perf: fix slice boundary panics, eliminate string allocation in stdio reader, fix lua table nesting bug, and optimize nvim socket chunk size

mcp-stdio/src/lib.rs

@@ -14,7 +14,9 @@ pub async fn read_mcp_message<R: tokio::io::AsyncRead + Unpin>(
         }
 
         if line.starts_with('{') {
-            return Some(line.trim_end().to_string());
+            let len = line.trim_end().len();
+            line.truncate(len);
+            return Some(line);
         }
 
         let line = line.trim_end();

nvim-core/src/lib.rs

@@ -25,7 +25,7 @@ pub async fn send_response(response: JsonRpcResponse) {
     tracing::info!(
         "Sending JSON-RPC response (id: {:?}): {}{}",
         response.id,
-        &msg[..std::cmp::min(msg.len(), 500)],
+        &msg[..msg.floor_char_boundary(500)],
         if msg.len() > 500 { "..." } else { "" }
     );
     // CRITICAL ARCHITECTURAL DECISION:
@@ -182,7 +182,7 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
     let pending_clone2 = Arc::clone(&pending_requests);
     tokio::spawn(async move {
         let mut resp_buf = Vec::new();
-        let mut chunk = vec![0u8; 8192];
+        let mut chunk = vec![0u8; 65536];
         let mut offset = 0;
 
         loop {
@@ -957,7 +957,7 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
                                 local first = vim.fn.line('w0')
                                 local last = vim.fn.line('w$')
                                 local lines = vim.api.nvim_buf_get_lines(0, first - 1, last, false)
-                                local res = {{}}
+                                local res = {}
                                 for i, line in ipairs(lines) do
                                     table.insert(res, tostring(first + i - 1) .. ': ' .. line)
                                 end

stub/src/main.rs

@@ -98,7 +98,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 ">>> [Stub] Forwarding {} to server (length: {}): {}{}",
                                 log_prefix,
                                 msg.len(),
-                                &msg[..std::cmp::min(msg.len(), 1000)],
+                                &msg[..msg.floor_char_boundary(1000)],
                                 if msg.len() > 1000 { "..." } else { "" }
                             );
                             if write
@@ -120,7 +120,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     "<<< [Stub] Received {} from server (length: {}): {}{}",
                                     log_prefix,
                                     text.len(),
-                                    &text[..std::cmp::min(text.len(), 1000)],
+                                    &text[..text.floor_char_boundary(1000)],
                                     if text.len() > 1000 { "..." } else { "" }
                                 );
                                 use tokio::io::AsyncWriteExt;