--- a/Tools/wasm/wasm_assets.py
+++ b/Tools/wasm/wasm_assets.py
@@ -47,13 +47,20 @@
     # webbrowser
     "antigravity.py",
     "webbrowser.py",
-    # Pure Python implementations of C extensions
-    "_pydecimal.py",
+    # Pure Python implementations of C extensions.
+    # NOTE: keep "_pydecimal.py" so decimal.py can fall back to it when the
+    # _decimal C extension is not built (NuttX targets do not link libmpdec).
     "_pyio.py",
     # concurrent threading
     "concurrent/futures/thread.py",
     # Misc unused or large files
     "pydoc_data/",
+    # Tooling/REPL extras not needed on a constrained embedded target.
+    "unittest/",
+    "_pyrepl/",
+    "idlelib/",
+    "turtledemo/",
+    "wsgiref/",
 )
 
 # Synchronous network I/O and protocols are not supported; for example,
@@ -80,7 +87,8 @@
     "_asyncio": ["asyncio/"],
     "_curses": ["curses/"],
     "_ctypes": ["ctypes/"],
-    "_decimal": ["decimal.py"],
+    # decimal.py is intentionally NOT omitted here: it ships a pure-Python
+    # fallback (_pydecimal) used when the _decimal C ext is unavailable.
     "_dbm": ["dbm/ndbm.py"],
     "_gdbm": ["dbm/gnu.py"],
     "_json": ["json/"],