Add standards-based OpenPLC target foundation

Author: C-White-1

ARCHITECTURE.md

@@ -87,6 +87,10 @@ conversion or target layers. Exporter-to-target imports are restricted to
 documented compatibility surfaces, and public package exports must be unique
 and resolvable.
 
+`targets.openplc` exposes a standards-only PLCopen 2.01 façade with no direct
+CODESYS dependency or emitted CODESYS metadata. Native OpenPLC import/runtime
+compatibility remains an evidence milestone rather than an inferred claim.
+
 ## Invariants
 
 - Unknown source data is preserved.

docs/roadmaps/architecture-refactoring-roadmap.md

@@ -305,7 +305,9 @@ Deferred until another device profile or target exists:
 - [x] Review public `__init__` re-exports as APIs grow
 - [x] Stop tracking generated `*.egg-info` metadata in a dedicated cleanup
   commit
-- [ ] Add an OpenPLC target without importing CODESYS assumptions
+- [x] Add an OpenPLC target without importing CODESYS assumptions
+- [ ] Validate generated standard PLCopen XML through a native OpenPLC import
+  and runtime smoke test
 - [ ] Revisit physical channel and CIP assembly entities when EDS or live
   evidence supports them
 - [ ] Review this document whenever a module gains a second independent
@@ -322,6 +324,12 @@ and `ir` layers and restrict exporter-to-target imports to the documented
 package façade and legacy compatibility shim. Public exporter and CODESYS
 target `__all__` surfaces are checked for duplicate or unresolved names.
 
+`targets.openplc.OpenPLCExporter` now provides a minimal standards-based
+target façade over PLCopen XML 2.01. It emits no CODESYS extensions and is
+byte-identical to the generic standard profile. This is an architecture
+foundation, not yet a claim of native OpenPLC import compatibility; that
+requires an external import and runtime smoke test.
+
 ## Refactor completion checklist
 
 A refactor is complete only when:

src/twinforge/targets/openplc/__init__.py

@@ -0,0 +1,5 @@
+"""OpenPLC target adapters using standards-based PLCopen XML."""
+
+from .exporter import OpenPLCExporter
+
+__all__ = ["OpenPLCExporter"]

src/twinforge/targets/openplc/exporter.py

@@ -0,0 +1,57 @@
+"""OpenPLC export foundation backed by standard PLCopen XML 2.01."""
+
+from __future__ import annotations
+
+from datetime import datetime
+from pathlib import Path
+import xml.etree.ElementTree as ET
+
+from twinforge.exporters.plcopen import PLCopenExporter
+from twinforge.exporters.plcopen_types import (
+    PLCopenExportResult,
+    PLCopenProfile,
+)
+from twinforge.model import Controller
+
+
+class OpenPLCExporter:
+    """Emit standard PLCopen XML for native OpenPLC evaluation.
+
+    No unverified OpenPLC extensions are added. Native import compatibility
+    remains a separate evidence milestone.
+    """
+
+    def __init__(self) -> None:
+        self._plcopen = PLCopenExporter(PLCopenProfile.STANDARD_201)
+
+    def build(
+        self,
+        controller: Controller,
+        *,
+        project_name: str | None = None,
+        creation_time: datetime | None = None,
+    ) -> ET.Element:
+        """Build a standard PLCopen 2.01 document."""
+
+        return self._plcopen.build(
+            controller,
+            project_name=project_name,
+            creation_time=creation_time,
+        )
+
+    def export(
+        self,
+        controller: Controller,
+        *,
+        destination: str | Path | None = None,
+        project_name: str | None = None,
+        creation_time: datetime | None = None,
+    ) -> PLCopenExportResult:
+        """Serialize standard PLCopen XML without CODESYS extensions."""
+
+        return self._plcopen.export(
+            controller,
+            destination=destination,
+            project_name=project_name,
+            creation_time=creation_time,
+        )

tests/test_architecture_dependencies.py

@@ -85,6 +85,7 @@ def test_exporter_to_target_imports_are_compatibility_only() -> None:
     [
         "twinforge.exporters",
         "twinforge.targets.codesys",
+        "twinforge.targets.openplc",
     ],
 )
 def test_public_exports_are_unique_and_resolvable(module_name: str) -> None:

tests/test_openplc_exporter.py

@@ -0,0 +1,96 @@
+import ast
+from datetime import datetime, timezone
+import inspect
+import xml.etree.ElementTree as ET
+
+from twinforge.exporters import (
+    PLCOPEN_201_NAMESPACE,
+    PLCopenExporter,
+    PLCopenProfile,
+)
+from twinforge.model import (
+    Controller,
+    Identity,
+    LadderRung,
+    Program,
+    Routine,
+    Tag,
+    Task,
+)
+from twinforge.targets.openplc import OpenPLCExporter
+from twinforge.targets.openplc import exporter as openplc_module
+
+
+FIXED_TIME = datetime(2026, 7, 30, tzinfo=timezone.utc)
+
+
+def _controller() -> Controller:
+    controller = Controller(name="OpenPLCTest", identity=Identity())
+    controller.add_tag(Tag(name="Enable", data_type="BOOL"))
+    controller.add_tag(Tag(name="Output", data_type="BOOL"))
+    program = Program(name="PLC_PRG")
+    routine = Routine(name="MainRoutine", language="RLL")
+    routine.ladder_rungs.append(
+        LadderRung(number=0, text="XIC(Enable)OTE(Output);")
+    )
+    program.add_routine(routine)
+    controller.add_program(program)
+    controller.add_task(
+        Task(
+            name="MainTask",
+            task_type="Periodic",
+            rate=20,
+            priority=1,
+            scheduled_program_names=[program.name],
+            scheduled_programs=[program],
+        )
+    )
+    return controller
+
+
+def test_openplc_target_matches_standard_plcopen_profile() -> None:
+    controller = _controller()
+    expected = PLCopenExporter(PLCopenProfile.STANDARD_201).export(
+        controller,
+        project_name="OpenPLC Project",
+        creation_time=FIXED_TIME,
+    )
+
+    actual = OpenPLCExporter().export(
+        controller,
+        project_name="OpenPLC Project",
+        creation_time=FIXED_TIME,
+    )
+
+    assert actual.xml == expected.xml
+    assert actual.diagnostics == expected.diagnostics
+
+
+def test_openplc_document_contains_no_codesys_extensions() -> None:
+    result = OpenPLCExporter().export(
+        _controller(),
+        creation_time=FIXED_TIME,
+    )
+    root = ET.fromstring(result.xml)
+
+    assert root.tag == f"{{{PLCOPEN_201_NAMESPACE}}}project"
+    assert "3s-software.com" not in result.xml
+    assert "ProjectStructure" not in result.xml
+    assert "ObjectId" not in result.xml
+
+
+def test_openplc_adapter_has_no_direct_codesys_import() -> None:
+    tree = ast.parse(inspect.getsource(openplc_module))
+    imported = {
+        alias.name
+        for node in ast.walk(tree)
+        if isinstance(node, ast.Import)
+        for alias in node.names
+    }
+    imported.update(
+        node.module or ""
+        for node in ast.walk(tree)
+        if isinstance(node, ast.ImportFrom)
+    )
+
+    assert not any("codesys" in module.casefold() for module in imported)