fix(cutter): read the active document from core configuration

Read file.path through CutterCore's scalar configuration API instead of invoking the debug-only currentlyOpenFile backup field. Preserve exact string paths and unknowns so existing discovery, generation admission and Evidence consumers receive the owning facts.

Validated 11 Python protocol tests, 66 relevant CLI/MCP/provider tests, full static/docs gates, and official Linux Cutter 2.5.0 Qt5 workflows with a Unicode/#? ELF path. Same-path reload identity remains partial and native document switching is unverified.

Fixes #4497.

bridge/cutter/rea_bridge.py

@@ -333,8 +333,8 @@ class _RequestDispatcher(QObject):
     @staticmethod
     def _read_current_file() -> str | None:
         try:
-            value = cutter.core().currentlyOpenFile()
-            return str(value) if value else None
+            value = cutter.core().getConfig("file.path")
+            return value if isinstance(value, str) and value else None
         except Exception:
             return None
 

tests/fixtures/cutter_bridge_protocol_test.py

@@ -14,6 +14,7 @@ import types
 import unittest
 import uuid
 from pathlib import Path
+from unittest.mock import patch
 
 
 def _install_host_stubs():
@@ -22,7 +23,7 @@ def _install_host_stubs():
     sys.modules["cutter"] = cutter
     qtcore = types.ModuleType("PySide6.QtCore")
     qtcore.QObject = type("QObject", (), {})
-    qtcore.Signal = lambda *_args: object()
+    qtcore.Signal = lambda *_args: types.SimpleNamespace(connect=lambda _handler: None)
     pyside = types.ModuleType("PySide6")
     pyside.QtCore = qtcore
     sys.modules["PySide6"] = pyside
@@ -221,6 +222,64 @@ def run_serve_mode():
         server.join(timeout=3)
 
 
+class DocumentIdentityTest(unittest.TestCase):
+    def test_document_config_drives_generation_and_command_admission(self):
+        first = "/tmp/Cutter 雪 #1?.elf"
+        second = "/tmp/another document.elf"
+        configuration = {"file.path": first}
+        core = types.SimpleNamespace(
+            getConfig=configuration.__getitem__,
+            getVersionInformation=lambda: "backend fixture",
+        )
+        commands = []
+        with patch.object(bridge.cutter, "core", lambda: core, create=True), patch.object(
+            bridge.cutter, "cmd", lambda command: commands.append(command) or "observed", create=True
+        ):
+            dispatcher = bridge._RequestDispatcher()
+            self.assertEqual(dispatcher.current_file, first)
+            self.assertEqual(dispatcher.generation, 0)
+
+            def handle(**values):
+                request = {**values, "_event": threading.Event(), "_cancelled": threading.Event()}
+                reply = {}
+                dispatcher._handle(request, reply)
+                self.assertTrue(request["_event"].is_set())
+                return reply
+
+            same = handle(kind="status")
+            self.assertEqual(same["current_file"], first)
+            self.assertEqual(same["document_generation"], 0)
+            configuration["file.path"] = second
+            changed = handle(kind="status")
+            self.assertEqual(changed["current_file"], second)
+            self.assertEqual(changed["document_generation"], 1)
+            stale = handle(kind="command", request_id=str(uuid.uuid4()), expected_generation=0, command="iI")
+            self.assertEqual(stale["error"], "active-document-generation-changed")
+            self.assertEqual(stale["execution_state"], "not_started")
+            self.assertEqual(commands, [])
+            current = handle(kind="command", request_id=str(uuid.uuid4()), expected_generation=1, command="iI")
+            self.assertEqual(current["output"], "observed")
+            self.assertEqual(current["document_generation"], 1)
+            self.assertEqual(commands, ["iI"])
+
+    def test_absent_or_unreadable_document_config_remains_unknown(self):
+        class UnreadableCore:
+            def getConfig(self, _key):
+                raise RuntimeError("document config unavailable")
+
+        for core in [
+            types.SimpleNamespace(getConfig=lambda _key: ""),
+            types.SimpleNamespace(getConfig=lambda _key: None),
+            types.SimpleNamespace(getConfig=lambda _key: object()),
+            types.SimpleNamespace(),
+            UnreadableCore(),
+        ]:
+            with self.subTest(core=type(core).__name__), patch.object(
+                bridge.cutter, "core", lambda: core, create=True
+            ):
+                self.assertIsNone(bridge._RequestDispatcher._read_current_file())
+
+
 class ProtocolProducerTest(unittest.TestCase):
     def test_rejects_legacy_peers_before_ui_dispatch(self):
         with socket.create_connection(("127.0.0.1", self.server.port), timeout=2) as connection: