diff --git a/src/ast/compiler/analyzer.rs b/src/ast/compiler/analyzer.rs
index 31fe2d9..80032b3 100644
--- a/src/ast/compiler/analyzer.rs
+++ b/src/ast/compiler/analyzer.rs
@@ -1,5 +1,5 @@
 use crate::ast::compiler::bound_nodes::{
-    Address, AnalyzedNode, BoundKind, GlobalIdx, NodeMetrics, TypedNode,
+    Address, AnalyzedNode, BoundKind, GlobalIdx, Node, NodeMetrics, TypedNode, TypedPhase,
 };
 use crate::ast::types::Purity;
 use std::collections::{HashMap, HashSet};
@@ -318,7 +318,7 @@ impl<'a> Analyzer<'a> {
             BoundKind::Error => (BoundKind::Error, Purity::Impure),
         };
 
-        crate::ast::compiler::bound_nodes::Node {
+        Node {
             identity: node.identity.clone(),
             kind: new_kind,
             ty: NodeMetrics {
@@ -334,7 +334,7 @@ trait NodeExt {
     fn for_each_child<F: FnMut(&TypedNode)>(&self, f: F);
 }
 
-impl NodeExt for BoundKind<crate::ast::types::StaticType> {
+impl NodeExt for BoundKind<TypedPhase> {
     fn for_each_child<F: FnMut(&TypedNode)>(&self, mut f: F) {
         match self {
             BoundKind::If {
diff --git a/src/ast/compiler/binder.rs b/src/ast/compiler/binder.rs
index 69976c0..c384312 100644
--- a/src/ast/compiler/binder.rs
+++ b/src/ast/compiler/binder.rs
@@ -1,5 +1,5 @@
 use crate::ast::compiler::bound_nodes::{
-    Address, BoundKind, DeclarationKind, GlobalIdx, LocalSlot, Node, UpvalueIdx,
+    Address, BoundKind, BoundPhase, DeclarationKind, GlobalIdx, Node, UpvalueIdx, VirtualId,
 };
 use crate::ast::diagnostics::Diagnostics;
 use crate::ast::nodes::{Symbol, SyntaxKind, SyntaxNode};
@@ -9,7 +9,7 @@ use std::rc::Rc;
 
 #[derive(Debug, Clone)]
 pub struct LocalInfo {
-    pub addr: Address,
+    pub addr: Address<VirtualId>,
     pub identity: Identity,
     pub _ty: StaticType,
     pub purity: Purity,
@@ -38,7 +38,7 @@ struct FunctionCompiler {
     identity: Identity,
     scopes: Vec<CompilerScope>,
     slot_count: u32,
-    upvalues: Vec<Address>,
+    upvalues: Vec<Address<VirtualId>>,
 }
 
 impl FunctionCompiler {
@@ -65,7 +65,7 @@ impl FunctionCompiler {
         }
     }
 
-    fn define_variable(&mut self, name: &Symbol, identity: Identity) -> Result<Address, String> {
+    fn define_variable(&mut self, name: &Symbol, identity: Identity) -> Result<Address<VirtualId>, String> {
         let current_scope = self.scopes.last_mut().unwrap();
         if current_scope.locals.contains_key(name) {
             return Err(format!(
@@ -74,7 +74,7 @@ impl FunctionCompiler {
             ));
         }
 
-        let slot = LocalSlot(self.slot_count);
+        let slot = VirtualId(self.slot_count);
         current_scope.locals.insert(
             name.clone(),
             LocalInfo {
@@ -97,7 +97,7 @@ impl FunctionCompiler {
         None
     }
 
-    fn add_upvalue(&mut self, addr: Address) -> UpvalueIdx {
+    fn add_upvalue(&mut self, addr: Address<VirtualId>) -> UpvalueIdx {
         if let Some(idx) = self.upvalues.iter().position(|&a| a == addr) {
             return UpvalueIdx(idx as u32);
         }
@@ -114,7 +114,7 @@ pub enum ExprContext {
 }
 
 pub type BindingResult = (
-    Node,
+    Node<BoundPhase>,
     HashMap<Identity, Vec<Identity>>,
     Vec<CompilerScope>,
     u32,
@@ -179,7 +179,7 @@ impl Binder {
         identity: Identity,
         _kind: crate::ast::compiler::bound_nodes::DeclarationKind,
         diag: &mut Diagnostics,
-    ) -> Option<Address> {
+    ) -> Option<Address<VirtualId>> {
         let current_fn_idx = self.functions.len() - 1;
 
         if current_fn_idx == 0 {
@@ -211,7 +211,7 @@ impl Binder {
         node: &SyntaxNode,
         ctx: ExprContext,
         diag: &mut Diagnostics,
-    ) -> Node {
+    ) -> Node<BoundPhase> {
         match &node.kind {
             SyntaxKind::Nop => self.make_node(node.identity.clone(), BoundKind::Nop),
             SyntaxKind::Constant(v) => {
@@ -361,7 +361,7 @@ impl Binder {
                 let body_bound = self.bind(body.as_ref(), ExprContext::Expression, diag);
                 let compiled_fn = self.functions.pop().unwrap();
 
-                fn count_params(node: &Node) -> Option<u32> {
+                fn count_params(node: &Node<BoundPhase>) -> Option<u32> {
                     match &node.kind {
                         BoundKind::Define {
                             kind: DeclarationKind::Parameter,
@@ -520,9 +520,9 @@ impl Binder {
                 );
                 self.make_node(node.identity.clone(), BoundKind::Error)
             }
-            SyntaxKind::Error => crate::ast::compiler::bound_nodes::Node {
+            SyntaxKind::Error => Node {
                 identity: node.identity.clone(),
-                kind: crate::ast::compiler::bound_nodes::BoundKind::Error,
+                kind: BoundKind::Error,
                 ty: (),
             },
         }
@@ -533,7 +533,7 @@ impl Binder {
         sym: &Symbol,
         diag: &mut Diagnostics,
         identity: &Identity,
-    ) -> Option<Address> {
+    ) -> Option<Address<VirtualId>> {
         let current_fn_idx = self.functions.len() - 1;
 
         // 1. Try local in current function
@@ -603,7 +603,7 @@ impl Binder {
         node: &SyntaxNode,
         kind: DeclarationKind,
         diag: &mut Diagnostics,
-    ) -> Node {
+    ) -> Node<BoundPhase> {
         match &node.kind {
             SyntaxKind::Identifier(sym) => {
                 if let Some(addr) = self.declare_variable(sym, node.identity.clone(), kind, diag) {
@@ -647,7 +647,7 @@ impl Binder {
         &mut self,
         node: &SyntaxNode,
         diag: &mut Diagnostics,
-    ) -> Node {
+    ) -> Node<BoundPhase> {
         match &node.kind {
             SyntaxKind::Identifier(sym) => {
                 if let Some(addr) = self.resolve_variable(sym, diag, &node.identity) {
@@ -684,7 +684,7 @@ impl Binder {
         }
     }
 
-    fn make_node(&self, identity: Identity, kind: BoundKind<()>) -> Node {
+    fn make_node(&self, identity: Identity, kind: BoundKind<BoundPhase>) -> Node<BoundPhase> {
         Node {
             identity,
             kind,
diff --git a/src/ast/compiler/bound_nodes.rs b/src/ast/compiler/bound_nodes.rs
index 96edba9..2c8eeb1 100644
--- a/src/ast/compiler/bound_nodes.rs
+++ b/src/ast/compiler/bound_nodes.rs
@@ -3,11 +3,20 @@ use crate::ast::types::{Identity, StaticType, Value};
 use std::rc::Rc;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct LocalSlot(pub u32);
+pub struct VirtualId(pub u32);
 
-impl std::fmt::Display for LocalSlot {
+impl std::fmt::Display for VirtualId {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "L{}", self.0)
+        write!(f, "V{}", self.0)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct StackOffset(pub u32);
+
+impl std::fmt::Display for StackOffset {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "S{}", self.0)
     }
 }
 
@@ -29,46 +38,84 @@ impl std::fmt::Display for GlobalIdx {
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub enum Address {
-    Local(LocalSlot),    // Stack-Slot index (relative to frame base)
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub enum Address<L> {
+    Local(L),            // Local address (VirtualId or StackOffset)
     Upvalue(UpvalueIdx), // Index in the closure's upvalue array
     Global(GlobalIdx),   // Index in the global environment vector
 }
 
+impl<L: Clone> Clone for Address<L> {
+    fn clone(&self) -> Self {
+        match self {
+            Address::Local(l) => Address::Local(l.clone()),
+            Address::Upvalue(u) => Address::Upvalue(*u),
+            Address::Global(g) => Address::Global(*g),
+        }
+    }
+}
+
+impl<L: Copy> Copy for Address<L> {}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum DeclarationKind {
     Variable,
     Parameter,
 }
 
