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Agent skill

Cyphal Parity Guard

by OpenCyphal in OpenCyphal/pycyphal

Keep the Python Cyphal rewrite in wire-visible behavioral parity with the C reference at reference/cy.

MITAuto-check passedTesting & QA

Install Cyphal Parity Guard

skills CLI
$ npx skills add OpenCyphal/pycyphal --skill cyphal-parity-guard -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install OpenCyphal/pycyphal cyphal-parity-guard --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/OpenCyphal/pycyphal.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.codex/skills/cyphal-parity-guard .claude/skills/cyphal-parity-guard && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
cyphal-parity-guard
GitHub stars
142
Token cost
~1.2k tokens
SKILL.md length
530 words
Files
3 (incl. references)
Skills in repo
3
Repo updated
First seen
Licence
MIT

At a glance

Keep the Python Cyphal rewrite in wire-visible behavioral parity with the C reference at reference/cy.

  • Works in 4 steps: reference/cy/cy/cy.h for constants/API… → reference/cy/cy/cy.c for wire-visible… → reference/cy/model/ when C code intent… → …
  • Auditing/reviewing parity drift
  • SKILL.md covers Overview, Mode Selection, Source-of-Truth Order and Workflow, plus 3 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Cyphal Parity Guard is an agent skill from OpenCyphal/pycyphal. Keep the Python Cyphal rewrite in wire-visible behavioral parity with the C reference at reference/cy. Use when auditing/reviewing parity drift, identifying wire/state-machine discrepancies, updating src/pycyphal2/ to match reference behavior, replacing conflicting Python tests with C-parity expectations, and adding regression tests for every discovered divergence. API-level discrepancies are by design and are to be ignored; this skill focuses on wire-visible and state-machine behavior only.

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including reference files (for example `agents/openai.yaml` and `references/parity-checklist.md`).

It sits in Testing & QA. It works with Python and Linux. The repository describes itself as: Python implementation of the Cyphal protocol stack. The licence is MIT.

When your agent uses it

  • Auditing/reviewing parity drift
  • Identifying wire/state-machine discrepancies
  • Updating src/pycyphal2/ to match reference behavior
  • Replacing conflicting Python tests with C-parity expectations

Example prompts

  • “/cyphal-parity-guard”

Requirements

  • Python 3

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

  1. reference/cy/cy/cy.h for constants/API semantics.
  2. reference/cy/cy/cy.c for wire-visible and state-machine behavior.
  3. reference/cy/model/ when C code intent is ambiguous.
  4. src/pycyphal2/ and existing tests as implementation artifacts, not normative authority.

What it can do on your machine

Read from SKILL.md and the folder at commit 34530f6. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Cyphal Parity Guard loads about 1.2k tokens when it runs, and up to ~1.5k if it reads all its reference files. Until then it costs about 130 tokens; SKILL.md has 530 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~130
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from OpenCyphal/pycyphal at commit 34530f6, republished under its MIT licence (© OpenCyphal). 530 words, ~1,153 tokens.

Download SKILL.mdSave it as .claude/skills/cyphal-parity-guard/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
cyphal-parity-guard
description
Keep the Python Cyphal rewrite in wire-visible behavioral parity with the C reference at `reference/cy`. Use when auditing/reviewing parity drift, identifying wire/state-machine discrepancies, updating `src/pycyphal2/` to match reference behavior, replacing conflicting Python tests with C-parity expectations, and adding regression tests for every discovered divergence. API-level discrepancies are by design and are to be ignored; this skill focuses on wire-visible and state-machine behavior only.

Cyphal Parity Guard

Overview

Run a deterministic parity workflow for pycyphal2 against reference/cy in two modes:

  • sync mode: identify divergences, patch Python implementation, and add/adjust regression tests.
  • review mode: report parity findings only, no edits.

Apply the following defaults unless the user overrides them:

  • Target wire+state parity with cy.c.
  • Treat cy.c behavior as source of truth when Python tests conflict.
  • Add Python regression coverage for each confirmed divergence.
  • Ignore API-level discrepancies that do not affect wire/state behavior (e.g., differences in API design, error handling style, etc).

Mode Selection

Select mode from user intent:

  • Use review mode when asked to "review", "audit", or "find discrepancies".
  • Use sync mode when asked to "fix", "update", "bring in sync", or "correct divergences".
  • If intent is ambiguous, start in review mode and then switch to sync when requested.

Source-of-Truth Order

Use this precedence:

  1. reference/cy/cy/cy.h for constants/API semantics.
  2. reference/cy/cy/cy.c for wire-visible and state-machine behavior.
  3. reference/cy/model/ when C code intent is ambiguous.
  4. src/pycyphal2/ and existing tests as implementation artifacts, not normative authority.

