fix(task-2): block_explode keeps the ATTRIB frame and writes into the owner layout

Two silent wrong-place defects in the BURST path. An ATTRIB is an OCS
entity, so the TEXT that replaces it now carries extrusion/thickness with
insert/align_point; a mirrored reference (ATTRIB reflected to (0,0,-1),
INSERT +Z with yscale=-1) put the tag 50 units across the mirror axis with
a clean audit. Members and TEXTs now go into the INSERT's owner layout
(ezdxf get_layout, COM ObjectIdToObject(OwnerID)) instead of the current
space: a sheet title block exploded while Model was current duplicated
geometry into model space and then died on delete_entity headless, and on
COM landed the tag text in model space with ok: True. A reference nested
in a block definition is refused before any write on both engines.

Five regression tests (mirrored INSERT, sheet-owned INSERT with Model
current, nested INSERT, and the COM owner-block / nested-refusal call
shapes) fail on the previous commit and pass here.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

backends/com_backend.py

@@ -193,6 +193,38 @@ def _msp():
         return doc.ModelSpace
 
 
+def _owner_layout_block(doc, ent, handle):
+    """The block table record that owns ``ent``, refused unless it is a layout.
+
+    ``Explode()`` places the members in the owner space, so anything this
+    method adds alongside them must go there too — never ``ActiveLayout``,
+    which is whatever tab the user happens to have open. An owner that is a
+    block definition means ``ent`` is a nested reference; exploding it in place
+    would redefine the block under every other reference, so it is refused
+    before any call is dispatched. An owner that cannot be read at all is
+    refused too rather than guessed.
+    """
+    try:
+        owner = doc.ObjectIdToObject(ent.OwnerID)
+        is_layout = bool(owner.IsLayout)
+    except Exception as exc:
+        raise RuntimeError(
+            f"Entity {handle} has no resolvable owner layout ({exc}); refusing to "
+            "explode into a guessed space"
+        ) from exc
+    if not is_layout:
+        try:
+            name = str(owner.Name)
+        except Exception:
+            name = "?"
+        raise RuntimeError(
+            f"Entity {handle} is nested inside block definition {name!r}; explode the "
+            "outer reference instead (exploding here would redefine the block under "
+            "every other reference)"
+        )
+    return owner
+
+
 def _require_block_defined(doc, name):
     """``doc.Blocks.Item(name)``, or a ``ValueError`` before ``InsertBlock`` runs.
 
@@ -3312,6 +3344,14 @@ class ComBackend(AutoCADBackend):
         surface; ``Explode()``'s return shape is the ActiveX documented one
         (an array of the new objects) and is exercised live by the settings
         smoke.
+
+        The TEXTs go into the reference's *owner* block
+        (``ObjectIdToObject(OwnerID)``), which is where ``Explode()`` puts the
+        members; ``HandleToObject`` resolves a handle in any layout, so a title
+        block on a sheet exploded while Model was active used to get its tag
+        text in model space with ``ok: True``. A reference nested inside a
+        block definition (owner ``IsLayout`` false) is refused before the
+        explode is dispatched.
         """
 
         def _sync():
@@ -3319,6 +3359,7 @@ class ComBackend(AutoCADBackend):
             ent = doc.HandleToObject(handle)
             if ent.ObjectName != "AcDbBlockReference":
                 raise RuntimeError(f"Entity {handle} is not a block reference (INSERT)")
+            owner = _owner_layout_block(doc, ent, handle)
             captured = []
             try:
                 attrs = ent.GetAttributes()
@@ -3347,11 +3388,10 @@ class ComBackend(AutoCADBackend):
                     obj.Delete()  # the tag placeholder EXPLODE leaves; the value is below
                     continue
                 inserted.append(str(obj.Handle))
-            mspace = _msp()
             attribute_texts = []
             for item in captured:
                 ins = item["insertion"]
-                text = mspace.AddText(
+                text = owner.AddText(
                     item["text"],
                     _apoint(ins[0], ins[1], ins[2] if len(ins) > 2 else 0.0),
                     item["height"],

backends/ezdxf_backend.py

@@ -4521,8 +4521,38 @@ class EzdxfBackend(AutoCADBackend):
 
         return await self._async(_sync)
 