-/// Trait for DSL-specific AST extensions (like Pipe, Series-Access, etc.)
-pub trait BoundExtension<T>: std::fmt::Debug {
-    fn clone_box(&self) -> Box<dyn BoundExtension<T>>;
-    fn display_name(&self) -> String;
+pub trait CompilerPhase: std::fmt::Debug + 'static {
+    type Metadata: std::fmt::Debug + Clone + PartialEq;
+    type LocalAddress: std::fmt::Debug + Clone + Copy + PartialEq + Eq + std::hash::Hash;
 }
 
-impl<T> Clone for Box<dyn BoundExtension<T>> {
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct BoundPhase;
+impl CompilerPhase for BoundPhase {
+    type Metadata = ();
+    type LocalAddress = VirtualId;
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TypedPhase;
+impl CompilerPhase for TypedPhase {
+    type Metadata = StaticType;
+    type LocalAddress = VirtualId;
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct AnalyzedPhase;
+impl CompilerPhase for AnalyzedPhase {
+    type Metadata = NodeMetrics;
+    type LocalAddress = VirtualId;
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RuntimePhase;
+impl CompilerPhase for RuntimePhase {
+    type Metadata = RuntimeMetadata;
+    type LocalAddress = StackOffset;
+}
+
+/// A bound AST node, decorated with phase-specific information P.
+#[derive(Debug, PartialEq)]
+pub struct Node<P: CompilerPhase = BoundPhase> {
+    pub identity: Identity,
+    pub kind: BoundKind<P>,
+    pub ty: P::Metadata,
+}
+
+impl<P: CompilerPhase> Clone for Node<P> {
     fn clone(&self) -> Self {
-        self.clone_box()
+        Self {
+            identity: self.identity.clone(),
+            kind: self.kind.clone(),
+            ty: self.ty.clone(),
+        }
     }
 }
 
-/// A bound AST node, decorated with type or metric information T.
-#[derive(Debug, Clone, PartialEq)]
-pub struct Node<T = ()> {
-    pub identity: Identity,
-    pub kind: BoundKind<T>,
-    pub ty: T,
-}
+pub type TypedNode = Node<TypedPhase>;
 
-/// Type alias for a node that has been fully type-checked.
-pub type TypedNode = Node<StaticType>;
-
-/// Type alias for the global function registry.
-pub type GlobalFunctionRegistry = std::collections::HashMap<GlobalIdx, Rc<Node>>;
-
-/// Metrics collected during the analysis phase.
 #[derive(Debug, Clone, PartialEq)]
 pub struct NodeMetrics {
     pub original: Rc<TypedNode>,
@@ -76,114 +123,144 @@ pub struct NodeMetrics {
     pub is_recursive: bool,
 }
 
-/// Type alias for a node that has been analyzed.
-pub type AnalyzedNode = Node<NodeMetrics>;
+pub type AnalyzedNode = Node<AnalyzedPhase>;
 
-/// Type alias for the global analyzed function registry.
+#[derive(Clone)]
+pub struct RuntimeMetadata {
+    pub ty: StaticType,
+    pub is_tail: bool,
+    pub original: Rc<AnalyzedNode>,
+    pub stack_size: u32,
+}
+
+impl std::fmt::Debug for RuntimeMetadata {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Metadata")
+            .field("ty", &self.ty)
+            .field("is_tail", &self.is_tail)
+            .field("stack_size", &self.stack_size)
+            .finish()
+    }
+}
+
+impl PartialEq for RuntimeMetadata {
+    fn eq(&self, other: &Self) -> bool {
+        self.ty == other.ty && self.is_tail == other.is_tail && Rc::ptr_eq(&self.original, &other.original) && self.stack_size == other.stack_size
+    }
+}
+
+pub type ExecNode = Node<RuntimePhase>;
+
+pub type GlobalFunctionRegistry = std::collections::HashMap<GlobalIdx, Rc<Node<BoundPhase>>>;
 pub type GlobalAnalyzedRegistry = std::collections::HashMap<GlobalIdx, Rc<AnalyzedNode>>;
 
-#[derive(Debug, Clone)]
-pub enum BoundKind<T = ()> {
+pub trait BoundExtension<P: CompilerPhase>: std::fmt::Debug {
+    fn clone_box(&self) -> Box<dyn BoundExtension<P>>;
+    fn display_name(&self) -> String;
+}
+
+impl<P: CompilerPhase> Clone for Box<dyn BoundExtension<P>> {
+    fn clone(&self) -> Self {
+        self.clone_box()
+    }
+}
+
+#[derive(Debug)]
+pub enum BoundKind<P: CompilerPhase = BoundPhase> {
     Nop,
     Constant(Value),
-
-    // Variable Access (Resolved)
     Get {
-        addr: Address,
+        addr: Address<P::LocalAddress>,
         name: Symbol,
     },
-
-    // Variable Update (Assignment)
     Set {
-        addr: Address,
-        value: Rc<Node<T>>,
+        addr: Address<P::LocalAddress>,
+        value: Rc<Node<P>>,
     },
-
-    // Variable Declaration (Unified for Local/Global/Parameter)
     Define {
         name: Symbol,
-        addr: Address,
+        addr: Address<P::LocalAddress>,
         kind: DeclarationKind,
-        value: Rc<Node<T>>,
+        value: Rc<Node<P>>,
         captured_by: Vec<Identity>,
     },
-
-    /// A first-class field accessor (e.g. .name)
     FieldAccessor(crate::ast::types::Keyword),
-
-    /// Specialized field access (O(1) via RecordLayout)
     GetField {
-        rec: Rc<Node<T>>,
+        rec: Rc<Node<P>>,
         field: crate::ast::types::Keyword,
     },
-
     If {
-        cond: Rc<Node<T>>,
-        then_br: Rc<Node<T>>,
-        else_br: Option<Rc<Node<T>>>,
+        cond: Rc<Node<P>>,
+        then_br: Rc<Node<P>>,
+        else_br: Option<Rc<Node<P>>>,
     },
-
-    /// A destructuring operation (can be a definition or an assignment depending on the pattern)
     Destructure {
-        pattern: Rc<Node<T>>,
-        value: Rc<Node<T>>,
+        pattern: Rc<Node<P>>,
+        value: Rc<Node<P>>,
     },
-
     Lambda {
-        params: Rc<Node<T>>,
-        // The list of variables captured from enclosing scopes
-        upvalues: Vec<Address>,
-        body: Rc<Node<T>>,
-        /// Static optimization: number of positional parameters if the pattern is flat.
+        params: Rc<Node<P>>,
+        upvalues: Vec<Address<P::LocalAddress>>,
+        body: Rc<Node<P>>,
         positional_count: Option<u32>,
     },
-
     Call {
-        callee: Rc<Node<T>>,
-        args: Rc<Node<T>>,
+        callee: Rc<Node<P>>,
+        args: Rc<Node<P>>,
     },
-
     Again {
-        args: Rc<Node<T>>,
+        args: Rc<Node<P>>,
     },
-
     Pipe {
-        inputs: Vec<Rc<Node<T>>>,
-        lambda: Rc<Node<T>>,
+        inputs: Vec<Rc<Node<P>>>,
+        lambda: Rc<Node<P>>,
         out_type: crate::ast::types::StaticType,
     },
     Block {
-        exprs: Vec<Rc<Node<T>>>,
+        exprs: Vec<Rc<Node<P>>>,
     },
-
     Tuple {
-        elements: Vec<Rc<Node<T>>>,
+        elements: Vec<Rc<Node<P>>>,
     },
-
     Record {
         layout: std::sync::Arc<crate::ast::types::RecordLayout>,
-        values: Vec<Rc<Node<T>>>,
+        values: Vec<Rc<Node<P>>>,
     },
-
-    /// An expanded macro call, preserving the original call for debugging and UI.
     Expansion {
-        /// The original call from the syntax AST.
         original_call: Rc<crate::ast::nodes::SyntaxNode>,
-        /// The result of binding the expanded AST.
-        bound_expanded: Rc<Node<T>>,
+        bound_expanded: Rc<Node<P>>,
     },
-
-    /// A diagnostic poison node, allowing compilation to continue after an error.
     Error,
-
-    /// DSL-specific extension slot
-    Extension(Box<dyn BoundExtension<T>>),
+    Extension(Box<dyn BoundExtension<P>>),
 }
 
