From 998aa1bff4806c733d87a9d28db024d5f5d5dfcd Mon Sep 17 00:00:00 2001
From: Ishaan Jaffer <ishaanjaffer0324@gmail.com>
Date: Wed, 21 Jan 2026 17:51:57 -0800
Subject: [PATCH] fix ALLOWED_VERTEX_AI_PASSTHROUGH_HEADERS

---
 litellm/constants.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/litellm/constants.py b/litellm/constants.py
index e142c7d6304..13a26c6d0ea 100644
--- a/litellm/constants.py
+++ b/litellm/constants.py
@@ -1122,6 +1122,15 @@ BEDROCK_AGENT_RUNTIME_PASS_THROUGH_ROUTES = [
     "generateQuery/",
     "optimize-prompt/",
 ]
+
+
+# Headers that are safe to forward from incoming requests to Vertex AI
+# Using an allowlist approach for security - only forward headers we explicitly trust
+ALLOWED_VERTEX_AI_PASSTHROUGH_HEADERS = {
+    "anthropic-beta",  # Required for Anthropic features like extended context windows
+    "content-type",  # Required for request body parsing
+}
+
 BASE_MCP_ROUTE = "/mcp"
 
 BATCH_STATUS_POLL_INTERVAL_SECONDS = int(