From 6ff7b6570c45d6d77b0812b1506fd618c9c8fb9b Mon Sep 17 00:00:00 2001
From: Prakersh Maheshwari <prakersh@live.com>
Date: Tue, 17 Mar 2026 02:03:45 +0530
Subject: [PATCH 1/2] fix(sse): add Claude-to-Claude passthrough for
 anthropic-compatible providers

When both source and target formats are Claude, skip all request
modification and forward the body untouched. This prevents
prepareClaudeRequest from corrupting valid Claude-native requests
destined for anthropic-compatible provider nodes.
---
 open-sse/handlers/chatCore.ts | 7 +++++++
 open-sse/translator/index.ts  | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/open-sse/handlers/chatCore.ts b/open-sse/handlers/chatCore.ts
index 1919add060..666ba975b0 100644
--- a/open-sse/handlers/chatCore.ts
+++ b/open-sse/handlers/chatCore.ts
@@ -182,10 +182,17 @@ export async function handleChatCore({
 
   // Translate request (pass reqLogger for intermediate logging)
   let translatedBody = body;
+  const isClaudePassthrough = sourceFormat === FORMATS.CLAUDE && targetFormat === FORMATS.CLAUDE;
   try {
     if (nativeCodexPassthrough) {
       translatedBody = { ...body, _nativeCodexPassthrough: true };
       log?.debug?.("FORMAT", "native codex passthrough enabled");
+    } else if (isClaudePassthrough) {
+      // Claude-to-Claude passthrough: forward body completely untouched.
+      // No translation, no field stripping, no thinking normalization.
+      // We are just a gateway -- do not interfere with the request in any way.
+      translatedBody = body;
+      log?.debug?.("FORMAT", "claude->claude passthrough -- forwarding untouched");
     } else {
       translatedBody = { ...body };
 
diff --git a/open-sse/translator/index.ts b/open-sse/translator/index.ts
index ce3f353f60..5b75f54685 100644
--- a/open-sse/translator/index.ts
+++ b/open-sse/translator/index.ts
@@ -131,7 +131,7 @@ export function translateRequest(
   }
 
   // Final step: prepare request for Claude format endpoints
-  if (targetFormat === FORMATS.CLAUDE) {
+  if (targetFormat === FORMATS.CLAUDE && sourceFormat !== FORMATS.CLAUDE) {
     result = prepareClaudeRequest(result, provider);
   }
 

From 1bdabf43db9e6aac726ead252ae87d63cf8f6ad1 Mon Sep 17 00:00:00 2001
From: Prakersh Maheshwari <prakersh@live.com>
Date: Tue, 17 Mar 2026 02:45:21 +0530
Subject: [PATCH 2/2] fix: prevent mutation of original request body in Claude
 passthrough

Use shallow copy ({ ...body }) instead of direct reference assignment
so that later translatedBody.model = model does not mutate the
caller's original body object.
---
 open-sse/handlers/chatCore.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/open-sse/handlers/chatCore.ts b/open-sse/handlers/chatCore.ts
index 666ba975b0..671c773a06 100644
--- a/open-sse/handlers/chatCore.ts
+++ b/open-sse/handlers/chatCore.ts
@@ -53,7 +53,9 @@ export function shouldUseNativeCodexPassthrough({
 }): boolean {
   if (provider !== "codex") return false;
   if (sourceFormat !== FORMATS.OPENAI_RESPONSES) return false;
-  return String(endpointPath || "").toLowerCase().endsWith("/responses");
+  return String(endpointPath || "")
+    .toLowerCase()
+    .endsWith("/responses");
 }
 
 /**
@@ -191,7 +193,7 @@ export async function handleChatCore({
       // Claude-to-Claude passthrough: forward body completely untouched.
       // No translation, no field stripping, no thinking normalization.
       // We are just a gateway -- do not interfere with the request in any way.
-      translatedBody = body;
+      translatedBody = { ...body };
       log?.debug?.("FORMAT", "claude->claude passthrough -- forwarding untouched");
     } else {
       translatedBody = { ...body };