diff --git a/cpp/rn-llama.hpp b/cpp/rn-llama.hpp
index f44cbbd..c7efc9d 100644
--- a/cpp/rn-llama.hpp
+++ b/cpp/rn-llama.hpp
@@ -5,6 +5,7 @@
 #include <iostream>
 #include "common.h"
 #include "llama.h"
+#include "grammar-parser.h"
 
 namespace rnllama {
 
@@ -141,6 +142,9 @@ struct llama_rn_context
     llama_context *ctx = nullptr;
     gpt_params params;
 
+    grammar_parser::parse_state parsed_grammar;
+    llama_grammar *grammar = nullptr;
+
     bool truncated = false;
     bool stopped_eos = false;
     bool stopped_word = false;
@@ -165,6 +169,7 @@ struct llama_rn_context
     void rewind()
     {
         params.antiprompt.clear();
+        params.grammar.clear();
         num_prompt_tokens = 0;
         num_tokens_predicted = 0;
         generated_text = "";
@@ -176,9 +181,13 @@ struct llama_rn_context
         stopped_limit = false;
         stopping_word = "";
         multibyte_pending = 0;
-
         n_remain = 0;
         n_past = 0;
+
+        if (grammar != nullptr) {
+            llama_grammar_free(grammar);
+            grammar = nullptr;
+        }
     }
 
     bool loadModel(gpt_params &params_)
@@ -196,6 +205,31 @@ struct llama_rn_context
         return true;
     }
 
+    bool loadGrammar()
+    {
+        if (!params.grammar.empty()) {
+            parsed_grammar = grammar_parser::parse(params.grammar.c_str());
+            // will be empty (default) if there are parse errors
+            if (parsed_grammar.rules.empty()) {
+                LOG_ERROR("grammar parse error, grammar: %s", params.grammar.c_str());
+                return false;
+            }
+            grammar_parser::print_grammar(stderr, parsed_grammar);
+
+            {
+                auto it = params.logit_bias.find(llama_token_eos());
+                if (it != params.logit_bias.end() && it->second == -INFINITY) {
+                    LOG_WARNING("EOS token is disabled, which will cause most grammars to fail");
+                }
+            }
+
+            std::vector<const llama_grammar_element *> grammar_rules(parsed_grammar.c_rules());
+            grammar = llama_grammar_init(
+                grammar_rules.data(), grammar_rules.size(), parsed_grammar.symbol_ids.at("root"));
+        }
+        return true;
+    }
+
     void loadPrompt()
     {
         params.prompt.insert(0, 1, ' '); // always add a first space
@@ -355,6 +389,10 @@ struct llama_rn_context
                 logits[llama_token_nl()] = nl_logit;
             }
 
+            if (grammar != nullptr) {
+                llama_sample_grammar(ctx, &candidates_p, grammar);
+            }
+
             if (temp <= 0)
             {
                 // Greedy sampling
@@ -392,6 +430,10 @@ struct llama_rn_context
                 }
             }
 
+            if (grammar != nullptr) {
+                llama_grammar_accept_token(ctx, grammar, result.tok);
+            }
+
             for (size_t i = 0; i < std::min(candidates_p.size, (size_t)n_probs); ++i)
             {
                 result.probs.push_back({candidates_p.data[i].id, candidates_p.data[i].p});
diff --git a/example/App.tsx b/example/App.tsx
index 46a870b..5ed6d6e 100644
--- a/example/App.tsx
+++ b/example/App.tsx
@@ -91,7 +91,7 @@ export default function App() {
     initLlama({
       model: file.uri,
       use_mlock: true,
-      n_gpu_layers: 1, // > 0: enable metal
+      n_gpu_layers: 0, // > 0: enable metal
     })
       .then((ctx) => {
         setContext(ctx)
diff --git a/ios/RNLlamaContext.mm b/ios/RNLlamaContext.mm
index d01f168..eca69cb 100644
--- a/ios/RNLlamaContext.mm
+++ b/ios/RNLlamaContext.mm
@@ -132,6 +132,10 @@ - (NSDictionary *)completion:(NSDictionary *)params
 
     self->llama->params.prompt = [prompt UTF8String];
 
+    if (params[@"grammar"]) {
+        self->llama->params.grammar = [params[@"grammar"] UTF8String];
+    }
+
     if (params[@"temperature"]) self->llama->params.temp = [params[@"temperature"] doubleValue];
 
     if (params[@"n_threads"]) {
@@ -188,6 +192,10 @@ - (NSDictionary *)completion:(NSDictionary *)params
             }
         }
     }
+
+    if (!self->llama->loadGrammar()) {
+        @throw [NSException exceptionWithName:@"LlamaException" reason:@"Failed to load grammar" userInfo:nil];
+    }
     
     self->llama->loadPrompt();
     self->llama->beginCompletion();
@@ -278,6 +286,9 @@ - (void)stopCompletion {
 }
 
 - (void)invalidate {
+    if (self->llama->grammar != nullptr) {
+        llama_grammar_free(self->llama->grammar);
+    }
     delete self->llama;
 
     // llama_backend_free();
diff --git a/scripts/bootstrap.sh b/scripts/bootstrap.sh
index 033004d..e09e858 100755
--- a/scripts/bootstrap.sh
+++ b/scripts/bootstrap.sh
@@ -17,6 +17,8 @@ cp ./llama.cpp/k_quants.h ./cpp/k_quants.h
 cp ./llama.cpp/k_quants.c ./cpp/k_quants.c
 cp ./llama.cpp/examples/common.h ./cpp/common.h
 cp ./llama.cpp/examples/common.cpp ./cpp/common.cpp
+cp ./llama.cpp/examples/grammar-parser.h ./cpp/grammar-parser.h
+cp ./llama.cpp/examples/grammar-parser.cpp ./cpp/grammar-parser.cpp
 
 # List of files to process
 files=(
diff --git a/src/NativeRNLlama.ts b/src/NativeRNLlama.ts
index 57d2b41..52462b1 100644
--- a/src/NativeRNLlama.ts
+++ b/src/NativeRNLlama.ts
@@ -27,6 +27,7 @@ export type NativeContextParams = {
 
 export type NativeCompletionParams = {
   prompt: string
+  grammar?: string
   stop?: Array<string> // -> antiprompt
 
   n_predict?: number