diff --git a/exe_main.cpp b/exe_main.cpp
index 8d19f99..f265224 100644
--- a/exe_main.cpp
+++ b/exe_main.cpp
@@ -1,7 +1,7 @@
 // Treat library files as a single-file (single translation unit) header
 #include "lib_main.cpp"
 
-#define BASE_RUN_TESTS 0
+#define BASE_RUN_TESTS BUILD_DEBUG
 #define BUILD_EXPLORER_APP_WIN32 1
 #define BUILD_CUSTOM_GUI 0
 
diff --git a/lib/Base/Arena_Array.h b/lib/Base/Arena_Array.h
index db9fbd4..2a192e5 100644
--- a/lib/Base/Arena_Array.h
+++ b/lib/Base/Arena_Array.h
@@ -209,6 +209,7 @@ template <typename T> void init_range (T* ptr, s64 start_offset, s64 end_offset)
 
 template <typename T> void array_poison_range (ArenaArray<T>& array, s64 start, s64 count) {
 #if BUILD_DEBUG
+  if (count == 0) return;
   Assert(start >= 0 && start < array.count);
   Assert(start + count <= array.count);
   // Check that these ranges make sense
diff --git a/lib/Base/Base.h b/lib/Base/Base.h
index bb65530..f95c7af 100644
--- a/lib/Base/Base.h
+++ b/lib/Base/Base.h
@@ -342,6 +342,7 @@ force_inline s64 Next_Power_Of_Two(s64 v) {
 #define temp()                allocator(thread_context()->temp)
 #define context_allocator()   thread_context()->allocator
 #define context_logger()      &thread_context()->logger
+#define context_builder()     thread_context()->string_builder
 
 // CHECK THAT THESE ARE CORRECT!
 constexpr f32 TAU = 6.283185f;
diff --git a/lib/Base/Base_Thread_Context.cpp b/lib/Base/Base_Thread_Context.cpp
index e46b65b..3e1a480 100644
--- a/lib/Base/Base_Thread_Context.cpp
+++ b/lib/Base/Base_Thread_Context.cpp
@@ -22,13 +22,14 @@ internal void Bootstrap_Main_Thread_Context () {
   ExpandableArena* arena_ex = bootstrap_expandable_arena(Arena_Reserve::Size_64M);
   
   thread_local_context = New<Thread_Context>(allocator(arena_ex));
-  thread_local_context->temp        = bootstrap_expandable_arena(Arena_Reserve::Size_2M);
-  thread_local_context->arena       = arena_ex;
-  thread_local_context->allocator   = allocator(arena_ex);
-  thread_local_context->thread_idx  = 0;
-  thread_local_context->thread_name = "Main Thread";
-  thread_local_context->log_builder = new_string_builder(Arena_Reserve::Size_64M);
-  thread_local_context->error_arena = bootstrap_arena(Arena_Reserve::Size_64M);
+  thread_local_context->temp           = bootstrap_expandable_arena(Arena_Reserve::Size_2M);
+  thread_local_context->arena          = arena_ex;
+  thread_local_context->allocator      = allocator(arena_ex);
+  thread_local_context->thread_idx     = 0;
+  thread_local_context->thread_name    = "Main Thread";
+  thread_local_context->log_builder    = new_string_builder(Arena_Reserve::Size_64M);
+  thread_local_context->string_builder = new_string_builder(Arena_Reserve::Size_2M);
+  thread_local_context->error_arena    = bootstrap_arena(Arena_Reserve::Size_64M);
 
   default_logger_initialize();
   thread_local_context->logger = {default_logger_proc, &default_logger};
diff --git a/lib/Base/Base_Thread_Context.h b/lib/Base/Base_Thread_Context.h
index fa6aacf..ce48a8b 100644
--- a/lib/Base/Base_Thread_Context.h
+++ b/lib/Base/Base_Thread_Context.h
@@ -24,7 +24,8 @@ struct Thread_Context {
   // u16 _padding0;
   u16 default_allocator_alignment = 16;
   Logger logger = {nullptr, nullptr};
-  String_Builder* log_builder;
+  String_Builder* log_builder;    // String builder used by log() and log_error_internal()
+  String_Builder* string_builder; // Secondary builder just for convenience!
   Stack_Trace_Node* stack_trace; // use `list(stack_trace)` in watch window of raddbg to view as array!
   
