-name.md
@@ -0,0 +1 @@
+- fix(api): restore the `name` field on non-streaming `/v1/responses` `function_call` output items — a plain (non-namespace) tool call's identity restore was blindly applying the `_toolNameMap` alias-table fallback as a `{namespace, name}` object, silently blanking `name` to `undefined` (dropped entirely by JSON.stringify) and leaving Codex unable to dispatch the call, so it re-narrated its intent in a loop instead (#12370)
diff --git a/open-sse/handlers/chatCore/nonStreamingClientTranslate.ts b/open-sse/handlers/chatCore/nonStreamingClientTranslate.ts
index 79821278f0..d328934140 100644
--- a/open-sse/handlers/chatCore/nonStreamingClientTranslate.ts
+++ b/open-sse/handlers/chatCore/nonStreamingClientTranslate.ts
@@ -130,7 +130,17 @@ export function translateNonStreamingClientResponse(
       for (const item of responseOutput) {
         if (item?.type !== "function_call") continue;
         const identity = requestToolIdentityMap.get(item.name);
-        if (identity) {
+        // `requestToolIdentityMap` is typed as Map<string, NamespaceIdentity>, but
+        // extractRequestToolIdentityMap() (chatCore/requestToolIdentity.ts) falls
+        // back to `_toolNameMap` when no namespace tools were present — and that
+        // side channel is a plain Map<string, string> alias table published by the
+        // openai->gemini/claude pivot (#9780), not {namespace, name} identities.
+        // Applying that fallback here unconditionally overwrote a perfectly valid
+        // `item.name` (e.g. "shell") with `("shell").name === undefined`, which
+        // JSON.stringify then drops the key entirely (#12370) — Codex receives a
+        // function_call with no name and cannot dispatch it. Only apply the
+        // restore when `identity` actually has the {namespace, name} shape.
+        if (identity && typeof identity === "object" && typeof identity.name === "string") {
           item.namespace = identity.namespace;
           item.name = identity.name;
         }
diff --git a/tests/unit/non-streaming-client-translate.test.ts b/tests/unit/non-streaming-client-translate.test.ts
index fb382929fa..d96b931773 100644
--- a/tests/unit/non-streaming-client-translate.test.ts
+++ b/tests/unit/non-streaming-client-translate.test.ts
@@ -270,6 +270,49 @@ test("Responses API format: sanitizeResponsesApiResponse is applied", () => {
   assert.equal(output[0]?.name, "get_weather", "#7936 restore original name");
 });
 
+test("#12370: alias-shaped requestToolIdentityMap must not blank out function_call name", () => {
+  // extractRequestToolIdentityMap() falls back to the `_toolNameMap` side channel
+  // when no namespace tools are present. For Gemini/Claude pivots that side
+  // channel is a plain Map<string, string> alias table (wire name -> original
+  // name), NOT the {namespace, name} identity shape the #7936 restore loop
+  // expects. A plain function tool like Codex's "shell" round-trips through
+  // this alias map as an identity mapping ("shell" -> "shell"): reproduces the
+  // exact live-VPS shape (tool_choice: auto, one `shell` function tool,
+  // gemini-3-flash-preview) where the non-streaming /v1/responses item lost
+  // its `name` key entirely.
+  const input = baseInput({
+    responsePayloadFormat: FORMATS.GEMINI,
+    clientResponseFormat: FORMATS.OPENAI_RESPONSES,
+    sourceFormat: FORMATS.OPENAI_RESPONSES,
+    provider: "gemini",
+    model: "gemini-3-flash-preview",
+    responseBody: {
+      candidates: [
+        {
+          content: {
+            role: "model",
+            parts: [{ functionCall: { name: "shell", args: { command: ["ls", "memory-bank/"] } } }],
+          },
+          finishReason: "STOP",
+          index: 0,
+        },
+      ],
+    },
+    // Alias-shaped map (string -> string), as published by the openai->gemini
+    // pivot — not a NamespaceIdentity map.
+    requestToolIdentityMap: new Map([["shell", "shell"]]) as unknown as Map<
+      string,
+      { namespace?: string; name: string }
+    >,
+  });
+  const result = translateNonStreamingClientResponse(input);
+  const output = result.response.output as Array<Record<string, unknown>>;
+  const functionCall = output.find((item) => item.type === "function_call");
+  assert.ok(functionCall, "expected a function_call output item");
+  assert.equal(functionCall?.name, "shell", "name must survive the alias-map fallback");
+  assert.equal("name" in (functionCall as object), true, "name key must be present, not stripped");
+});
+
 test("empty content response: passthrough without crash", () => {
   const input = baseInput({
     responseBody: {},