diff --git a/scripts/sync_vendor.py b/scripts/sync_vendor.py
index 0ddef236a..658f7326b 100755
--- a/scripts/sync_vendor.py
+++ b/scripts/sync_vendor.py
@@ -5,7 +5,7 @@ import os
 import sys
 import subprocess
 
-HTTPLIB_VERSION = "refs/tags/v0.44.0"
+HTTPLIB_VERSION = "refs/tags/v0.45.0"
 
 vendor = {
     "https://github.com/nlohmann/json/releases/latest/download/json.hpp":     "vendor/nlohmann/json.hpp",
diff --git a/vendor/cpp-httplib/httplib.cpp b/vendor/cpp-httplib/httplib.cpp
index ed9b09ba0..b28549607 100644
--- a/vendor/cpp-httplib/httplib.cpp
+++ b/vendor/cpp-httplib/httplib.cpp
@@ -4723,17 +4723,24 @@ write_multipart_ranges_data(Stream &strm, const Request &req, Response &res,
       });
 }
 
+bool has_framed_body(const Request &req) {
+  return is_chunked_transfer_encoding(req.headers) ||
+         req.get_header_value_u64("Content-Length") > 0;
+}
+
+bool is_connection_persistent(const Request &req) {
+  auto conn = req.get_header_value("Connection");
+  if (conn == "close") { return false; }
+  if (req.version == "HTTP/1.0" && conn != "Keep-Alive") { return false; }
+  return true;
+}
+
 bool expect_content(const Request &req) {
   if (req.method == "POST" || req.method == "PUT" || req.method == "PATCH" ||
       req.method == "DELETE") {
     return true;
   }
-  if (req.has_header("Content-Length") &&
-      req.get_header_value_u64("Content-Length") > 0) {
-    return true;
-  }
-  if (is_chunked_transfer_encoding(req.headers)) { return true; }
-  return false;
+  return has_framed_body(req);
 }
 
 #ifdef _WIN32
@@ -7449,29 +7456,18 @@ bool Server::read_content_core(
                      size_t /*len*/) { return receiver(buf, n); };
   }
 
-  // RFC 7230 Section 3.3.3: If this is a request message and none of the above
-  // are true (no Transfer-Encoding and no Content-Length), then the message
-  // body length is zero (no message body is present).
-  //
-  // For non-SSL builds, detect clients that send a body without a
-  // Content-Length header (raw HTTP over TCP). Check both the stream's
-  // internal read buffer (data already read from the socket during header
-  // parsing) and the socket itself for pending data. If data is found and
-  // exceeds the configured payload limit, reject with 413.
-  // For SSL builds we cannot reliably peek the decrypted application bytes,
-  // so keep the original behaviour.
+  // RFC 9112 §6: no Transfer-Encoding and no Content-Length means no body.
+  // For non-SSL builds we still scan non-persistent connections for stray
+  // body bytes so the payload limit is enforced (413). On keep-alive,
+  // pending bytes may be the next request (issue #2450), so skip.
 #if !defined(CPPHTTPLIB_SSL_ENABLED)
   if (!req.has_header("Content-Length") &&
       !detail::is_chunked_transfer_encoding(req.headers)) {
-    // Only check if payload_max_length is set to a finite value
-    if (payload_max_length_ > 0 &&
+    if (!detail::is_connection_persistent(req) && payload_max_length_ > 0 &&
         payload_max_length_ < (std::numeric_limits<size_t>::max)()) {
-      // Check if there is data already buffered in the stream (read during
-      // header parsing) or pending on the socket. Use a non-blocking socket
-      // check to avoid deadlock when the client sends no body.
-      bool has_data = strm.is_readable();
+      auto has_data = strm.is_readable();
       if (!has_data) {
-        socket_t s = strm.socket();
+        auto s = strm.socket();
         if (s != INVALID_SOCKET) {
           has_data = detail::select_read(s, 0, 0) > 0;
         }
@@ -8033,6 +8029,11 @@ get_client_ip(const std::string &x_forwarded_for,
                   ip_list.emplace_back(std::string(b + r.first, b + r.second));
                 });
 
+  // A malformed X-Forwarded-For (empty, comma-only, whitespace-only) yields
+  // no segments. Signal "no client IP derived" with an empty string so the
+  // caller can fall back to the connection-level remote address.
+  if (ip_list.empty()) { return std::string(); }
+
   for (size_t i = 0; i < ip_list.size(); ++i) {
     auto ip = ip_list[i];
 
@@ -8123,7 +8124,8 @@ Server::process_request(Stream &strm, const std::string &remote_addr,
 
   if (!trusted_proxies_.empty() && req.has_header("X-Forwarded-For")) {
     auto x_forwarded_for = req.get_header_value("X-Forwarded-For");
-    req.remote_addr = get_client_ip(x_forwarded_for, trusted_proxies_);
+    auto derived = get_client_ip(x_forwarded_for, trusted_proxies_);
+    req.remote_addr = derived.empty() ? remote_addr : derived;
   } else {
     req.remote_addr = remote_addr;
   }
@@ -8325,15 +8327,14 @@ Server::process_request(Stream &strm, const std::string &remote_addr,
     ret = write_response(strm, close_connection, req, res);
   }
 
-  // Drain any unconsumed request body to prevent request smuggling on
-  // keep-alive connections.
-  if (!req.body_consumed_ && detail::expect_content(req)) {
-    int drain_status = 200; // required by read_content signature
+  // Drain any unconsumed framed body to prevent request smuggling on
+  // keep-alive. Without framing there is no body to drain — reading would
+  // consume the next request (issue #2450).
+  if (!req.body_consumed_ && detail::has_framed_body(req)) {
+    int dummy_status;
     if (!detail::read_content(
-            strm, req, payload_max_length_, drain_status, nullptr,
+            strm, req, payload_max_length_, dummy_status, nullptr,
             [](const char *, size_t, size_t, size_t) { return true; }, false)) {
-      // Body exceeds payload limit or read error — close the connection
-      // to prevent leftover bytes from being misinterpreted.
       connection_closed = true;
     }
   }
diff --git a/vendor/cpp-httplib/httplib.h b/vendor/cpp-httplib/httplib.h
index b954b94af..af750cdd9 100644
--- a/vendor/cpp-httplib/httplib.h
+++ b/vendor/cpp-httplib/httplib.h
@@ -8,8 +8,8 @@
 #ifndef CPPHTTPLIB_HTTPLIB_H
 #define CPPHTTPLIB_HTTPLIB_H
 
-#define CPPHTTPLIB_VERSION "0.44.0"
-#define CPPHTTPLIB_VERSION_NUM "0x002c00"
+#define CPPHTTPLIB_VERSION "0.45.0"
+#define CPPHTTPLIB_VERSION_NUM "0x002d00"
 
 #ifdef _WIN32
 #if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00