feat: upgrade Python SDK to UCP v2026-04-08

README.md

@@ -35,6 +35,17 @@ This repository contains the Python SDK for the
 models for UCP schemas, making it easy to build UCP-compliant applications in
 Python.
 
+### UCP Version Compatibility
+
+Each version of the Python SDK is generated against a specific version of the
+UCP schema:
+
+| SDK Version       | UCP Schema Version |
+| ----------------- | ------------------ |
+| **`0.4.x`**       | **`2026-04-08`**   |
+| `0.3.x`           | `2026-01-23`       |
+| `0.2.x` / `0.1.x` | `2026-01-11`       |
+
 ## Installation
 
 To use this SDK in your own project, install it from PyPI:
@@ -70,8 +81,8 @@ for item in checkout.line_items:
 
 | Package                                 | Description                                         |
 | --------------------------------------- | --------------------------------------------------- |
-| `ucp_sdk.models.schemas.shopping`       | Checkout, cart, order, payment models               |
-| `ucp_sdk.models.schemas.shopping.types` | Line items, totals, buyer, fulfillment, etc.        |
+| `ucp_sdk.models.schemas.shopping`       | Checkout, cart, catalog, order, payment models      |
+| `ucp_sdk.models.schemas.shopping.types` | Line items, totals, buyer, fulfillment, signals     |
 | `ucp_sdk.models.schemas.transports`     | REST, MCP, and embedded protocol bindings           |
 | `ucp_sdk.models.schemas`                | Service definitions, capabilities, payment handlers |
 
