diff --git a/loopx/chat_actions.py b/loopx/chat_actions.py
index 0328fac6e3..cbf269ee76 100644
--- a/loopx/chat_actions.py
+++ b/loopx/chat_actions.py
@@ -13,7 +13,11 @@
 from .control_plane.coordination.new_goal_storage_transport import initialize_goal_storage_target
 from .chat import apply_todo_review_preview, build_todo_review_preview
 from .chat_action_normalization import ChatActionNormalizationMixin
-from .chat_action_store import ActionConflictError, ChatActionStore
+from .chat_action_store import (
+    ACTION_KINDS as SUPPORTED_ACTION_KINDS,
+    ActionConflictError,
+    ChatActionStore,
+)
 from .chat_goal_lifecycle_actions import ChatGoalLifecycleActionMixin
 from .chat_monitor_actions import ChatMonitorActionMixin
 from .chat_store import ChatSessionStore
@@ -40,22 +44,7 @@
 
 
 CHAT_ACTION_RESPONSE_SCHEMA_VERSION = "loopx_chat_action_response_v1"
-SUPPORTED_ACTION_KINDS = {
-    "goal.acceptance.check",
-    "todo.create",
-    "todo.update",
-    "run.correct",
-    "goal.create",
-    "goal.update",
-    "goal.lifecycle",
-    "agent.bind",
-    "heartbeat.bind",
-    "monitor.create",
-    "monitor.update",
-    "gate.resolve",
-    "operation.execute",
-    "team.plan",
-}
+
 # Runtime Endpoint ids and durable Goal agent ids are chosen independently, so
 # a family token collapses both onto the host that produced them: Endpoint
 # `codex` has to resolve to a registered `codex-main-control`. Every host that
diff --git a/tests/architecture/test_chat_action_kind_owner.py b/tests/architecture/test_chat_action_kind_owner.py
new file mode 100644
index 0000000000..8f94565eb9
--- /dev/null
+++ b/tests/architecture/test_chat_action_kind_owner.py
@@ -0,0 +1,90 @@
+"""The Chat action-kind vocabulary has one owner, so a new kind cannot land twice.
+
+``loopx/chat_action_store.py`` decides which action kinds a proposal may be stored
+for, and ``loopx/chat_server.py`` publishes that same set to hosts.
+``loopx/chat_actions.py`` kept a byte-identical copy under a different name and
+gated dispatch on it, so a kind added to one side stayed invisible to the other
+and a proposal could be accepted by the service while the store rejected it.
+"""
+
+from __future__ import annotations
+
+import ast
+from pathlib import Path
+
+import pytest
+
+from loopx import chat_action_store, chat_actions
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+OWNER_PATH = "loopx/chat_action_store.py"
+OWNER_NAME = "ACTION_KINDS"
+KIND_VALUE = frozenset(
+    {
+        "agent.bind",
+        "gate.resolve",
+        "goal.acceptance.check",
+        "goal.create",
+        "goal.lifecycle",
+        "goal.update",
+        "heartbeat.bind",
+        "monitor.create",
+        "monitor.update",
+        "operation.execute",
+        "run.correct",
+        "team.plan",
+        "todo.create",
+        "todo.update",
+    }
+)
+
+
+def set_literal(node: ast.AST) -> frozenset[str] | None:
+    """Return the string members of a set literal, including a frozenset call."""
+    if isinstance(node, ast.Call) and getattr(node.func, "id", "") == "frozenset":
+        if not node.args:
+            return None
+        node = node.args[0]
+    if not isinstance(node, ast.Set):
+        return None
+    members: set[str] = set()
+    for element in node.elts:
+        if not isinstance(element, ast.Constant) or not isinstance(element.value, str):
+            return None
+        members.add(element.value)
+    return frozenset(members)
+
+
+def modules_holding_the_vocabulary() -> list[str]:
+    offenders: list[str] = []
+    for path in sorted(REPO_ROOT.glob("loopx/**/*.py")):
+        relative = path.relative_to(REPO_ROOT).as_posix()
+        try:
+            tree = ast.parse(path.read_text(encoding="utf-8"))
+        except (SyntaxError, UnicodeDecodeError):  # pragma: no cover - guarded tree
+            continue
+        for statement in tree.body:
+            if not isinstance(statement, ast.Assign):
+                continue
+            vocabulary = set_literal(statement.value)
+            if vocabulary == KIND_VALUE:
+                offenders.append(relative)
+                break
+    return offenders
+
+
+def test_the_store_owns_the_declared_action_kind_vocabulary() -> None:
+    assert frozenset(chat_action_store.ACTION_KINDS) == KIND_VALUE
+
+
+def test_the_action_service_applies_the_owner_object() -> None:
+    assert chat_actions.SUPPORTED_ACTION_KINDS is chat_action_store.ACTION_KINDS
+
+
+def test_no_module_outside_the_owner_holds_its_own_copy() -> None:
+    assert modules_holding_the_vocabulary() == [OWNER_PATH]
+
+
+@pytest.mark.parametrize("action_kind", sorted(KIND_VALUE))
+def test_every_declared_kind_is_dispatchable(action_kind: str) -> None:
+    assert action_kind in chat_actions.SUPPORTED_ACTION_KINDS