diff --git a/source/quickjs.c b/source/quickjs.c
index 52e62a29..741b091c 100644
--- a/source/quickjs.c
+++ b/source/quickjs.c
@@ -387,7 +387,6 @@ struct JSRuntime {
   /* User data */
   void *user_opaque;
 
-
   /* Interrupt handler for checking execution limits */
   JSInterruptHandler *interrupt_handler;
   void *interrupt_opaque;
@@ -474,7 +473,6 @@ typedef struct {
   int is_tail_call;
 } VMCallInfo;
 
-
 static inline objhdr_t objhdr_set_s (objhdr_t h, bool s) {
   return s ? (h | OBJHDR_S_MASK) : (h & ~OBJHDR_S_MASK);
 }
@@ -1564,7 +1562,6 @@ typedef struct JSFunction {
   JSValue name;    /* function name as JSValue text */
   int16_t length;  /* arity: max allowed arguments (-1 = variadic) */
   uint8_t kind;
-  uint8_t free_mark : 1;
   union {
     struct {
       JSContext *realm;
@@ -28873,31 +28870,265 @@ char *JS_AST (JSContext *ctx, const char *source, size_t len, const char *filena
    Register-Based Machine Code Generator
    ============================================================ */
 
+/* Variable kinds */
+#define MACH_VAR_ARG    0
+#define MACH_VAR_LOCAL  1
+#define MACH_VAR_CLOSED 2
+
+/* Variable resolution result */
+typedef enum MachVarResolution {
+  MACH_VAR_LOCAL_SLOT,    /* variable is in current scope */
+  MACH_VAR_CLOSURE,       /* variable is in parent scope */
+  MACH_VAR_UNBOUND        /* variable not found in any scope */
+} MachVarResolution;
+
+typedef struct MachVarInfo {
+  char *name;
+  int slot;
+  int kind;
+} MachVarInfo;
+
+typedef struct MachClosureRef {
+  char *name;
+  int parent_slot;
+  int depth;
+  int local_slot;
+} MachClosureRef;
+
+typedef struct MachResolveResult {
+  MachVarResolution type;
+  int slot;
+  int depth;
+} MachResolveResult;
+
 typedef struct MachGenState {
   JSContext *ctx;
   cJSON *instructions;
   cJSON *data;
   cJSON *functions;
-  int next_slot;
-  int max_slot;
+
+  int this_slot;          /* always 0 */
   int nr_args;
+  int nr_close_slots;     /* captured from parents */
+  int nr_local_slots;
+  int next_temp_slot;
+  int max_slot;
+
+  MachVarInfo *vars;
+  int var_count;
+  int var_capacity;
+
+  MachClosureRef *closure_refs;
+  int closure_ref_count;
+  int closure_ref_capacity;
+
   int label_counter;
   int func_counter;
+
   struct MachGenState *parent;
-  /* Loop labels for break/continue */
   const char *loop_break;
   const char *loop_continue;
+
+  int is_arrow;
 } MachGenState;
 
 static int mach_gen_expr (MachGenState *s, cJSON *expr);
 static void mach_gen_statement (MachGenState *s, cJSON *stmt);
 
+/* Allocate a temporary slot */
 static int mach_alloc_slot (MachGenState *s) {
-  int slot = s->next_slot++;
+  int slot = s->next_temp_slot++;
   if (slot > s->max_slot) s->max_slot = slot;
   return slot;
 }
 
