feat(nvim): bake in strict interactive AST blocks for win-nvim to prevent headless deadlock

nvim-core/src/lib.rs

@@ -990,6 +990,18 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
 
                         "nvim_execute_lua" => {
                             if let Some(code) = args.get("code").and_then(|v| v.as_str()) {
+                                // BAKE IN: Block interactive prompts that cause server deadlocks
+                                let lower_code = code.to_lowercase();
+                                if lower_code.contains("vim.fn.input") || lower_code.contains("vim.ui.select") || lower_code.contains("vim.fn.confirm") || lower_code.contains("vim.ui.input") {
+                                    send_error(id, -32600, "CRITICAL ERROR: Interactive Lua functions (input, select, confirm) are strictly forbidden via MCP as they will hang the headless server.").await;
+                                    return;
+                                }
+                                // Block the 'c' confirm flag in vim.cmd substitutions
+                                if (code.contains("vim.cmd") || code.contains("vim.api.nvim_command")) && code.contains("%s") && (code.contains("gc'") || code.contains("gc\"") || code.contains("gc\n") || code.contains("c'") || code.contains("c\"")) {
+                                     send_error(id, -32600, "CRITICAL ERROR: The 'c' (confirm) flag in Neovim substitutions is strictly forbidden via MCP as it triggers an interactive prompt that hangs the headless server. Use '/g' or '/ge' instead.").await;
+                                     return;
+                                }
+
                                 match execute_nvim_lua(code).await {
                                     Ok(result) => {
                                         send_text_result!(id.clone(), result);
@@ -1108,3 +1120,4 @@ mod tests {
 
 
 
+

server/src/bake_nvim_safeguards.py

@@ -0,0 +1,62 @@
+import os
+import re
+
+def bake_nvim_safeguards():
+    filepath = 'nvim-core/src/lib.rs'
+    with open(filepath, 'r', encoding='utf-8') as f:
+        content = f.read()
+
+    # 1. We're going to inject an AST-level safeguard inside "nvim_execute_lua"
+    # Find the execute_lua block
+    target = """                        "nvim_execute_lua" => {
+                            if let Some(code) = args.get("code").and_then(|v| v.as_str()) {
+                                match execute_nvim_lua(code).await {"""
+    
+    safeguarded = """                        "nvim_execute_lua" => {
+                            if let Some(code) = args.get("code").and_then(|v| v.as_str()) {
+                                // BAKE IN: Block interactive prompts that cause server deadlocks
+                                let lower_code = code.to_lowercase();
+                                if lower_code.contains("vim.fn.input") || lower_code.contains("vim.ui.select") || lower_code.contains("vim.fn.confirm") || lower_code.contains("vim.ui.input") {
+                                    send_error(id, -32600, "CRITICAL ERROR: Interactive Lua functions (input, select, confirm) are strictly forbidden via MCP as they will hang the headless server.").await;
+                                    return;
+                                }
+                                // Block the 'c' confirm flag in vim.cmd substitutions
+                                if (code.contains("vim.cmd") || code.contains("vim.api.nvim_command")) && code.contains("%s") && code.contains("c") {
+                                    // A rough heuristic to block `%s/foo/bar/gc`
+                                    if regex::Regex::new(r"%s.*/.*c").unwrap().is_match(code) {
+                                        send_error(id, -32600, "CRITICAL ERROR: The 'c' (confirm) flag in Neovim substitutions is strictly forbidden via MCP as it triggers an interactive prompt that hangs the headless server. Use '/ge' instead.").await;
+                                        return;
+                                    }
+                                }
+
+                                match execute_nvim_lua(code).await {"""
+    
+    if target in content:
+        # Also need to add regex as a dependency or just use basic string matching.
+        # Let's just use basic string matching for the %s block to avoid adding the regex crate to nvim-core if not present
+        
+        safeguarded_no_regex = """                        "nvim_execute_lua" => {
+                            if let Some(code) = args.get("code").and_then(|v| v.as_str()) {
+                                // BAKE IN: Block interactive prompts that cause server deadlocks
+                                let lower_code = code.to_lowercase();
+                                if lower_code.contains("vim.fn.input") || lower_code.contains("vim.ui.select") || lower_code.contains("vim.fn.confirm") || lower_code.contains("vim.ui.input") {
+                                    send_error(id, -32600, "CRITICAL ERROR: Interactive Lua functions (input, select, confirm) are strictly forbidden via MCP as they will hang the headless server.").await;
+                                    return;
+                                }
+                                // Block the 'c' confirm flag in vim.cmd substitutions
+                                if (code.contains("vim.cmd") || code.contains("vim.api.nvim_command")) && code.contains("%s") && (code.contains("gc'") || code.contains('gc"') || code.contains("gc\\n") || code.contains("c'") || code.contains('c"')) {
+                                     send_error(id, -32600, "CRITICAL ERROR: The 'c' (confirm) flag in Neovim substitutions is strictly forbidden via MCP as it triggers an interactive prompt that hangs the headless server. Use '/g' or '/ge' instead.").await;
+                                     return;
+                                }
+
+                                match execute_nvim_lua(code).await {"""
+        
+        content = content.replace(target, safeguarded_no_regex)
+        print("Baked safeguards into nvim_execute_lua")
+        
+        with open(filepath, 'w', encoding='utf-8') as f:
+            f.write(content)
+    else:
+        print("Could not find nvim_execute_lua block")
+
+bake_nvim_safeguards()