diff --git a/packages/smithy-core/.changes/next-release/smithy-core-bugfix-7c2e4f1a9b8d4e6f8a3c5d2b1e0f9a7c.json b/packages/smithy-core/.changes/next-release/smithy-core-bugfix-7c2e4f1a9b8d4e6f8a3c5d2b1e0f9a7c.json
new file mode 100644
index 000000000..bb651e154
--- /dev/null
+++ b/packages/smithy-core/.changes/next-release/smithy-core-bugfix-7c2e4f1a9b8d4e6f8a3c5d2b1e0f9a7c.json
@@ -0,0 +1,4 @@
+{
+  "type": "bugfix",
+  "description": "Fixed the registered Smithy IDs for `DefaultTrait`, `IdempotencyTokenTrait`, and `UnitTypeTrait` so schemas resolve these traits correctly."
+}
diff --git a/packages/smithy-core/src/smithy_core/traits.py b/packages/smithy-core/src/smithy_core/traits.py
index 99a5ae8cc..63ad9199e 100644
--- a/packages/smithy-core/src/smithy_core/traits.py
+++ b/packages/smithy-core/src/smithy_core/traits.py
@@ -93,7 +93,7 @@ def new(id: ShapeID, value: "DocumentValue" = None) -> "Trait | DynamicTrait":
 
 
 @dataclass(init=False, frozen=True)
-class DefaultTrait(Trait, id=ShapeID("smithy.appi#default")):
+class DefaultTrait(Trait, id=ShapeID("smithy.api#default")):
     @property
     def value(self) -> "DocumentValue":
         return self.document_value
@@ -161,7 +161,7 @@ def __post_init__(self):
 
 
 @dataclass(init=False, frozen=True)
-class UnitTypeTrait(Trait, id=ShapeID("smithy.api#UnitTypeTrait")):
+class UnitTypeTrait(Trait, id=ShapeID("smithy.api#unitType")):
     def __post_init__(self):
         assert self.document_value is None
 
@@ -203,7 +203,7 @@ def value(self) -> str:
 
 
 @dataclass(init=False, frozen=True)
-class IdempotencyTokenTrait(Trait, id=ShapeID("smithy.api#IdempotencyToken")):
+class IdempotencyTokenTrait(Trait, id=ShapeID("smithy.api#idempotencyToken")):
     def __post_init__(self):
         assert self.document_value is None
 
diff --git a/packages/smithy-core/tests/unit/test_schemas.py b/packages/smithy-core/tests/unit/test_schemas.py
index c6b835228..30fbe4db0 100644
--- a/packages/smithy-core/tests/unit/test_schemas.py
+++ b/packages/smithy-core/tests/unit/test_schemas.py
@@ -4,13 +4,15 @@
 from typing import Any
 
 import pytest
+from smithy_core.documents import TypeRegistry
 from smithy_core.exceptions import ExpectationNotMetError
-from smithy_core.schemas import Schema
+from smithy_core.schemas import APIOperation, Schema
 from smithy_core.shapes import ShapeID, ShapeType
 from smithy_core.traits import (
     DynamicTrait,
     InternalTrait,
     SensitiveTrait,
+    Trait,
 )
 
 ID: ShapeID = ShapeID("ns.foo#bar")
@@ -171,3 +173,29 @@ def test_contains(item: Any, contains: bool):
     )
 
     assert (item in schema) == contains
+
+
+def test_operation_idempotency_token_member():
+    input_schema = Schema.collection(
+        id=ShapeID("com.example#OperationInput"),
+        members={
+            "other": {"target": STRING},
+            "token": {
+                "target": STRING,
+                "traits": [Trait.new(id=ShapeID("smithy.api#idempotencyToken"))],
+            },
+        },
+    )
+    operation = APIOperation[Any, Any](
+        input=object,
+        output=object,
+        schema=Schema(
+            id=ShapeID("com.example#Operation"), shape_type=ShapeType.OPERATION
+        ),
+        input_schema=input_schema,
+        output_schema=input_schema,
+        error_registry=TypeRegistry({}),
+        effective_auth_schemes=[],
+        error_schemas=[],
+    )
+    assert operation.idempotency_token_member is input_schema.members["token"]
diff --git a/packages/smithy-core/tests/unit/test_traits.py b/packages/smithy-core/tests/unit/test_traits.py
index 5d60970ef..623387411 100644
--- a/packages/smithy-core/tests/unit/test_traits.py
+++ b/packages/smithy-core/tests/unit/test_traits.py
@@ -3,13 +3,16 @@
 from dataclasses import dataclass
 
 import pytest
+from smithy_core.prelude import UNIT
 from smithy_core.shapes import ShapeID
 from smithy_core.traits import (
+    DefaultTrait,
     DynamicTrait,
     ErrorFault,
     ErrorTrait,
     JSONNameTrait,
     Trait,
+    UnitTypeTrait,
 )
 
 
@@ -40,6 +43,17 @@ class NewTrait(Trait, id=trait_id):
     assert NewTrait.id is trait_id
 
 
+def test_trait_factory_constructs_default_trait():
+    trait = Trait.new(ShapeID("smithy.api#default"), 0)
+    assert isinstance(trait, DefaultTrait)
+    assert trait.value == 0
+
+
+def test_unit_schema_uses_canonical_trait_id():
+    trait = UNIT.get_trait(ShapeID("smithy.api#unitType"))
+    assert isinstance(trait, UnitTypeTrait)
+
+
 def test_cant_construct_base_trait():
     with pytest.raises(TypeError):
         Trait("foo")