diff --git a/pyproject.toml b/pyproject.toml
index 74e6e8d2..13063f53 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "ezmsg"
-version = "3.9.0"
+version = "3.10.0b3"
 description = "A simple DAG-based computation model"
 authors = [
   { name = "Griffin Milsap", email = "griffin.milsap@gmail.com" },
diff --git a/src/ezmsg/core/settingsmeta.py b/src/ezmsg/core/settingsmeta.py
index 1260e8ef..c7478945 100644
--- a/src/ezmsg/core/settingsmeta.py
+++ b/src/ezmsg/core/settingsmeta.py
@@ -15,12 +15,18 @@ def _type_name(tp: object) -> str:
 
 
 def _sanitize(value: Any) -> Any:
-    if value is None or isinstance(value, (bool, int, float, str)):
-        return value
+    # Enums first: a mixin enum (IntEnum, StrEnum, IntFlag) is an instance of
+    # its mixed-in builtin, so the primitives check below would return the
+    # member itself and leak the defining package onto the wire.
     if isinstance(value, enum.Enum):
         return _sanitize(value.value)
+    if value is None or isinstance(value, (bool, int, float, str)):
+        return value
     if isinstance(value, Mapping):
-        return {str(key): _sanitize(val) for key, val in value.items()}
+        # Sanitize keys too, so an enum key renders as its value rather than
+        # through str(), whose output for an IntEnum changed in 3.11 -- the same
+        # settings would otherwise key differently per interpreter version.
+        return {str(_sanitize(key)): _sanitize(val) for key, val in value.items()}
     if isinstance(value, (list, tuple, set, frozenset)):
         return [_sanitize(val) for val in value]
     if is_dataclass(value):
diff --git a/tests/test_settingsmeta.py b/tests/test_settingsmeta.py
new file mode 100644
index 00000000..7a8ee62b
--- /dev/null
+++ b/tests/test_settingsmeta.py
@@ -0,0 +1,166 @@
+import enum
+import io
+import pickle
+from dataclasses import dataclass, field
+from typing import Any
+
+import ezmsg.core as ez
+from ezmsg.core.settingsmeta import (
+    _sanitize,
+    settings_repr_value,
+    settings_schema_from_type,
+    settings_structured_value,
+)
+
+# Exactly the types a JSON encoder accepts. Membership is checked by identity
+# rather than isinstance so that a mixin enum -- whose members are instances of
+# int or str -- does not pass as its mixed-in builtin.
+_JSON_TYPES = (type(None), bool, int, float, str, list, dict)
+
+
+def _assert_wire_safe(value: Any, path: str = "<root>") -> None:
+    """Assert nothing but plain builtins survived sanitization.
+
+    Anything else means the defining package has to be importable wherever the
+    payload is unpickled, which is precisely what sanitization exists to avoid.
+    """
+    assert type(value) in _JSON_TYPES, (
+        f"{path}: {type(value)!r} is not wire-safe ({value!r})"
+    )
+    if isinstance(value, dict):
+        for key, val in value.items():
+            assert type(key) is str, f"{path}: key {key!r} is {type(key)!r}, not str"
+            _assert_wire_safe(val, f"{path}.{key}")
+    elif isinstance(value, list):
+        for idx, val in enumerate(value):
+            _assert_wire_safe(val, f"{path}[{idx}]")
+
+
+class Rate(enum.IntEnum):
+    SLOW = 1
+    FAST = 5
+
+
+class Mode(str, enum.Enum):
+    """A str-mixin enum, spelled the pre-3.11 way so this runs on 3.10.
+
+    ``enum.StrEnum`` is 3.11+, but it is this mixin that matters here: members
+    are instances of ``str`` either way.