   Array<Thread*> child_threads; // maybe should be linked-list?
@@ -127,7 +128,8 @@ struct Push_Stack_Trace {
 };
 
 // #TODO: precede with something like: os_write_string_unsynchronized("Fatal Error!\n\nStack trace:", true);
-string generate_stack_trace (Thread_Context* context) { // #no_context
+string generate_stack_trace (Thread_Context* context) {
+  // #no_context - we want this to work even if context is utterly broken.
   String_Builder* sb = new_string_builder(Arena_Reserve::Size_64K);
   
   Stack_Trace_Node* node = context->stack_trace;
@@ -143,7 +145,12 @@ string generate_stack_trace (Thread_Context* context) { // #no_context
   append(sb, "\n");
   
   push_allocator(default_allocator());
-  return builder_to_string(sb);
+  
+  string stack_trace_copy = builder_to_string(sb);
+  
+  free_string_builder(sb);
+  
+  return stack_trace_copy;
 }
 
 // We don't want to use context logger here!
diff --git a/lib/Base/String.cpp b/lib/Base/String.cpp
index b2446c3..ab45329 100644
--- a/lib/Base/String.cpp
+++ b/lib/Base/String.cpp
@@ -282,7 +282,7 @@ internal force_inline void reset_string_builder (String_Builder* sb, bool keep_m
 force_inline string builder_to_string (String_Builder* sb) {
   string final_string = copy_string(to_string(to_view(*sb)));
   
-  free_string_builder(sb);
+  // reset_string_builder(sb, false); // maybe this shouldn't be here! Too magical...
   
   return final_string;
 }
diff --git a/lib/Base/String_Builder.h b/lib/Base/String_Builder.h
index 62d3322..f0d657f 100644
--- a/lib/Base/String_Builder.h
+++ b/lib/Base/String_Builder.h
@@ -1,10 +1,14 @@
 // #string_builder
 // #limitations This won't be as fast as Jon's String_Builder in jai because we're backing it with an 
-// Arena, which requires a variable number of cycles depending on if our process has
-// memory available already. It also has a max capacity depending on what Arena_Reserve we choose.
-// That being said, the implementation is much simpler.
+// Arena, which calls VirtualAlloc, which is much slower than just using stack space to start. 
+// It also has a max capacity depending on what Arena_Reserve we choose. 
+// That being said, the implementation is much simpler, and we can keep it around for a bit.
+// We can make it a lot faster by always having a string builder available in the thread_context, 
+// and just fetching that when we need it.
+
 typedef ArenaArray<u8> String_Builder; // struct String_Builder
 
+
 force_inline String_Builder* new_string_builder (Arena_Reserve new_reserve=Arena_Reserve::Size_64K);
 force_inline void append (String_Builder* sb, string s);
 void append (String_Builder* sb, ArrayView<string> strings); 
@@ -18,3 +22,5 @@ internal force_inline void reset_string_builder (String_Builder* sb, bool keep_m
 // #rename copy_string_and_free_builder
 force_inline string builder_to_string (String_Builder* sb); // returns copy and frees string_builder
 internal force_inline void free_string_builder (String_Builder* sb);
+
+
diff --git a/lib/Base/run_tests.cpp b/lib/Base/run_tests.cpp
index cadf5ea..99b440e 100644
--- a/lib/Base/run_tests.cpp
+++ b/lib/Base/run_tests.cpp
@@ -19,7 +19,9 @@ void run_post_setup_tests() {
     // String builder example:
     // OK. I can work with this.
     
