python3-development

Performs holistic code review and validation after feature implementation. Checks that code follows project development standards, utilizes shared utilities instead of reinventing, takes advantage of installed dependencies, and identifies gaps requiring additional tasks. Creates follow-up task files when issues are found. Use after implementation is complete.

Creates, enhances, and reviews Python CLI code using Typer and Rich — use for CLI tools, scripts with progress bars or tables, async processing, modernizing existing CLIs, or any Python implementation task. Expert in type annotations, Rich components (tables, progress bars, panels), async patterns, and clean architecture. <example> Context -- User wants to create a new CLI script for file processing. user -- "I need to build a CLI tool that processes multiple files and shows progress" assistant -- "I'll use python-cli-architect to create a modern CLI with Typer, Rich progress bars, and error handling." </example> <example> Context -- User needs to implement async CLI operations. user -- "I need a CLI that can process multiple API requests concurrently" assistant -- "I'll use python-cli-architect to implement async patterns with semaphores and progress feedback." </example>

Use when designing a Python CLI tool's architecture before implementation — command interfaces, technology stack selection, data models, and contracts. Activates on architecture planning requests for new CLI tools or major feature additions. Produces WHAT to build (interfaces, schemas, contracts); python-cli-architect handles the HOW (implementation).

Use when creating, reviewing, or modernizing Python 3.11+ pytest test suites. Activates on requests to write tests, improve coverage, migrate from unittest.mock to pytest-mock, add hypothesis property-based tests, integrate pytest-asyncio or pytest-bdd, or audit test quality. Enforces 80% coverage minimum, AAA pattern, and mutation testing for critical paths.

Uses CocoIndex Code MCP server to search codebases by semantic meaning — finds code by concept, behavior, or natural language description rather than exact keywords. Use when exploring unfamiliar codebases, finding implementations of a concept, or when exact identifiers are unknown. MCP server launches automatically via uvx when the python3-development plugin is installed.

Use when building Textual TUI apps — creating widgets, laying out screens, handling events, managing reactivity, testing with Pilot, or running background workers. Covers App lifecycle, CSS styling, screen stack, reactive attributes, custom messages, actions, bindings, and the Worker API.

Use when reading or writing pyproject.toml or .toml config files in Python, editing TOML while preserving comments and formatting, designing configuration file formats for Python tools, working with tomlkit or tomllib, or implementing atomic config file updates.

Progressive Python quality improvement with static analysis, type refinement, modernization planning, plan review, and test-driven implementation. Use when addressing technical debt, eliminating Any types, applying modern Python patterns, or refactoring for better design.

Use when encountering failing tests, diagnosing test errors, or establishing a systematic approach to test failure investigation. Activates on "test failure analysis", "debugging tests", or "why tests fail" requests. Establishes the mindset that treats test failures as valuable diagnostic signals requiring root-cause investigation — not automatic code fixes or test dismissal.

Use when creating a new feature task with structured tracking, phases, and documentation. Activates on "create a feature task", "set up development tracking", or "plan a feature implementation" requests. Produces a comprehensive feature development task with acceptance criteria, phase breakdown, and tracking artifacts ready for SAM pipeline execution.