diff --git a/similarity_search.c b/similarity_search.c
index 00e3fe8..9cb8b33 100644
--- a/similarity_search.c
+++ b/similarity_search.c
@@ -141,6 +141,8 @@ void generate_random_string(char *string, int max_len) {
 
 // Create a new search index
 SearchIndex* create_search_index(int capacity) {
+    if (capacity <= 0) return NULL;
+    
     SearchIndex* index = (SearchIndex*)malloc(sizeof(SearchIndex));
     if (!index) return NULL;
     
@@ -151,6 +153,7 @@ SearchIndex* create_search_index(int capacity) {
     }
     
     index->num_strings = 0;
+    index->capacity = capacity;
     return index;
 }
 
@@ -158,6 +161,16 @@ SearchIndex* create_search_index(int capacity) {
 int add_string_to_index(SearchIndex* index, const char* string) {
     if (!index || !string) return -1;
     
+    // Check if we've reached capacity
+    if (index->num_strings >= index->capacity) {
+        return -1;
+    }
+    
+    // Check if string is too long
+    if (strlen(string) >= MAX_STRING_LEN) {
+        return -1;
+    }
+    
     index->strings[index->num_strings] = strdup(string);
     if (!index->strings[index->num_strings]) return -1;
     
@@ -181,6 +194,18 @@ void free_search_index(SearchIndex* index) {
 SearchResult* search_index(SearchIndex* index, const char* query, float cutoff, int* num_results) {
     if (!index || !query || !num_results) return NULL;
     
+    // Validate input string length
+    if (strlen(query) >= MAX_STRING_LEN) {
+        *num_results = 0;
+        return NULL;
+    }
+    
+    // Validate cutoff
+    if (cutoff < 0.0f || cutoff > 1.0f) {
+        *num_results = 0;
+        return NULL;
+    }
+    
     // Allocate temporary array for results
     SearchResult* temp_results = (SearchResult*)malloc(index->num_strings * sizeof(SearchResult));
     if (!temp_results) return NULL;
@@ -192,7 +217,16 @@ SearchResult* search_index(SearchIndex* index, const char* query, float cutoff,
         float similarity = calculate_similarity(query, index->strings[i], cutoff);
         
         if (similarity >= cutoff) {
-            temp_results[*num_results].string = index->strings[i];
+            // Store a copy of the string in the result
+            temp_results[*num_results].string = strdup(index->strings[i]);
+            if (!temp_results[*num_results].string) {
+                // Free any already allocated strings on error
+                for (int j = 0; j < *num_results; j++) {
+                    free(temp_results[j].string);
+                }
+                free(temp_results);
+                return NULL;
+            }
             temp_results[*num_results].similarity = similarity;
             (*num_results)++;
         }
@@ -204,6 +238,10 @@ SearchResult* search_index(SearchIndex* index, const char* query, float cutoff,
     // Allocate final result array with exact size
     SearchResult* results = (SearchResult*)malloc(*num_results * sizeof(SearchResult));
     if (!results) {
+        // Free all strings in temp_results
+        for (int i = 0; i < *num_results; i++) {
+            free(temp_results[i].string);
+        }
         free(temp_results);
         return NULL;
     }
@@ -217,5 +255,11 @@ SearchResult* search_index(SearchIndex* index, const char* query, float cutoff,
 
 // Free the search results
 void free_search_results(SearchResult* results, int num_results) {
+    if (!results) return;
+    
+    // Free all strings in the results
+    for (int i = 0; i < num_results; i++) {
+        free(results[i].string);
+    }
     free(results);
 } 
\ No newline at end of file
diff --git a/similarity_search.h b/similarity_search.h
index 9f12c33..613dd99 100644
--- a/similarity_search.h
+++ b/similarity_search.h
@@ -14,6 +14,7 @@ extern "C" {
 typedef struct {
     char **strings;
     int num_strings;
+    int capacity;
 } SearchIndex;
 
 // Structure to hold a search result
diff --git a/similarity_search_addon.cc b/similarity_search_addon.cc
index 6d68880..362ad84 100644
--- a/similarity_search_addon.cc
+++ b/similarity_search_addon.cc
@@ -66,7 +66,24 @@ Napi::Value SearchIndexWrapper::AddString(const Napi::CallbackInfo& info) {
   }
   
   std::string str = info[0].As<Napi::String>().Utf8Value();
+  
+  // Check if string is too long
+  if (str.length() >= MAX_STRING_LEN) {
+    Napi::Error::New(env, "String too long").ThrowAsJavaScriptException();
+    return env.Null();
+  }
+  
+  // Check if we've reached capacity
+  if (this->index_->num_strings >= this->index_->capacity) {
+    Napi::Error::New(env, "Search index capacity exceeded").ThrowAsJavaScriptException();
+    return env.Null();
+  }
+  
   int result = add_string_to_index(this->index_, str.c_str());
+  if (result != 0) {
+    Napi::Error::New(env, "Failed to add string to index").ThrowAsJavaScriptException();
+    return env.Null();
+  }
   
   return Napi::Number::New(env, result);
 }
@@ -81,10 +98,20 @@ Napi::Value SearchIndexWrapper::Search(const Napi::CallbackInfo& info) {
   }
   
   std::string query = info[0].As<Napi::String>().Utf8Value();
-  float cutoff = 0.2f; // Default cutoff
   
+  // Check if query string is too long
+  if (query.length() >= MAX_STRING_LEN) {
+    Napi::Error::New(env, "Query string too long").ThrowAsJavaScriptException();
+    return env.Null();
+  }
+  
+  float cutoff = 0.2f; // Default cutoff
   if (info.Length() > 1 && info[1].IsNumber()) {
     cutoff = info[1].As<Napi::Number>().FloatValue();
+    if (cutoff < 0.0f || cutoff > 1.0f) {
+      Napi::Error::New(env, "Cutoff must be between 0 and 1").ThrowAsJavaScriptException();
+      return env.Null();
+    }
   }
   
   int num_results = 0;