Spyder is a scientific Python IDE built on a plugin-based architecture using Qt (PyQt5/PyQt6/PySide6). It provides a multi-language code editor with Language Server Protocol (LSP) integration for completions, diagnostics, and formatting, an IPython/Jupyter console with custom kernel management, a variable explorer for inspecting NumPy/Pandas objects, a debugger, profiler, and a help system that renders documentation with MathJax for mathematical notation. The main entry point is `spyder.app.start:main`, which initializes the main window and loads plugins discovered via setuptools entry points under the `spyder.plugins` group. Each plugin (e.g., Editor, IPythonConsole, VariableExplorer) is a self-contained module with its own configuration page, container widget, and status bar integration. External dependencies include `spyder-kernels` (custom Jupyter kernels), `python-lsp-server` (LSP backend), `qtconsole` (Qt-based console widget), and `spyder-remote-services` (remote kernel execution via JupyterHub). Data flows: user edits code in the editor, which communicates with the LSP server for completions and diagnostics; running code sends it to the IPython kernel, which executes and returns results displayed in the console and variable explorer. The architecture is a monolith with a formal plugin API that supports lifecycle hooks, dependency management, and configuration observers.