+    @staticmethod
+    def _owner_layout_for_explode(ent, handle: str):
+        """The layout that owns ``ent`` — model space or a paper-space layout.
+
+        Raises before any write when the owner is a block definition (a nested
+        reference) or cannot be resolved at all; guessing the current space
+        instead is how geometry ends up duplicated into the wrong tab.
+        """
+        try:
+            layout = ent.get_layout()
+        except Exception as exc:
+            raise RuntimeError(
+                f"Entity {handle} has no resolvable owner layout ({exc}); refusing to "
+                "explode into a guessed space"
+            ) from exc
+        if layout is None or not layout.is_any_layout:
+            owner = getattr(layout, "name", None) or ent.dxf.get("owner", "?")
+            raise RuntimeError(
+                f"Entity {handle} is nested inside block definition {owner!r}; explode "
+                "the outer reference instead (exploding here would redefine the block "
+                "under every other reference)"
+            )
+        return layout
+
     #: ATTRIB DXF attributes carried onto the TEXT that replaces it on explode.
-    #: ``insert``/``align_point`` are already WCS on an attached ATTRIB.
+    #: An ATTRIB is an OCS entity: ``insert``/``align_point`` are numbers in the
+    #: plane of its own ``extrusion``, so the frame travels with them. Without
+    #: it the TEXT took the OCS numbers with the default +Z frame, and a
+    #: mirrored reference (ezdxf reflects the ATTRIB to extrusion ``(0, 0, -1)``
+    #: while the INSERT keeps +Z with ``yscale=-1``) put the tag 50 units away
+    #: on the other side of the mirror axis — audit clean, ``plane_normal``
+    #: None, nothing said. Same numbers in the same frame is the same place.
     _ATTRIB_TO_TEXT = (
         "layer",
         "color",
@@ -4536,6 +4566,8 @@ class EzdxfBackend(AutoCADBackend):
         "text_generation_flag",
         "insert",
         "align_point",
+        "extrusion",
+        "thickness",
     )
 
     async def block_explode(self, handle) -> dict:
@@ -4548,13 +4580,21 @@ class EzdxfBackend(AutoCADBackend):
         style and layer, carrying the *value*; an invisible ATTRIB becomes an
         invisible TEXT rather than appearing. The new handles are reported as
         ``attribute_texts``, separate from the geometry's ``inserted_handles``.
+
+        The members and the TEXTs go into the INSERT's *owner* layout, not the
+        current one: ``_get_entity`` resolves a handle in any layout, so a title
+        block on a sheet exploded while Model was current used to have its
+        geometry copied into model space and then die on ``delete_entity``
+        with the reference still alive on the sheet. A reference nested inside
+        a block definition is refused before anything is written — exploding
+        it there would redefine the block under every other reference.
         """
 
         def _sync():
             ent = self._get_entity(handle)
             if ent.dxftype() != "INSERT":
                 raise RuntimeError(f"Entity {handle} is not a block reference (INSERT)")
-            msp = self._msp()
+            msp = self._owner_layout_for_explode(ent, handle)
             inserted = []
             for sub in ent.virtual_entities():
                 sub_copy = sub.copy()

server.py

@@ -3032,10 +3032,14 @@ async def block_explode(
     Every attached ATTRIB becomes a TEXT with the same value, placement,
     height, rotation and layer (an invisible attribute becomes an invisible
     TEXT); AutoCAD's plain EXPLODE would keep only the tag-name placeholders
-    and drop the values. Returns `inserted_handles` (the geometry),
-    `attribute_texts` (one TEXT handle per attribute), `exploded_handle` and
-    `backend`. Refused: a handle that is not a block reference (nothing is
-    written). Not undoable except through `drawing_undo` / a transaction.
+    and drop the values. Everything lands in the layout that owns the
+    reference (model space or its paper-space sheet), whichever tab is
+    current. Returns `inserted_handles` (the geometry), `attribute_texts`
+    (one TEXT handle per attribute), `exploded_handle` and `backend`.
+    Refused, with nothing written: a handle that is not a block reference,
+    and a reference nested inside a block definition (explode the outer
+    reference instead). Not undoable except through `drawing_undo` / a
+    transaction.
     """
     await ctx.warning(f"Exploding block reference {handle}")
     return await _backend(ctx).block_explode(handle)

tests/test_track_a_hardening.py

@@ -103,12 +103,14 @@ class _FakeLayers:
 
 
 class _FakeSpace:
-    """The active layout block: records InsertBlock / AddText and hands back styled objects."""
+    """A layout block: records InsertBlock / AddText and hands back styled objects."""
 