-    auto sb = new_string_builder(Arena_Reserve::Size_64K);
+    String_Builder* sb = context_builder();
+    reset_string_builder(sb, true);
+    
     append(sb, "string_literal_example");
     append(sb, " ");
     print_to_builder(sb, "There are %d cats in the %s", 64, "house.\n");
@@ -47,9 +49,9 @@ void run_post_setup_tests() {
     // push_allocator(allocator(thread_context()->arena));
     push_allocator(default_allocator());
     string file_path = "D:/Work/OpenBCI/ToolZ/prototyping-gui-main/modules/native-proto-lib/native-sdk-prototyping/src/SignalProcessing.cpp";
-    ArrayView<u8> file_data = read_entire_file(file_path, true);
+    ArrayView<u8> file_data = read_entire_file(file_path, true, true);
     log("file_data: \n");
-    log("%s\n", file_data.data);
+    log("%s\n", file_data.data); // #note this is not null-terminated
   }
   { // Test hashing:
     u64 start = 0x512585;
diff --git a/lib/OS/OS_Filesystem.cpp b/lib/OS/OS_Filesystem.cpp
index a33f838..5085869 100644
--- a/lib/OS/OS_Filesystem.cpp
+++ b/lib/OS/OS_Filesystem.cpp
@@ -84,8 +84,8 @@ string get_full_path (string drive_label, Dense_FS* dfs, s32 first_parent_index,
   
   array_add(path_list_reverse, drive_letter_with_colon);
   
-  // reset_string_builder(sb, true);
-  String_Builder* sb = new_string_builder();
+  String_Builder* sb = context_builder();
+  reset_string_builder(sb, true);
   
   for (s64 i = path_list_reverse.count-1; i >= 0; i -= 1) {
     append(sb, path_list_reverse[i]);
diff --git a/lib/OS/OS_Win32.cpp b/lib/OS/OS_Win32.cpp
index 9218596..a5d2754 100644
--- a/lib/OS/OS_Win32.cpp
+++ b/lib/OS/OS_Win32.cpp
@@ -296,15 +296,16 @@ internal bool thread_init (Thread* thread, Thread_Proc proc, string thread_name)
   
   // #NOTE: we don't assign thread_local_context until we hit the #thread_entry_point
   thread->context = New<Thread_Context>();
-  thread->context->temp        = bootstrap_expandable_arena(Arena_Reserve::Size_2M);
-  thread->context->arena       = arena_ex;
-  thread->context->allocator   = allocator(arena_ex);
-  thread->context->thread_idx  = (s32)this_thread_index;
+  thread->context->temp           = bootstrap_expandable_arena(Arena_Reserve::Size_2M);
+  thread->context->arena          = arena_ex;
+  thread->context->allocator      = allocator(arena_ex);
+  thread->context->thread_idx     = (s32)this_thread_index;
   // #NOTE: This will disappear once the thread is de-initted. If we want this string, copy it!
-  thread->context->thread_name = copy_string(thread_name);
-  thread->context->log_builder = new_string_builder(Arena_Reserve::Size_64M);
-  thread->context->error_arena = bootstrap_arena(Arena_Reserve::Size_64M);
-  thread->context->logger      = {default_logger_proc, &default_logger};
+  thread->context->thread_name    = copy_string(thread_name);
+  thread->context->log_builder    = new_string_builder(Arena_Reserve::Size_64M);
+  thread->context->string_builder = new_string_builder(Arena_Reserve::Size_2M);
+  thread->context->error_arena    = bootstrap_arena(Arena_Reserve::Size_64M);
+  thread->context->logger         = {default_logger_proc, &default_logger};
   
   thread->context->parent_thread_context = thread_context();
   
@@ -557,7 +558,7 @@ internal bool file_set_position (File file, s64 position) {
   return (bool)SetFilePointerEx(file.handle, position_li, nullptr, FILE_BEGIN);
 }
 
-internal ArrayView<u8> read_entire_file (File file) {
+ArrayView<u8> read_entire_file (File file, bool add_null_terminator) {
   ArrayView<u8> file_data;
 
   bool result = file_length(file, &file_data.count);
@@ -565,7 +566,13 @@ internal ArrayView<u8> read_entire_file (File file) {
   result = file_set_position(file, 0);
   if (!result) return {};
   
