diff --git a/parser/src/grammar_builder.rs b/parser/src/grammar_builder.rs
index 8a43a457..55e214a2 100644
--- a/parser/src/grammar_builder.rs
+++ b/parser/src/grammar_builder.rs
@@ -2,7 +2,9 @@ use std::{collections::HashMap, sync::atomic::AtomicU32};
 
 use anyhow::{ensure, Result};
 
-use crate::api::{GrammarWithLexer, Node, NodeId, NodeProps, RegexSpec, TopLevelGrammar};
+use crate::api::{
+    GrammarWithLexer, Node, NodeId, NodeProps, RegexId, RegexNode, RegexSpec, TopLevelGrammar,
+};
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub struct NodeRef {
@@ -16,6 +18,7 @@ pub struct GrammarBuilder {
     strings: HashMap<String, NodeRef>,
     curr_grammar_id: u32,
     nodes: Vec<Node>,
+    rx_nodes: Vec<RegexNode>,
 }
 
 impl GrammarBuilder {
@@ -49,9 +52,16 @@ impl GrammarBuilder {
             strings: HashMap::new(),
             curr_grammar_id: 0,
             nodes: vec![],
+            rx_nodes: vec![],
         }
     }
 
+    pub fn add_regex_node(&mut self, node: RegexNode) -> RegexId {
+        let id = RegexId(self.rx_nodes.len());
+        self.rx_nodes.push(node);
+        id
+    }
+
     fn shift_nodes(&mut self) {
         if self.top_grammar.grammars.len() == 0 {
             assert!(self.nodes.is_empty(), "nodes added before add_grammar()");
@@ -62,6 +72,8 @@ impl GrammarBuilder {
                 "no nodes added before add_grammar() or finalize()"
             );
             self.top_grammar.grammars.last_mut().unwrap().nodes = nodes;
+            self.top_grammar.grammars.last_mut().unwrap().rx_nodes =
+                std::mem::take(&mut self.rx_nodes);
         }
     }
 
diff --git a/parser/src/lark/compiler.rs b/parser/src/lark/compiler.rs
new file mode 100644
index 00000000..6262be8f
--- /dev/null
+++ b/parser/src/lark/compiler.rs
@@ -0,0 +1,65 @@
+use std::collections::HashMap;
+
+use anyhow::Result;
+
+use crate::{
+    api::{RegexSpec, TopLevelGrammar},
+    GrammarBuilder, NodeRef,
+};
+
+use super::ast::*;
+
+struct Compiler {
+    builder: GrammarBuilder,
+    items: Vec<Item>,
+    nodes: HashMap<String, NodeInfo>,
+}
+
+struct NodeInfo {
+    id: NodeRef,
+    is_terminal: bool,
+    regex: Option<RegexSpec>,
+}
+
+pub fn lark_to_llguidance(items: Vec<Item>) -> Result<TopLevelGrammar> {
+    let mut c = Compiler {
+        builder: GrammarBuilder::new(),
+        items,
+        nodes: HashMap::new(),
+    };
+    c.execute()?;
+    c.builder.finalize()
+}
+
+impl Compiler {
+    fn execute(&mut self) -> Result<()> {
+        for item in self.items.iter() {
+            match item {
+                Item::Rule(rule) => {
+                    let id = self.builder.placeholder();
+                    self.nodes.insert(
+                        rule.name.clone(),
+                        NodeInfo {
+                            id,
+                            is_terminal: false,
+                            regex: None,
+                        },
+                    );
+                }
+                Item::Token(token_def) => {
+                    let id = self.builder.placeholder();
+                    self.nodes.insert(
+                        token_def.name.clone(),
+                        NodeInfo {
+                            id,
+                            is_terminal: true,
+                            regex: None,
+                        },
+                    );
+                }
+                Item::Statement(statement) => todo!(),
+            }
+        }
+        Ok(())
+    }
+}
diff --git a/parser/src/lark/mod.rs b/parser/src/lark/mod.rs
index cb8a0a4c..a1e9a1a5 100644
--- a/parser/src/lark/mod.rs
+++ b/parser/src/lark/mod.rs
@@ -1,4 +1,5 @@
 mod ast;
+mod compiler;
 mod lexer;
 mod parser;