@@ -122,7 +133,7 @@ uv sync
 ```
 
 Where `<version>` is the version of the UCP specification to use (for example,
-"2026-01-23").
+"2026-04-08").
 
 If no version is specified, the `main` branch of the
 [UCP repo](https://github.com/Universal-Commerce-Protocol/ucp) will be used.

preprocess_schemas.py

@@ -343,7 +343,7 @@ def update_variant_identity(variant_schema, op, stem):
 def rewrite_refs_to_variants(root, op, file_path, variant_needs):
     """
     Walks a schema tree and updates external links to point to variant files.
-    Example: product.json -> product_create_request.json
+    Example: product.json -> product_create_request.json.
     """
     for node in iter_nodes(root):
         if isinstance(node, dict) and "$ref" in node:
@@ -500,7 +500,7 @@ def main():
     1. Pass 1: Local flattening (allOf) and discovery of needed variants
     2. metadata normalization: unifies ucp properties
     3. Pass 2: Transitive propagation (ensuring matched variants for linked schemas)
-    4. Pass 3: Variant file generation (*_request.json)
+    4. Pass 3: Variant file generation (*_request.json).
     """
     target_dir = Path(
         sys.argv[1] if len(sys.argv) > 1 else "ucp/source/schemas"

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "ucp-sdk"
-version = "0.3.0"
+version = "0.4.0"
 description = "UCP Python SDK"
 readme = "README.md"
 license = {file = "LICENSE"}
@@ -68,6 +68,9 @@ indent-style = "space"
 skip-magic-trailing-comma = false
 line-ending = "auto"
 
+[tool.ruff.lint.per-file-ignores]
+"src/ucp_sdk/models/schemas/**/*.py" = ["E501", "D"]
+
 [tool.ruff.lint]
 select = ["E", "F", "W", "B", "C4", "SIM", "N", "UP", "D", "PTH", "T20"]
 ignore = ["D212", "D200"]

src/ucp_sdk/models/schemas/capability.py

@@ -33,6 +33,114 @@ class UcpCapability(RootModel[Any]):
     """
 
 
+class Extends(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends1Item(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+
+
+class Extends1(RootModel[list[Extends1Item]]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: list[Extends1Item] = Field(..., min_length=1)
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends2(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends3Item(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+
+
+class Extends3(RootModel[list[Extends3Item]]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: list[Extends3Item] = Field(..., min_length=1)
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends4(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends5Item(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+
+
+class Extends5(RootModel[list[Extends5Item]]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: list[Extends5Item] = Field(..., min_length=1)
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends6(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
+class Extends7Item(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$")
+
+
+class Extends7(RootModel[list[Extends7Item]]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: list[Extends7Item] = Field(..., min_length=1)
+    """
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
+    """
+
+
 class Version(RootModel[Any]):
     model_config = ConfigDict(
         frozen=True,
@@ -64,11 +172,9 @@ class Base(BaseModel):
     """
     Entity-specific configuration. Structure defined by each entity's schema.
     """
-    extends: str | None = Field(
-        None, pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$"
-    )
+    extends: Extends | Extends1 | None = None
     """
-    Parent capability this extends. Present for extensions, absent for root capabilities.
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
     """
 
 
@@ -100,11 +206,9 @@ class PlatformSchema(BaseModel):
     """
     Entity-specific configuration. Structure defined by each entity's schema.
     """
-    extends: str | None = Field(
-        None, pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$"
-    )
+    extends: Extends2 | Extends3 | None = None
     """
-    Parent capability this extends. Present for extensions, absent for root capabilities.
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
     """
 
 
@@ -136,11 +240,9 @@ class BusinessSchema(BaseModel):
     """
     Entity-specific configuration. Structure defined by each entity's schema.
     """
-    extends: str | None = Field(
-        None, pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$"
-    )
+    extends: Extends4 | Extends5 | None = None
     """
-    Parent capability this extends. Present for extensions, absent for root capabilities.
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
     """
 
 
@@ -172,9 +274,7 @@ class ResponseSchema(BaseModel):
     """
     Entity-specific configuration. Structure defined by each entity's schema.
     """
-    extends: str | None = Field(
-        None, pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+$"
-    )
+    extends: Extends6 | Extends7 | None = None
     """
-    Parent capability this extends. Present for extensions, absent for root capabilities.
+    Parent capability(s) this extends. Present for extensions, absent for root capabilities. Use array for multi-parent extensions.
     """

src/ucp_sdk/models/schemas/common/__init__.py

@@ -0,0 +1,17 @@
+# Copyright 2026 UCP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# generated by datamodel-codegen
+# pylint: disable=all
+# pyformat: disable

src/ucp_sdk/models/schemas/common/identity_linking/__init__.py

@@ -0,0 +1,61 @@
+# Copyright 2026 UCP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# generated by datamodel-codegen
+# pylint: disable=all
+# pyformat: disable
+
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import BaseModel, ConfigDict, Field, RootModel
+
+from ...shopping.types import description as description_1
+
+
+class IdentityLinking(RootModel[Any]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: Any = Field(..., title="Identity Linking")
+    """
+    Capability schema for identity linking. Businesses declare the user-authenticated scopes they offer in a flat 'scopes' map. Each key is the OAuth scope string as it appears on the wire ('{capability}:{scope}', e.g. 'dev.ucp.shopping.order:read'). Scope presence implies that the corresponding operations require user authentication. Operations not gated by any listed scope operate at whatever access level the business permits; UCP does not prescribe a default.
+    """
+
+
+class ScopePolicy(BaseModel):
+    """
+    Per-scope policy and metadata — auth constraints (e.g. min_acr, max_token_age), declarative metadata (e.g. claims produced, consent descriptions), or any other scope-specific configuration. An empty object means user authentication is required with no additional policy. Open for non-breaking extension.
+    """
+
+    model_config = ConfigDict(
+        extra="allow",
+    )
+    description: description_1.Description | None = None
+    """
+    Optional human-readable description of the scope that platforms can use to present and explain context (requirement and value) to the user.
+    """
+
+
+class ScopeToken(RootModel[str]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: str = Field(
+        ..., pattern="^[a-z][a-z0-9]*(?:\\.[a-z][a-z0-9_]*)+:[a-z][a-z0-9_]*$"
+    )
+    """
+    OAuth scope string formed by joining a capability name and a scope name with a colon: '{capability}:{scope}', e.g. 'dev.ucp.shopping.order:read'. Capability names use reverse-DNS naming; scope names denote the permission granted, defined by each capability's spec (e.g. 'read', 'manage', 'create'). Platforms request these strings verbatim in OAuth 'scope' parameters; issued tokens carry them in the 'scope' claim.
+    """

src/ucp_sdk/models/schemas/common/identity_linking/dev/__init__.py

@@ -0,0 +1,17 @@
+# Copyright 2026 UCP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# generated by datamodel-codegen
+# pylint: disable=all
+# pyformat: disable

src/ucp_sdk/models/schemas/common/identity_linking/dev/ucp/__init__.py

@@ -0,0 +1,17 @@
+# Copyright 2026 UCP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# generated by datamodel-codegen
+# pylint: disable=all
+# pyformat: disable

src/ucp_sdk/models/schemas/common/identity_linking/dev/ucp/common.py

@@ -0,0 +1,30 @@
+# Copyright 2026 UCP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# generated by datamodel-codegen
+# pylint: disable=all
+# pyformat: disable
+
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import ConfigDict, RootModel
+
+
+class IdentityLinking(RootModel[Any]):
+    model_config = ConfigDict(
+        frozen=True,
+    )
+    root: Any