diff --git a/codex/codex_patcher.py b/codex/codex_patcher.py
index dd93071..80f68dd 100755
--- a/codex/codex_patcher.py
+++ b/codex/codex_patcher.py
@@ -221,25 +221,56 @@ def read_toml_raw(path):
         return f.read()
 
 
+def _toml_str(s):
+    """Escape a Python string as a TOML basic-string literal.
+
+    Backslashes (Windows paths!) and double-quotes must be escaped per
+    TOML spec — otherwise the parser sees `C:\\Windows` as `C:Windows`
+    or fails with `Unescaped '\\' in a string`.
+    """
+    escaped = s.replace("\\", "\\\\").replace('"', '\\"')
+    return f'"{escaped}"'
+
+
 def toml_value(v):
-    """Format a Python value as TOML."""
+    """Format a Python value as TOML.
+
+    Dicts → inline table `{ key = "val", k2 = "v2" }` (NOT Python str(dict)
+    which uses single quotes + colons and breaks `tomllib.load`).
+    Strings → basic-string with backslash/quote escapes (Windows paths).
+    """
     if isinstance(v, bool):
         return "true" if v else "false"
     if isinstance(v, str):
-        return f'"{v}"'
+        return _toml_str(v)
     if isinstance(v, (int, float)):
         return str(v)
     if isinstance(v, list):
         items = ", ".join(toml_value(i) for i in v)
         return f"[{items}]"
-    return str(v)
+    if isinstance(v, dict):
+        # TOML inline table: keys may need quoting (special chars / dots),
+        # values recurse through toml_value.
+        items = ", ".join(
+            f"{toml_key(k)} = {toml_value(val)}" for k, val in v.items()
+        )
+        return f"{{ {items} }}" if items else "{}"
+    return _toml_str(str(v))
 
 
 def toml_key(k):
-    """Format a TOML key, quoting if it contains dots or special chars."""
-    if "." in k or " " in k:
-        return f'"{k}"'
-    return k
+    """Format a TOML key, quoting if it contains anything other than the
+    bare-key charset (A-Z a-z 0-9 _ -). Examples that MUST be quoted:
+        "PROGRAMFILES(X86)"  — parens
+        "key.with.dots"      — would parse as nested
+        "key with spaces"
+    """
+    import re as _re
+    if _re.fullmatch(r"[A-Za-z0-9_-]+", k):
+        return k
+    # Quote, escape backslashes and quotes
+    escaped = k.replace("\\", "\\\\").replace('"', '\\"')
+    return f'"{escaped}"'
 
 
 def generate_config_toml(existing, config, home_dir=None):