+/* Add a variable to the tracking table */
+static void mach_add_var (MachGenState *s, const char *name, int slot, int kind) {
+  if (s->var_count >= s->var_capacity) {
+    int new_cap = s->var_capacity ? s->var_capacity * 2 : 16;
+    s->vars = sys_realloc (s->vars, new_cap * sizeof(MachVarInfo));
+    s->var_capacity = new_cap;
+  }
+  MachVarInfo *v = &s->vars[s->var_count++];
+  v->name = sys_malloc (strlen (name) + 1);
+  strcpy (v->name, name);
+  v->slot = slot;
+  v->kind = kind;
+}
+
+/* Find a variable in the current scope only */
+static int mach_find_var_local (MachGenState *s, const char *name) {
+  for (int i = 0; i < s->var_count; i++) {
+    if (strcmp (s->vars[i].name, name) == 0) {
+      return s->vars[i].slot;
+    }
+  }
+  return -1;
+}
+
+/* Scan a node for var/def declarations and register them (hoisting) */
+static void mach_scan_vars (MachGenState *s, cJSON *node) {
+  if (!node) return;
+
+  const char *kind = cJSON_GetStringValue (cJSON_GetObjectItem (node, "kind"));
+  if (!kind) return;
+
+  /* var/def declaration - register the variable */
+  if (strcmp (kind, "var") == 0 || strcmp (kind, "def") == 0) {
+    cJSON *left = cJSON_GetObjectItem (node, "left");
+    const char *name = cJSON_GetStringValue (cJSON_GetObjectItem (left, "name"));
+    if (name && mach_find_var_local (s, name) < 0) {
+      int slot = 1 + s->nr_args + s->nr_local_slots++;
+      mach_add_var (s, name, slot, MACH_VAR_LOCAL);
+    }
+    return;
+  }
+
+  /* Block - scan children */
+  if (strcmp (kind, "block") == 0) {
+    cJSON *stmts = cJSON_GetObjectItem (node, "statements");
+    cJSON *child;
+    cJSON_ArrayForEach (child, stmts) {
+      mach_scan_vars (s, child);
+    }
+    return;
+  }
+
+  /* If - scan then/else branches */
+  if (strcmp (kind, "if") == 0) {
+    cJSON *then_stmts = cJSON_GetObjectItem (node, "then");
+    cJSON *else_stmts = cJSON_GetObjectItem (node, "else");
+    cJSON *child;
+    cJSON_ArrayForEach (child, then_stmts) {
+      mach_scan_vars (s, child);
+    }
+    if (else_stmts) {
+      cJSON_ArrayForEach (child, else_stmts) {
+        mach_scan_vars (s, child);
+      }
+    }
+    return;
+  }
+
+  /* While - scan body */
+  if (strcmp (kind, "while") == 0) {
+    cJSON *stmts = cJSON_GetObjectItem (node, "statements");
+    cJSON *child;
+    cJSON_ArrayForEach (child, stmts) {
+      mach_scan_vars (s, child);
+    }
+    return;
+  }
+
+  /* Do-while - scan body */
+  if (strcmp (kind, "do") == 0) {
+    cJSON *stmts = cJSON_GetObjectItem (node, "statements");
+    cJSON *child;
+    cJSON_ArrayForEach (child, stmts) {
+      mach_scan_vars (s, child);
+    }
+    return;
+  }
+
+  /* For - scan init and body */
+  if (strcmp (kind, "for") == 0) {
+    cJSON *init = cJSON_GetObjectItem (node, "init");
+    cJSON *stmts = cJSON_GetObjectItem (node, "statements");
+    if (init) mach_scan_vars (s, init);
+    cJSON *child;
+    cJSON_ArrayForEach (child, stmts) {
+      mach_scan_vars (s, child);
+    }
+    return;
+  }
+
+  /* Switch - scan case bodies */
+  if (strcmp (kind, "switch") == 0) {
+    cJSON *cases = cJSON_GetObjectItem (node, "cases");
+    cJSON *case_node;
+    cJSON_ArrayForEach (case_node, cases) {
+      cJSON *case_stmts = cJSON_GetObjectItem (case_node, "statements");
+      cJSON *child;
+      cJSON_ArrayForEach (child, case_stmts) {
+        mach_scan_vars (s, child);
+      }
+    }
+    return;
+  }
+
+  /* Try-catch-finally - scan all blocks */
+  if (strcmp (kind, "try") == 0) {
+    cJSON *try_stmts = cJSON_GetObjectItem (node, "statements");
+    cJSON *catch_node = cJSON_GetObjectItem (node, "catch");
+    cJSON *finally_node = cJSON_GetObjectItem (node, "finally");
+    cJSON *child;
+    cJSON_ArrayForEach (child, try_stmts) {
+      mach_scan_vars (s, child);
+    }
+    if (catch_node) {
+      cJSON *catch_stmts = cJSON_GetObjectItem (catch_node, "statements");
+      cJSON_ArrayForEach (child, catch_stmts) {
+        mach_scan_vars (s, child);
+      }
+    }
+    if (finally_node) {
+      cJSON *finally_stmts = cJSON_GetObjectItem (finally_node, "statements");
+      cJSON_ArrayForEach (child, finally_stmts) {
+        mach_scan_vars (s, child);
+      }
+    }
+    return;
+  }
+
+  /* NOTE: Do NOT recurse into nested function nodes - they have their own scope */
+}
+
+/* Resolve a variable - returns resolution type and slot/depth info */
+static MachResolveResult mach_resolve_var (MachGenState *s, const char *name) {
+  MachResolveResult result = {MACH_VAR_UNBOUND, -1, 0};
+
+  /* Check current scope */
+  int local_slot = mach_find_var_local (s, name);
+  if (local_slot >= 0) {
+    result.type = MACH_VAR_LOCAL_SLOT;
+    result.slot = local_slot;
+    return result;
+  }
+
+  /* Check parent scopes */
+  MachGenState *parent = s->parent;
+  int depth = 1;
+  while (parent) {
+    int parent_slot = mach_find_var_local (parent, name);
+    if (parent_slot >= 0) {
+      /* Found in parent scope - add closure ref */
+      if (s->closure_ref_count >= s->closure_ref_capacity) {
+        int new_cap = s->closure_ref_capacity ? s->closure_ref_capacity * 2 : 8;
+        s->closure_refs = sys_realloc (s->closure_refs, new_cap * sizeof(MachClosureRef));
+        s->closure_ref_capacity = new_cap;
+      }
+      int close_slot = 1 + s->nr_args + s->nr_close_slots;
+      MachClosureRef *ref = &s->closure_refs[s->closure_ref_count++];
+      ref->name = sys_malloc (strlen (name) + 1);
+      strcpy (ref->name, name);
+      ref->parent_slot = parent_slot;
+      ref->depth = depth;
+      ref->local_slot = close_slot;
+      s->nr_close_slots++;
+
+      result.type = MACH_VAR_CLOSURE;
+      result.slot = parent_slot;
+      result.depth = depth;
+      return result;
+    }
+    parent = parent->parent;
+    depth++;
+  }
+
+  /* Not found - unbound */
+  return result;
+}
+
 static char *mach_gen_label (MachGenState *s, const char *prefix) {
   char *label = sys_malloc (64);
   snprintf (label, 64, "%s_%d", prefix, s->label_counter++);
@@ -28909,6 +29140,7 @@ static void mach_emit_label (MachGenState *s, const char *label) {
   cJSON_AddItemToArray (s->instructions, item);
 }
 