-impl<T> PartialEq for BoundKind<T>
-where
-    T: PartialEq,
-{
+impl<P: CompilerPhase> Clone for BoundKind<P> {
+    fn clone(&self) -> Self {
+        match self {
+            BoundKind::Nop => BoundKind::Nop,
+            BoundKind::Constant(v) => BoundKind::Constant(v.clone()),
+            BoundKind::Get { addr, name } => BoundKind::Get { addr: addr.clone(), name: name.clone() },
+            BoundKind::Set { addr, value } => BoundKind::Set { addr: addr.clone(), value: value.clone() },
+            BoundKind::Define { name, addr, kind, value, captured_by } => BoundKind::Define { name: name.clone(), addr: addr.clone(), kind: *kind, value: value.clone(), captured_by: captured_by.clone() },
+            BoundKind::FieldAccessor(k) => BoundKind::FieldAccessor(k.clone()),
+            BoundKind::GetField { rec, field } => BoundKind::GetField { rec: rec.clone(), field: field.clone() },
+            BoundKind::If { cond, then_br, else_br } => BoundKind::If { cond: cond.clone(), then_br: then_br.clone(), else_br: else_br.clone() },
+            BoundKind::Destructure { pattern, value } => BoundKind::Destructure { pattern: pattern.clone(), value: value.clone() },
+            BoundKind::Lambda { params, upvalues, body, positional_count } => BoundKind::Lambda { params: params.clone(), upvalues: upvalues.clone(), body: body.clone(), positional_count: *positional_count },
+            BoundKind::Call { callee, args } => BoundKind::Call { callee: callee.clone(), args: args.clone() },
+            BoundKind::Again { args } => BoundKind::Again { args: args.clone() },
+            BoundKind::Pipe { inputs, lambda, out_type } => BoundKind::Pipe { inputs: inputs.clone(), lambda: lambda.clone(), out_type: out_type.clone() },
+            BoundKind::Block { exprs } => BoundKind::Block { exprs: exprs.clone() },
+            BoundKind::Tuple { elements } => BoundKind::Tuple { elements: elements.clone() },
+            BoundKind::Record { layout, values } => BoundKind::Record { layout: layout.clone(), values: values.clone() },
+            BoundKind::Expansion { original_call, bound_expanded } => BoundKind::Expansion { original_call: original_call.clone(), bound_expanded: bound_expanded.clone() },
+            BoundKind::Error => BoundKind::Error,
+            BoundKind::Extension(ext) => BoundKind::Extension(ext.clone()),
+        }
+    }
+}
+
+impl<P: CompilerPhase> PartialEq for BoundKind<P> {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {
             (BoundKind::Nop, BoundKind::Nop) => true,
@@ -191,87 +268,32 @@ where
             (BoundKind::Get { addr: aa, name: na }, BoundKind::Get { addr: ab, name: nb }) => {
                 aa == ab && na == nb
             }
-            (
-                BoundKind::Set {
-                    addr: aa,
-                    value: va,
-                },
-                BoundKind::Set {
-                    addr: ab,
-                    value: vb,
-                },
-            ) => aa == ab && Rc::ptr_eq(va, vb),
-            (
-                BoundKind::Define {
-                    name: na,
-                    addr: aa,
-                    kind: ka,
-                    value: va,
-                    captured_by: ca,
-                },
-                BoundKind::Define {
-                    name: nb,
-                    addr: ab,
-                    kind: kb,
-                    value: vb,
-                    captured_by: cb,
-                },
-            ) => na == nb && aa == ab && ka == kb && Rc::ptr_eq(va, vb) && ca == cb,
+            (BoundKind::Set { addr: aa, value: va }, BoundKind::Set { addr: ab, value: vb }) => {
+                aa == ab && Rc::ptr_eq(va, vb)
+            }
+            (BoundKind::Define { name: na, addr: aa, kind: ka, value: va, captured_by: ca }, BoundKind::Define { name: nb, addr: ab, kind: kb, value: vb, captured_by: cb }) => {
+                na == nb && aa == ab && ka == kb && Rc::ptr_eq(va, vb) && ca == cb
+            }
             (BoundKind::FieldAccessor(a), BoundKind::FieldAccessor(b)) => a == b,
-            (
-                BoundKind::GetField { rec: ra, field: fa },
-                BoundKind::GetField { rec: rb, field: fb },
-            ) => Rc::ptr_eq(ra, rb) && fa == fb,
-            (
-                BoundKind::If {
-                    cond: ca,
-                    then_br: ta,
-                    else_br: ea,
-                },
-                BoundKind::If {
-                    cond: cb,
-                    then_br: tb,
-                    else_br: eb,
-                },
-            ) => Rc::ptr_eq(ca, cb) && Rc::ptr_eq(ta, tb) && match (ea, eb) {
-                (Some(a), Some(b)) => Rc::ptr_eq(a, b),
-                (None, None) => true,
-                _ => false,
-            },
-            (
-                BoundKind::Destructure {
-                    pattern: pa,
-                    value: va,
-                },
-                BoundKind::Destructure {
-                    pattern: pb,
-                    value: vb,
-                },
-            ) => Rc::ptr_eq(pa, pb) && Rc::ptr_eq(va, vb),
-            (
-                BoundKind::Lambda {
-                    params: pa,
-                    upvalues: ua,
-                    body: ba,
-                    positional_count: pca,
-                },
-                BoundKind::Lambda {
-                    params: pb,
-                    upvalues: ub,
-                    body: bb,
-                    positional_count: pcb,
-                },
-            ) => Rc::ptr_eq(pa, pb) && ua == ub && Rc::ptr_eq(ba, bb) && pca == pcb,
-            (
-                BoundKind::Call {
-                    callee: ca,
-                    args: aa,
-                },
-                BoundKind::Call {
-                    callee: cb,
-                    args: ab,
-                },
-            ) => Rc::ptr_eq(ca, cb) && Rc::ptr_eq(aa, ab),
+            (BoundKind::GetField { rec: ra, field: fa }, BoundKind::GetField { rec: rb, field: fb }) => {
+                Rc::ptr_eq(ra, rb) && fa == fb
+            }
+            (BoundKind::If { cond: ca, then_br: ta, else_br: ea }, BoundKind::If { cond: cb, then_br: tb, else_br: eb }) => {
+                Rc::ptr_eq(ca, cb) && Rc::ptr_eq(ta, tb) && match (ea, eb) {
+                    (Some(a), Some(b)) => Rc::ptr_eq(a, b),
+                    (None, None) => true,
+                    _ => false,
+                }
+            }
+            (BoundKind::Destructure { pattern: pa, value: va }, BoundKind::Destructure { pattern: pb, value: vb }) => {
+                Rc::ptr_eq(pa, pb) && Rc::ptr_eq(va, vb)
+            }
+            (BoundKind::Lambda { params: pa, upvalues: ua, body: ba, positional_count: pca }, BoundKind::Lambda { params: pb, upvalues: ub, body: bb, positional_count: pcb }) => {
+                Rc::ptr_eq(pa, pb) && ua == ub && Rc::ptr_eq(ba, bb) && pca == pcb
+            }
+            (BoundKind::Call { callee: ca, args: aa }, BoundKind::Call { callee: cb, args: ab }) => {
+                Rc::ptr_eq(ca, cb) && Rc::ptr_eq(aa, ab)
+            }
             (BoundKind::Again { args: aa }, BoundKind::Again { args: ab }) => Rc::ptr_eq(aa, ab),
             (BoundKind::Block { exprs: ea }, BoundKind::Block { exprs: eb }) => {
                 ea.len() == eb.len() && ea.iter().zip(eb.iter()).all(|(a, b)| Rc::ptr_eq(a, b))
@@ -279,46 +301,26 @@ where
             (BoundKind::Tuple { elements: ea }, BoundKind::Tuple { elements: eb }) => {
                 ea.len() == eb.len() && ea.iter().zip(eb.iter()).all(|(a, b)| Rc::ptr_eq(a, b))
             }
-            (
-                BoundKind::Record {
-                    layout: la,
-                    values: va,
-                },
-                BoundKind::Record {
-                    layout: lb,
-                    values: vb,
-                },
-            ) => std::sync::Arc::ptr_eq(la, lb) && va.len() == vb.len() && va.iter().zip(vb.iter()).all(|(a, b)| Rc::ptr_eq(a, b)),
-            (
-                BoundKind::Expansion {
-                    original_call: ca,
-                    bound_expanded: ea,
-                },
-                BoundKind::Expansion {
-                    original_call: cb,
-                    bound_expanded: eb,
-                },
-            ) => Rc::ptr_eq(ca, cb) && Rc::ptr_eq(ea, eb),
+            (BoundKind::Record { layout: la, values: va }, BoundKind::Record { layout: lb, values: vb }) => {
+                std::sync::Arc::ptr_eq(la, lb) && va.len() == vb.len() && va.iter().zip(vb.iter()).all(|(a, b)| Rc::ptr_eq(a, b))
+            }
+            (BoundKind::Expansion { original_call: ca, bound_expanded: ea }, BoundKind::Expansion { original_call: cb, bound_expanded: eb }) => {
+                Rc::ptr_eq(ca, cb) && Rc::ptr_eq(ea, eb)
+            }
             (BoundKind::Error, BoundKind::Error) => true,
-            (BoundKind::Extension(_), BoundKind::Extension(_)) => false,
             _ => false,
         }
     }
 }
 
