diff --git a/transpiler/codegen/contract.py b/transpiler/codegen/contract.py
index bd8edde9..acad694c 100644
--- a/transpiler/codegen/contract.py
+++ b/transpiler/codegen/contract.py
@@ -402,12 +402,15 @@ def _generate_mapping_mutator(
             key_name = f'key{key_index}'
             key_params.append(f'{key_name}: {key_ts_type}')
 
+            # Convert non-string keys to string for Record indexing
+            key_access = key_name if key_ts_type == 'string' else f'String({key_name})'
+
             if current_type.value_type.is_mapping:
                 null_coalesce_lines.append(
-                    f'{body_indent}{access_path}[{key_name}] ??= {{}};'
+                    f'{body_indent}{access_path}[{key_access}] ??= {{}};'
                 )
 
-            access_path = f'{access_path}[{key_name}]'
+            access_path = f'{access_path}[{key_access}]'
             current_type = current_type.value_type
             key_index += 1
 
diff --git a/transpiler/codegen/statement.py b/transpiler/codegen/statement.py
index 77e867b8..cf66b2ff 100644
--- a/transpiler/codegen/statement.py
+++ b/transpiler/codegen/statement.py
@@ -72,7 +72,7 @@ def __init__(
         super().__init__(ctx)
         self._expr = expr_generator
         self._type_converter = type_converter
-        self._yul_transpiler = YulTranspiler()
+        self._yul_transpiler = YulTranspiler(known_constants=ctx.known_constants)
 
     # =========================================================================
     # MAIN DISPATCH
diff --git a/transpiler/codegen/type_converter.py b/transpiler/codegen/type_converter.py
index d8bcc12a..02ba96dd 100644
--- a/transpiler/codegen/type_converter.py
+++ b/transpiler/codegen/type_converter.py
@@ -190,15 +190,22 @@ def generate_type_cast(
             if expr != 'this' and not expr.startswith('"') and not expr.startswith("'"):
                 return f'{expr}._contractAddress'
 
-        # Handle bytes32 literals
+        # Handle bytes32 literals and expressions
         if type_name == 'bytes32':
             if isinstance(inner_expr, Literal) and inner_expr.kind in ('number', 'hex'):
                 return self._to_padded_bytes32(inner_expr.value)
+            # Non-literal: convert bigint to padded hex string at runtime
+            expr = generate_expression_fn(inner_expr)
+            return f'`0x${{{expr}.toString(16).padStart(64, "0")}}`'
 
         # Handle bytes types
         if type_name.startswith('bytes') and type_name != 'bytes':
             if isinstance(inner_expr, Literal) and inner_expr.kind in ('number', 'hex'):
                 return self._to_padded_bytes32(inner_expr.value)
+            # Non-literal: convert bigint to padded hex string at runtime
+            byte_size = int(type_name[5:]) if type_name[5:].isdigit() else 32
+            expr = generate_expression_fn(inner_expr)
+            return f'`0x${{{expr}.toString(16).padStart({byte_size * 2}, "0")}}`'
 
         # For numeric types (uint256, int128, etc.), just generate the inner expression
         # TypeScript's bigint handles the underlying value
diff --git a/transpiler/codegen/yul.py b/transpiler/codegen/yul.py
index ba8a1d6f..0b93bf84 100644
--- a/transpiler/codegen/yul.py
+++ b/transpiler/codegen/yul.py
@@ -48,6 +48,14 @@ class YulTranspiler:
     - mstore/mload → memory operations (usually no-op for simulation)
     """
 
+    def __init__(self, known_constants: set = None):
+        """Initialize with optional set of known constant names.
+
+        Args:
+            known_constants: Set of constant names that should be prefixed with 'Constants.'
+        """
+        self._known_constants = known_constants or set()
+
     def transpile(self, yul_code: str) -> str:
         """
         Transpile a Yul assembly block to TypeScript.
@@ -285,6 +293,10 @@ def _transpile_expr(self, expr: str, slot_vars: Dict[str, str]) -> str:
         if expr.isdigit():
             return f'{expr}n'
 
+        # Check if identifier is a known constant from type registry
+        if expr in self._known_constants:
+            return f'Constants.{expr}'
+
         # Return as-is (identifier)
         return expr
 
diff --git a/transpiler/sol2ts.py b/transpiler/sol2ts.py
index e1d7b64d..4ac08d7a 100644
--- a/transpiler/sol2ts.py
+++ b/transpiler/sol2ts.py
@@ -13,7 +13,7 @@
 - Interface and contract inheritance
 
 Usage:
-    python -m transpiler src/
+    python transpiler/sol2ts.py src/
 
 This refactored version uses a modular architecture with separate packages for:
 - lexer: Tokenization (tokens.py, lexer.py)
@@ -244,6 +244,8 @@ def main():
     parser.add_argument('input', help='Input Solidity file or directory')
     parser.add_argument('-o', '--output', default='transpiler/ts-output', help='Output directory')
     parser.add_argument('--stdout', action='store_true', help='Print to stdout instead of file')
+    parser.add_argument('-d', '--discover', action='append', metavar='DIR',
+                        help='Directory to scan for type discovery')
     parser.add_argument('--stub', action='append', metavar='CONTRACT',
                         help='Contract name to generate as minimal stub')
     parser.add_argument('--emit-metadata', action='store_true',
@@ -254,12 +256,15 @@ def main():
     args = parser.parse_args()
 
     input_path = Path(args.input)
-    discovery_dirs = [str(input_path)] if input_path.is_dir() else [str(input_path.parent)]
+    discovery_dirs = args.discover or ([str(input_path)] if input_path.is_dir() else [str(input_path.parent)])
     stubbed_contracts = args.stub or []
     emit_metadata = args.emit_metadata or args.metadata_only
 
     if input_path.is_file():
+        # Use first discovery dir as source_dir for correct import path calculation
+        source_dir = discovery_dirs[0] if discovery_dirs else str(input_path.parent)
         transpiler = SolidityToTypeScriptTranspiler(
+            source_dir=source_dir,
             output_dir=args.output,
             discovery_dirs=discovery_dirs,
             stubbed_contracts=stubbed_contracts,