+/* Emit instruction with string opcode */
 static void mach_emit_0 (MachGenState *s, const char *op) {
   cJSON *instr = cJSON_CreateArray ();
   cJSON_AddItemToArray (instr, cJSON_CreateString (op));
@@ -28939,38 +29171,45 @@ static void mach_emit_3 (MachGenState *s, const char *op, int a, int b, int c) {
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+static void mach_emit_4 (MachGenState *s, const char *op, int a, int b, int c, int d) {
+  cJSON *instr = cJSON_CreateArray ();
+  cJSON_AddItemToArray (instr, cJSON_CreateString (op));
+  cJSON_AddItemToArray (instr, cJSON_CreateNumber (a));
+  cJSON_AddItemToArray (instr, cJSON_CreateNumber (b));
+  cJSON_AddItemToArray (instr, cJSON_CreateNumber (c));
+  cJSON_AddItemToArray (instr, cJSON_CreateNumber (d));
+  cJSON_AddItemToArray (s->instructions, instr);
+}
+
+/* Emit number constant - inline literal */
 static void mach_emit_const_num (MachGenState *s, int dest, double val) {
   cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("const"));
+  cJSON_AddItemToArray (instr, cJSON_CreateString ("access"));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (val));
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+/* Emit string constant - inline literal */
 static void mach_emit_const_str (MachGenState *s, int dest, const char *val) {
   cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("const"));
+  cJSON_AddItemToArray (instr, cJSON_CreateString ("access"));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, cJSON_CreateString (val));
+  cJSON_AddItemToArray (instr, cJSON_CreateString (val ? val : ""));
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+/* Emit boolean constant */
 static void mach_emit_const_bool (MachGenState *s, int dest, int val) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("const"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, val ? cJSON_CreateTrue () : cJSON_CreateFalse ());
-  cJSON_AddItemToArray (s->instructions, instr);
+  mach_emit_1 (s, val ? "true" : "false", dest);
 }
 
+/* Emit null constant */
 static void mach_emit_const_null (MachGenState *s, int dest) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("const"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, cJSON_CreateNull ());
-  cJSON_AddItemToArray (s->instructions, instr);
+  mach_emit_1 (s, "null", dest);
 }
 
+/* Emit jump with label */
 static void mach_emit_jump (MachGenState *s, const char *label) {
   cJSON *instr = cJSON_CreateArray ();
   cJSON_AddItemToArray (instr, cJSON_CreateString ("jump"));
@@ -28978,6 +29217,7 @@ static void mach_emit_jump (MachGenState *s, const char *label) {
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+/* Emit conditional jump */
 static void mach_emit_jump_cond (MachGenState *s, const char *op, int slot, const char *label) {
   cJSON *instr = cJSON_CreateArray ();
   cJSON_AddItemToArray (instr, cJSON_CreateString (op));
@@ -28986,81 +29226,150 @@ static void mach_emit_jump_cond (MachGenState *s, const char *op, int slot, cons
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+/* Emit get variable - resolves variable and emits appropriate opcode */
 static void mach_emit_get_var (MachGenState *s, int dest, const char *name) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("get_var"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, cJSON_CreateString (name));
-  cJSON_AddItemToArray (s->instructions, instr);
+  MachResolveResult res = mach_resolve_var (s, name);
+  if (res.type == MACH_VAR_LOCAL_SLOT) {
+    /* Local variable - emit move */
+    mach_emit_2 (s, "move", dest, res.slot);
+  } else if (res.type == MACH_VAR_CLOSURE) {
+    /* Closure variable - emit get */
+    mach_emit_3 (s, "get", dest, res.slot, res.depth);
+  } else {
+    /* Unbound variable - emit cap_name for linker to resolve */
+    cJSON *instr = cJSON_CreateArray ();
+    cJSON_AddItemToArray (instr, cJSON_CreateString ("cap_name"));
+    cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
+    cJSON_AddItemToArray (instr, cJSON_CreateString (name));
+    cJSON_AddItemToArray (s->instructions, instr);
+  }
 }
 
