diff --git a/benchmarks/binarytree.ce b/benchmarks/binarytree.ce
index ed95a31e..c317a2e3 100644
--- a/benchmarks/binarytree.ce
+++ b/benchmarks/binarytree.ce
@@ -7,7 +7,7 @@ function mainThread() {
 
   var longLivedTree = bottomUpTree(maxDepth);
 
-  for (let depth = 4; depth <= maxDepth; depth += 2) {
+  for (var depth = 4; depth <= maxDepth; depth += 2) {
     var iterations = 1 << maxDepth - depth + 4;
     work(iterations, depth);
   }
@@ -16,8 +16,8 @@ function mainThread() {
 }
 
 function work(iterations, depth) {
-  let check = 0;
-  for (let i = 0; i < iterations; i++)
+  var check = 0;
+  for (var i = 0; i < iterations; i++)
     check += itemCheck(bottomUpTree(depth));
   log.console(`${iterations}\t trees of depth ${depth}\t check: ${check}`);
 }
diff --git a/benchmarks/fannkuch.ce b/benchmarks/fannkuch.ce
index 0651f4c7..a2f371f5 100644
--- a/benchmarks/fannkuch.ce
+++ b/benchmarks/fannkuch.ce
@@ -1,6 +1,6 @@
 function fannkuch(n) {
    var perm1 = [n]   
-   for (let i = 0; i < n; i++) perm1[i] = i      
+   for (var i = 0; i < n; i++) perm1[i] = i      
    var perm = [n]
    var count = [n]       
    var f = 0, flips = 0, nperm = 0, checksum = 0      
@@ -18,7 +18,7 @@ function fannkuch(n) {
       while (k != 0) {
          i = 0  
          while (2*i < k) {          
-            let t = perm[i]; perm[i] = perm[k-i]; perm[k-i] = t  
+            var t = perm[i]; perm[i] = perm[k-i]; perm[k-i] = t  
             i += 1           
          }
          k = perm[0]
@@ -34,10 +34,10 @@ function fannkuch(n) {
             log.console( checksum )               
             return flips 
          }
-         let p0 = perm1[0]
+         var p0 = perm1[0]
          i = 0
          while (i < r) {
-            let j = i + 1
+            var j = i + 1
             perm1[i] = perm1[j]
             i = j            
          }
diff --git a/benchmarks/mandelbrot.ce b/benchmarks/mandelbrot.ce
index a900816a..e6f9ce22 100644
--- a/benchmarks/mandelbrot.ce
+++ b/benchmarks/mandelbrot.ce
@@ -8,15 +8,15 @@ var w = h
 
 log.console(`P4\n${w} ${h}`);
 
-for (let y = 0; y < h; ++y) {
+for (var y = 0; y < h; ++y) {
   // Create a blob for the row - we need w bits
   var row = new blob(w);
 
-  for (let x = 0; x < w; ++x) {
+  for (var x = 0; x < w; ++x) {
     zr = zi = tr = ti = 0;
     cr = 2 * x / w - 1.5;
     ci = 2 * y / h - 1;
-    for (let i = 0; i < iter && (tr + ti <= limit * limit); ++i) {
+    for (var i = 0; i < iter && (tr + ti <= limit * limit); ++i) {
       zi = 2 * zr * zi + ci;
       zr = tr - ti + cr;
       tr = zr * zr;
diff --git a/benchmarks/nota.ce b/benchmarks/nota.ce
index aba95555..c2aed58c 100644
--- a/benchmarks/nota.ce
+++ b/benchmarks/nota.ce
@@ -19,15 +19,15 @@ var notaDecodeTimes = [];
 var notaSizes = [];
 
 // Run 100 tests
-for (let i = 0; i < 100; i++) {
+for (var i = 0; i < 100; i++) {
     // JSON Decode test
-    let start = os.now();
+    var start = os.now();
     var jll = json.decode(ll);
     jsonDecodeTimes.push((os.now() - start) * 1000);
 
     // JSON Encode test
     start = os.now();
-    let jsonStr = JSON.stringify(jll);
+    var jsonStr = JSON.stringify(jll);
     jsonEncodeTimes.push((os.now() - start) * 1000);
 