-  file_data.data = NewArray<u8>(file_data.count, false);
+  s64 total_file_size = file_data.count;
+  
+  if (add_null_terminator) {
+    total_file_size += 1;
+  }
+  
+  file_data.data = NewArray<u8>(total_file_size, false);
   if (file_data.data == nullptr) return {};  
   
   s64 bytes_read = 0;
@@ -575,17 +582,21 @@ internal ArrayView<u8> read_entire_file (File file) {
     return {};
   }
   
+  if (add_null_terminator) {
+    file_data[total_file_size-1] = 0;
+  }
+  
   Assert(bytes_read == file_data.count);
   file_data.count = bytes_read;
   
   return file_data;
 }
 
-internal ArrayView<u8> read_entire_file (string file_path, bool log_errors) {
+internal ArrayView<u8> read_entire_file (string file_path, bool add_null_terminator, bool log_errors) {
   File f = file_open(file_path, false, false, log_errors);
   if (!file_is_valid(f)) return {};
   
-  ArrayView<u8> file_data = read_entire_file(f);
+  ArrayView<u8> file_data = read_entire_file(f, add_null_terminator);
   
   file_close(&f);
   
@@ -1416,7 +1427,7 @@ bool Deserialize_ST_File_Enumeration (string file_path) {
   push_allocator(temp());
   auto_release_temp();
   
-  Deserializer deserializer = read_entire_file(file_path, true);
+  Deserializer deserializer = read_entire_file(file_path, false, true);
   if (deserializer.count == 0) return false;
   auto d = &deserializer;
   
diff --git a/lib/OS/OS_Win32.h b/lib/OS/OS_Win32.h
index 7bc37fb..4616590 100644
--- a/lib/OS/OS_Win32.h
+++ b/lib/OS/OS_Win32.h
@@ -41,8 +41,8 @@ internal bool file_length (File file, s64* length);
 internal bool file_length (string file_path, s64* length);
 internal s64 file_current_position (File file);
 internal bool file_set_position (File file, s64 position);
-internal ArrayView<u8> read_entire_file (File file);
-internal ArrayView<u8> read_entire_file (string file_path, bool log_errors=false);
+internal ArrayView<u8> read_entire_file (File file, bool add_null_terminator);
+internal ArrayView<u8> read_entire_file (string file_path, bool add_null_terminator=false, bool log_errors=false);
 
 // use to_byte_view to convert ArrayView<non-u8> to ArrayView<u8>
 internal bool file_write (File* file, void* data, s64 length);
diff --git a/lib/OS/OS_Win32_File_Enumeration.cpp b/lib/OS/OS_Win32_File_Enumeration.cpp
index a35ffed..e1567fe 100644
--- a/lib/OS/OS_Win32_File_Enumeration.cpp
+++ b/lib/OS/OS_Win32_File_Enumeration.cpp
@@ -105,7 +105,9 @@ string directory_get_full_path (Thread_Group* group, Parent_Index pid, string di
   }
   
   // go in reverse order and add together string
-  String_Builder* sb = new_string_builder(Arena_Reserve::Size_64K);
+  String_Builder* sb = context_builder();
+  reset_string_builder(sb, true);
+  
   for (s64 i = paths.count-1; i >= 0; i -= 1) {
     append(sb, paths[i]);
     append(sb, "\\");
diff --git a/lib/OS/OS_Win32_NTFS.cpp b/lib/OS/OS_Win32_NTFS.cpp
index 40a6834..b00dd4a 100644
--- a/lib/OS/OS_Win32_NTFS.cpp
+++ b/lib/OS/OS_Win32_NTFS.cpp
@@ -457,7 +457,7 @@ bool Deserialize_Win32_Drives (string file_path) {
   push_allocator(temp());
   auto_release_temp();
   
-  Deserializer deserializer = read_entire_file(file_path, true);
+  Deserializer deserializer = read_entire_file(file_path, false, true);
   if (deserializer.count == 0) return false;
   auto d = &deserializer;