+/* Emit set variable - resolves variable and emits appropriate opcode */
 static void mach_emit_set_var (MachGenState *s, const char *name, int slot) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("set_var"));
-  cJSON_AddItemToArray (instr, cJSON_CreateString (name));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (slot));
-  cJSON_AddItemToArray (s->instructions, instr);
+  int local_slot = mach_find_var_local (s, name);
+  if (local_slot >= 0) {
+    /* Local variable - emit move */
+    mach_emit_2 (s, "move", local_slot, slot);
+  } else {
+    /* Try to resolve in parent scopes for closure write */
+    MachResolveResult res = mach_resolve_var (s, name);
+    if (res.type == MACH_VAR_CLOSURE) {
+      /* Closure variable - emit put */
+      mach_emit_3 (s, "put", slot, res.slot, res.depth);
+    } else {
+      /* Unbound - emit set_var with name for linker to resolve */
+      cJSON *instr = cJSON_CreateArray ();
+      cJSON_AddItemToArray (instr, cJSON_CreateString ("set_var"));
+      cJSON_AddItemToArray (instr, cJSON_CreateString (name));
+      cJSON_AddItemToArray (instr, cJSON_CreateNumber (slot));
+      cJSON_AddItemToArray (s->instructions, instr);
+    }
+  }
 }
 
+/* Emit property access with inline key */
 static void mach_emit_get_prop (MachGenState *s, int dest, int obj, const char *prop) {
   cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("get_prop"));
+  cJSON_AddItemToArray (instr, cJSON_CreateString ("load_prop"));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (obj));
   cJSON_AddItemToArray (instr, cJSON_CreateString (prop));
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+/* Emit property store with inline key */
 static void mach_emit_set_prop (MachGenState *s, int obj, const char *prop, int val) {
   cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("set_prop"));
+  cJSON_AddItemToArray (instr, cJSON_CreateString ("store_prop"));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (obj));
-  cJSON_AddItemToArray (instr, cJSON_CreateString (prop));
   cJSON_AddItemToArray (instr, cJSON_CreateNumber (val));
+  cJSON_AddItemToArray (instr, cJSON_CreateString (prop));
   cJSON_AddItemToArray (s->instructions, instr);
 }
 
+/* Emit element access */
 static void mach_emit_get_elem (MachGenState *s, int dest, int obj, int idx) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("get_elem"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (obj));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (idx));
-  cJSON_AddItemToArray (s->instructions, instr);
+  mach_emit_3 (s, "load_idx", dest, obj, idx);
 }
 
+/* Emit element store */
 static void mach_emit_set_elem (MachGenState *s, int obj, int idx, int val) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("set_elem"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (obj));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (idx));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (val));
-  cJSON_AddItemToArray (s->instructions, instr);
+  mach_emit_3 (s, "store_idx", obj, idx, val);
 }
 
+/* Emit function call using frame/arg/invoke sequence */
 static void mach_emit_call (MachGenState *s, int dest, int func_slot, cJSON *args) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("call"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (func_slot));
+  int argc = cJSON_GetArraySize (args);
+  int frame_slot = mach_alloc_slot (s);
+
+  /* frame frame_slot, func_slot, argc */
+  mach_emit_3 (s, "frame", frame_slot, func_slot, argc);
+
+  /* set_this frame_slot, null (or global for non-method calls) */
+  int null_slot = mach_alloc_slot (s);
+  mach_emit_1 (s, "null", null_slot);
+  mach_emit_2 (s, "set_this", frame_slot, null_slot);
+
+  /* arg frame_slot, arg_index, val_slot for each arg */
+  int arg_idx = 1;
   cJSON *arg;
   cJSON_ArrayForEach (arg, args) {
-    cJSON_AddItemToArray (instr, cJSON_CreateNumber (arg->valueint));
+    mach_emit_3 (s, "arg", frame_slot, arg_idx++, arg->valueint);
   }
-  cJSON_AddItemToArray (s->instructions, instr);
+
+  /* invoke frame_slot, ret_slot */
+  mach_emit_2 (s, "invoke", frame_slot, dest);
 }
 
