diff --git a/headroom/transforms/code_compressor.py b/headroom/transforms/code_compressor.py
index fe05e86b7..03acb1648 100644
--- a/headroom/transforms/code_compressor.py
+++ b/headroom/transforms/code_compressor.py
@@ -860,7 +860,7 @@ class CodeAwareCompressor(Transform):
         body_line_counts: dict[str, int] = {}
         for qname, node in definitions.items():
             collect_calls_in_function(node, qname)
-            node_text = code[node.start_byte : node.end_byte]
+            node_text = _slice_code_bytes(code, node.start_byte, node.end_byte)
             body_line_counts[qname] = max(1, len(node_text.split("\n")) - 2)
 
         # Reference counts: subtract definition occurrences
@@ -1266,8 +1266,8 @@ class CodeAwareCompressor(Transform):
                             child, code, language, lang_config, body_limits, analysis
                         )
                         # Reconstruct export with compressed inner definition
-                        export_prefix = code[node.start_byte : child.start_byte]
-                        export_suffix = code[child.end_byte : node.end_byte]
+                        export_prefix = _slice_code_bytes(code, node.start_byte, child.start_byte)
+                        export_suffix = _slice_code_bytes(code, child.end_byte, node.end_byte)
                         structure.function_signatures.append(
                             export_prefix + compressed + export_suffix
                         )
@@ -1582,7 +1582,7 @@ class CodeAwareCompressor(Transform):
         if signature_lines:
             result_parts.extend(signature_lines)
         else:
-            sig_text = code[node.start_byte : body_node.start_byte].rstrip()
+            sig_text = _slice_code_bytes(code, node.start_byte, body_node.start_byte).rstrip()
             result_parts.append(sig_text)
 
         if opening_brace_line is not None:
@@ -2010,9 +2010,14 @@ class CodeAwareCompressor(Transform):
 # =========================================================================
 
 
+def _slice_code_bytes(code: str, start_byte: int, end_byte: int) -> str:
+    """Extract source text using tree-sitter UTF-8 byte offsets."""
+    return code.encode("utf-8")[start_byte:end_byte].decode("utf-8")
+
+
 def _get_node_text(node: Any, code: str) -> str:
     """Extract text from AST node."""
-    return code[node.start_byte : node.end_byte]
+    return _slice_code_bytes(code, node.start_byte, node.end_byte)
 
 
 def _get_same_line_trailing_semicolon(node: Any) -> Any | None:
diff --git a/tests/test_transforms/test_code_compressor.py b/tests/test_transforms/test_code_compressor.py
index 76de4e3ae..774d9b6eb 100644
--- a/tests/test_transforms/test_code_compressor.py
+++ b/tests/test_transforms/test_code_compressor.py
@@ -1591,6 +1591,50 @@ class TestRealASTRuns:
         # Output is still valid Python.
         compile(result.compressed, "<test>", "exec")
 
+    def test_get_node_text_uses_utf8_byte_offsets(self):
+        """tree-sitter byte offsets must not be sliced as Python str indexes."""
+        from headroom.transforms.code_compressor import _get_node_text, _get_parser
+
+        code = 'def first():\n    """中文占位"""\n    return 1\n\ndef second():\n    return 2\n'
+        root = _get_parser("python").parse(code.encode("utf-8")).root_node
+        functions = [node for node in root.children if node.type == "function_definition"]
+
+        assert _get_node_text(functions[1], code) == "def second():\n    return 2"
+
+    def test_ast_compresses_python_after_non_ascii_source(self):
+        """CJK/emoji before a later function must not corrupt downstream slices."""
+        compressor = CodeAwareCompressor(
+            CodeCompressorConfig(
+                min_tokens_for_compression=1,
+                max_body_lines=2,
+                enable_ccr=False,
+                semantic_analysis=False,
+            )
+        )
+        code = (
+            "def first():\n"
+            '    """中文占位 with emoji 🔥."""\n'
+            "    return 1\n"
+            "\n"
+            "def second():\n"
+            "    values = []\n"
+            "    for i in range(10):\n"
+            "        values.append(i)\n"
+            "        values.append(i * 2)\n"
+            "        values.append(i * 3)\n"
+            "        values.append(i * 4)\n"
+            "    return sum(values)\n"
+        )
+
+        result = compressor.compress(code, language="python")
+
+        assert result.language == CodeLanguage.PYTHON
+        assert result.syntax_valid is True
+        assert result.compression_ratio < 1.0
+        assert "def second():" in result.compressed
+        assert "中文占位" in result.compressed
+        compile(result.compressed, "<test>", "exec")
+
     def test_ast_runs_for_rust_no_fallback(self):
         """A second supported language (Rust) also runs through real AST."""
         code = (