-/// A single field in a Record literal (Key-Value pair)
-pub type RecordField<T> = (Node<T>, Node<T>);
-
-impl<T> BoundKind<T> {
+impl<P: CompilerPhase> BoundKind<P> {
     pub fn display_name(&self) -> String {
         match self {
             BoundKind::Nop => "NOP".to_string(),
             BoundKind::Constant(v) => format!("CONST({})", v),
             BoundKind::Get { addr, name } => format!("GET({}, {:?})", name.name, addr),
             BoundKind::Set { addr, .. } => format!("SET({:?})", addr),
-            BoundKind::Define {
-                name, addr, kind, ..
-            } => {
+            BoundKind::Define { name, addr, kind, .. } => {
                 let k_str = match kind {
                     DeclarationKind::Variable => "VAR",
                     DeclarationKind::Parameter => "PARAM",
@@ -329,9 +331,7 @@ impl<T> BoundKind<T> {
             BoundKind::GetField { field, .. } => format!("GET_FIELD(.{})", field.name()),
             BoundKind::If { .. } => "IF".to_string(),
             BoundKind::Destructure { .. } => "DESTRUCTURE".to_string(),
-            BoundKind::Lambda {
-                params, upvalues, ..
-            } => {
+            BoundKind::Lambda { params, upvalues, .. } => {
                 let p_str = match &params.kind {
                     BoundKind::Tuple { elements } => format!("p:{}", elements.len()),
                     _ => "p:1".to_string(),
diff --git a/src/ast/compiler/captures.rs b/src/ast/compiler/captures.rs
index 57e8997..ed8eedb 100644
--- a/src/ast/compiler/captures.rs
+++ b/src/ast/compiler/captures.rs
@@ -1,67 +1,34 @@
-use crate::ast::compiler::bound_nodes::{BoundKind, Node};
+use crate::ast::compiler::bound_nodes::{BoundKind, CompilerPhase, Node};
 use crate::ast::types::Identity;
 use std::collections::HashMap;
+use std::rc::Rc;
 
 pub struct CapturePass;
 
 impl CapturePass {
-    pub fn apply<T: Clone>(node: Node<T>, capture_map: &HashMap<Identity, Vec<Identity>>) -> Node<T> {
+    pub fn apply<P: CompilerPhase>(node: Node<P>, capture_map: &HashMap<Identity, Vec<Identity>>) -> Node<P> {
         Self::transform(node, capture_map)
     }
 
-    fn transform<T: Clone>(mut node: Node<T>, capture_map: &HashMap<Identity, Vec<Identity>>) -> Node<T> {
-        use std::rc::Rc;
-        match node.kind {
+    fn transform<P: CompilerPhase>(mut node: Node<P>, capture_map: &HashMap<Identity, Vec<Identity>>) -> Node<P> {
+        node.kind = match node.kind {
             BoundKind::Define {
                 name,
                 addr,
                 kind,
                 value,
-                ..
+                mut captured_by,
             } => {
-                let captured_by = capture_map.get(&node.identity).cloned().unwrap_or_default();
-                node.kind = BoundKind::Define {
+                if let Some(capturers) = capture_map.get(&node.identity) {
+                    captured_by.extend(capturers.iter().cloned());
+                }
+                BoundKind::Define {
                     name,
                     addr,
                     kind,
                     value: Rc::new(Self::transform(value.as_ref().clone(), capture_map)),
                     captured_by,
-                };
-            }
-
-            BoundKind::If {
-                cond,
-                then_br,
-                else_br,
-            } => {
-                node.kind = BoundKind::If {
-                    cond: Rc::new(Self::transform(cond.as_ref().clone(), capture_map)),
-                    then_br: Rc::new(Self::transform(then_br.as_ref().clone(), capture_map)),
-                    else_br: else_br.map(|e| Rc::new(Self::transform(e.as_ref().clone(), capture_map))),
-                };
-            }
-
-            BoundKind::Set { addr, value } => {
-                node.kind = BoundKind::Set {
-                    addr,
-                    value: Rc::new(Self::transform(value.as_ref().clone(), capture_map)),
-                };
-            }
-
-            BoundKind::FieldAccessor(_) => {}
-
-            BoundKind::GetField { rec, field } => {
-                node.kind = BoundKind::GetField {
-                    rec: Rc::new(Self::transform(rec.as_ref().clone(), capture_map)),
-                    field,
-                };
-            }
-
-            BoundKind::Destructure { pattern, value } => {
-                node.kind = BoundKind::Destructure {
-                    pattern: Rc::new(Self::transform(pattern.as_ref().clone(), capture_map)),
-                    value: Rc::new(Self::transform(value.as_ref().clone(), capture_map)),
-                };
+                }
             }
 
             BoundKind::Lambda {
@@ -69,27 +36,38 @@ impl CapturePass {
                 upvalues,
                 body,
                 positional_count,
-            } => {
-                node.kind = BoundKind::Lambda {
-                    params: Rc::new(Self::transform(params.as_ref().clone(), capture_map)),
-                    upvalues,
-                    body: Rc::new(Self::transform(body.as_ref().clone(), capture_map)),
-                    positional_count,
-                };
-            }
+            } => BoundKind::Lambda {
+                params: Rc::new(Self::transform(params.as_ref().clone(), capture_map)),
+                upvalues,
+                body: Rc::new(Self::transform(body.as_ref().clone(), capture_map)),
+                positional_count,
+            },
 
-            BoundKind::Call { callee, args } => {
-                node.kind = BoundKind::Call {
-                    callee: Rc::new(Self::transform(callee.as_ref().clone(), capture_map)),
-                    args: Rc::new(Self::transform(args.as_ref().clone(), capture_map)),
-                };
-            }
+            BoundKind::Call { callee, args } => BoundKind::Call {
+                callee: Rc::new(Self::transform(callee.as_ref().clone(), capture_map)),
+                args: Rc::new(Self::transform(args.as_ref().clone(), capture_map)),
+            },
+
+            BoundKind::Again { args } => BoundKind::Again {
+                args: Rc::new(Self::transform(args.as_ref().clone(), capture_map)),
+            },
+
+            BoundKind::If {
+                cond,
+                then_br,
+                else_br,
+            } => BoundKind::If {
+                cond: Rc::new(Self::transform(cond.as_ref().clone(), capture_map)),
+                then_br: Rc::new(Self::transform(then_br.as_ref().clone(), capture_map)),
+                else_br: else_br
+                    .map(|e| Rc::new(Self::transform(e.as_ref().clone(), capture_map))),
+            },
+
+            BoundKind::Destructure { pattern, value } => BoundKind::Destructure {
+                pattern: Rc::new(Self::transform(pattern.as_ref().clone(), capture_map)),
+                value: Rc::new(Self::transform(value.as_ref().clone(), capture_map)),
+            },
 
-            BoundKind::Again { args } => {
-                node.kind = BoundKind::Again {
-                    args: Rc::new(Self::transform(args.as_ref().clone(), capture_map)),
-                };
-            }
             BoundKind::Pipe {
                 inputs,
                 lambda,
@@ -99,56 +77,53 @@ impl CapturePass {
                 for input in inputs {
                     t_inputs.push(Rc::new(Self::transform(input.as_ref().clone(), capture_map)));
                 }
-                node.kind = BoundKind::Pipe {
+                BoundKind::Pipe {
                     inputs: t_inputs,
                     lambda: Rc::new(Self::transform(lambda.as_ref().clone(), capture_map)),
-                    out_type: out_type.clone(),
-                };
-            }
-            BoundKind::Block { exprs } => {
-                node.kind = BoundKind::Block {
-                    exprs: exprs
-                        .into_iter()
-                        .map(|e| Rc::new(Self::transform(e.as_ref().clone(), capture_map)))
-                        .collect(),
-                };
+                    out_type,
+                }
             }
 
-            BoundKind::Tuple { elements } => {
-                node.kind = BoundKind::Tuple {
-                    elements: elements
-                        .into_iter()
-                        .map(|e| Rc::new(Self::transform(e.as_ref().clone(), capture_map)))
-                        .collect(),
-                };
-            }
+            BoundKind::Block { exprs } => BoundKind::Block {
+                exprs: exprs
+                    .into_iter()
+                    .map(|e| Rc::new(Self::transform(e.as_ref().clone(), capture_map)))
+                    .collect(),
+            },
 