     // NOTA Encode test
diff --git a/benchmarks/wota.ce b/benchmarks/wota.ce
index 759eae49..14aad1f6 100644
--- a/benchmarks/wota.ce
+++ b/benchmarks/wota.ce
@@ -14,18 +14,18 @@
 // Helper to run a function repeatedly and measure total time in seconds.
 // Returns elapsed time in seconds.
 function measureTime(fn, iterations) {
-    let t1 = os.now();
-    for (let i = 0; i < iterations; i++) {
+    var t1 = os.now();
+    for (var i = 0; i < iterations; i++) {
         fn();
     }
-    let t2 = os.now();
+    var t2 = os.now();
     return t2 - t1;
 }
 
 // We'll define a function that does `encode -> decode` for a given value:
 function roundTripWota(value) {
-    let encoded = wota.encode(value);
-    let decoded = wota.decode(encoded);
+    var encoded = wota.encode(value);
+    var decoded = wota.decode(encoded);
     // Not doing a deep compare here, just measuring performance.
     // (We trust the test suite to verify correctness.)
 }
@@ -79,22 +79,22 @@ log.console("Wota Encode/Decode Benchmark");
 log.console("===================\n");
 
 // We'll run each benchmark scenario in turn.
-for (let bench of benchmarks) {
+for (var bench of benchmarks) {
     // We'll measure how long it takes to do 'iterations' *for each test value*
     // in bench.data. The total loop count is `bench.iterations * bench.data.length`.
     // Then we compute an overall encode+decode throughput (ops/s).
-    let totalIterations = bench.iterations * bench.data.length;
+    var totalIterations = bench.iterations * bench.data.length;
     
     // We'll define a function that does a roundTrip for *each* data item in bench.data
     // to measure in one loop iteration. Then we multiply by bench.iterations.
     function runAllData() {
-        for (let val of bench.data) {
+        for (var val of bench.data) {
             roundTripWota(val);
         }
     }
 
-    let elapsedSec = measureTime(runAllData, bench.iterations);
-    let opsPerSec  = (totalIterations / elapsedSec).toFixed(1);
+    var elapsedSec = measureTime(runAllData, bench.iterations);
+    var opsPerSec  = (totalIterations / elapsedSec).toFixed(1);
 
     log.console(`${bench.name}:`);
     log.console(`  Iterations: ${bench.iterations} × ${bench.data.length} data items = ${totalIterations}`);
diff --git a/benchmarks/wota_nota_json.ce b/benchmarks/wota_nota_json.ce
index 2a504705..f9ef5bbb 100644
--- a/benchmarks/wota_nota_json.ce
+++ b/benchmarks/wota_nota_json.ce
@@ -108,9 +108,9 @@ def benchmarks = [
 ////////////////////////////////////////////////////////////////////////////////
 
 function measureTime(fn) {
-  let start = os.now();
+  var start = os.now();
   fn();
-  let end   = os.now();
+  var end   = os.now();
   return (end - start);  // in seconds
 }
 
@@ -128,15 +128,15 @@ function runBenchmarkForLibrary(lib, bench) {
 
   // Pre-store the encoded results for all items so we can measure decode time
   // in a separate pass. Also measure total size once.
-  let encodedList = [];
-  let totalSize = 0;
+  var encodedList = [];
+  var totalSize = 0;
 
   // 1) Measure ENCODING
-  let encodeTime = measureTime(() => {
-    for (let i = 0; i < bench.iterations; i++) {
+  var encodeTime = measureTime(() => {
+    for (var i = 0; i < bench.iterations; i++) {
       // For each data item, encode it
-      for (let j = 0; j < bench.data.length; j++) {
-        let e = lib.encode(bench.data[j]);
+      for (var j = 0; j < bench.data.length; j++) {
+        var e = lib.encode(bench.data[j]);
         // store only in the very first iteration, so we can decode them later
         // but do not store them every iteration or we blow up memory.
         if (i == 0) {
@@ -148,11 +148,11 @@ function runBenchmarkForLibrary(lib, bench) {
   });
 
