diff --git a/fold.mach b/fold.mach
index 54952d4c..f637ed3b 100644
Binary files a/fold.mach and b/fold.mach differ
diff --git a/internal/engine.mach b/internal/engine.mach
index 2f76ed14..8fc4257b 100644
Binary files a/internal/engine.mach and b/internal/engine.mach differ
diff --git a/mcode.mach b/mcode.mach
index 45d0685b..3584d85c 100644
Binary files a/mcode.mach and b/mcode.mach differ
diff --git a/parse.mach b/parse.mach
index 8474151c..e2202fe5 100644
Binary files a/parse.mach and b/parse.mach differ
diff --git a/qbe_emit.mach b/qbe_emit.mach
index c14c23d3..bb65861c 100644
Binary files a/qbe_emit.mach and b/qbe_emit.mach differ
diff --git a/source/cell.c b/source/cell.c
index 5937b01d..1c14d76b 100644
--- a/source/cell.c
+++ b/source/cell.c
@@ -207,7 +207,6 @@ void script_startup(cell_rt *prt)
 
   // Set args to null for actor spawn (not CLI mode)
   JS_SetPropertyStr(js, hidden_env, "args", JS_NULL);
-  /* use_mcode no longer needed — new bootstrap always uses mcode pipeline */
 
   if (core_path)
     JS_SetPropertyStr(js, hidden_env, "core_path", JS_NewString(js, core_path));
@@ -398,7 +397,6 @@ int cell_init(int argc, char **argv)
   JS_SetPropertyStr(ctx, hidden_env, "core_path", JS_NewString(ctx, core_path));
   JS_SetPropertyStr(ctx, hidden_env, "shop_path",
     shop_path ? JS_NewString(ctx, shop_path) : JS_NULL);
-  /* use_mcode no longer needed — new bootstrap always uses mcode pipeline */
   JS_SetPropertyStr(ctx, hidden_env, "emit_qbe", JS_NewBool(ctx, emit_qbe));
   JS_SetPropertyStr(ctx, hidden_env, "actorsym", JS_DupValue(ctx, cli_rt->actor_sym_ref.val));
   JS_SetPropertyStr(ctx, hidden_env, "json", js_json_use(ctx));
diff --git a/source/mach.c b/source/mach.c
index 757035d7..82be2da3 100644
--- a/source/mach.c
+++ b/source/mach.c
@@ -2224,7 +2224,6 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
   cJSON *nr_slots_j = cJSON_GetObjectItemCaseSensitive(fobj, "nr_slots");
   int nr_slots = (int)cJSON_GetNumberValue(nr_slots_j);
   *out_old_nr_slots = nr_slots;
-  return NULL; /* TEMP: disable compression to test */
   if (nr_slots <= 255) return NULL;
 
   int nr_args = (int)cJSON_GetNumberValue(
@@ -2237,8 +2236,9 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
   int *last_ref  = sys_malloc(nr_slots * sizeof(int));
   for (int i = 0; i < nr_slots; i++) { first_ref[i] = -1; last_ref[i] = -1; }
 
-  /* Args are live for the whole function */
-  for (int i = 0; i < nr_args; i++) { first_ref[i] = 0; last_ref[i] = n; }
+  /* this + args are live for the whole function */
+  int pinned = 1 + nr_args;
+  for (int i = 0; i < pinned; i++) { first_ref[i] = 0; last_ref[i] = n; }
 
   for (int i = 0; i < n; i++) {
     cJSON *it = cJSON_GetArrayItem(instrs, i);
@@ -2310,7 +2310,7 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
         /* Backward jump: extend registers that are live INTO the loop
            (first_ref < loop start but used inside).  Temporaries born
            inside the loop body don't need extension — they are per-iteration. */
-        for (int s = nr_args; s < nr_slots; s++) {
+        for (int s = pinned; s < nr_slots; s++) {
           if (first_ref[s] < 0) continue;
           if (first_ref[s] >= tpos) continue; /* born inside loop — skip */
           if (last_ref[s] < tpos) continue;   /* dead before loop — skip */
@@ -2326,7 +2326,7 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
   typedef struct { int slot, first, last; } SlotInfo;
   int cnt = 0;
   SlotInfo *sorted = sys_malloc(nr_slots * sizeof(SlotInfo));
-  for (int s = nr_args; s < nr_slots; s++)
+  for (int s = pinned; s < nr_slots; s++)
     if (first_ref[s] >= 0)
       sorted[cnt++] = (SlotInfo){s, first_ref[s], last_ref[s]};
 
