python-component-implementation

A guide for implementing Python components from accepted SysML v2 contracts. SysML v2 is a language for describing systems, their parts, behavior, constraints, and connections before or alongside code.

In plain words
What is it for?
Use it to create or review Python protocols, component classes, reference implementations, bindings, and contract tests based on a SysML model.
Why use it?
It keeps Python code aligned with the approved system design instead of relying on undocumented implementation details. It also clarifies expected behavior, failures, state changes, and tests.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/volantlabs/vellis/python-component-implementation
Any agent
npx skills add volantlabs/vellis --skill python-component-implementation
Clone the repo
git clone --depth 1 https://github.com/volantlabs/vellis

Made for: Claude Code, Codex.

Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 829 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00051 $0.00829
Opus 5 $0.00026 $0.00415
Sonnet 5 $0.00010 $0.00166
Haiku 4.5 $0.00005 $0.00083

Measured yesterday against content hash 4272714490f8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-component-implementation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/python-component-implementation/SKILL.md · 81 lines

How it starts

The opening of the file, as written. The whole thing — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Component Implementation

Use the accepted SysML/KPAR model and its generated component view as the contract. Python is one realization of that language-neutral design.

Judge the realization at modeled boundaries. Matching private structure, algorithms, helper decomposition, or another implementation's incidental behavior is neither required nor preferred. The same accepted model may be realized in another language when it preserves the modeled structure, behavior, state effects, failures, invariants, composition contracts, and verification obligations.

Workflow

  1. Locate the component by stable ID in the repository's canonical model package.
  2. Resolve the accepted library package version and read its public values, actions, retained collaborator roles, state, required constraints, asserted satisfiers, failures, and verification cases. Treat top-level documentation as explanation, not as an unmodeled obligation.
  3. Locate the matching concrete realization and confirm its code root and symbol from @ImplementationBinding; do not expect language bindings on the reusable logical component.
  4. Implement or revise the consumer-facing Python protocol.
  5. Encapsulate canonical state and invariant enforcement inside the component root.
  6. Supply action-scoped collaborators and wire retained referential roles only through modeled public boundaries; do not reach through another component's internals.
  7. Consume structured implementation-neutral conformance objectives when available; add or update black-box tests derived from their subject-compatible verification cases and evidence groups.
  8. When implementation work forces an observable choice the model does not settle, stop treating it as a private coding decision: propose the language-neutral contract clarification or record realization drift. Incidental helper, library, and representation choices remain private.
  9. Run the narrowest component tests, just model-check, and relevant repository checks.

Read the full file on GitHub · 81 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 81 lines · 51 tokens per session scan A 4272714490f8

Subscribe to this mod's changes

python-component-implementation is a skill published in the GitHub repository volantlabs/vellis (8 stars, last pushed 8d ago), licensed Apache-2.0. It adds 51 tokens to every session and 829 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.