   // 2) Measure DECODING
-  let decodeTime = measureTime(() => {
-    for (let i = 0; i < bench.iterations; i++) {
+  var decodeTime = measureTime(() => {
+    for (var i = 0; i < bench.iterations; i++) {
       // decode everything we stored during the first iteration
-      for (let e of encodedList) {
-        let decoded = lib.decode(e);
+      for (var e of encodedList) {
+        var decoded = lib.decode(e);
         // not verifying correctness here, just measuring speed
       }
     }
diff --git a/internal/engine.cm b/internal/engine.cm
index 5eae1b3b..0221bcd5 100644
--- a/internal/engine.cm
+++ b/internal/engine.cm
@@ -133,7 +133,7 @@ log.error = function(msg = new Error())
 {
   var caller = caller_data(1)
   
-  if (msg instanceof Error)
+  if (is_proto(msg, Error))
     msg = msg.name + ": " + msg.message + "\n" + msg.stack 
   
   os.print(console_rec(caller.line,caller.file,msg))
@@ -149,7 +149,7 @@ function disrupt(err)
   if (overling) {
     if (err) {
       // with an err, this is a forceful disrupt
-      var reason = (err instanceof Error) ? err.stack : err
+      var reason = (is_proto(err, Error)) ? err.stack : err
       report_to_overling({type:'disrupt', reason})
     } else
       report_to_overling({type:'stop'})
@@ -766,8 +766,6 @@ if (!locator)
 
 stone(globalThis)
 
-var rads = use_core("math/radians")
-
 $_.clock(_ => {
   // Get capabilities for the main program
   var file_info = shop.file_info ? shop.file_info(locator.path) : null
diff --git a/internal/shop.cm b/internal/shop.cm
index 890e4e49..52d24e2d 100644
--- a/internal/shop.cm
+++ b/internal/shop.cm
@@ -677,7 +677,7 @@ Shop.open_package_dylib = function(pkg) {
   }
   
   // 3. Check core internal symbols (core is never a dynamic library)
-  var core_sym = `js_${path}_use`
+  var core_sym = `js_${path.replaceAll('/', '_')}_use`
   if (os.internal_exists(core_sym)) {
     return {
       symbol: function() { return os.load_internal(core_sym) },
@@ -1174,22 +1174,22 @@ Shop.get_package_dir = function(pkg) {
 // e.g., c_symbol_for_file('gitea.pockle.world/john/prosperon', 'sprite.c') 
 //       -> 'js_gitea_pockle_world_john_prosperon_sprite_use'
 Shop.c_symbol_for_file = function(pkg, file) {
-  var pkg_safe = pkg.replace(/\//g, '_').replace(/\./g, '_').replace(/-/g, '_')
-  var file_safe = file.substring(0, file.lastIndexOf('.')).replace(/\//g, '_').replace(/\./g, '_').replace(/-/g, '_')
+  var pkg_safe = pkg.replaceAll(/\//g, '_').replaceAll(/\./g, '_').replaceAll(/-/g, '_')
+  var file_safe = file.substring(0, file.lastIndexOf('.')).replaceAll(/\//g, '_').replaceAll(/\./g, '_').replaceAll(/-/g, '_')
   return 'js_' + pkg_safe + '_' + file_safe + '_use'
 }
 
 // Generate C symbol prefix for a package
 // e.g., c_symbol_prefix('gitea.pockle.world/john/prosperon') -> 'js_gitea_pockle_world_john_prosperon_'
 Shop.c_symbol_prefix = function(pkg) {
-  var pkg_safe = pkg.replace(/\//g, '_').replace(/\./g, '_').replace(/-/g, '_')
+  var pkg_safe = pkg.replaceAll(/\//g, '_').replaceAll(/\./g, '_').replaceAll(/-/g, '_')
   return 'js_' + pkg_safe + '_'
 }
 
 // Get the library name for a package (without extension)
 // e.g., 'gitea.pockle.world/john/prosperon' -> 'gitea_pockle_world_john_prosperon'
 Shop.lib_name_for_package = function(pkg) {
-  return pkg.replace(/\//g, '_').replace(/\./g, '_').replace(/-/g, '_')
+  return pkg.replaceAll(/\//g, '_').replaceAll(/\./g, '_').replaceAll(/-/g, '_')
 }
 
