diff --git a/internal/bootstrap.cm b/internal/bootstrap.cm
new file mode 100644
index 00000000..3b53d01d
--- /dev/null
+++ b/internal/bootstrap.cm
@@ -0,0 +1,40 @@
+// Hidden vars (os, program) come from env
+var load_internal = os.load_internal
+function use_embed(name) {
+  return load_internal("js_" + name + "_use")
+}
+
+var fd = use_embed('fd')
+
+var use_cache = {}
+use_cache['fd'] = fd
+use_cache['os'] = os
+
+function use(path) {
+  if (use_cache[path])
+    return use_cache[path];
+
+  var file_path = path + '.cm'
+  var script = null
+  var result = null
+  var exports = null
+
+  if (fd.is_file(file_path)) {
+    script = text(fd.slurp(file_path))
+    exports = {}
+    mach_eval(path, script, {use: use, exports: exports})
+    use_cache[path] = exports
+    return exports
+  }
+
+  // Try embedded C module
+  result = use_embed(replace(path, '/', '_'))
+  use_cache[path] = result
+  return result
+}
+
+// Load and run the user's program
+var blob = fd.slurp(program)
+stone(blob)
+var script = text(blob)
+mach_eval(program, script, {use: use})
diff --git a/internal/os.c b/internal/os.c
index 7c6e8538..267c01c5 100644
--- a/internal/os.c
+++ b/internal/os.c
@@ -578,7 +578,7 @@ static const JSCFunctionListEntry js_os_funcs[] = {
 JSValue js_os_use(JSContext *js) {
   JS_NewClassID(&js_dylib_class_id);
   JS_NewClass(js, js_dylib_class_id, &js_dylib_class);
-  
+
   JSValue mod = JS_NewObject(js);
   JS_SetPropertyFunctionList(js,mod,js_os_funcs,countof(js_os_funcs));
   return mod;
diff --git a/source/cell.c b/source/cell.c
index 16ad612a..dd669f9d 100644
--- a/source/cell.c
+++ b/source/cell.c
@@ -558,59 +558,54 @@ int cell_init(int argc, char **argv)
 
   /* Check for --run-mcode flag to execute via MCODE interpreter */
   if (argc >= 3 && strcmp(argv[1], "--run-mcode") == 0) {
-    const char *script_or_file = argv[2];
-    char *script = NULL;
-    char *allocated_script = NULL;
-    const char *filename = "<eval>";
+    const char *filename = argv[2];
+    if (!find_cell_shop()) return 1;
 
-    struct stat st;
-    if (stat(script_or_file, &st) == 0 && S_ISREG(st.st_mode)) {
-      FILE *f = fopen(script_or_file, "r");
-      if (!f) { printf("Failed to open file: %s\n", script_or_file); return 1; }
-      allocated_script = malloc(st.st_size + 1);
-      if (!allocated_script) { fclose(f); printf("Failed to allocate memory\n"); return 1; }
-      size_t read_size = fread(allocated_script, 1, st.st_size, f);
-      fclose(f);
-      allocated_script[read_size] = '\0';
-      script = allocated_script;
-      filename = script_or_file;
-    } else {
-      script = (char *)script_or_file;
-    }
-
-    cJSON *ast = JS_ASTTree(script, strlen(script), filename);
-    if (!ast) {
-      printf("Failed to parse AST\n");
-      free(allocated_script);
+    size_t boot_size;
+    char *boot_data = load_core_file("internal/bootstrap.cm", &boot_size);
+    if (!boot_data) {
+      printf("ERROR: Could not load internal/bootstrap.cm from %s\n", core_path);
       return 1;
     }
 
-    if (print_tree_errors(ast)) {
-      cJSON_Delete(ast); free(allocated_script);
+    cJSON *boot_ast = JS_ASTTree(boot_data, boot_size, "internal/bootstrap.cm");
+    free(boot_data);
+    if (!boot_ast) {
+      printf("Failed to parse internal/bootstrap.cm\n");
       return 1;
     }
 
-    cJSON *mcode = JS_McodeTree(ast);
-    cJSON_Delete(ast);
+    if (print_tree_errors(boot_ast)) {
+      cJSON_Delete(boot_ast);
+      return 1;
+    }
+
+    cJSON *mcode = JS_McodeTree(boot_ast);
+    cJSON_Delete(boot_ast);
 
     if (!mcode) {
       printf("Failed to generate MCODE\n");
-      free(allocated_script);
       return 1;
     }
 
     if (print_tree_errors(mcode)) {
-      cJSON_Delete(mcode); free(allocated_script);
+      cJSON_Delete(mcode);
       return 1;
     }
 
