Fix SCXML parallel transition domains

AGENTS.md

@@ -86,7 +86,9 @@ Working:
 
 Known gaps:
 
-- Full SCXML conformance still has known `more-parallel` failures.
+- The configured 54-case SCXML suite passes, including the enabled
+  `more-parallel` cases, but broader W3C datamodel and executable-content
+  conformance is not claimed.
 - Graphviz export and graph/test helper APIs beyond Mermaid are future work.
 - SCXML condition support is intentionally not a general JavaScript evaluator.
 

CHANGELOG.md

@@ -24,6 +24,12 @@ All notable changes to this project will be documented here.
 - Updated PyPI-facing installation docs to use `pip install xstate` for the
   released package.
 
+### Fixed
+
+- Corrected SCXML transition-domain resolution so external transitions inside
+  parallel states re-enter every affected region and resolve conflicts in
+  document order.
+
 ## 0.6.0 - 2026-06-28
 
 ### Added

CONTRIBUTING.md

@@ -48,9 +48,8 @@ git submodule update --init
 poetry run python -m pytest tests/test_scxml.py
 ```
 
-The current known full-SCXML gap is the `more-parallel` conformance group.
-Do not treat those existing failures as caused by unrelated docs or tooling
-changes.
+The configured SCXML suite must pass in full. It is a focused subset and does
+not yet claim broad W3C datamodel or executable-content conformance.
 
 ## Pull Requests
 

README.md

@@ -427,9 +427,10 @@ git submodule update --init
 poetry run python -m pytest tests/test_scxml.py
 ```
 
-Current branch result: `45 passed`, `8 failed`; the remaining failures are the
-known `more-parallel` conformance cases. The `cond-js` subset passes with the
-safe Boolean evaluator.
+Current configured-suite result: `54 passed`, `0 failed`, including all enabled
+`more-parallel` cases. This is a focused SCXML subset rather than a claim of full
+W3C conformance; broader datamodel and executable-content coverage remains
+future work. The `cond-js` subset passes with the safe Boolean evaluator.
 
 ## Developing
 
@@ -470,7 +471,7 @@ release target needs to be checked against different refs.
 | Snapshot queries | `tags`, `meta`, `has_tag`/`hasTag`, and `state_in`/`stateIn` are present |
 | Diagrams | Dependency-free Mermaid export is present |
 | Async | `AsyncInterpreter`, async actors, `from_observable`, and `to_promise` are present |
-| SCXML | XML import works; safe Boolean cond subset works; `more-parallel` conformance remains open |
+| SCXML | Configured 54-case suite passes; broader W3C datamodel and executable-content coverage remains open |
 | Persistence | Snapshot serialization and restore helpers are present |
 
 ## Related Projects

docs/PRODUCT.md

@@ -36,7 +36,7 @@ bridge between XState's JSON ecosystem and Python backends.
 | Actor model | `create_actor`, `ActorSystem`, spawn, parent/child tree, `send_parent`, `send_to` |
 | Actor logic | `from_promise`, `from_callback`, `from_observable`, `to_promise` |
 | Invoke | Child actor lifetime reconciliation with `done.invoke.*` and `error.platform.*` events |
-| SCXML XML import | Present; safe Boolean cond subset; known `more-parallel` failures remain |
+| SCXML XML import | Present; safe Boolean cond subset; configured 54-case suite passes |
 
 ## What Works Today
 
@@ -57,7 +57,8 @@ bridge between XState's JSON ecosystem and Python backends.
   `MachineSnapshot`, `create_actor`, and `setup`.
 - Primary suite passes in current Python 3.13/3.14 CI.
 - SCXML `cond-js` subset result: `4 passed`.
-- Full SCXML result: `45 passed`, `8 failed` in known `more-parallel` cases.
+- Configured SCXML result: `54 passed`, `0 failed`, including all enabled
+  `more-parallel` cases.
 
