From 595230177846b2182cef0dd834fc73661d2416c5 Mon Sep 17 00:00:00 2001
From: luvs01 <luvs01@hanmail.net>
Date: Fri, 7 Aug 2026 20:12:37 +0900
Subject: [PATCH] fix: avoid spreading hosted-tool indices

---
 src/adapters/openai-responses.ts           | 11 ++++-----
 tests/openai-responses-passthrough.test.ts | 28 ++++++++++++++++++++++
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/src/adapters/openai-responses.ts b/src/adapters/openai-responses.ts
index 5ed43ba381..8201644b12 100644
--- a/src/adapters/openai-responses.ts
+++ b/src/adapters/openai-responses.ts
@@ -705,14 +705,14 @@ function preferConfiguredHostedTools(
   }
 
   let input = body.input;
-  const strippedAdditionalToolsIndices = new Set<number>();
+  let firstStrippedAdditionalToolsIndex: number | undefined;
   if (Array.isArray(body.input)) {
     let nestedChanged = false;
     const mappedInput = body.input.map((item, index) => {
       if (!isPlainObject(item) || item.type !== "additional_tools" || !Array.isArray(item.tools)) return item;
       const nestedTools = stripGroup(item.tools);
       if (nestedTools === item.tools) return item;
-      strippedAdditionalToolsIndices.add(index);
+      firstStrippedAdditionalToolsIndex ??= index;
       nestedChanged = true;
       return { ...item, tools: nestedTools };
     });
@@ -731,17 +731,16 @@ function preferConfiguredHostedTools(
     || (Array.isArray(input) && input.some(item => isPlainObject(item)
       && item.type === "additional_tools"
       && hasHostedImageGenTool(item.tools)));
-  if ((strippedTopLevelImageGenTool || strippedAdditionalToolsIndices.size > 0) && !hasHostedImageGenDeclaration) {
+  if ((strippedTopLevelImageGenTool || firstStrippedAdditionalToolsIndex !== undefined) && !hasHostedImageGenDeclaration) {
     if (strippedTopLevelImageGenTool && Array.isArray(tools)) {
       tools = [...tools, { type: HOSTED_IMAGE_GENERATION_TOOL }];
-    } else if (strippedAdditionalToolsIndices.size > 0 && Array.isArray(input)) {
+    } else if (firstStrippedAdditionalToolsIndex !== undefined && Array.isArray(input)) {
       // Restore into the FIRST stripped container only. Tool declarations are
       // request-scoped, not container-scoped — the containers are separate carriers for
       // one tool set, so a single hosted declaration covers the request. An earlier
       // revision restored into every stripped container and put `image_generation` on
       // the wire twice; review caught it.
-      const firstStripped = Math.min(...strippedAdditionalToolsIndices);
-      input = input.map((item, index) => index === firstStripped
+      input = input.map((item, index) => index === firstStrippedAdditionalToolsIndex
         && isPlainObject(item)
         && Array.isArray(item.tools)
         ? { ...item, tools: [...item.tools, { type: HOSTED_IMAGE_GENERATION_TOOL }] }
diff --git a/tests/openai-responses-passthrough.test.ts b/tests/openai-responses-passthrough.test.ts
index 59f58237ba..0f52b9a3a7 100644
--- a/tests/openai-responses-passthrough.test.ts
+++ b/tests/openai-responses-passthrough.test.ts
@@ -1223,6 +1223,34 @@ describe("OpenAI Responses hosted-tool name conflicts", () => {
     expect(containers[0].tools).toContainEqual({ type: "image_generation" });
   });
 
+  test("additional_tools restoration does not spread stripped indices into Math.min", () => {
+    const adapter = createResponsesPassthroughAdapter({
+      ...keyedProvider,
+      modelPreferHostedTools: { "provider-image-model": ["image_generation"] },
+    });
+    const input = Array.from({ length: 3 }, () => ({
+      type: "additional_tools",
+      tools: [{ type: "namespace", name: "image_gen", tools: [] }],
+    }));
+    const originalMin = Math.min;
+    Math.min = (...values: number[]) => {
+      if (values.length > 2) throw new RangeError("too many arguments");
+      return originalMin(...values);
+    };
+
+    try {
+      expect(() => adapter.buildRequest({
+        modelId: "provider-image-model",
+        context: { messages: [] },
+        stream: true,
+        options: {},
+        _rawBody: { model: "provider-image-model", input },
+      }, meta)).not.toThrow();
+    } finally {
+      Math.min = originalMin;
+    }
+  });
+
   test("configured model rewrites a custom image-gen selector", () => {
     const adapter = createResponsesPassthroughAdapter({
       ...keyedProvider,