fix(responses): reject duplicate historical call ids

(cherry picked from commit dc948dc)

Author: YotuAI

src/responses/custom-tool-compat.ts

@@ -319,8 +319,11 @@ function rewriteHistoricalCustomItems(
       continue;
     }
     const existing = calls.get(item.call_id);
-    if (existing && !sameHistoricalIdentity(existing, identity)) {
-      throw new RoutedCustomToolCompatError("historical_item", "call_id");
+    if (existing) {
+      throw new RoutedCustomToolCompatError(
+        "historical_item",
+        sameHistoricalIdentity(existing, identity) ? "duplicate_call_id" : "call_id",
+      );
     }
     calls.set(item.call_id, identity);
     if (item.type === "custom_tool_call") historicalCustomCallIds.add(item.call_id);

tests/responses/custom-tool-compat.test.ts

@@ -342,6 +342,15 @@ describe("undeclared historical custom-tool replay", () => {
     }, false)).toThrow(/historical_collision: declared_function_name/);
   });
 
+  test("rejects duplicate call IDs even when the historical call identity matches", () => {
+    expect(() => rewriteRoutedCustomToolsForUpstream({
+      input: [
+        { type: "custom_tool_call", call_id: "call_dup", name: "exec", input: "a" },
+        { type: "custom_tool_call", call_id: "call_dup", name: "exec", input: "a" },
+      ],
+    }, false)).toThrow(/historical_item: duplicate_call_id/);
+  });
+
   test("refuses call_id identity collisions", () => {
     expect(() => rewriteRoutedCustomToolsForUpstream({
       input: [