 // Returns { ok: bool, results: [{pkg, ok, error}] }
diff --git a/link.ce b/link.ce
index ab8ed3d9..88edcde3 100644
--- a/link.ce
+++ b/link.ce
@@ -114,7 +114,7 @@ if (cmd == 'list') {
       if (target.startsWith('./')) {
         target = cwd + target.substring(1)
       } else {
-        // For ../ paths, let fd.realpath handle it if possible
+        // For ../ paths, var fd.realpath handle it if possible
         target = fd.realpath(target) || target
       }
     }
diff --git a/parseq.cm b/parseq.cm
index 396222be..9c376e07 100644
--- a/parseq.cm
+++ b/parseq.cm
@@ -29,7 +29,7 @@ function is_requestor (fn) {
 }
 
 function check_requestors (list, factory) {
-  if (!isa(list, array) || list.some(r => !is_requestor(r)))
+  if (!is_array(list) || list.some(r => !is_requestor(r)))
     throw make_reason(factory, 'Bad requestor list.', list)
 }
 
@@ -47,9 +47,9 @@ function schedule (fn, seconds) {
 // ———————————————————————————————————————— core runner
 
 function run (factory, requestors, initial, action, time_limit, throttle = 0) {
-  let cancel_list = new Array(requestors.length)
-  let next = 0
-  let timer_cancel
+  var cancel_list = new Array(requestors.length)
+  var next = 0
+  var timer_cancel
 
   function cancel (reason = make_reason(factory, 'Cancel.')) {
     if (timer_cancel) timer_cancel(), timer_cancel = null
@@ -60,7 +60,7 @@ function run (factory, requestors, initial, action, time_limit, throttle = 0) {
 
   function start_requestor (value) {
     if (!cancel_list || next >= requestors.length) return
-    let idx = next++
+    var idx = next++
     def req = requestors[idx]
 
     try {
@@ -87,7 +87,7 @@ function run (factory, requestors, initial, action, time_limit, throttle = 0) {
   }
 
   def concurrent = throttle ? number.min(throttle, requestors.length) : requestors.length
-  for (let i = 0; i < concurrent; i++) start_requestor(initial)
+  for (var i = 0; i < concurrent; i++) start_requestor(initial)
 
   return cancel
 }
@@ -95,10 +95,10 @@ function run (factory, requestors, initial, action, time_limit, throttle = 0) {
 // ———————————————————————————————————————— factories
 
 function _normalize (collection, factory) {
-  if (isa(collection)) return { names: null, list: collection }
+  if (is_array(collection)) return { names: null, list: collection }
   if (collection && is_object(collection)) {
     def names = array(collection)
-    def list = names.map(k => collection[k]).filter(is_requestor)
+    def list = names.map(k => collection[k]).filter(is_requestor)
     return { names, list }
   }
   throw make_reason(factory, 'Expected array or record.', collection)
@@ -119,7 +119,7 @@ function par_all (collection, time_limit, throttle) {
 
   return function par_all_req (cb, initial) {
     check_callback(cb, factory)
-    let pending = list.length
+    var pending = list.length
     def results = new Array(list.length)
 
     def cancel = run(factory, list, initial, (val, reason, idx) => {
@@ -143,7 +143,7 @@ function par_any (collection, time_limit, throttle) {
 
   return function par_any_req (cb, initial) {
     check_callback(cb, factory)
-    let pending = list.length
+    var pending = list.length
     def successes = new Array(list.length)
 
     def cancel = run(factory, list, initial, (val, reason, idx) => {
@@ -161,14 +161,14 @@ function par_any (collection, time_limit, throttle) {
 }
 
 function race (list, time_limit, throttle) {
-  def factory = throttle == 1 ? 'fallback' : 'race'
-  if (!isa(list, array) || list.length == 0)
+  def factory = throttle == 1 ? 'fallback' : 'race'
+  if (!is_array(list) || list.length == 0)
     throw make_reason(factory, 'No requestors.')
   check_requestors(list, factory)
 
   return function race_req (cb, initial) {
     check_callback(cb, factory)
-    let done = false
+    var done = false
     def cancel = run(factory, list, initial, (val, reason, idx) => {
       if (done) return
       if (val != null) {
@@ -190,14 +190,14 @@ function fallback (list, time_limit) {
 }
 