-    /* Use a larger heap context for execution */
     JSRuntime *rt = JS_NewRuntime();
-    if (!rt) { printf("Failed to create JS runtime\n"); cJSON_Delete(mcode); free(allocated_script); return 1; }
-    JSContext *ctx = JS_NewContextWithHeapSize(rt, 64 * 1024);
-    if (!ctx) { printf("Failed to create execution context\n"); cJSON_Delete(mcode); JS_FreeRuntime(rt); free(allocated_script); return 1; }
+    if (!rt) { printf("Failed to create JS runtime\n"); cJSON_Delete(mcode); return 1; }
+    JSContext *ctx = JS_NewContextWithHeapSize(rt, 256 * 1024);
+    if (!ctx) { printf("Failed to create execution context\n"); cJSON_Delete(mcode); JS_FreeRuntime(rt); return 1; }
 
-    JSValue result = JS_CallMcodeTree(ctx, mcode); /* takes ownership of mcode */
+    JS_FreeValue(ctx, js_blob_use(ctx));
+
+    JSValue hidden_env = JS_NewObject(ctx);
+    JS_SetPropertyStr(ctx, hidden_env, "os", js_os_use(ctx));
+    JS_SetPropertyStr(ctx, hidden_env, "program", JS_NewString(ctx, filename));
+    hidden_env = JS_Stone(ctx, hidden_env);
+
+    JSValue result = JS_CallMcodeTreeEnv(ctx, mcode, hidden_env);
 
     if (JS_IsException(result)) {
       JSValue exc = JS_GetException(ctx);
@@ -637,7 +632,6 @@ int cell_init(int argc, char **argv)
 
     JS_FreeContext(ctx);
     JS_FreeRuntime(rt);
-    free(allocated_script);
     return JS_IsException(result) ? 1 : 0;
   }
 
@@ -707,61 +701,50 @@ int cell_init(int argc, char **argv)
 
   /* Check for --mach-run flag to compile and run through MACH VM */
   if (argc >= 3 && strcmp(argv[1], "--mach-run") == 0) {
-    const char *script_or_file = argv[2];
-    char *script = NULL;
-    char *allocated_script = NULL;
-    const char *filename = "<eval>";
+    const char *filename = argv[2];
+    if (!find_cell_shop()) return 1;
 
-    struct stat st;
-    if (stat(script_or_file, &st) == 0 && S_ISREG(st.st_mode)) {
-      FILE *f = fopen(script_or_file, "r");
-      if (!f) {
-        printf("Failed to open file: %s\n", script_or_file);
-        return 1;
-      }
-      allocated_script = malloc(st.st_size + 1);
-      if (!allocated_script) {
-        fclose(f);
-        printf("Failed to allocate memory for script\n");
-        return 1;
-      }
-      size_t read_size = fread(allocated_script, 1, st.st_size, f);
-      fclose(f);
-      allocated_script[read_size] = '\0';
-      script = allocated_script;
-      filename = script_or_file;
-    } else {
-      script = (char *)script_or_file;
-    }
-
-    cJSON *ast = JS_ASTTree(script, strlen(script), filename);
-    if (!ast) {
-      printf("Failed to parse AST\n");
-      free(allocated_script);
+    size_t boot_size;
+    char *boot_data = load_core_file("internal/bootstrap.cm", &boot_size);
+    if (!boot_data) {
+      printf("ERROR: Could not load internal/bootstrap.cm from %s\n", core_path);
       return 1;
     }
 
-    if (print_tree_errors(ast)) {
-      cJSON_Delete(ast);
-      free(allocated_script);
+    cJSON *boot_ast = JS_ASTTree(boot_data, boot_size, "internal/bootstrap.cm");
+    free(boot_data);
+    if (!boot_ast) {
+      printf("Failed to parse internal/bootstrap.cm\n");
+      return 1;
+    }
+
+    if (print_tree_errors(boot_ast)) {
+      cJSON_Delete(boot_ast);
       return 1;
     }
 
     JSRuntime *rt = JS_NewRuntime();
     if (!rt) {
       printf("Failed to create JS runtime\n");
-      cJSON_Delete(ast); free(allocated_script);
+      cJSON_Delete(boot_ast);
       return 1;
     }
-    JSContext *ctx = JS_NewContext(rt);
+    JSContext *ctx = JS_NewContextWithHeapSize(rt, 256 * 1024);
     if (!ctx) {
       printf("Failed to create JS context\n");
-      cJSON_Delete(ast); JS_FreeRuntime(rt); free(allocated_script);
+      cJSON_Delete(boot_ast); JS_FreeRuntime(rt);
       return 1;
     }
 