-    def __init__(self, attributes: dict[str, str] | None = None):
+    def __init__(self, attributes: dict[str, str] | None = None, name: str = "*Model_Space"):
         self.calls: list[tuple[str, tuple]] = []
         self.attributes = attributes or {}
         self.inserted: list[_FakeObject] = []
+        self.Name = name
+        self.IsLayout = True
 
     def InsertBlock(self, point, name, sx, sy, sz, rotation):
         self.calls.append(("InsertBlock", (tuple(point.value), name, sx, sy, sz, rotation)))
@@ -132,9 +134,14 @@ def com(monkeypatch):
     """A ComBackend over a recording fake: ``document`` and ``space`` are inspectable."""
     from backends import com_backend as module
 
-    document = types.SimpleNamespace(Blocks=_FakeBlocks("TB"), Layers=_FakeLayers(), objects={})
+    document = types.SimpleNamespace(
+        Blocks=_FakeBlocks("TB"), Layers=_FakeLayers(), objects={}, owners={}
+    )
     document.HandleToObject = lambda handle: document.objects[handle]
+    # ``OwnerID`` -> block table record, the way ``ObjectIdToObject`` resolves it live.
+    document.ObjectIdToObject = lambda object_id: document.owners[object_id]
     space = _FakeSpace()
+    document.owners[1] = space  # the active layout; a sheet registers itself under 2
     monkeypatch.setattr(module, "_acad_doc", lambda: document)
     monkeypatch.setattr(module, "_msp", lambda: space)
     monkeypatch.setattr(module, "_regen", lambda: None)
@@ -308,6 +315,7 @@ async def test_com_explode_deletes_attdefs_adds_text_per_attrib_and_deletes_the_
         "AcDbBlockReference",
         "2F",
         Name="TB",
+        OwnerID=1,
         GetAttributes=lambda: (visible, hidden),
         Explode=lambda: (line, attdef),
     )
@@ -337,3 +345,125 @@ async def test_com_explode_refuses_a_non_insert_before_any_call(com):
     with pytest.raises(RuntimeError, match="not a block reference"):
         await backend.block_explode("3A")
     assert space.calls == []
+
+
+async def test_com_explode_adds_the_text_to_the_owner_block_not_the_active_layout(com):
+    """ActiveX ``Explode()`` places the members in the owner space; the tag
+    TEXT must land beside them, not in whatever tab is active."""
+    backend, document, space = com
+    sheet = _FakeSpace(name="Sheet")
+    document.owners[2] = sheet
+    title = _FakeObject(
+        "AcDbAttribute",
+        "A1",
+        TagString="TITLE",
+        TextString="GEAR-01",
+        InsertionPoint=(100.0, 50.0, 0.0),
+        Height=3.5,
+        Rotation=0.0,
+        Layer="TITLEBLOCK",
+        Invisible=False,
+    )
+    line = _FakeObject("AcDbLine", "L1")
+    ref = _FakeObject(
+        "AcDbBlockReference",
+        "4B",
+        Name="TB",
+        OwnerID=2,
+        GetAttributes=lambda: (title,),
+        Explode=lambda: (line,),
+    )
+    document.objects["4B"] = ref
+
+    result = await backend.block_explode("4B")
+
+    assert result["ok"] is True and result["inserted_handles"] == ["L1"]
+    assert sheet.calls == [("AddText", ("GEAR-01", (100.0, 50.0, 0.0), 3.5))]
+    assert space.calls == [], "nothing may be written into the active layout"
+    assert ref.deleted is True
+
+
+async def test_com_explode_refuses_a_nested_reference_before_explode(com):
+    backend, document, space = com
+    document.owners[3] = _FakeBlock("OUTER")  # a block definition, IsLayout False
+    dispatched = []
+
+    def _explode():
+        dispatched.append("Explode")
+        return ()
+
+    ref = _FakeObject(
+        "AcDbBlockReference",
