diff --git a/server/src/tools/def_symbols.py b/server/src/tools/def_symbols.py
new file mode 100644
index 0000000..8e48b9c
--- /dev/null
+++ b/server/src/tools/def_symbols.py
@@ -0,0 +1,36 @@
+"""Block templates and addresses declared in NX post definition (.def) files."""
+
+import re
+from dataclasses import dataclass, field
+from pathlib import Path
+
+_BLOCK_TEMPLATE_RE = re.compile(r"^\s*BLOCK_TEMPLATE\s+([^\s{]+)", re.MULTILINE)
+_ADDRESS_RE = re.compile(r"^\s*ADDRESS\s+([^\s{]+)", re.MULTILINE)
+
+
+@dataclass(frozen=True)
+class DefSymbols:
+    block_templates: tuple[str, ...] = ()
+    addresses: tuple[str, ...] = ()
+
+
+def _names(pattern: re.Pattern, source: str) -> tuple[str, ...]:
+    return tuple(dict.fromkeys(pattern.findall(source)))
+
+
+def parse_def_symbols(source: str) -> DefSymbols:
+    """Return the BLOCK_TEMPLATE and ADDRESS names of a .def source in declaration order."""
+    return DefSymbols(
+        block_templates=_names(_BLOCK_TEMPLATE_RE, source),
+        addresses=_names(_ADDRESS_RE, source),
+    )
+
+
+def read_def_symbols(path: Path) -> DefSymbols:
+    data = path.read_bytes()
+    try:
+        source = data.decode("utf-8-sig")
+    except UnicodeDecodeError:
+        # Older Windows NX layers use the ANSI code page.
+        source = data.decode("cp1252")
+    return parse_def_symbols(source)