From f6c59d30b0215986e703ff38e2ce31dfea7d2a0a Mon Sep 17 00:00:00 2001
From: decolua <decoluadt@gmail.com>
Date: Thu, 3 Sep 2026 09:05:57 +0700
Subject: [PATCH] fix(gemini): convert prefixItems and ensure array items in
 schema sanitizer

Co-Authored-By: Claude Code <noreply@anthropic.com>
---
 open-sse/translator/formats/gemini.js | 35 +++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/open-sse/translator/formats/gemini.js b/open-sse/translator/formats/gemini.js
index 6393a78b..8a965fee 100644
--- a/open-sse/translator/formats/gemini.js
+++ b/open-sse/translator/formats/gemini.js
@@ -14,6 +14,8 @@ export const UNSUPPORTED_SCHEMA_CONSTRAINTS = [
   "uniqueItems", "contains",
   // 2020-12 keywords with no Gemini equivalent
   "unevaluatedProperties", "unevaluatedItems", "contentSchema",
+  // Tuple-array keywords; converted to items first, leftovers stripped
+  "prefixItems", "additionalItems",
   // Claude rejects these in VALIDATED mode
   "default", "examples",
   // JSON Schema meta keywords
@@ -308,6 +310,37 @@ function ensureObjectType(obj) {
   for (const v of Object.values(obj)) if (v && typeof v === "object") ensureObjectType(v);
 }
 
+// Convert prefixItems (tuple validation) to items — Gemini cannot express tuples,
+// and a type:"array" schema without items is rejected with "missing field"
+function convertPrefixItems(obj) {
+  if (!obj || typeof obj !== "object") return;
+
+  if (Array.isArray(obj.prefixItems) && obj.prefixItems.length > 0) {
+    const variants = obj.prefixItems.filter(s => s && s.type !== "null");
+    if (!obj.items && variants.length === 1) {
+      obj.items = variants[0];
+    } else if (!obj.items && variants.length > 1) {
+      obj.items = { anyOf: variants };
+    }
+    delete obj.prefixItems;
+  }
+
+  for (const value of Object.values(obj)) {
+    if (value && typeof value === "object") {
+      convertPrefixItems(value);
+    }
+  }
+}
+
+// Gemini requires items on every type:"array" schema — fill a permissive placeholder
+function ensureArrayItems(obj) {
+  if (!obj || typeof obj !== "object") return;
+  if (obj.type === "array" && !obj.items) {
+    obj.items = { type: "string" };
+  }
+  for (const v of Object.values(obj)) if (v && typeof v === "object") ensureArrayItems(v);
+}
+
 // Clean JSON Schema for Antigravity API compatibility - removes unsupported keywords recursively
 export function cleanJSONSchemaForAntigravity(schema) {
   if (!schema || typeof schema !== "object") return schema;
@@ -321,11 +354,13 @@ export function cleanJSONSchemaForAntigravity(schema) {
 
   // Phase 2: Flatten complex structures
   mergeAllOf(cleaned);
+  convertPrefixItems(cleaned);
   flattenAnyOfOneOf(cleaned);
   flattenTypeArrays(cleaned);
 
   // Phase 2.5: Infer missing type=object when properties exist (Gemini requirement)
   ensureObjectType(cleaned);
+  ensureArrayItems(cleaned);
 
   // Phase 3: Remove all unsupported keywords at ALL levels (including inside arrays)
   removeUnsupportedKeywords(cleaned, UNSUPPORTED_SCHEMA_CONSTRAINTS);