 ## Competitive Position
 
@@ -77,7 +78,7 @@ JavaScript and wanting the same machine shape in Python services.
 |---|---|
 | High | Publish 0.7.0 to PyPI as `xstate` |
 | High | Document the public API by concept: machines, guards/actions, context, interpreter, actors, async, SCXML |
-| High | Fix the remaining SCXML `more-parallel` conformance cases |
+| High | Expand SCXML coverage beyond the configured subset without adding JavaScript evaluation |
 | Medium | Document snapshot persistence and restore helpers |
 | Medium | Inspector protocol compatibility |
 | Medium | More XState v5 utilities: `provide`, action helpers, graph/test helpers |
@@ -89,7 +90,7 @@ JavaScript and wanting the same machine shape in Python services.
 |---|---|
 | PyPI release | `pip install xstate` works after the 0.7.0 GitHub Release |
 | Primary test count | Maintain 300+ focused tests |
-| SCXML pass rate | Resolve known `more-parallel` group |
+| SCXML pass rate | Keep the configured suite green while expanding supported coverage |
 | Docs | README plus concept docs for the main public APIs |
 | Examples | JSON, sync, async, actor, and integration examples |
 

docs/comparison.md

@@ -13,7 +13,7 @@ release-readiness work.
 | XState JSON | No | No | **Yes, native** | Yes | No | No |
 | SCXML algorithm | No | Yes | **Yes, partial conformance** | Partial | Yes | No |
 | Hierarchical states | Yes, extension | Yes | Yes | Yes | Yes | No |
-| Parallel states | Yes, extension | Yes | Yes, with known SCXML `more-parallel` gaps | Yes | Yes | No |
+| Parallel states | Yes, extension | Yes | Yes; configured `more-parallel` cases pass | Yes | Yes | No |
 | Guards/actions | Yes | Yes | Yes, named or inline | Yes | Yes | Limited |
 | Context/extended state | No native XState-style context | Yes | Yes, with `assign` and snapshot isolation | Yes | Yes | No |
 | Eventless transitions | No | Yes | Yes, `always` and legacy empty-event form | Yes | Yes | No |
@@ -72,7 +72,7 @@ structure with a JavaScript/XState frontend or a Stately-authored design.
 | Gap | Notes |
 |---|---|
 | PyPI release | 0.7.0 packaging metadata and release workflow are ready; publish via GitHub Release. |
-| SCXML conformance | Current full SCXML run is `45 passed`, `8 failed`; remaining failures are the known `more-parallel` cases. |
+| SCXML conformance | Configured SCXML suite is `54 passed`, `0 failed`; broader W3C coverage is not yet claimed. |
 | Full ECMAScript cond support | Intentionally not implemented; unsupported SCXML expressions raise `InvalidConfigError`. |
 | Graph/test utilities | Mermaid export exists; no graph traversal/test-path helpers yet. |
 | Inspector protocol | No `@statelyai/inspect` compatibility yet. |

src/xstate/algorithm.py

@@ -225,8 +225,11 @@ def get_transition_domain(
 
 
 def find_lcca(state_list: list[StateNode]) -> StateNode | None:
+    """Return the least common compound ancestor for SCXML transition domains."""
     for anc in get_proper_ancestors(state_list[0], state2=None):
-        if all(is_descendent(s, state2=anc) for s in state_list[1:]):
+        if is_compound_state(anc) and all(
+            is_descendent(s, state2=anc) for s in state_list[1:]
+        ):
             return anc
     return None
 

tests/test_parallel.py

@@ -1,6 +1,8 @@
 """Tests for parallel (orthogonal) states (0.2.0)."""
 