+/* Emit method call using frame/arg/invoke sequence */
 static void mach_emit_call_method (MachGenState *s, int dest, int obj, const char *prop, cJSON *args) {
-  cJSON *instr = cJSON_CreateArray ();
-  cJSON_AddItemToArray (instr, cJSON_CreateString ("call_method"));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
-  cJSON_AddItemToArray (instr, cJSON_CreateNumber (obj));
-  cJSON_AddItemToArray (instr, cJSON_CreateString (prop));
+  /* First get the method */
+  int func_slot = mach_alloc_slot (s);
+  mach_emit_get_prop (s, func_slot, obj, prop);
+
+  int argc = cJSON_GetArraySize (args);
+  int frame_slot = mach_alloc_slot (s);
+
+  /* frame frame_slot, func_slot, argc */
+  mach_emit_3 (s, "frame", frame_slot, func_slot, argc);
+
+  /* set_this frame_slot, obj */
+  mach_emit_2 (s, "set_this", frame_slot, obj);
+
+  /* arg frame_slot, arg_index, val_slot for each arg */
+  int arg_idx = 1;
   cJSON *arg;
   cJSON_ArrayForEach (arg, args) {
-    cJSON_AddItemToArray (instr, cJSON_CreateNumber (arg->valueint));
+    mach_emit_3 (s, "arg", frame_slot, arg_idx++, arg->valueint);
   }
-  cJSON_AddItemToArray (s->instructions, instr);
+
+  /* invoke frame_slot, ret_slot */
+  mach_emit_2 (s, "invoke", frame_slot, dest);
+}
+
+/* Map JS operator to opcode string */
+static const char *mach_binop_to_string (const char *kind) {
+  if (strcmp (kind, "+") == 0) return "add";
+  if (strcmp (kind, "-") == 0) return "sub";
+  if (strcmp (kind, "*") == 0) return "mul";
+  if (strcmp (kind, "/") == 0) return "div";
+  if (strcmp (kind, "%") == 0) return "mod";
+  if (strcmp (kind, "**") == 0) return "pow";
+  if (strcmp (kind, "&") == 0) return "bitand";
+  if (strcmp (kind, "|") == 0) return "bitor";
+  if (strcmp (kind, "^") == 0) return "bitxor";
+  if (strcmp (kind, "<<") == 0) return "shl";
+  if (strcmp (kind, ">>") == 0) return "shr";
+  if (strcmp (kind, ">>>") == 0) return "ushr";
+  if (strcmp (kind, "==") == 0 || strcmp (kind, "===") == 0) return "eq";
+  if (strcmp (kind, "!=") == 0 || strcmp (kind, "!==") == 0) return "ne";
+  if (strcmp (kind, "<") == 0) return "lt";
+  if (strcmp (kind, "<=") == 0) return "le";
+  if (strcmp (kind, ">") == 0) return "gt";
+  if (strcmp (kind, ">=") == 0) return "ge";
+  if (strcmp (kind, "in") == 0) return "in";
+  return "add";
 }
 
 /* Generate code for binary operators */
@@ -29114,28 +29423,7 @@ static int mach_gen_binary (MachGenState *s, cJSON *node) {
   int right_slot = mach_gen_expr (s, right);
   int dest = mach_alloc_slot (s);
 
-  const char *op = NULL;
-  if (strcmp (kind, "+") == 0) op = "add";
-  else if (strcmp (kind, "-") == 0) op = "sub";
-  else if (strcmp (kind, "*") == 0) op = "mul";
-  else if (strcmp (kind, "/") == 0) op = "div";
-  else if (strcmp (kind, "%") == 0) op = "mod";
-  else if (strcmp (kind, "**") == 0) op = "pow";
-  else if (strcmp (kind, "&") == 0) op = "bitand";
-  else if (strcmp (kind, "|") == 0) op = "bitor";
-  else if (strcmp (kind, "^") == 0) op = "bitxor";
-  else if (strcmp (kind, "<<") == 0) op = "shl";
-  else if (strcmp (kind, ">>") == 0) op = "shr";
-  else if (strcmp (kind, ">>>") == 0) op = "ushr";
-  else if (strcmp (kind, "==") == 0 || strcmp (kind, "===") == 0) op = "eq";
-  else if (strcmp (kind, "!=") == 0 || strcmp (kind, "!==") == 0) op = "ne";
-  else if (strcmp (kind, "<") == 0) op = "lt";
-  else if (strcmp (kind, "<=") == 0) op = "le";
-  else if (strcmp (kind, ">") == 0) op = "gt";
-  else if (strcmp (kind, ">=") == 0) op = "ge";
-  else if (strcmp (kind, "in") == 0) op = "in";
-  else op = kind;
-
+  const char *op = mach_binop_to_string (kind);
   mach_emit_3 (s, op, dest, left_slot, right_slot);
   return dest;
 }
@@ -29272,9 +29560,8 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
   }
 
   if (strcmp (kind, "this") == 0) {
-    int slot = mach_alloc_slot (s);
-    mach_emit_1 (s, "this", slot);
-    return slot;
+    /* this is always slot 0 */
+    return s->this_slot;
   }
 
