Coding Skills

Codex skills for designing, planning, implementing, and reviewing software, with domain guidance for Python, JAX/Equinox, Polars, and Rust.

Contents

The repository is packaged as a local Codex plugin named coding-skills. Each skill is user-invocable and can also be triggered conversationally by its frontmatter description.

Skill	What it does
design-software	Grounds design decisions in the repository and defines observable acceptance criteria.
plan-implementation	Turns agreed requirements into dependency-ordered tasks and verification steps.
implement-plan	Executes authorized work, tracks progress, verifies behavior, and handles review findings.
review-code	Reviews changes or existing code for actionable defects against requirements and repository contracts.
functional-core-imperative-shell	Separates domain computation from effects while preserving cohesive modules and transaction semantics.
property-based-testing	Designs generated tests with meaningful properties, constrained inputs, and reproducible failures.
systematic-debugging	Investigates failures with reproductions, discriminating experiments, and causal verification.
writing-good-tests	Chooses test oracles, scope, isolation, and dependency boundaries around observable contracts.
jax-equinox-numerics	Applies JAX and Equinox numerics rules: JIT boundaries, PyTrees, static/dynamic fields, dtype stability, solver/sampler contracts, AD, and batching tests.
jax-project-engineering	Covers project-level engineering for JAX/Equinox code: public APIs, CLI contracts, docs, packaging, serialization, type checks, and CI gates.
polars-data-engineering	Guides Polars LazyFrame/DataFrame workflows: lazy planning, materialization boundaries, joins, reconciliation, null policy, and to_jax() export.
python-module-design	Reviews Python package structure: file/module granularity, subpackage boundaries, passive type placement, helper organization, and over-fragmentation.
python-rust-bridge	Designs Python packages backed by Rust: product shape, PyO3 boundaries, conversion ownership, GIL policy, error mapping, maturin packaging, and bridge tests.
pragmatic-rust-guidelines	Applies pragmatic Rust review rules: API design, unsafe/FFI, PyO3 adapter hygiene, feature flags, lint policy, performance, and Rust documentation.

See plugins/coding-skills/docs/skill-boundaries.md for the boundary between overlapping skills, especially the Python/JAX/Polars/Python-Rust split.

Use the workflows

Start at the stage you need. A small fix can go straight to implementation; a review does not require a design or plan. For a larger change:

Use $design-software to design resumable imports for this repository.
Use $plan-implementation to turn the agreed design into executable tasks.
Use $implement-plan to carry out that plan and verify the changes.
Use $review-code to review the working-tree changes against the requirements.

The workflows use the relevant domain skills from this bundle. They do not require scientific-software-playbook, other home skills, custom agents, hooks, MCP servers, or a fresh session between stages. Existing authorization carries forward; design-only and review-only requests stay within their requested scope. Delegation is optional and subject to the session's permissions.

Install

Plugin install

Use the plugin install when you want Codex to treat these skills as one bundle. From the repository root:

codex plugin marketplace add .
codex plugin add coding-skills@coding-skills-local

Start a new Codex session. You can also install from the Coding Skills Local marketplace in /plugins.

To refresh after pulling changes:

git pull
codex plugin add coding-skills@coding-skills-local

Then start a new session to load the refreshed skills. marketplace upgrade refreshes configured Git marketplace snapshots; this setup uses a local checkout.

Direct skill install

For local authoring without the plugin, copy the skills into Codex's user skill directory:

mkdir -p "$HOME/.agents/skills"
rsync -a --exclude __pycache__ --exclude '*.pyc' \
  plugins/coding-skills/skills/ "$HOME/.agents/skills/"

Choose either plugin installation or direct installation to avoid duplicate skill discovery. Direct installation includes:

• design-software
• plan-implementation
• implement-plan
• review-code
• functional-core-imperative-shell
• property-based-testing
• writing-good-tests
• systematic-debugging
• jax-equinox-numerics
• jax-project-engineering
• polars-data-engineering
• python-module-design
• python-rust-bridge
• pragmatic-rust-guidelines

For repo-scoped installation, replace the destination with /path/to/repo/.agents/skills/.

Verify

Start a new Codex session and invoke a skill explicitly:

Use $python-rust-bridge to review this package boundary.

For direct installs, you can also check the installed files:

find "$HOME/.agents/skills" -maxdepth 2 -name SKILL.md | sort

Licensing

The original six domain skills remain MIT-licensed. The four workflow skills and four architecture, testing, and debugging skills are adapted from Scientific Software Playbook and distributed under CC BY-SA 4.0. See the attribution and file-scope notice and the license files bundled with the plugin.