 function sequence (list, time_limit) {
-  def factory = 'sequence'
-  if (!isa(list, array)) throw make_reason(factory, 'Not an array.', list)
+  def factory = 'sequence'
+  if (!is_array(list)) throw make_reason(factory, 'Not an array.', list)
   check_requestors(list, factory)
   if (list.length == 0) return (cb, v) => cb(v)
 
   return function sequence_req (cb, initial) {
     check_callback(cb, factory)
-    let idx = 0
+    var idx = 0
 
     function next (value) {
       if (idx >= list.length) return cb(value)
diff --git a/source/quickjs.c b/source/quickjs.c
index 3a03b28d..0e9c2a0e 100644
--- a/source/quickjs.c
+++ b/source/quickjs.c
@@ -5584,16 +5584,6 @@ static void mark_children(JSRuntime *rt, JSGCObjectHeader *gp,
             for(i = 0; i < sh->prop_count; i++) {
                 JSProperty *pr = &p->prop[i];
                 if (prs->atom != JS_ATOM_NULL) {
-                    /* Mark object-key symbol payload to keep key object alive */
-                    if (!__JS_AtomIsTaggedInt(prs->atom)) {
-                        JSAtomStruct *ap = rt->atom_array[prs->atom];
-                        if (ap && ap->atom_type == JS_ATOM_TYPE_SYMBOL) {
-                            JSAtomSymbol *sp = js_atom_as_symbol(ap);
-                            if (!JS_IsNull(sp->obj_key)) {
-                                JS_MarkValue(rt, sp->obj_key, mark_func);
-                            }
-                        }
-                    }
                     if (prs->flags & JS_PROP_TMASK) {
                         if ((prs->flags & JS_PROP_TMASK) == JS_PROP_GETSET) {
                             if (pr->u.getset.getter)
diff --git a/test.ce b/test.ce
index 298a93fa..f446119a 100644
--- a/test.ce
+++ b/test.ce
@@ -314,7 +314,7 @@ function run_tests(package_name, specific_test) {
 
                         if (is_text(ret)) {
                              throw new Error(ret)
-                        } else if (ret && (is_text(ret.message) || ret instanceof Error)) {
+                        } else if (ret && (is_text(ret.message) || is_proto(ret, Error))) {
                              throw ret
                         }
 