   /* Variable reference */
@@ -29432,12 +29719,7 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
       cJSON *idx = cJSON_GetObjectItem (operand, "right");
       int obj_slot = mach_gen_expr (s, obj);
       int idx_slot = mach_gen_expr (s, idx);
-      cJSON *instr = cJSON_CreateArray ();
-      cJSON_AddItemToArray (instr, cJSON_CreateString ("delete_elem"));
-      cJSON_AddItemToArray (instr, cJSON_CreateNumber (slot));
-      cJSON_AddItemToArray (instr, cJSON_CreateNumber (obj_slot));
-      cJSON_AddItemToArray (instr, cJSON_CreateNumber (idx_slot));
-      cJSON_AddItemToArray (s->instructions, instr);
+      mach_emit_3 (s, "delete_idx", slot, obj_slot, idx_slot);
     } else {
       mach_emit_const_bool (s, slot, 1);
     }
@@ -29496,7 +29778,7 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
 
     int dest = mach_alloc_slot (s);
     cJSON *instr = cJSON_CreateArray ();
-    cJSON_AddItemToArray (instr, cJSON_CreateString ("array"));
+    cJSON_AddItemToArray (instr, cJSON_CreateString ("mkarray"));
     cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
     cJSON_AddItemToArray (instr, cJSON_CreateNumber (count));
     cJSON *el;
@@ -29515,7 +29797,7 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
 
     int dest = mach_alloc_slot (s);
     cJSON *instr = cJSON_CreateArray ();
-    cJSON_AddItemToArray (instr, cJSON_CreateString ("record"));
+    cJSON_AddItemToArray (instr, cJSON_CreateString ("mkrecord"));
     cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
     cJSON_AddItemToArray (instr, cJSON_CreateNumber (count));
 
@@ -29532,9 +29814,9 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
         const char *name = cJSON_GetStringValue (cJSON_GetObjectItem (key, "value"));
         cJSON_AddItemToArray (instr, cJSON_CreateString (name ? name : ""));
       } else {
-        /* Computed property - emit the key slot */
+        /* Computed property - emit the key slot (negative to distinguish) */
         int key_slot = mach_gen_expr (s, key);
-        cJSON_AddItemToArray (instr, cJSON_CreateNumber (key_slot));
+        cJSON_AddItemToArray (instr, cJSON_CreateNumber (-1 - key_slot));
       }
 
       int val_slot = mach_gen_expr (s, val);
@@ -29550,8 +29832,14 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
     cJSON *func = mach_gen_function (s, expr);
     cJSON_AddItemToArray (s->functions, func);
 
+    /* Check if it's an arrow function */
+    cJSON *is_arrow = cJSON_GetObjectItem (expr, "arrow");
     int dest = mach_alloc_slot (s);
-    mach_emit_2 (s, "function", dest, func_id);
+    if (is_arrow && cJSON_IsTrue (is_arrow)) {
+      mach_emit_2 (s, "mkfunc_arrow", dest, func_id);
+    } else {
+      mach_emit_2 (s, "mkfunc", dest, func_id);
+    }
     return dest;
   }
 
@@ -29563,11 +29851,13 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
     int func_slot = mach_gen_expr (s, callee);
 
     cJSON *arg_slots = cJSON_CreateArray ();
+    int argc = 0;
     if (args_list) {
       cJSON *arg;
       cJSON_ArrayForEach (arg, args_list) {
         int slot = mach_gen_expr (s, arg);
         cJSON_AddItemToArray (arg_slots, cJSON_CreateNumber (slot));
+        argc++;
       }
     }
 
@@ -29576,6 +29866,7 @@ static int mach_gen_expr (MachGenState *s, cJSON *expr) {
     cJSON_AddItemToArray (instr, cJSON_CreateString ("new"));
     cJSON_AddItemToArray (instr, cJSON_CreateNumber (dest));
     cJSON_AddItemToArray (instr, cJSON_CreateNumber (func_slot));
+    cJSON_AddItemToArray (instr, cJSON_CreateNumber (argc));
     cJSON *el;
     cJSON_ArrayForEach (el, arg_slots) {
       cJSON_AddItemToArray (instr, cJSON_CreateNumber (el->valueint));
@@ -29607,13 +29898,20 @@ static void mach_gen_statement (MachGenState *s, cJSON *stmt) {
     cJSON *right = cJSON_GetObjectItem (stmt, "right");
     const char *name = cJSON_GetStringValue (cJSON_GetObjectItem (left, "name"));
 
