GSoC 2026 proposal: Hardening astropy's core stability

_projects/2026/astropy/astropy_core_improvements.md

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+---
+name: Hardening astropy's core stability
+# Add a short one line description of your project
+desc: Improvements to astropy low level extension modules (C/C++/Cython)
+# Student requirements:
+requirements:
+ - at least one low level language (C or C++ prefered)
+ - testing in Python
+# How difficult would you consider the project to be: low, medium, high
+difficulty: medium to high, depending on candidate
+# Related issues (if any) to this project.
+# Ideally you want at least one that describes the problem it is trying to solve
+issues:
+ - https://github.com/neutrinoceros/astropy-APEs/pull/1
+ - https://github.com/astropy/astropy/issues/17760
+ - https://github.com/astropy/astropy/issues/19249
+
+# First person in contact; mentors may change before project starts.
+# GitHub or GitLab handles
+mentors:
+ - neutrinoceros
+# The programme under this project wish to run. At the moment only GSOC is available
+initiatives:
+ - GSOC
+project_size:
+ - 175 h
+# Different technologies needed
+tags:
+ - python
+ - meson-python
+ - C
+ - C++
+ - Cython
+ - pytest
+# suborganisation(s) to which this project belongs.
+collaborating_projects:
+ - astropy
+---
+
+# Hardening astropy's core stability
+
+## Description
+
+Astropy is a mixed-language code base. Most of it is pure Python, but many hotpaths are
+written in lower level languages (Cython, C and C++). The former is where the vast
+majority of past and current development is conducted, while the latter in much more
+slowly paced. Meanwhile, the low-level layer overwhemingly dominates other important
+aspects like complexity of *building* and distributing astropy releases, and takes an
+estimated 20 to 50% share of astropy CI time for recompilation *of code that almost never changes*.
+
+It would be possible to decouple the bulk of the code base from its low level layer,
+for instance by splitting the latter into a separate package, but this new package would
+be insufficiently tested on its own, as much of astropy's test suite currently only
+checks the behavior of the public API, which doesn't intersect with the low level layer.
+
+We want to build a more fundamental test suite for this low level layer, making it much
+more independent from astropy's existing tests.
+
+This project would be highly related to (although separable from) the [following draft
+APE](https://github.com/neutrinoceros/astropy-APEs/pull/1), which also contains more details on why the separation is desirable
+
+As such, it would also provide opportunities for exploratory works like
+- migrating to a modern, externally maintained build system like Meson
+- rewritting, or incorporating `rust`-based extensions
+- exploring PEP 803/809 Limited API for Python 3.15
+
+All of the above would be in scope for this project, depending on the candidate's own
+interests and time allocated.
+
+## Project Milestones
+
+### Coding starts
+
+* TBD
+
+### 1st evaluation
+
+* TBD
+
+### Final evaluation
+
+* TBD