diff --git a/tests/nota.cm b/tests/nota.cm
index a70a19d5..fc592886 100644
--- a/tests/nota.cm
+++ b/tests/nota.cm
@@ -54,8 +54,8 @@ function deepCompare(expected, actual, path) {
         passed: false,
         messages: [`Array length mismatch at ${path}: expected ${expected.length}, got ${actual.length}`]
       };
-    let messages = [];
-    for (let i = 0; i < expected.length; i++) {
+    var messages = [];
+    for (var i = 0; i < expected.length; i++) {
       var result = deepCompare(expected[i], actual[i], `${path}[${i}]`);
       if (!result.passed) {
           for(var m of result.messages) messages.push(m);
@@ -72,8 +72,8 @@ function deepCompare(expected, actual, path) {
         passed: false,
         messages: [`Object keys mismatch at ${path}: expected ${expKeys}, got ${actKeys}`]
       };
-    let messages = [];
-    for (let key of expKeys) {
+    var messages = [];
+    for (var key of expKeys) {
       var result = deepCompare(expected[key], actual[key], `${path}.${key}`);
       if (!result.passed) {
           for(var m of result.messages) messages.push(m);
diff --git a/tests/num.cm b/tests/num.cm
deleted file mode 100644
index ebe924e3..00000000
--- a/tests/num.cm
+++ /dev/null
@@ -1,100 +0,0 @@
-var num = use('num');
-
-return {
-    test_num_basic: function() {
-        // Test matrix creation and operations
-        var A = new num.Matrix([
-            [1, 2, 3],
-            [4, 5, 6],
-            [7, 8, 10]
-        ]);
-        
-        log.console("Matrix A:");
-        log.console(A.toArray());
-        
-        // Test matrix inversion
-        var A_inv = A.inverse();
-        log.console("\nMatrix A inverse:");
-        log.console(A_inv.toArray());
-        
-        // Verify A * A_inv = I (approximately)
-        var I = A.multiply(A_inv);
-        log.console("\nA * A_inv (should be identity):");
-        log.console(I.toArray());
-        
-        // Test array creation
-        var v = new num.Array([1, 2, 3]);
-        log.console("\nVector v:");
-        log.console(v.toArray());
-        
-        // Test matrix-vector multiplication
-        var result = A.multiply(v);
-        log.console("\nA * v:");
-        log.console(result.toArray());
-        
-        // Test dot product
-        var u = new num.Array([4, 5, 6]);
-        var dot_product = v.dot(u);
-        log.console("\nv · u =", dot_product);
-        
-        // Test norm
-        var v_norm = v.norm();
-        log.console("||v|| =", v_norm);
-        
-        // Test matrix-matrix multiplication
-        var B = new num.Matrix([
-            [1, 0, 0],
-            [0, 2, 0],
-            [0, 0, 3]
-        ]);
-        
-        var C = A.multiply(B);
-        log.console("\nA * B:");
-        log.console(C.toArray());
-    },
-
-    test_num_property: function() {
-        // Create an array
-        var arr = new num.Array([10, 20, 30, 40, 50]);
-        
-        if (arr[0] != 10) throw "arr[0] mismatch"
-        if (arr[1] != 20) throw "arr[1] mismatch"
-        if (arr[4] != 50) throw "arr[4] mismatch"
-        
-        arr[0] = 15
-        if (arr[0] != 15) throw "arr[0] set failed"
-        
-        // arr[10] should be null or undefined, check behavior
-        // log.console("arr[10] =", arr[10]); 
-        
-        if (arr.length != 5) throw "arr.length mismatch"
-        
-        if (!(arr instanceof num.Array)) throw "instanceof check failed"
-    },
-
-    test_num_setter: function() {
-        // Create an array
-        var arr = new num.Array([1, 2, 3, 4, 5]);
-        
-        // Test setting values
-        arr[0] = 100;
-        arr[1] = 200;
-        arr[2] = 300.5;
-        
-        if (arr[0] != 100) throw "Setter failed index 0"
-        if (arr[1] != 200) throw "Setter failed index 1"
-        if (arr[2] != 300.5) throw "Setter failed index 2"
-        
-        // Test setting with different types
-        arr[3] = "123.7"; // Should convert string to number
-        arr[4] = true;    // Should convert boolean to number
-        
-        // Loose comparison for converted values if needed, or check specific behavior
-        // Assuming implementation converts:
-        // log.console("arr[3] =", arr[3]);
-        // log.console("arr[4] =", arr[4]);
-        
-        // Test bounds checking - this should fail silently or throw depending on impl
-        arr[10] = 999;
-    }
-}
diff --git a/tests/suite.cm b/tests/suite.cm
index 960760ea..867753ce 100644
--- a/tests/suite.cm
+++ b/tests/suite.cm
@@ -1052,6 +1052,15 @@ return {
         if (is_null(object)) throw "null not object"
     },
 
+    test_is_proto: function() {
+        var a = {}
+        var b = meme(a)
+        if (!is_proto(b, a)) throw "is_proto failed on meme"
+
+        var c = new Error()
+        if (!is_proto(c, Error)) throw "is_proto failed new"
+    },
+
     // ============================================================================
     // GLOBAL FUNCTIONS - LENGTH
     // ============================================================================
diff --git a/tests/wota.cm b/tests/wota.cm
index 9fcf239b..31e72a12 100644
--- a/tests/wota.cm
+++ b/tests/wota.cm
@@ -19,7 +19,7 @@ function deep_compare(expected, actual, path) {
     return { passed: false, messages: [`Value mismatch at ${path}: ${expected} vs ${actual} (diff ${diff})`] }
   }
 
-  if ((expected instanceof blob) && (actual instanceof blob)) {
+  if (is_blob(expected) && is_blob(actual)) {
     stone_if_needed(expected); stone_if_needed(actual)
     if (expected.length != actual.length)
       return { passed: false, messages: [`blob length mismatch at ${path}: ${expected.length} vs ${actual.length}`] }
@@ -110,7 +110,7 @@ var testCases = [
 function make_test(t) {
   return function() {
     var enc = wota.encode(t.input)
-    if (!(enc instanceof blob)) throw 'encode() should return a blob'
+    if (!is_blob(enc)) throw 'encode() should return a blob'
 
     var dec = wota.decode(enc)