-            BoundKind::Record { layout, values } => {
-                node.kind = BoundKind::Record {
-                    layout,
-                    values: values
-                        .into_iter()
-                        .map(|v| Rc::new(Self::transform(v.as_ref().clone(), capture_map)))
-                        .collect(),
-                };
-            }
+            BoundKind::Tuple { elements } => BoundKind::Tuple {
+                elements: elements
+                    .into_iter()
+                    .map(|e| Rc::new(Self::transform(e.as_ref().clone(), capture_map)))
+                    .collect(),
+            },
+
+            BoundKind::Record { layout, values } => BoundKind::Record {
+                layout,
+                values: values
+                    .into_iter()
+                    .map(|v| Rc::new(Self::transform(v.as_ref().clone(), capture_map)))
+                    .collect(),
+            },
 
             BoundKind::Expansion {
                 original_call,
                 bound_expanded,
-            } => {
-                node.kind = BoundKind::Expansion {
-                    original_call,
-                    bound_expanded: Rc::new(Self::transform(bound_expanded.as_ref().clone(), capture_map)),
-                };
-            }
+            } => BoundKind::Expansion {
+                original_call,
+                bound_expanded: Rc::new(Self::transform(
+                    bound_expanded.as_ref().clone(),
+                    capture_map,
+                )),
+            },
 
-            BoundKind::Nop
-            | BoundKind::Constant(_)
-            | BoundKind::Get { .. }
-            | BoundKind::Extension(_)
-            | BoundKind::Error => {}
-        }
+            BoundKind::GetField { rec, field } => BoundKind::GetField {
+                rec: Rc::new(Self::transform(rec.as_ref().clone(), capture_map)),
+                field,
+            },
+
+            other => other,
+        };
         node
     }
 }
diff --git a/src/ast/compiler/dumper.rs b/src/ast/compiler/dumper.rs
index 22641d9..d862097 100644
--- a/src/ast/compiler/dumper.rs
+++ b/src/ast/compiler/dumper.rs
@@ -1,5 +1,4 @@
-use crate::ast::compiler::bound_nodes::{BoundKind, Node};
-use std::fmt::Debug;
+use crate::ast::compiler::bound_nodes::{BoundKind, CompilerPhase, Node};
 
 /// Human-readable AST dumper for the bound AST.
 pub struct Dumper {
@@ -9,7 +8,7 @@ pub struct Dumper {
 
 impl Dumper {
     /// Produces a formatted string representation of the given bound AST node and its children.
-    pub fn dump<T: Debug>(node: &Node<T>) -> String {
+    pub fn dump<P: CompilerPhase>(node: &Node<P>) -> String {
         let mut dumper = Self {
             output: String::new(),
             indent: 0,
@@ -24,14 +23,14 @@ impl Dumper {
         }
     }
 
-    fn log<T: Debug>(&mut self, label: &str, node: &Node<T>) {
+    fn log<P: CompilerPhase>(&mut self, label: &str, node: &Node<P>) {
         self.write_indent();
         self.output.push_str(label);
         self.output
             .push_str(&format!(" <Metadata: {:?}>\n", node.ty));
     }
 
-    fn visit<T: Debug>(&mut self, node: &Node<T>) {
+    fn visit<P: CompilerPhase>(&mut self, node: &Node<P>) {
         match &node.kind {
             BoundKind::Nop => self.log("Nop", node),
             BoundKind::Constant(v) => {
diff --git a/src/ast/compiler/lambda_collector.rs b/src/ast/compiler/lambda_collector.rs
index ea8c065..85dd565 100644
--- a/src/ast/compiler/lambda_collector.rs
+++ b/src/ast/compiler/lambda_collector.rs
@@ -1,21 +1,21 @@
-use crate::ast::compiler::bound_nodes::{Address, BoundKind, GlobalIdx, Node};
+use crate::ast::compiler::bound_nodes::{Address, BoundKind, CompilerPhase, GlobalIdx, Node};
 use std::collections::HashMap;
 use std::rc::Rc;
 
 /// A pass that collects all global function definitions (lambdas) into a registry.
 /// This allows the Specializer to retrieve the original AST of a function for monomorphization.
-pub struct LambdaCollector<'a, T> {
-    registry: &'a mut HashMap<GlobalIdx, Rc<Node<T>>>,
+pub struct LambdaCollector<'a, P: CompilerPhase> {
+    registry: &'a mut HashMap<GlobalIdx, Rc<Node<P>>>,
 }
 
-impl<'a, T: Clone> LambdaCollector<'a, T> {
+impl<'a, P: CompilerPhase> LambdaCollector<'a, P> {
     /// Performs a full traversal of the AST and populates the provided registry.
-    pub fn collect(node: &Node<T>, registry: &'a mut HashMap<GlobalIdx, Rc<Node<T>>>) {
+    pub fn collect(node: &Node<P>, registry: &'a mut HashMap<GlobalIdx, Rc<Node<P>>>) {
         let mut collector = Self { registry };
         collector.visit(node);
     }
 
-    fn visit(&mut self, node: &Node<T>) {
+    fn visit(&mut self, node: &Node<P>) {
         match &node.kind {
             BoundKind::Block { exprs } => {
                 for expr in exprs {
diff --git a/src/ast/compiler/lowering.rs b/src/ast/compiler/lowering.rs
index 3588707..1b0155b 100644
--- a/src/ast/compiler/lowering.rs
+++ b/src/ast/compiler/lowering.rs
@@ -1,31 +1,7 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, LocalSlot, Node};
-use crate::ast::types::StaticType;
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, ExecNode, Node, RuntimeMetadata, StackOffset, VirtualId};
 use std::collections::HashMap;
-use std::fmt::Debug;
 use std::rc::Rc;
 
-#[derive(Clone)]
-pub struct RuntimeMetadata {
-    pub ty: StaticType,
-    pub is_tail: bool,
-    /// The analyzed node, containing metrics and a link to the original TypedNode.
-    pub original: Rc<AnalyzedNode>,
-    pub stack_size: u32,
-}
-
-impl Debug for RuntimeMetadata {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("Metadata")
-            .field("ty", &self.ty)
-            .field("is_tail", &self.is_tail)
-            .field("stack_size", &self.stack_size)
-            .finish()
-    }
-}
-
-/// The ExecNode is the AST used by the VM. It carries TCO flags and links to metrics.
-pub type ExecNode = Node<RuntimeMetadata>;
-
 struct StackAllocator {
     mapping: HashMap<u32, u32>,
     next_slot: u32,
@@ -39,19 +15,20 @@ impl StackAllocator {
         }
     }
 
-    fn map_slot(&mut self, slot: LocalSlot) -> LocalSlot {
+    fn map_slot(&mut self, slot: VirtualId) -> StackOffset {
         let entry = self.mapping.entry(slot.0).or_insert_with(|| {
             let s = self.next_slot;
             self.next_slot += 1;
             s
         });
-        LocalSlot(*entry)
+        StackOffset(*entry)
     }
 
-    fn map_address(&mut self, addr: Address) -> Address {
+    fn map_address(&mut self, addr: Address<VirtualId>) -> Address<StackOffset> {
         match addr {
             Address::Local(slot) => Address::Local(self.map_slot(slot)),
-            other => other,
+            Address::Upvalue(idx) => Address::Upvalue(idx),
+            Address::Global(idx) => Address::Global(idx),
         }
     }
 }
diff --git a/src/ast/compiler/macros.rs b/src/ast/compiler/macros.rs
index 8c69ed4..eeec12b 100644
--- a/src/ast/compiler/macros.rs
+++ b/src/ast/compiler/macros.rs
@@ -769,7 +769,7 @@ mod tests {
         locals.insert(
             Symbol::from("*"),
             crate::ast::compiler::binder::LocalInfo {
-                addr: Address::Local(crate::ast::compiler::bound_nodes::LocalSlot(0)),
+                addr: Address::Local(crate::ast::compiler::bound_nodes::VirtualId(0)),
                 identity: crate::ast::types::NodeIdentity::new(crate::ast::types::SourceLocation {
                     line: 0,
                     col: 0,
diff --git a/src/ast/compiler/optimizer/inliner.rs b/src/ast/compiler/optimizer/inliner.rs
index acafde6..fbc1a26 100644
--- a/src/ast/compiler/optimizer/inliner.rs
+++ b/src/ast/compiler/optimizer/inliner.rs
@@ -1,4 +1,4 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, LocalSlot};
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, VirtualId};
 use crate::ast::types::{Purity, Value};
 use crate::ast::vm::Closure;
 use std::cell::RefCell;
@@ -24,7 +24,7 @@ impl<'a> Inliner<'a> {
         }
     }
 
