RustPython
diff --git a/‎crates/stdlib/src/ssl.rs‎
Lines changed: 7 additions & 3 deletions b/‎crates/stdlib/src/ssl.rs‎
Lines changed: 7 additions & 3 deletions
diff --git a/‎crates/stdlib/src/ssl/compat.rs‎
Lines changed: 15 additions & 1 deletion b/‎crates/stdlib/src/ssl/compat.rs‎
Lines changed: 15 additions & 1 deletion
@@ -2344,7 +2344,7 @@ mod _ssl {
         // This prevents data loss when write_tls() drains rustls' internal buffer
         // but the socket cannot accept all the data immediately
         #[pytraverse(skip)]
-        pending_tls_output: PyMutex<Vec<u8>>,
+        pub(crate) pending_tls_output: PyMutex<Vec<u8>>,
         // Deferred client certificate verification error (for TLS 1.3)
         // Stores error message if client cert verification failed during handshake
         // Error is raised on first I/O operation after handshake
@@ -2762,7 +2762,9 @@ mod _ssl {
                 if timed_out {
                     // Keep unsent data in pending buffer
                     *pending = pending[sent_total..].to_vec();
-                    return Err(vm.new_os_error("Write operation timed out"));
+                    return Err(
+                        timeout_error_msg(vm, "The write operation timed out".to_string()).upcast(),
+                    );
                 }
 
                 let to_send = pending[sent_total..].to_vec();
@@ -2819,7 +2821,9 @@ mod _ssl {
                     self.pending_tls_output
                         .lock()
                         .extend_from_slice(&buf[sent_total..]);
-                    return Err(vm.new_os_error("Write operation timed out"));
+                    return Err(
+                        timeout_error_msg(vm, "The write operation timed out".to_string()).upcast(),
+                    );
                 }
 
                 let to_send = buf[sent_total..].to_vec();
 
@@ -1026,15 +1026,29 @@ fn send_all_bytes(socket: &PySSLSocket, buf: Vec<u8>, vm: &VirtualMachine) -> Ss
                     .try_into()
                     .map_err(|_| SslError::Syscall("Invalid send return value".to_string()))?;
                 if sent == 0 {
-                    // No progress - would block
+                    // No progress - save unsent bytes to pending buffer
+                    socket
+                        .pending_tls_output
+                        .lock()
+                        .extend_from_slice(&buf[sent_total..]);
                     return Err(SslError::WantWrite);
                 }
                 sent_total += sent;
             }
             Err(e) => {
                 if is_blocking_io_error(&e, vm) {
+                    // Save unsent bytes to pending buffer
+                    socket
+                        .pending_tls_output
+                        .lock()
+                        .extend_from_slice(&buf[sent_total..]);
                     return Err(SslError::WantWrite);
                 }
+                // For other errors, also save unsent bytes
+                socket
+                    .pending_tls_output
+                    .lock()
+                    .extend_from_slice(&buf[sent_total..]);
                 return Err(SslError::Py(e));
             }
         }