fix: update Python SDK schemas for UCP release 2026-01-23

[cusell-google]

Overview

The python-sdk was previously stuck on the older 2026-01-11 release. This Pull Request updates the SDK tooling and regenerates the Pydantic models to ensure full compatibility with the (currently latest) Universal Commerce Protocol release: UCP 2026-01-23 Specification.

Detailed Changes

Documentation & Developer Experience

• README: Fixed setup instructions to clarify the correct directory navigation during environment bootstrapping.
• Code Generation Safety: Simplified the ruff format output pipeline inside generate_models.sh to prevent masking terminal lint failures with silent grep fallback logic.

Schema Pre-Processor Architecture (preprocess_schemas.py)

This PR significantly rewrites the schema pre-processor logic to improve maintainability and generate safer representations used by datamodel-codegen. Key updates include:

• Decoupling the Monolith: Split the massive merge_all_of_to_node function into modular helper functions (_process_all_of_item, _apply_merged_state) reducing unsafe variable mutations and nested conditions.
• Purer Side-effects: Rewrote fix_metadata_structure into a purely functional normalize_metadata_schemas which performs mutations exclusively in memory instead of committing midway disk writes.
• Safer Polymorphic Types: Flattening entity variants now correctly throws a ValueError rather than silently swallowing issues if entity_definition mappings are inadvertently empty.
• Operation Variants Expansion: Re-factored the generate_variants routine by splitting out operation iterations (e.g., create vs update) into _create_single_variant builders.

Lints & Formats

• ruff Compliance Fixes: Resolved Python stylistic debt surfaced by pre-commit, including fixing trailing whitespace limits, adjusting EOF sequences, and converting open() calls to Path().open(encoding="utf-8") (PTH123). Also removed built-in print tracing points with generic I/O stream writes (sys.stdout/sys.stderr) to comply with code-quality metrics.
• Clean Model Inheritance: As a result of the schema property metadata normalizer (ucp_prop), Pydantic models like PlatformSchema, BusinessSchema, and ResponseCheckoutSchema finally generate correctly to extend Base classes natively rather than rendering as disconnected blobs.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly refactors the Universal Commerce Protocol (UCP) Python SDK's schema generation process. It introduces a robust preprocessing step that normalizes complex JSON schemas, flattens inheritance, and creates operation-specific model variants, resulting in a more streamlined and maintainable codebase. The changes also update the model generation script to support versioning and align project configurations with modern Python development standards.

Highlights

• Enhanced Schema Generation Logic: Introduced a new Python script, preprocess_schemas.py, to perform advanced normalization and flattening of JSON schemas before model generation. This script handles allOf merging, distributes properties to anyOf/oneOf branches, and flattens entity references, leading to cleaner and more Pydantic-friendly models.
• Versioned Schema Generation: The generate_models.sh script now supports specifying a UCP specification version, allowing for targeted model generation from different branches or releases of the UCP repository.
• Model File Restructuring and Renaming: A significant refactoring of the generated model files has occurred, including renaming many *_req.py and *_resp.py files to more generic names (e.g., *_create_request.py, *.py) and reorganizing directories to better reflect the schema structure.
• Pydantic V2 Compatibility: Added a new Jinja2 template specifically for generating Pydantic V2 RootModel classes, ensuring compatibility with the latest version of Pydantic.
• Updated Project Configuration: The pyproject.toml file has been updated with a new project version, an additional author, and adjusted Ruff linting rules, including a change in indent width and ignoring specific docstring conventions.

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[gemini-code-assist]

Code Review

This pull request introduces a new schema preprocessing script (preprocess_schemas.py) and refactors the model generation workflow. Key changes include updates to generate_models.sh for improved UCP repository cloning, schema preprocessing, and post-generation formatting with ruff. The README.md installation instructions have been simplified, and pyproject.toml has been updated to reflect new ruff configurations and project metadata. Numerous generated model files have been updated or removed to align with the new schema processing and Pydantic v2 compatibility. Review feedback suggests addressing a potential error masking issue in the generate_models.sh script's ruff check command, clarifying installation instructions in README.md, and explicitly specifying UTF-8 encoding in preprocess_schemas.py for JSON file operations to enhance robustness.