-from xstate import Machine
+import pytest
+
+from xstate import Machine, interpret
 
 
 def make_word():
@@ -131,3 +133,153 @@ def test_parallel_on_done_when_all_regions_final():
     # Both regions final -> done.state.running -> onDone.
     state = machine.transition(state, "FINISH_B")
     assert state.value == "done"
+
+
+def test_external_region_transition_reenters_parallel_siblings():
+    calls: list[str] = []
+    machine = Machine(
+        {
+            "id": "workflow",
+            "initial": "running",
+            "states": {
+                "running": {
+                    "type": "parallel",
+                    "states": {
+                        "a": {
+                            "initial": "a1",
+                            "on": {"RESET_A": "#a1"},
+                            "states": {
+                                "a1": {"id": "a1"},
+                                "a2": {},
+                            },
+                        },
+                        "b": {
+                            "entry": "enterB",
+                            "exit": "exitB",
+                            "initial": "b1",
+                            "states": {
+                                "b1": {"on": {"ADVANCE_B": "b2"}},
+                                "b2": {},
+                            },
+                        },
+                    },
+                }
+            },
+        },
+        actions={
+            "enterB": lambda: calls.append("enterB"),
+            "exitB": lambda: calls.append("exitB"),
+        },
+    )
+    service = interpret(machine).start()
+    calls.clear()
+
+    service.send("ADVANCE_B")
+    assert service.state.value == {"running": {"a": "a1", "b": "b2"}}
+
+    service.send("RESET_A")
+
+    assert service.state.value == {"running": {"a": "a1", "b": "b1"}}
+    assert calls == ["exitB", "enterB"]
+    service.stop()
+
+
+def _parallel_conflict_machine(first_region: str) -> Machine:
+    a = {
+        "initial": "a1",
+        "on": {"T": "#a2"},
+        "states": {
+            "a1": {},
+            "a2": {"id": "a2"},
+        },
+    }
+    b = {
+        "initial": "b1",
+        "states": {
+            "b1": {"on": {"T": "b2"}},
+            "b2": {},
+        },
+    }
+    regions = {"a": a, "b": b} if first_region == "a" else {"b": b, "a": a}
+    return Machine(
+        {
+            "id": "conflict",
+            "initial": "running",
+            "states": {
+                "running": {
+                    "type": "parallel",
+                    "states": regions,
+                }
+            },
+        }
+    )
+
+
+@pytest.mark.parametrize(
+    ("first_region", "expected"),
+    [
+        ("a", {"running": {"a": "a2", "b": "b1"}}),
+        ("b", {"running": {"a": "a1", "b": "b2"}}),
+    ],
+)
+def test_parallel_conflicts_follow_document_order(first_region, expected):
+    machine = _parallel_conflict_machine(first_region)
+
+    state = machine.transition(machine.initial_state, "T")
+
+    assert state.value == expected
+
+
+def test_parallel_conflict_with_nested_target_reenters_sibling_initial_state():
+    machine = Machine(
+        {
+            "id": "nested-conflict",
+            "initial": "running",
+            "states": {
+                "running": {
+                    "type": "parallel",
+                    "states": {
+                        "a": {
+                            "initial": "a1",
+                            "on": {"T": "#a22"},
+                            "states": {
+                                "a1": {
+                                    "initial": "a11",
+                                    "states": {"a11": {}, "a12": {}},
+                                },
+                                "a2": {
+                                    "initial": "a21",
+                                    "states": {
+                                        "a21": {},
+                                        "a22": {"id": "a22"},
+                                    },
+                                },
+                            },
+                        },
+                        "b": {
+                            "initial": "b1",
+                            "states": {
+                                "b1": {
+                                    "initial": "b11",
+                                    "states": {
+                                        "b11": {"on": {"T": "b12"}},
+                                        "b12": {},
+                                    },
+                                },
+                                "b2": {},
+                            },
+                        },
+                    },
+                }
+            },
+        }
+    )
+
+    state = machine.transition(machine.initial_state, "T")
+
+    assert state.value == {
+        "running": {
+            "a": {"a2": "a22"},
+            "b": {"b1": "b11"},
+        }
+    }

tests/test_scxml.py

@@ -73,6 +73,7 @@
     "hierarchy+documentOrder",
     "parallel",
     "parallel+interrupt",
+    "more-parallel",
 }
 
 test_files = [