diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..5994bb5
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,32 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  ascii-check:
+    name: ascii-check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Fail on non-ASCII bytes in src/*.py
+        run: python3 tools/ci/check_ascii.py
+
+  ironpython:
+    name: ironpython
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Download IronPython 2.7.12
+        shell: pwsh
+        run: |
+          curl.exe -sL -o ipy.zip https://github.com/IronLanguages/ironpython2/releases/download/ipy-2.7.12/IronPython.2.7.12.zip
+          Expand-Archive ipy.zip -DestinationPath ipy
+      - name: Compile all src files with IronPython 2.7
+        shell: pwsh
+        run: .\ipy\net45\ipy.exe tools\ci\compile_all.py
+      - name: Import smoke test with stubbed scriptengine
+        shell: pwsh
+        run: .\ipy\net45\ipy.exe tools\ci\import_smoke.py
diff --git a/tools/ci/check_ascii.py b/tools/ci/check_ascii.py
new file mode 100644
index 0000000..c6b5286
--- /dev/null
+++ b/tools/ci/check_ascii.py
@@ -0,0 +1,35 @@
+"""Fail if any file in src/ contains a non-ASCII byte.
+
+CODESYS ScriptEngine is IronPython 2.7, which enforces PEP 263: source files
+must be pure ASCII unless an encoding is declared. A stray em-dash or smart
+quote in a comment makes CODESYS refuse to load the file at all. Python 3
+py_compile cannot catch this because Python 3 source defaults to UTF-8.
+
+Runs under Python 3 (CI) or Python 2 - byte scanning only, no imports.
+"""
+
+import os
+import sys
+
+SRC = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "..", "src")
+
+failures = []
+for name in sorted(os.listdir(SRC)):
+    if not name.endswith(".py"):
+        continue
+    path = os.path.join(SRC, name)
+    with open(path, "rb") as f:
+        data = f.read()
+    line = 1
+    for i in range(len(data)):
+        b = data[i] if isinstance(data[i], int) else ord(data[i])
+        if b == 0x0A:
+            line += 1
+        elif b > 0x7F:
+            failures.append("%s:%d: non-ASCII byte 0x%02X" % (name, line, b))
+
+for failure in failures:
+    print("FAIL    " + failure)
+if not failures:
+    print("OK      all src/*.py files are pure ASCII")
+sys.exit(1 if failures else 0)
diff --git a/tools/ci/compile_all.py b/tools/ci/compile_all.py
new file mode 100644
index 0000000..51b9561
--- /dev/null
+++ b/tools/ci/compile_all.py
@@ -0,0 +1,37 @@
+# REMEMBER: this is python 2.7 - runs under IronPython, the engine CODESYS embeds.
+"""Compile every file in src/ with the real IronPython 2.7 compiler.
+
+This catches Python 2 syntax errors the way CODESYS ScriptEngine would,
+which py_compile under Python 3 cannot.
+
+Note: IronPython's compile() of an in-memory string does NOT enforce PEP 263
+(verified empirically; only the file-based execute/import paths do). Encoding
+violations are covered by check_ascii.py, and by import_smoke.py for the
+library modules, so this script owns the syntax class only.
+"""
+from __future__ import print_function
+
+import os
+import sys
+
+SRC = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "..", "src")
+
+failures = []
+for name in sorted(os.listdir(SRC)):
+    if not name.endswith(".py"):
+        continue
+    path = os.path.join(SRC, name)
+    f = open(path, "rU")
+    try:
+        source = f.read()
+    finally:
+        f.close()
+
+    try:
+        compile(source, path, "exec")
+        print("OK      " + name)
+    except SyntaxError as e:
+        failures.append(name)
+        print("FAIL    %s: %s" % (name, e))
+
+sys.exit(1 if failures else 0)
diff --git a/tools/ci/import_smoke.py b/tools/ci/import_smoke.py
new file mode 100644
index 0000000..d7eb9c1
--- /dev/null
+++ b/tools/ci/import_smoke.py
@@ -0,0 +1,39 @@
+# REMEMBER: this is python 2.7 - runs under IronPython, the engine CODESYS embeds.
+"""Import every library module in src/ with a stubbed scriptengine.
+
+Compilation alone misses module-scope mistakes (bad names in dispatch tables,
+broken imports between modules). Importing executes module-level code, which
+is as close as CI can get to CODESYS loading the scripts.
+
+The script_*.py entry scripts are excluded: they execute their main logic at
+import time and require a live CODESYS project.
+"""
+from __future__ import print_function
+
+import os
+import sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, os.path.join(HERE, "..", "..", "src"))
+sys.path.insert(0, HERE)  # provides the scriptengine stub
+
+MODULES = [
+    "object_type",
+    "util",
+    "entrypoint",
+    "import_export",
+    "communication_import_export",
+    "import_from_files",
+    "project_template",
+]
+
+failures = []
+for module in MODULES:
+    try:
+        __import__(module)
+        print("OK      import " + module)
+    except Exception as e:
+        failures.append(module)
+        print("FAIL    import %s: %r" % (module, e))
+
+sys.exit(1 if failures else 0)
diff --git a/tools/ci/scriptengine.py b/tools/ci/scriptengine.py
new file mode 100644
index 0000000..d828958
--- /dev/null
+++ b/tools/ci/scriptengine.py
@@ -0,0 +1,25 @@
+# REMEMBER: this is python 2.7
+"""Stub of the CODESYS-injected scriptengine module, for CI import tests only.
+
+The real module exists solely inside the CODESYS ScriptEngine host. The src
+modules only touch it inside function bodies, so an attribute sponge is enough
+to let them import. If a future change accesses scriptengine at module scope
+in a way this stub cannot satisfy, the import smoke test fails - which is
+exactly the kind of regression it exists to catch.
+"""
+
+
+class _Anything(object):
+    def __getattr__(self, name):
+        return _Anything()
+
+    def __call__(self, *args, **kwargs):
+        return _Anything()
+
+
+projects = _Anything()
+system = _Anything()
+online = _Anything()
+ImplementationLanguages = _Anything()
+PromptChoice = _Anything()
+PromptResult = _Anything()