+        "5C",
+        Name="TB",
+        OwnerID=3,
+        GetAttributes=lambda: (),
+        Explode=_explode,
+    )
+    document.objects["5C"] = ref
+    with pytest.raises(RuntimeError, match="nested inside block definition 'OUTER'"):
+        await backend.block_explode("5C")
+    assert dispatched == [] and space.calls == [] and ref.deleted is False
+
+
+async def test_explode_of_a_mirrored_reference_keeps_the_tag_where_the_attrib_was(backend):
+    """An ATTRIB is an OCS entity. Mirroring reflects it to extrusion
+    ``(0, 0, -1)`` while the INSERT keeps +Z with ``yscale=-1``; the TEXT
+    that replaces it must carry the frame, or it lands on the other side
+    of the mirror axis with a clean audit."""
+    from backends.ocs import to_wcs_2d
+
+    blk = backend._doc.blocks.new(name="SYM")
+    blk.add_line((0, 0), (10, 0))
+    blk.add_attdef("TAG", insert=(5, 3), text="", dxfattribs={"height": 2.5})
+    ref = await backend.block_insert("SYM", 20, 10, attributes={"TAG": "P-101"})
+    mirrored = await backend.entity_mirror(ref.handle, 0, 0, 0, 1, delete_original=True)
+    raw = backend._doc.entitydb[mirrored.handle]
+    (attrib,) = raw.attribs
+    assert tuple(attrib.dxf.extrusion) == (0.0, 0.0, -1.0), "the premise: a reflected ATTRIB"
+    expected = to_wcs_2d(attrib.dxf.extrusion, *attrib.dxf.insert)
+    assert expected == pytest.approx([-25.0, 13.0])
+
+    result = await backend.block_explode(mirrored.handle)
+
+    (line_handle,) = result["inserted_handles"]
+    (text_handle,) = result["attribute_texts"]
+    line = await backend.entity_get(line_handle)
+    text = await backend.entity_get(text_handle)
+    assert text.properties["insertion"] == pytest.approx(expected)
+    assert text.properties["insertion"][0] < 0 and line.properties["start"][0] < 0, (
+        "tag and geometry stay on the same side of the mirror axis"
+    )
+    assert backend._doc.audit().errors == []
+
+
+async def test_explode_writes_into_the_inserts_owner_layout_not_the_current_one(backend):
+    _define_tagged_block(backend)
+    await backend.layout_create("Sheet")
+    await backend.layout_set_current("Sheet")
+    ref = await backend.block_insert("TB", 100, 50, attributes={"TAG": "GEAR-01"})
+    await backend.layout_set_current("Model")
+    model_before = len(list(backend._doc.modelspace()))
+
+    result = await backend.block_explode(ref.handle)
+
+    assert result["ok"] is True
+    sheet = backend._doc.layouts.get("Sheet")
+    assert sorted(e.dxftype() for e in sheet) == ["LINE", "TEXT"]
+    assert len(list(backend._doc.modelspace())) == model_before, "model space untouched"
+    for handle in result["inserted_handles"] + result["attribute_texts"]:
+        assert backend._doc.entitydb[handle].get_layout().name == "Sheet"
+    with pytest.raises(RuntimeError, match="not found"):
+        await backend.entity_get(ref.handle)
+    assert backend._doc.audit().errors == []
+
+
+async def test_explode_refuses_a_nested_reference_before_writing(backend):
+    _define_tagged_block(backend)
+    outer = backend._doc.blocks.new(name="OUTER")
+    nested = outer.add_blockref("TB", (0, 0))
+    before = (len(list(backend._doc.modelspace())), len(list(outer)))
+    with pytest.raises(RuntimeError, match="nested inside block definition 'OUTER'"):
+        await backend.block_explode(nested.dxf.handle)
+    assert (len(list(backend._doc.modelspace())), len(list(outer))) == before
+    assert backend._doc.entitydb[nested.dxf.handle].is_alive