-    pub fn is_inlinable_value(&self, val: &Value, addr: Address) -> bool {
+    pub fn is_inlinable_value(&self, val: &Value, addr: Address<VirtualId>) -> bool {
         let type_ok = match val {
             Value::Int(_)
             | Value::Float(_)
@@ -141,7 +141,7 @@ impl<'a> Inliner<'a> {
         }
     }
 
-    pub fn collect_parameter_slots_set(&self, node: &AnalyzedNode, slots: &mut HashSet<LocalSlot>) {
+    pub fn collect_parameter_slots_set(&self, node: &AnalyzedNode, slots: &mut HashSet<VirtualId>) {
         match &node.kind {
             BoundKind::Define {
                 addr: Address::Local(slot),
diff --git a/src/ast/compiler/optimizer/substitution_map.rs b/src/ast/compiler/optimizer/substitution_map.rs
index 15c7aa7..3505d4c 100644
--- a/src/ast/compiler/optimizer/substitution_map.rs
+++ b/src/ast/compiler/optimizer/substitution_map.rs
@@ -1,17 +1,17 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, LocalSlot, Node, UpvalueIdx};
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, Node, UpvalueIdx, VirtualId};
 use crate::ast::types::Value;
 use std::collections::{HashMap, HashSet};
 use std::rc::Rc;
 
 #[derive(Default)]
 pub struct SubstitutionMap {
-    pub values: HashMap<Address, Value>,
-    pub ast_substitutions: HashMap<Address, Rc<AnalyzedNode>>,
-    pub slot_mapping: HashMap<LocalSlot, LocalSlot>,
-    pub assigned: HashSet<Address>,
+    pub values: HashMap<Address<VirtualId>, Value>,
+    pub ast_substitutions: HashMap<Address<VirtualId>, Rc<AnalyzedNode>>,
+    pub slot_mapping: HashMap<VirtualId, VirtualId>,
+    pub assigned: HashSet<Address<VirtualId>>,
     pub next_slot: u32,
-    pub used: HashSet<Address>,
-    pub captured_slots: HashSet<LocalSlot>,
+    pub used: HashSet<Address<VirtualId>>,
+    pub captured_slots: HashSet<VirtualId>,
 }
 
 impl SubstitutionMap {
@@ -43,40 +43,40 @@ impl SubstitutionMap {
         inner
     }
 
-    pub fn add_ast_substitution(&mut self, addr: Address, node: AnalyzedNode) {
+    pub fn add_ast_substitution(&mut self, addr: Address<VirtualId>, node: AnalyzedNode) {
         self.ast_substitutions.insert(addr, Rc::new(node));
     }
 
-    pub fn map_slot(&mut self, old_slot: LocalSlot) -> LocalSlot {
+    pub fn map_slot(&mut self, old_slot: VirtualId) -> VirtualId {
         if let Some(&new_slot) = self.slot_mapping.get(&old_slot) {
             return new_slot;
         }
-        let new_slot = LocalSlot(self.next_slot);
+        let new_slot = VirtualId(self.next_slot);
         self.slot_mapping.insert(old_slot, new_slot);
         self.next_slot += 1;
         new_slot
     }
 
-    pub fn map_address(&mut self, addr: Address) -> Address {
+    pub fn map_address(&mut self, addr: Address<VirtualId>) -> Address<VirtualId> {
         match addr {
             Address::Local(slot) => Address::Local(self.map_slot(slot)),
             other => other,
         }
     }
 
-    pub fn add_value(&mut self, addr: Address, val: Value) {
+    pub fn add_value(&mut self, addr: Address<VirtualId>, val: Value) {
         self.values.insert(addr, val);
     }
 
-    pub fn get_value(&self, addr: &Address) -> Option<&Value> {
+    pub fn get_value(&self, addr: &Address<VirtualId>) -> Option<&Value> {
         self.values.get(addr)
     }
 
-    pub fn remove_value(&mut self, addr: &Address) {
+    pub fn remove_value(&mut self, addr: &Address<VirtualId>) {
         self.values.remove(addr);
     }
 
-    fn reindex_addr(&self, addr: Address, mapping: &[Option<u32>]) -> Address {
+    fn reindex_addr(&self, addr: Address<VirtualId>, mapping: &[Option<u32>]) -> Address<VirtualId> {
         if let Address::Upvalue(idx) = addr
             && let Some(res) = mapping.get(idx.0 as usize)
             && let Some(new_idx) = res
diff --git a/src/ast/compiler/optimizer/utils.rs b/src/ast/compiler/optimizer/utils.rs
index 2790a67..470284d 100644
--- a/src/ast/compiler/optimizer/utils.rs
+++ b/src/ast/compiler/optimizer/utils.rs
@@ -1,4 +1,4 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, GlobalIdx};
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, GlobalIdx, VirtualId};
 use crate::ast::types::{Identity, Value};
 use crate::ast::vm::Closure;
 use std::collections::HashSet;
@@ -32,17 +32,17 @@ impl PathTracker {
 // --- UsageInfo ---
 #[derive(Default)]
 pub struct UsageInfo {
-    pub used: HashSet<Address>,
-    pub assigned: HashSet<Address>,
+    pub used: HashSet<Address<VirtualId>>,
+    pub assigned: HashSet<Address<VirtualId>>,
     pub used_identities: HashSet<Identity>,
 }
 
 impl UsageInfo {
-    pub fn is_assigned(&self, addr: &Address) -> bool {
+    pub fn is_assigned(&self, addr: &Address<VirtualId>) -> bool {
         self.assigned.contains(addr)
     }
 
-    pub fn is_used(&self, addr: &Address) -> bool {
+    pub fn is_used(&self, addr: &Address<VirtualId>) -> bool {
         self.used.contains(addr)
     }
 
diff --git a/src/ast/compiler/specializer.rs b/src/ast/compiler/specializer.rs
index 20f2a2a..e967288 100644
--- a/src/ast/compiler/specializer.rs
+++ b/src/ast/compiler/specializer.rs
@@ -1,4 +1,4 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, Node, NodeMetrics};
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, AnalyzedPhase, BoundKind, Node, NodeMetrics, VirtualId};
 use crate::ast::types::{Purity, Signature, StaticType, Value};
 use std::cell::RefCell;
 use std::collections::HashMap;
@@ -6,16 +6,16 @@ use std::rc::Rc;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct MonoCacheKey {
-    pub address: Address,
+    pub address: Address<VirtualId>,
     pub arg_types: Vec<StaticType>,
 }
 
-pub type CompileFunc = Rc<dyn Fn(Rc<Node>, &[StaticType]) -> Result<(Value, StaticType), String>>;
+pub type CompileFunc = Rc<dyn Fn(Rc<Node<AnalyzedPhase>>, &[StaticType]) -> Result<(Value, StaticType), String>>;
 pub type RtlLookupFunc = Rc<dyn Fn(&str, &[StaticType]) -> Option<(Value, StaticType)>>;
 
 pub trait FunctionRegistry {
-    fn resolve(&self, addr: Address) -> Option<Rc<Node>>;
-    fn resolve_analyzed(&self, _addr: Address) -> Option<Rc<AnalyzedNode>> {
+    fn resolve(&self, addr: Address<VirtualId>) -> Option<Rc<Node<AnalyzedPhase>>>;
+    fn resolve_analyzed(&self, _addr: Address<VirtualId>) -> Option<Rc<AnalyzedNode>> {
         None
     }
 }
diff --git a/src/ast/compiler/type_checker.rs b/src/ast/compiler/type_checker.rs
index 63239ff..a0f23b3 100644
--- a/src/ast/compiler/type_checker.rs
+++ b/src/ast/compiler/type_checker.rs
@@ -1,4 +1,4 @@
-use crate::ast::compiler::bound_nodes::{Address, BoundKind, Node, TypedNode};
+use crate::ast::compiler::bound_nodes::{Address, BoundKind, BoundPhase, CompilerPhase, Node, TypedNode, VirtualId};
 use crate::ast::diagnostics::Diagnostics;
 use crate::ast::types::StaticType;
 use std::collections::HashMap;
@@ -33,7 +33,7 @@ impl<'a> TypeContext<'a> {
         }
     }
 
-    fn get_type(&self, addr: Address) -> StaticType {
+    fn get_type(&self, addr: Address<VirtualId>) -> StaticType {
         match addr {
             Address::Local(slot) => self
                 .slots
@@ -54,7 +54,7 @@ impl<'a> TypeContext<'a> {
         }
     }
 
-    fn set_type(&mut self, addr: Address, ty: StaticType) {
+    fn set_type(&mut self, addr: Address<VirtualId>, ty: StaticType) {
         match addr {
             Address::Local(slot) => {
                 self.slots.insert(slot.0, ty);
@@ -81,7 +81,18 @@ impl TypeChecker {
 
     pub fn check(
         &self,
-        node: &Node,
+        node: &Node<BoundPhase>,
+        arg_types: &[StaticType],
+        diag: &mut Diagnostics,
+    ) -> TypedNode {
+        self.check_node_as_bound(node, arg_types, diag)
+    }
+
+    /// Allows re-checking a node from any phase as if it were a bound node.
+    /// This is useful for specialization where we re-type a TypedNode with more specific info.
+    pub fn check_node_as_bound<P: CompilerPhase<LocalAddress = VirtualId>>(
+        &self,
+        node: &Node<P>,
         arg_types: &[StaticType],
         diag: &mut Diagnostics,
     ) -> TypedNode {
@@ -92,20 +103,17 @@ impl TypeChecker {
                 body,
                 positional_count,
             } => {
-                // 1. Determine types of captured variables (Root lambdas have none)
                 let mut upvalue_types = Vec::with_capacity(upvalues.len());
-                for _ in upvalues {
+                for &_addr in upvalues {
                     upvalue_types.push(StaticType::Any);
                 }
 
-                // 2. Create the specialized context
                 let root_ctx = TypeContext::new(0, vec![], &self.root_types, None);
                 let mut lambda_ctx =
                     TypeContext::new(64, upvalue_types, &self.root_types, Some(&root_ctx));
 
-                // 3. INJECT specialized argument types into slots
                 let arg_tuple_ty = if arg_types.is_empty() {
-                    StaticType::Any // No specialized info
+                    StaticType::Any
                 } else {
                     StaticType::Tuple(arg_types.to_vec())
                 };
@@ -117,11 +125,8 @@ impl TypeChecker {
                     diag,
                 );
 
-                // 4. Check body with the new types
                 let body_typed = self.check_node(body, &mut lambda_ctx, diag);
                 let ret_ty = body_typed.ty.clone();
-
-                // 5. Construct specialized function type
                 let final_params_ty = params_typed.ty.clone();
 
                 let fn_ty = StaticType::Function(Box::new(crate::ast::types::Signature {
@@ -147,9 +152,9 @@ impl TypeChecker {
         }
     }
 
-    fn check_params(
+    fn check_params<P: CompilerPhase<LocalAddress = VirtualId>>(
         &self,
-        node: &Node,
+        node: &Node<P>,
         specialized_ty: &StaticType,
         ctx: &mut TypeContext,
         diag: &mut Diagnostics,
@@ -182,10 +187,6 @@ impl TypeChecker {
                 addr,
                 value: _value,
             } => {
-                // In an assignment pattern, 'value' is just a Nop placeholder from the Binder.
-                // We update the type of the address (if it's a local or global) to match the specialized type.
-                // Note: For now, we assume assignments are compatible if types were already inferred,
-                // or we could add a check here against existing type.
                 (
                     BoundKind::Set {
                         addr: *addr,
@@ -240,7 +241,7 @@ impl TypeChecker {
                         StaticType::Error => StaticType::Error,
                         _ => StaticType::Any,
                     };
-                    let t = self.check_params(el, &sub_ty, ctx, diag);
+                    let t = self.check_params(el.as_ref(), &sub_ty, ctx, diag);
                     elem_types.push(t.ty.clone());
                     typed_elements.push(Rc::new(t));
                 }
@@ -268,9 +269,9 @@ impl TypeChecker {
         }
     }
 
-    fn check_node(
+    fn check_node<P: CompilerPhase<LocalAddress = VirtualId>>(
         &self,
-        node: &Node,
+        node: &Node<P>,
         ctx: &mut TypeContext,
         diag: &mut Diagnostics,
     ) -> TypedNode {
@@ -373,7 +374,7 @@ impl TypeChecker {
 
             BoundKind::Destructure { pattern, value } => {
                 let val_typed = self.check_node(value, ctx, diag);
-                let pat_typed = self.check_params(pattern, &val_typed.ty, ctx, diag);
+                let pat_typed = self.check_params(pattern.as_ref(), &val_typed.ty, ctx, diag);
                 let ty = val_typed.ty.clone();
                 (
                     BoundKind::Destructure {
@@ -397,13 +398,11 @@ impl TypeChecker {
 
                 if let Some(e) = else_br {
                     let et = self.check_node(e, ctx, diag);
-                    // Basic type promotion: if types differ, fall back to Any
                     if et.ty != final_ty {
                         final_ty = StaticType::Any;
                     }
                     else_typed = Some(Rc::new(et));
                 } else {
-                    // If without else returns Optional(Then) (T | Void)
                     final_ty = StaticType::Optional(Box::new(then_typed.ty.clone()));
                 }
 
@@ -422,7 +421,6 @@ impl TypeChecker {
                 let mut arg_types = Vec::with_capacity(inputs.len());
                 for input in inputs {
                     let typed_input = self.check_node(input, ctx, diag);
-                    // Unwrap Series(T) or Stream(T) to T for the lambda argument
                     let arg_ty = if let StaticType::Series(inner) = &typed_input.ty {
                         *inner.clone()
                     } else if let StaticType::Stream(inner) = &typed_input.ty {
@@ -434,11 +432,9 @@ impl TypeChecker {
                     typed_inputs.push(Rc::new(typed_input));
                 }
 
-                // Specialized check for the lambda using the input types!
-                let typed_lambda = self.check(lambda, &arg_types, diag);
+                let typed_lambda = self.check_node_as_bound(lambda.as_ref(), &arg_types, diag);
 
                 let ret_ty = if let StaticType::Function(sig) = &typed_lambda.ty {
-                    // If the lambda returns an Optional(T), the pipeline filters Void and stores T!
                     if let StaticType::Optional(inner) = &sig.ret {
                         *inner.clone()
                     } else {
@@ -476,17 +472,14 @@ impl TypeChecker {
                 body,
                 positional_count,
             } => {
-                // 1. Determine types of captured variables
                 let mut upvalue_types = Vec::with_capacity(upvalues.len());
                 for &addr in upvalues {
                     upvalue_types.push(ctx.get_type(addr));
                 }
 
-                // 2. Create nested context for lambda body
                 let mut lambda_ctx =
                     TypeContext::new(64, upvalue_types, ctx.root_types, Some(ctx));
 
-                // 3. Check parameters and body
                 let params_typed = self.check_params(
                     params.as_ref(),
                     &StaticType::Any,
@@ -494,13 +487,11 @@ impl TypeChecker {
                     diag,
                 );
 
-                // Set current params type for 'again' validation
                 lambda_ctx.current_params_ty = Some(params_typed.ty.clone());
 
                 let body_typed = self.check_node(body, &mut lambda_ctx, diag);
                 let ret_ty = body_typed.ty.clone();
 
-                // 4. Construct function type
                 let fn_ty = StaticType::Function(Box::new(crate::ast::types::Signature {
                     params: params_typed.ty.clone(),
                     ret: ret_ty,
@@ -520,7 +511,6 @@ impl TypeChecker {
             BoundKind::Call { callee, args } => {
                 let callee_typed = self.check_node(callee, ctx, diag);
 
-                // Manually check args (Tuple) to prevent Vector/Matrix promotion
                 let args_typed = if let BoundKind::Tuple { elements } = &args.kind {
                     let mut typed_elements = Vec::new();
                     let mut elem_types = Vec::new();
@@ -537,7 +527,6 @@ impl TypeChecker {
                         ty: StaticType::Tuple(elem_types),
                     }
                 } else {
-                    // Should not happen as parser wraps args in Tuple, but fallback safely
                     self.check_node(args, ctx, diag)
                 };
 
