diff --git a/src/scripts/list_project_libraries.py b/src/scripts/list_project_libraries.py
index 87665b4..a9d9953 100644
--- a/src/scripts/list_project_libraries.py
+++ b/src/scripts/list_project_libraries.py
@@ -160,7 +160,21 @@ try:
     project_info = collect_project_info(primary_project)
     devices = collect_devices(primary_project)
     ide_version = sys.version  # IronPython under CODESYS reports the IDE
+    # Project-wide compiler version selector. Available since ScriptEngine
+    # 4.2.0.0; older IDEs return None / raise. Captured here so a manual
+    # change in the IDE ("Project > Project Settings > Compiler version")
+    # leaves a textual trace in mcp-mirror/library.md instead of being
+    # invisible to the release classifier (binary-only diff -> SHA fallback).
+    compiler_version = None
+    try:
+        if hasattr(primary_project, 'get_compilerversion'):
+            cv = primary_project.get_compilerversion()
+            if cv is not None:
+                compiler_version = str(cv)
+    except Exception as e:
+        print("DEBUG: get_compilerversion() failed: %s" % e)
     print("DEBUG: project_info: %s" % project_info)
+    print("DEBUG: compiler_version: %s" % compiler_version)
     print("DEBUG: %d device(s) found." % len(devices))
 
     containers = find_libman_containers(primary_project)
@@ -170,6 +184,7 @@ try:
         'project': project_basename,
         'project_info': project_info,
         'ide_version': ide_version,
+        'compiler_version': compiler_version,
         'devices': devices,
         'containers': [],
         'total_references': 0,
diff --git a/src/server.ts b/src/server.ts
index f10bab8..4ec9a9c 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -253,7 +253,7 @@ interface ContainerData {
 interface LibrariesData {
   project?: string;
   project_info?: { version?: string | null; title?: string | null; company?: string | null; author?: string | null };
-  ide_version?: string; devices?: DeviceData[]; containers: ContainerData[]; total_references: number;
+  ide_version?: string; compiler_version?: string | null; devices?: DeviceData[]; containers: ContainerData[]; total_references: number;
 }
 interface PouEntry { path: string; type?: string; declaration?: string; implementation?: string; }
 
@@ -273,6 +273,7 @@ function renderLibraryMd(libs: LibrariesData, runtimeAnchorVersion?: string): st
   if (pi.company) L.push(`| Project Information.Company | ${pi.company} |`);
   if (pi.author) L.push(`| Project Information.Author | ${pi.author} |`);
   if (libs.ide_version) L.push(`| CODESYS Development System | \`${libs.ide_version.replace(/\s+/g, ' ').trim()}\` |`);
+  if (libs.compiler_version) L.push(`| Project compiler version | \`${libs.compiler_version}\` |`);
   if (runtimeAnchorVersion) L.push(`| Runtime anchor | \`_MCP_PROJECT_VERSION.sVersion := "${runtimeAnchorVersion}"\` |`);
   L.push('');
   if (libs.devices && libs.devices.length > 0) {
@@ -1692,6 +1693,7 @@ export async function startMcpServer(config: ServerConfig): Promise<void> {
           project?: string;
           project_info?: ProjectInfo;
           ide_version?: string;
+          compiler_version?: string | null;
           devices?: Device[];
           containers: Container[];
           total_references: number;
@@ -1760,6 +1762,9 @@ export async function startMcpServer(config: ServerConfig): Promise<void> {
         if (parsed.ide_version) {
           headerLines.push(`IDE: ${parsed.ide_version.replace(/\s+/g, ' ').trim()}`);
         }
+        if (parsed.compiler_version) {
+          headerLines.push(`Compiler version: ${parsed.compiler_version}`);
+        }
         if (parsed.devices && parsed.devices.length > 0) {
           headerLines.push(`Devices (${parsed.devices.length}):`);
           for (const d of parsed.devices) {