+    /* Variable should already be registered from scan phase */
+    int local_slot = mach_find_var_local (s, name);
+
     if (right) {
       int val_slot = mach_gen_expr (s, right);
-      mach_emit_set_var (s, name, val_slot);
-    } else {
-      int slot = mach_alloc_slot (s);
-      mach_emit_const_null (s, slot);
-      mach_emit_set_var (s, name, slot);
+      if (local_slot >= 0) {
+        mach_emit_2 (s, "move", local_slot, val_slot);
+      } else {
+        /* Fallback for unregistered (shouldn't happen) */
+        mach_emit_set_var (s, name, val_slot);
+      }
+    } else if (local_slot >= 0) {
+      /* Initialize to null */
+      mach_emit_const_null (s, local_slot);
     }
     return;
   }
@@ -29833,7 +30131,6 @@ static void mach_gen_statement (MachGenState *s, cJSON *stmt) {
 
     /* First pass: generate case tests and jumps */
     cJSON *case_node;
-    int case_num = 0;
     cJSON_ArrayForEach (case_node, cases) {
       const char *case_kind = cJSON_GetStringValue (cJSON_GetObjectItem (case_node, "kind"));
       if (strcmp (case_kind, "default") == 0) {
@@ -29849,7 +30146,6 @@ static void mach_gen_statement (MachGenState *s, cJSON *stmt) {
         cJSON_AddStringToObject (case_node, "_label", case_label);
         sys_free (case_label);
       }
-      case_num++;
     }
 
     /* Jump to default or end */
@@ -29955,7 +30251,7 @@ static void mach_gen_statement (MachGenState *s, cJSON *stmt) {
       cJSON_AddItemToArray (s->functions, func);
 
       int dest = mach_alloc_slot (s);
-      mach_emit_2 (s, "function", dest, func_id);
+      mach_emit_2 (s, "mkfunc", dest, func_id);
       mach_emit_set_var (s, name, dest);
     }
     return;
@@ -29993,16 +30289,36 @@ static cJSON *mach_gen_function (MachGenState *parent, cJSON *func_node) {
     cJSON_AddStringToObject (result, "name", "<anonymous>");
   }
 
-  /* Parameters - allocate slots 0..nr_args-1 */
+  /* Check if arrow function */
+  cJSON *is_arrow = cJSON_GetObjectItem (func_node, "arrow");
+  s.is_arrow = is_arrow && cJSON_IsTrue (is_arrow);
+
+  /* Parameters - slot 0 is this, slots 1..nr_args are args */
   cJSON *params = cJSON_GetObjectItem (func_node, "list");
   s.nr_args = cJSON_GetArraySize (params);
-  s.next_slot = s.nr_args;
-  s.max_slot = s.nr_args;
+  s.this_slot = 0;
+  s.nr_close_slots = 0;
+  s.nr_local_slots = 0;
+
+  /* Register parameters as variables (slots 1..nr_args) */
+  int param_slot = 1;
+  cJSON *param;
+  cJSON_ArrayForEach (param, params) {
+    const char *param_name = cJSON_GetStringValue (cJSON_GetObjectItem (param, "name"));
+    if (param_name) {
+      mach_add_var (&s, param_name, param_slot, MACH_VAR_ARG);
+      param_slot++;
+    }
+  }
+
+  /* Temps start after this (0), args (1..nr_args), closed vars, and locals */
+  /* For now start at 1 + nr_args, will be adjusted after scanning for vars */
+  s.next_temp_slot = 1 + s.nr_args;
+  s.max_slot = 1 + s.nr_args;
 
   cJSON_AddNumberToObject (result, "nr_args", s.nr_args);
 
   cJSON *vars = cJSON_AddArrayToObject (result, "vars");
-  cJSON *param;
   cJSON_ArrayForEach (param, params) {
     const char *param_name = cJSON_GetStringValue (cJSON_GetObjectItem (param, "name"));
     if (param_name) {
@@ -30010,16 +30326,26 @@ static cJSON *mach_gen_function (MachGenState *parent, cJSON *func_node) {
     }
   }
 
