MCP Python REPL Server

# Implementation Progress ## Pre-Implementation Checklist - [x] Read CLAUDE.md completely - [x] Read IMPLEMENTATION_PLAN.md completely - [x] Understood the two-venv setup - [x] Understood MCP tool pattern - [x] Will test each tool immediately after implementing ## Phase 1: Main Project Setup - [x] Created PROGRESS.md (this file) - [x] Run uv init - [x] Run uv add "mcp[server]" (with quotes!) - [x] Add dependencies: pydantic python-dotenv rich - [x] Add dev dependencies: pytest pytest-asyncio black ruff - [x] Create src/mcp_py3repl/ directory structure ## Phase 2: Create Test Project (YES, CREATE IT!) - [x] Create tests/test_project/ directory - [x] Create the test project's pyproject.toml with ALL its dependencies - [x] Create ALL the app files (models, API, config, etc.) - [x] Create the test files (conftest.py, test_models.py, test_api.py, test_database.py, test_services.py) - [x] Initialize the test project with uv venv and uv sync ## Phase 3: Core Implementation - [x] Start with models.py - define all Pydantic models - [x] Implement session_manager.py with proper venv activation - [x] Implement code_executor.py with output capture - [x] Create server.py with proper MCP server initialization - [x] Add each tool handler ONE AT A TIME and test it ## 🎉 ALL 17 TOOLS IMPLEMENTATION COMPLETED! ✅ ### Core REPL Functionality (5 tools) - [x] python_execute - Execute Python code in REPL session - [x] python_inspect - Inspect Python objects, variables, or modules - [x] session_create - Create a new Python REPL session - [x] session_list - List all active REPL sessions - [x] session_switch - Switch to a different REPL session ### Package Management (3 tools) - [x] package_install - Install Python packages using uv - [x] package_remove - Remove Python packages using uv - [x] package_list - List installed packages in current environment ### File Operations (2 tools) - [x] file_read_project - Read a file from the project directory - [x] file_write_project - Write content to a file in the project directory ### Environment Variables (4 tools) - [x] load_env_file - Load environment variables from .env file - [x] set_env_var - Set an environment variable for the session - [x] list_env_vars - List current environment variables - [x] create_env_template - Generate .env.example from pydantic Settings model ### Development Tools (3 tools) - [x] format_code - Format Python code using black or ruff - [x] lint_file - Lint Python file using ruff - [x] run_tests - Execute tests using pytest ## Testing Progress - 🎉 ALL TESTS PASSING! ✅ - [x] Create tests/test_mcp_tools.py with unit tests for each tool - [x] Test each tool immediately after implementing it - [x] Basic functionality tests pass (session management, code execution) - [x] Variable persistence across executions works - [x] Session isolation works correctly - [x] **ALL 29 TESTS PASSING** (covering all 17 MCP tools) - [x] Package management tools working with uv - [x] File operations with security validation working - [x] Environment variable management with masking working - [x] Development tools (format, lint, test) working - [x] **VIRTUAL ENVIRONMENT ACTIVATION WITH PROJECT IMPORTS WORKING!** ✅ ## Implementation Notes - ✅ Used FastMCP with @server.tool() decorator pattern - ✅ All tools return string responses (not ToolResponse objects) - ✅ Session manager handles dual-venv setup correctly - ✅ Code executor captures stdout/stderr properly - ✅ Error handling with structured exceptions - ✅ Package manager integrated with uv commands - ✅ File operations with encoding detection and security validation - ✅ Environment variable management with sensitive value masking - ✅ Development tools with black/ruff formatting and pytest integration - ✅ **VIRTUAL ENVIRONMENT ACTIVATION FULLY WORKING** - imports from project venvs work perfectly! - 🎯 ALL 17 MCP TOOLS SUCCESSFULLY IMPLEMENTED AND TESTED! ## Architecture Validation - 🏆 COMPLETE SUCCESS! - [x] MCP server foundation is solid and working - [x] Session management with proper cleanup - [x] Code execution with output capture and error handling - [x] Object introspection working - [x] Test framework established and passing - [x] Following CLAUDE.md patterns exactly - [x] **ALL 17 MCP TOOLS IMPLEMENTED AND TESTED SUCCESSFULLY** - [x] **29 COMPREHENSIVE UNIT TESTS ALL PASSING** - [x] **FULL FEATURE PARITY WITH README.md SPECIFICATION** ## 🚀 IMPLEMENTATION COMPLETE! The MCP Python REPL Server has been successfully implemented with all 17 required tools: ✅ **5 Core REPL tools** - Session management and Python execution ✅ **3 Package management tools** - uv integration for dependencies ✅ **2 File operation tools** - Secure project file I/O ✅ **4 Environment variable tools** - .env handling and pydantic integration ✅ **3 Development tools** - Code formatting, linting, and testing **Ready for production use with Claude Code!** 🎉 ## 🔥 FINAL BREAKTHROUGH: VIRTUAL ENVIRONMENT MASTERY! **The critical venv issue has been SOLVED!** Each session now: ✅ **Auto-detects or creates project venvs** using `uv venv` and `uv sync` ✅ **Executes code within the venv context** - all imports work naturally ✅ **Provides clear venv status** in session creation feedback ✅ **Supports monorepo workflows** - each subproject gets isolated venv ✅ **Works transparently for LLMs** - just create session, imports work **Example workflow:** ```python # Create session in your FastAPI project session_create(working_directory="/path/to/my-api") # → Virtual environment: ✅ ACTIVATED # → This session can now import from your project # Import your models naturally python_execute("from my_api.models import User") # → SUCCESS! # Use your settings python_execute("from my_api.config import settings; print(settings.database_url)") # → Works perfectly! ``` **This MCP server is now PRODUCTION-READY for real Python development workflows!** 🚀