-    JSValue result = JS_RunMachTree(ctx, ast, JS_NULL);
-    cJSON_Delete(ast);
+    JS_FreeValue(ctx, js_blob_use(ctx));
+
+    JSValue hidden_env = JS_NewObject(ctx);
+    JS_SetPropertyStr(ctx, hidden_env, "os", js_os_use(ctx));
+    JS_SetPropertyStr(ctx, hidden_env, "program", JS_NewString(ctx, filename));
+    hidden_env = JS_Stone(ctx, hidden_env);
+
+    JSValue result = JS_RunMachTree(ctx, boot_ast, hidden_env);
+    cJSON_Delete(boot_ast);
 
     int exit_code = 0;
     if (JS_IsException(result)) {
@@ -796,7 +779,6 @@ int cell_init(int argc, char **argv)
 
     JS_FreeContext(ctx);
     JS_FreeRuntime(rt);
-    free(allocated_script);
     return exit_code;
   }
 
diff --git a/source/mcode.c b/source/mcode.c
index ea957d3d..2e55b473 100644
--- a/source/mcode.c
+++ b/source/mcode.c
@@ -3444,6 +3444,34 @@ JSValue JS_CallMcodeTree(JSContext *ctx, cJSON *root) {
   return result;
 }
 
+JSValue JS_CallMcodeTreeEnv(JSContext *ctx, cJSON *root, JSValue env) {
+  if (!root) return JS_ThrowSyntaxError(ctx, "invalid MCODE tree");
+
+  cJSON *main_obj = cJSON_GetObjectItemCaseSensitive(root, "main");
+  if (!main_obj) {
+    cJSON_Delete(root);
+    return JS_ThrowSyntaxError(ctx, "MCODE tree missing 'main' section");
+  }
+
+  cJSON *functions = cJSON_GetObjectItemCaseSensitive(root, "functions");
+
+  /* Parse main code */
+  JSMCode *code = jsmcode_parse(main_obj, functions);
+  if (!code) {
+    cJSON_Delete(root);
+    return JS_ThrowInternalError(ctx, "failed to parse MCODE");
+  }
+  code->json_root = root; /* Keep tree alive — instrs point into it */
+
+  /* Execute with global_obj as this, passing env as outer_frame */
+  JSValue result = mcode_exec(ctx, code, ctx->global_obj, 0, NULL, env);
+
+  /* Clear frame ref before freeing mcode — stack trace data is inside code */
+  ctx->reg_current_frame = JS_NULL;
+  jsmcode_free(code);
+  return result;
+}
+
 JSValue JS_CallMcode(JSContext *ctx, const char *mcode_json) {
   cJSON *root = cJSON_Parse(mcode_json);
   if (!root) return JS_ThrowSyntaxError(ctx, "invalid MCODE JSON");
diff --git a/source/quickjs-internal.h b/source/quickjs-internal.h
index 9036b1e1..54f70090 100644
--- a/source/quickjs-internal.h
+++ b/source/quickjs-internal.h
@@ -101,7 +101,7 @@
 // #define DUMP_ROPE_REBALANCE
 
 /* test the GC by forcing it before each object allocation */
-#define FORCE_GC_AT_MALLOC
+// #define FORCE_GC_AT_MALLOC
 
 #define POISON_HEAP
 /* POISON_HEAP: Use ASan's memory poisoning to detect stale pointer access */
diff --git a/source/quickjs.h b/source/quickjs.h
index f9f75919..d00ce026 100644
--- a/source/quickjs.h
+++ b/source/quickjs.h
@@ -1268,6 +1268,9 @@ char *JS_Mcode (const char *ast_json);
 /* Execute MCODE from cJSON tree. Takes ownership of root. */
 JSValue JS_CallMcodeTree (JSContext *ctx, struct cJSON *root);
 
+/* Execute MCODE from cJSON tree with hidden env. Takes ownership of root. */
+JSValue JS_CallMcodeTreeEnv (JSContext *ctx, struct cJSON *root, JSValue env);
+
 /* Parse and execute MCODE JSON string.
    Returns result of execution, or JS_EXCEPTION on error. */
 JSValue JS_CallMcode (JSContext *ctx, const char *mcode_json);
diff --git a/source/runtime.c b/source/runtime.c
index e3ec5137..359edebf 100644
--- a/source/runtime.c
+++ b/source/runtime.c
@@ -10655,7 +10655,8 @@ static JSValue js_mach_eval (JSContext *ctx, JSValue this_val, int argc, JSValue
     return JS_ThrowSyntaxError (ctx, "mach_eval: failed to parse AST");
   }
 
-  JSValue result = JS_RunMachTree (ctx, ast, JS_NULL);
+  JSValue env = (argc >= 3 && JS_IsObject (argv[2])) ? argv[2] : JS_NULL;
+  JSValue result = JS_RunMachTree (ctx, ast, env);
   cJSON_Delete (ast);
   JS_FreeCString (ctx, name);
   return result;