-  /* Generate body */
+  /* Scan for var/def declarations and register them (hoisting) */
   cJSON *stmts = cJSON_GetObjectItem (func_node, "statements");
   cJSON *stmt;
+  cJSON_ArrayForEach (stmt, stmts) {
+    mach_scan_vars (&s, stmt);
+  }
+
+  /* Adjust temp slot start after all locals are allocated */
+  s.next_temp_slot = 1 + s.nr_args + s.nr_local_slots;
+  if (s.next_temp_slot > s.max_slot) s.max_slot = s.next_temp_slot;
+
+  /* Generate body */
   cJSON_ArrayForEach (stmt, stmts) {
     mach_gen_statement (&s, stmt);
   }
 
-  /* Add implicit return null */
+  /* Add implicit return */
   mach_emit_0 (&s, "return_undef");
 
+  cJSON_AddNumberToObject (result, "nr_close_slots", s.nr_close_slots);
   cJSON_AddNumberToObject (result, "nr_slots", s.max_slot + 1);
   cJSON_AddItemToObject (result, "labels", cJSON_CreateObject ());
   cJSON_AddItemToObject (result, "instructions", s.instructions);
@@ -30028,6 +30354,16 @@ static cJSON *mach_gen_function (MachGenState *parent, cJSON *func_node) {
   parent->label_counter = s.label_counter;
   parent->func_counter = s.func_counter;
 
+  /* Free variable tracking arrays */
+  for (int i = 0; i < s.var_count; i++) {
+    sys_free (s.vars[i].name);
+  }
+  if (s.vars) sys_free (s.vars);
+  for (int i = 0; i < s.closure_ref_count; i++) {
+    sys_free (s.closure_refs[i].name);
+  }
+  if (s.closure_refs) sys_free (s.closure_refs);
+
   return result;
 }
 
@@ -30045,7 +30381,27 @@ static cJSON *mach_gen_program (MachGenState *s, cJSON *ast) {
   /* Functions array */
   s->functions = cJSON_AddArrayToObject (result, "functions");
 
-  /* Process top-level function declarations first */
+  /* Main scope setup */
+  s->this_slot = 0;
+  s->nr_args = 0;
+  s->nr_close_slots = 0;
+  s->nr_local_slots = 0;
+  s->next_temp_slot = 1;  /* slot 0 is this */
+  s->max_slot = 1;
+
+  /* Scan main scope for var/def declarations FIRST (hoisting) */
+  /* This must happen before compiling functions so closure resolution works */
+  cJSON *statements = cJSON_GetObjectItem (ast, "statements");
+  cJSON *stmt;
+  cJSON_ArrayForEach (stmt, statements) {
+    mach_scan_vars (s, stmt);
+  }
+
+  /* Adjust temp slot start after all locals are allocated */
+  s->next_temp_slot = 1 + s->nr_local_slots;
+  if (s->next_temp_slot > s->max_slot) s->max_slot = s->next_temp_slot;
+
+  /* Process top-level function declarations */
   cJSON *functions = cJSON_GetObjectItem (ast, "functions");
   cJSON *func_node;
   cJSON_ArrayForEach (func_node, functions) {
@@ -30057,20 +30413,20 @@ static cJSON *mach_gen_program (MachGenState *s, cJSON *ast) {
       cJSON_AddItemToArray (s->functions, func);
 
       int dest = mach_alloc_slot (s);
-      mach_emit_2 (s, "function", dest, func_id);
+      mach_emit_2 (s, "mkfunc", dest, func_id);
       mach_emit_set_var (s, name, dest);
     }
   }
 
   /* Generate main code */
-  cJSON *statements = cJSON_GetObjectItem (ast, "statements");
-  cJSON *stmt;
   cJSON_ArrayForEach (stmt, statements) {
     mach_gen_statement (s, stmt);
   }
 
   /* Main section */
   cJSON *main_obj = cJSON_CreateObject ();
+  cJSON_AddNumberToObject (main_obj, "nr_args", 0);
+  cJSON_AddNumberToObject (main_obj, "nr_close_slots", 0);
   cJSON_AddNumberToObject (main_obj, "nr_slots", s->max_slot + 1);
   cJSON_AddItemToObject (main_obj, "vars", cJSON_CreateArray ());
   cJSON_AddItemToObject (main_obj, "labels", cJSON_CreateObject ());
@@ -30091,6 +30447,16 @@ char *JS_Mach (JSContext *ctx, const char *ast_json) {
   cJSON *mach = mach_gen_program (&s, ast);
   cJSON_Delete (ast);
 
+  /* Free any allocated variable tracking */
+  for (int i = 0; i < s.var_count; i++) {
+    sys_free (s.vars[i].name);
+  }
+  if (s.vars) sys_free (s.vars);
+  for (int i = 0; i < s.closure_ref_count; i++) {
+    sys_free (s.closure_refs[i].name);
+  }
+  if (s.closure_refs) sys_free (s.closure_refs);
+
   if (!mach) return NULL;
 
   char *json = cJSON_Print (mach);