+    """
+
+    IDLE = "idle"
+    BUSY = "busy"
+
+
+class Flags(enum.IntFlag):
+    NONE = 0
+    READ = 1
+    WRITE = 2
+
+
+class Plain(enum.Enum):
+    X = "x"
+
+
+@dataclass
+class NestedSettings:
+    rate: Rate = Rate.SLOW
+    modes: list[Mode] = field(default_factory=lambda: [Mode.IDLE])
+
+
+class MixinEnumSettings(ez.Settings):
+    rate: Rate = Rate.FAST
+    mode: Mode = Mode.BUSY
+    flags: Flags = Flags.READ | Flags.WRITE
+    plain: Plain = Plain.X
+    by_rate: dict[Rate, Mode] = field(default_factory=lambda: {Rate.SLOW: Mode.IDLE})
+    nested: NestedSettings = field(default_factory=NestedSettings)
+
+
+def test_sanitize_unwraps_mixin_enums():
+    """IntEnum/StrEnum/IntFlag members must reduce to their values, not pass through.
+
+    They are instances of int/str, so a primitives check that runs before the
+    enum check returns the member itself.
+    """
+    assert _sanitize(Rate.FAST) == 5
+    assert type(_sanitize(Rate.FAST)) is int
+    assert _sanitize(Mode.BUSY) == "busy"
+    assert type(_sanitize(Mode.BUSY)) is str
+    assert _sanitize(Flags.READ | Flags.WRITE) == 3
+    assert type(_sanitize(Flags.READ | Flags.WRITE)) is int
+    assert _sanitize(Plain.X) == "x"
+
+
+def test_sanitize_unwraps_enums_in_containers():
+    assert _sanitize([Rate.SLOW, Mode.IDLE]) == [1, "idle"]
+    assert _sanitize(NestedSettings()) == {"rate": 1, "modes": ["idle"]}
+
+
+def test_sanitize_renders_enum_keys_by_value():
+    """Enum mapping keys must render the same on every supported interpreter.
+
+    ``str()`` of an IntEnum member changed in 3.11 -- ``'Rate.SLOW'`` before,
+    ``'1'` after -- so keying by ``str(key)`` alone makes the payload depend on
+    the Python version the graph happens to run under.
+    """
+    assert _sanitize({Rate.SLOW: Mode.IDLE}) == {"1": "idle"}
+    assert _sanitize({Mode.BUSY: 1}) == {"busy": 1}
+    assert _sanitize({Plain.X: 1}) == {"x": 1}
+
+
+def test_structured_value_is_wire_safe():
+    structured = settings_structured_value(MixinEnumSettings())
+    _assert_wire_safe(structured)
+    assert structured == {
+        "rate": 5,
+        "mode": "busy",
+        "flags": 3,
+        "plain": "x",
+        "by_rate": {"1": "idle"},
+        "nested": {"rate": 1, "modes": ["idle"]},
+    }
+
+
+def test_repr_value_is_wire_safe():
+    _assert_wire_safe(settings_repr_value(MixinEnumSettings()))
+
+
+def test_schema_defaults_and_choices_are_wire_safe():
+    schema = settings_schema_from_type(MixinEnumSettings)
+    assert schema is not None
+    defaults = {f.name: f.default for f in schema.fields}
+    for name, default in defaults.items():
+        _assert_wire_safe(default, f"<default {name}>")
+    assert defaults["rate"] == 5
+    assert defaults["mode"] == "busy"
+
+    for f in schema.fields:
+        if f.choices is not None:
+            _assert_wire_safe(f.choices, f"<choices {f.name}>")
+
+
+class _ObserverUnpickler(pickle.Unpickler):
+    """Unpickles as an observer that has only ezmsg installed.
+
+    Every settings payload crosses to clients that deliberately do not depend on
+    the graph's own packages, so anything a payload forces them to import is a
+    leak. Refusing every module but ``ezmsg`` reproduces the ``ModuleNotFoundError``
+    such a client would hit, without needing a second interpreter.
+    """
+
+    def find_class(self, module: str, name: str) -> Any:
+        if module != "builtins" and not module.startswith("ezmsg."):
+            raise ModuleNotFoundError(f"payload requires {module}.{name}")
+        return super().find_class(module, name)
+
+
+def test_sanitized_payloads_need_no_package_but_ezmsg():
+    settings = MixinEnumSettings()
+    payloads = [
+        settings_structured_value(settings),
+        settings_repr_value(settings),
+        settings_schema_from_type(MixinEnumSettings),
+    ]
+    for payload in payloads:
+        _ObserverUnpickler(io.BytesIO(pickle.dumps(payload))).load()