@@ -565,7 +554,6 @@ impl TypeChecker {
             }
 
             BoundKind::Again { args } => {
-                // Manually check args (Tuple) to prevent Vector/Matrix promotion
                 let args_typed = if let BoundKind::Tuple { elements } = &args.kind {
                     let mut typed_elements = Vec::new();
                     let mut elem_types = Vec::new();
diff --git a/src/ast/environment.rs b/src/ast/environment.rs
index 607c1d6..7af98ec 100644
--- a/src/ast/environment.rs
+++ b/src/ast/environment.rs
@@ -10,12 +10,12 @@ use std::path::{Path, PathBuf};
 use std::rc::Rc;
 
 use crate::ast::compiler::bound_nodes::{
-    Address, AnalyzedNode, BoundKind, GlobalAnalyzedRegistry, GlobalFunctionRegistry, GlobalIdx,
-    Node, 
+    Address, AnalyzedNode, BoundKind, ExecNode, GlobalAnalyzedRegistry, GlobalFunctionRegistry, GlobalIdx,
+    Node, VirtualId,
 };
 use crate::ast::compiler::dumper::Dumper;
 use crate::ast::compiler::lambda_collector::LambdaCollector;
-use crate::ast::compiler::lowering::{Lowering, ExecNode};
+use crate::ast::compiler::lowering::Lowering;
 use crate::ast::compiler::macros::{MacroEvaluator, MacroExpander, MacroRegistry};
 use crate::ast::compiler::optimizer::Optimizer;
 use crate::ast::compiler::specializer::{FunctionRegistry, MonoCache, Specializer};
@@ -89,19 +89,11 @@ pub struct Environment {
 }
 
 struct EnvFunctionRegistry {
-    registry: Rc<RefCell<GlobalFunctionRegistry>>,
     analyzed_registry: Rc<RefCell<GlobalAnalyzedRegistry>>,
 }
 
 impl FunctionRegistry for EnvFunctionRegistry {
-    fn resolve(&self, addr: Address) -> Option<Rc<Node>> {
-        if let Address::Global(idx) = addr {
-            self.registry.borrow().get(&idx).cloned()
-        } else {
-            None
-        }
-    }
-    fn resolve_analyzed(&self, addr: Address) -> Option<Rc<AnalyzedNode>> {
+    fn resolve(&self, addr: Address<VirtualId>) -> Option<Rc<Node<crate::ast::compiler::bound_nodes::AnalyzedPhase>>> {
         if let Address::Global(idx) = addr {
             self.analyzed_registry.borrow().get(&idx).cloned()
         } else {
@@ -406,7 +398,7 @@ impl Environment {
 
                     if !current_scope.locals.contains_key(sym) {
                         let mut slot_count = self.root_slot_count.borrow_mut();
-                        let slot = crate::ast::compiler::bound_nodes::LocalSlot(*slot_count);
+                        let slot = VirtualId(*slot_count);
                         current_scope.locals.insert(
                             sym.clone(),
                             crate::ast::compiler::binder::LocalInfo {
@@ -484,15 +476,15 @@ impl Environment {
         LambdaCollector::collect(&bound_ast, &mut self.function_registry.borrow_mut());
 
         let checker = TypeChecker::new(self.root_types.clone());
-        let wrapped_ast = if let crate::ast::compiler::bound_nodes::BoundKind::Lambda { .. } = bound_ast.kind {
+        let wrapped_ast = if let BoundKind::Lambda { .. } = bound_ast.kind {
             bound_ast
         } else {
-            crate::ast::compiler::bound_nodes::Node {
+            Node {
                 identity: bound_ast.identity.clone(),
-                kind: crate::ast::compiler::bound_nodes::BoundKind::Lambda {
-                    params: std::rc::Rc::new(crate::ast::compiler::bound_nodes::Node {
+                kind: BoundKind::Lambda {
+                    params: std::rc::Rc::new(Node {
                         identity: bound_ast.identity.clone(),
-                        kind: crate::ast::compiler::bound_nodes::BoundKind::Tuple { elements: vec![] },
+                        kind: BoundKind::Tuple { elements: vec![] },
                         ty: (),
                     }),
                     upvalues: vec![],
@@ -668,7 +660,7 @@ impl Environment {
         {
             let closure = Rc::new(crate::ast::vm::Closure::new(
                 params.clone(),
-                body.ty.original.clone(),
+                body.ty.original.clone(), 
                 body.clone(),
                 Vec::new(),
                 *positional_count,
@@ -717,13 +709,11 @@ impl Environment {
 
     fn specialize_node(&self, node: AnalyzedNode) -> AnalyzedNode {
         let registry = Rc::new(EnvFunctionRegistry {
-            registry: self.function_registry.clone(),
             analyzed_registry: self.typed_function_registry.clone(),
         });
 
         let rtl_lookup = Rc::new(|name: &str, args: &[StaticType]| intrinsics::lookup(name, args));
         let typed_reg = self.typed_function_registry.clone();
-        let syntax_reg = self.function_registry.clone();
         let mono_cache = self.monomorph_cache.clone();
         let root_values = self.root_values.clone();
         let root_types = self.root_types.clone();
@@ -731,12 +721,30 @@ impl Environment {
         let optimization = self.optimization;
 
         let compiler = Rc::new(
-            move |func_template: Rc<Node>,
+            move |func_template: Rc<Node<crate::ast::compiler::bound_nodes::AnalyzedPhase>>,
                   arg_types: &[StaticType]|
                   -> Result<(Value, StaticType), String> {
                 let mut diag = Diagnostics::new();
                 let checker = TypeChecker::new(root_types.clone());
-                let retyped_ast = checker.check(func_template.as_ref(), arg_types, &mut diag);
+                
+                // For specialization, we re-type-check the analyzed node.
+                // Note: AnalyzedNode.ty.original is the TypedNode.
+                // But TypeChecker expects Node<BoundPhase>. We need to go from TypedNode -> BoundNode.
+                // However, since TypedNode is just Node<TypedPhase>, we can't easily "un-type" it.
+                // Instead, we access the original AST from the binder if we had it, 
+                // OR we make the TypeChecker generic.
+                // For now, we assume the TypedNode can be used where a BoundNode is expected 
+                // if we strip the metadata. 
+                // A better way is to store the BoundNode in NodeMetrics as well.
+                
+                // Temporary fix: Re-binding from source would be too expensive.
+                // Let's assume for now that we can specialize directly on the TypedNode 
+                // or that we need a small helper to transform TypedNode -> BoundNode.
+                
+                // Realizing that TypedNode (StaticType) is very similar to BoundNode (()),
+                // we can just use the internal transform.
+                
+                let retyped_ast = checker.check_node_as_bound(func_template.ty.original.as_ref(), arg_types, &mut diag);
 
                 if diag.has_errors() {
                     return Err(diag
@@ -750,7 +758,6 @@ impl Environment {
                 let analyzed = Analyzer::analyze(&retyped_ast, &root_purity.borrow());
 
                 let sub_registry = Rc::new(EnvFunctionRegistry {
-                    registry: syntax_reg.clone(),
                     analyzed_registry: typed_reg.clone(),
                 });
                 let sub_rtl_lookup =
diff --git a/src/ast/vm.rs b/src/ast/vm.rs
index 787dede..16e32d9 100644
--- a/src/ast/vm.rs
+++ b/src/ast/vm.rs
@@ -1,5 +1,4 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind};
-use crate::ast::compiler::lowering::ExecNode;
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, ExecNode, StackOffset};
 use crate::ast::types::{Object, Value};
 use std::any::Any;
 use std::cell::RefCell;
@@ -335,7 +334,7 @@ impl VM {
                     val.clone()
                 };
 
-                self.set_value(addr.clone(), store_val)?;
+                self.set_value(*addr, store_val)?;
                 // Define always evaluates to the unwrapped value for immediate use.
                 Ok(val)
             }
@@ -351,7 +350,7 @@ impl VM {
                 }
                 Ok(val)
             }
-            BoundKind::Get { addr, .. } => self.get_value(addr.clone()),
+            BoundKind::Get { addr, .. } => self.get_value(*addr),
 
             BoundKind::FieldAccessor(k) => Ok(Value::FieldAccessor(k.clone())),
 
@@ -399,7 +398,7 @@ impl VM {
 
             BoundKind::Set { addr, value } => {
                 let val = self.eval_internal(obs, value)?;
-                self.set_value(addr.clone(), val.clone())?;
+                self.set_value(*addr, val.clone())?;
                 Ok(val)
             }
             BoundKind::If {
@@ -882,7 +881,7 @@ impl VM {
         }
     }
 
-    fn capture_upvalue(&mut self, addr: Address) -> Result<Rc<RefCell<Value>>, String> {
+    fn capture_upvalue(&mut self, addr: Address<StackOffset>) -> Result<Rc<RefCell<Value>>, String> {
         match addr {
             Address::Local(slot) => {
                 let frame = self.frames.last().ok_or("No call frame")?;
@@ -918,7 +917,7 @@ impl VM {
         }
     }
 
-    fn get_value(&self, addr: Address) -> Result<Value, String> {
+    fn get_value(&self, addr: Address<StackOffset>) -> Result<Value, String> {
         match addr {
             Address::Local(slot) => {
                 let frame = self.frames.last().ok_or("No call frame")?;
@@ -958,7 +957,7 @@ impl VM {
         }
     }
 
-    fn set_value(&mut self, addr: Address, value: Value) -> Result<(), String> {
+    fn set_value(&mut self, addr: Address<StackOffset>, value: Value) -> Result<(), String> {
         match addr {
             Address::Local(slot) => {
                 let frame = self.frames.last().ok_or("No call frame")?;