From ade3f57d4ca1eedeffa398b30f94d7cf3e46ff29 Mon Sep 17 00:00:00 2001
From: Anurag Saxena <anuragg.saxenaa@gmail.com>
Date: Thu, 26 Mar 2026 23:40:29 -0400
Subject: [PATCH] fix: sanitize Gemini function names to meet API requirements
 (closes #369) (#403)

---
 .../translator/request/openai-to-gemini.js    | 25 +++++++++++++++----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/open-sse/translator/request/openai-to-gemini.js b/open-sse/translator/request/openai-to-gemini.js
index 03661bd..bfa84d1 100644
--- a/open-sse/translator/request/openai-to-gemini.js
+++ b/open-sse/translator/request/openai-to-gemini.js
@@ -20,6 +20,21 @@ import {
 } from "../helpers/geminiHelper.js";
 import { deriveSessionId } from "../../utils/sessionManager.js";
 
+// Sanitize function names for Gemini API.
+// Gemini requires: starts with [a-zA-Z_], followed by [a-zA-Z0-9_.:\-], max 64 chars.
+// Replace any invalid character with '_' and truncate to 64.
+function sanitizeGeminiFunctionName(name) {
+  if (!name) return "_unknown";
+  // Replace any char not in [a-zA-Z0-9_.:\-] with '_'
+  let sanitized = name.replace(/[^a-zA-Z0-9_.:\-]/g, "_");
+  // First char must be letter or underscore
+  if (!/^[a-zA-Z_]/.test(sanitized)) {
+    sanitized = "_" + sanitized;
+  }
+  // Truncate to 64 chars
+  return sanitized.substring(0, 64);
+}
+
 // Core: Convert OpenAI request to Gemini format (base for all variants)
 function openaiToGeminiBase(model, body, stream) {
   const result = {
@@ -116,7 +131,7 @@ function openaiToGeminiBase(model, body, stream) {
               thoughtSignature: DEFAULT_THINKING_GEMINI_SIGNATURE,
               functionCall: {
                 id: tc.id,
-                name: tc.function.name,
+                name: sanitizeGeminiFunctionName(tc.function.name),
                 args: args
               }
             });
@@ -156,7 +171,7 @@ function openaiToGeminiBase(model, body, stream) {
               toolParts.push({
                 functionResponse: {
                   id: fid,
-                  name: name,
+                  name: sanitizeGeminiFunctionName(name),
                   response: { result: parsedResp }
                 }
               });
@@ -180,7 +195,7 @@ function openaiToGeminiBase(model, body, stream) {
       if (t.name && t.input_schema) {
         const cleanedSchema = cleanJSONSchemaForAntigravity(structuredClone(t.input_schema || { type: "object", properties: {} }));
         functionDeclarations.push({
-          name: t.name,
+          name: sanitizeGeminiFunctionName(t.name),
           description: t.description || "",
           parameters: cleanedSchema
         });
@@ -190,7 +205,7 @@ function openaiToGeminiBase(model, body, stream) {
         const fn = t.function;
         const cleanedSchema = cleanJSONSchemaForAntigravity(structuredClone(fn.parameters || { type: "object", properties: {} }));
         functionDeclarations.push({
-          name: fn.name,
+          name: sanitizeGeminiFunctionName(fn.name),
           description: fn.description || "",
           parameters: cleanedSchema
         });
@@ -372,7 +387,7 @@ function wrapInCloudCodeEnvelopeForClaude(model, claudeRequest, credentials = nu
       if (tool.name && tool.input_schema) {
         const cleanedSchema = cleanJSONSchemaForAntigravity(tool.input_schema);
         functionDeclarations.push({
-          name: tool.name,
+          name: sanitizeGeminiFunctionName(tool.name),
           description: tool.description || "",
           parameters: cleanedSchema
         });