@@ -2348,7 +2348,7 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
   /* Free-register pool (min-heap would be ideal but a flat scan is fine) */
   int *pool = sys_malloc(nr_slots * sizeof(int));
   int pool_n = 0;
-  int next_phys = nr_args;
+  int next_phys = pinned;
 
   typedef struct { int phys, last; } ActiveAlloc;
   ActiveAlloc *active = sys_malloc(cnt * sizeof(ActiveAlloc));
@@ -2381,7 +2381,7 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
   }
 
   /* Compute new nr_slots */
-  int new_max = nr_args;
+  int new_max = pinned;
   for (int s = 0; s < nr_slots; s++)
     if (first_ref[s] >= 0 && remap[s] >= new_max)
       new_max = remap[s] + 1;
@@ -2391,7 +2391,7 @@ static int *mcode_compress_regs(cJSON *fobj, int *out_old_nr_slots,
     fprintf(stderr, "  WARNING: %d live regs still exceeds 255\n", new_max);
 
   /* Verify: check no two registers with overlapping live ranges share phys */
-  for (int a = nr_args; a < nr_slots; a++) {
+  for (int a = pinned; a < nr_slots; a++) {
     if (first_ref[a] < 0) continue;
     for (int b = a + 1; b < nr_slots; b++) {
       if (first_ref[b] < 0) continue;
@@ -2846,9 +2846,9 @@ void verify_getup(MachCode *mc, const char *path) {
     MachInstr32 instr = mc->instructions[i];
     if (MACH_GET_OP(instr) == MACH_GETUP) {
       int depth = MACH_GET_B(instr);
-      if (depth > 2)
-        fprintf(stderr, "VERIFY: bad GETUP at %s[%d]: depth=%d slot=%d dest=%d instr=0x%08x nr_slots=%d\n",
-          path, i, depth, MACH_GET_C(instr), MACH_GET_A(instr), instr, mc->nr_slots);
+      if (depth > 10)
+        fprintf(stderr, "VERIFY: suspicious GETUP at %s[%d]: depth=%d slot=%d dest=%d\n",
+          path, i, depth, MACH_GET_C(instr), MACH_GET_A(instr));
     }
   }
   for (uint32_t i = 0; i < mc->func_count; i++) {
@@ -3309,16 +3309,6 @@ JSValue JS_RunMachBin(JSContext *ctx, const uint8_t *data, size_t size, JSValue
   if (!mc)
     return JS_ThrowSyntaxError(ctx, "failed to deserialize MACH bytecode");
 
-  fprintf(stderr, "DEBUG RunMachBin: mc=%p instr_count=%d cpool_count=%d func_count=%d nr_slots=%d\n",
-    (void*)mc, mc->instr_count, mc->cpool_count, mc->func_count, mc->nr_slots);
-  verify_getup(mc, "DESER_BOOT");
-  if (mc->instr_count > 0) {
-    fprintf(stderr, "DEBUG first 5 instrs:");
-    for (uint32_t i = 0; i < 5 && i < mc->instr_count; i++)
-      fprintf(stderr, " 0x%08x", mc->instructions[i]);
-    fprintf(stderr, "\n");
-  }
-
   JSGCRef env_ref;
   JS_PushGCRef(ctx, &env_ref);
   env_ref.val = env;
@@ -3326,9 +3316,6 @@ JSValue JS_RunMachBin(JSContext *ctx, const uint8_t *data, size_t size, JSValue
   JSCodeRegister *code = JS_LoadMachCode(ctx, mc, env_ref.val);
   JS_FreeMachCode(mc);
 
-  fprintf(stderr, "DEBUG LoadMachCode: code=%p instr_count=%d cpool_count=%d func_count=%d\n",
-    (void*)code, code->instr_count, code->cpool_count, code->func_count);
-
   JSValue result = JS_CallRegisterVM(ctx, code, ctx->global_obj, 0, NULL, env_ref.val, JS_NULL);
   JS_PopGCRef(ctx, &env_ref);
   return result;
diff --git a/streamline.mach b/streamline.mach
index 699b76cf..88a7e3ee 100644
Binary files a/streamline.mach and b/streamline.mach differ
diff --git a/tokenize.mach b/tokenize.mach
index d6cca1b7..6b7682f1 100644
Binary files a/tokenize.mach and b/tokenize.mach differ