Workflow

  1. Prepare context.
  • Confirm repository root.
  • Inspect touched files and current test baseline.
  • Load references/parity-checklist.md and use it as the audit checklist.
  1. Build a discrepancy matrix.
  • Compare reference/cy behavior with src/pycyphal2/_node.py, _wire.py, and related modules.
  • Ignore differences that are not visible on the wire or in state machines (e.g., differences in API design, error handling style, etc).
  • Keep in mind that error handling differs significantly between C and Python; therefore, certain error-path-related discrepancies may be expected and should be noted as such in the matrix (e.g., where C would clamp invalid arguments, Python should raise ValueError, etc). Error handling must be Pythonic first of all.
  • For each discrepancy, record:
    • C anchor (file:line + behavior statement).
    • Python anchor (file:line + divergent behavior).
    • Impact and severity.
    • Needed test coverage.
  1. Execute mode-specific actions.
  • In review mode:
    • Produce findings ordered by severity.
    • Include exact file/line anchors and missing regression tests.
    • Do not edit code.
  • In sync mode:
    • Implement fixes in src/pycyphal2/.
    • Update/remove conflicting test expectations when they contradict cy.c.
    • Add at least one regression test per divergence under tests/.
Show full SKILL.md (185 more words)Show less
  1. Validate.
  • Run targeted tests first for changed behavior.
  • Run full quality gates when feasible:
    • nox -s test-3.12
    • nox -s mypy
    • nox -s format
  • If full matrix is requested or practical, also run test-3.11 and test-3.13.
  1. Report.
  • Always return the discrepancy matrix (resolved or unresolved).
  • For sync mode, map every fixed divergence to specific tests.
  • Call out residual risks if any discrepancy remains untested.

Repository Constraints

Enforce project constraints while implementing parity fixes:

  • Preserve behavior across GNU/Linux, Windows, and macOS.
  • Keep support for all declared Python versions in pyproject.toml (currently >=3.11).
  • Keep async I/O in async/await style and maintain strict typing.
  • Keep formatting Black-compatible with line length 120.
  • Keep logging rich and appropriately leveled for unusual/error paths.

Output Contract

For parity reviews, return:

  • Findings first, ordered high to low severity.
  • File/line references for C and Python anchors.
  • Explicit statement when no discrepancies are found.
  • Testing gaps and confidence level.

For parity sync work, return:

  • What changed in implementation.
  • What changed in tests and which divergences they cover.
  • Commands executed and notable pass/fail outcomes.

Reference Map

  • references/parity-checklist.md: hotspot checklist, anchor patterns, and discrepancy matrix template.

© OpenCyphal, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (references) in .codex/skills/cyphal-parity-guard of OpenCyphal/pycyphal.

  • SKILL.md
  • agents/openai.yaml
  • references/parity-checklist.md

Open the folder on GitHubat commit 34530f6

Compare with similar skills

Cyphal Parity Guard next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Cyphal Parity Guard compared with similar skills
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Cyphal Parity Guard this skillOpenCyphal/pycyphal142—~1.2kAutomated safety check: PassMIT
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Cross Platform Pathsmicrosoft/vscode-python-environments141—~1.5kAutomated safety check: PassMIT
Xhs Auto PublisherDjangoPeng/agentic-ai152—~570Automated safety check: PassMIT
CCC Dashboard Runtime Testingamirfish1/claude-command-center178—~1.1kAutomated safety check: PassCustom licence
Verify Changes389ds/389-ds-base294—~1.9kAutomated safety check: PassCustom licence

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Works with

Categories

Questions about Cyphal Parity Guard

What does Cyphal Parity Guard do?

Keep the Python Cyphal rewrite in wire-visible behavioral parity with the C reference at reference/cy. Cyphal Parity Guard is an agent skill from OpenCyphal/pycyphal. Keep the Python Cyphal rewrite in wire-visible behavioral parity with the C reference at reference/cy.

When should I use Cyphal Parity Guard?

Cyphal Parity Guard fits situations like: auditing/reviewing parity drift; identifying wire/state-machine discrepancies; updating src/pycyphal2/ to match reference behavior; replacing conflicting Python tests with C-parity expectations.

How do I install Cyphal Parity Guard in Claude Code?

Run `npx skills add OpenCyphal/pycyphal --skill cyphal-parity-guard -a claude-code`. Or copy the skill folder (.codex/skills/cyphal-parity-guard in OpenCyphal/pycyphal) into .claude/skills/cyphal-parity-guard in your project. Claude Code loads it when a task matches its description.

How do I install Cyphal Parity Guard in Codex?

Run `npx skills add OpenCyphal/pycyphal --skill cyphal-parity-guard -a codex`. Or copy the skill folder (.codex/skills/cyphal-parity-guard in OpenCyphal/pycyphal) into .agents/skills/cyphal-parity-guard in your project. Codex loads it when a task matches its description.

Can I use Cyphal Parity Guard in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add OpenCyphal/pycyphal --skill cyphal-parity-guard -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cyphal-parity-guard, .gemini/skills/cyphal-parity-guard, .github/skills/cyphal-parity-guard and .opencode/skills/cyphal-parity-guard in your project.

What does Cyphal Parity Guard need to run?

SKILL.md names no scripts, command-line tools or credentials: Cyphal Parity Guard is instructions for the agent only. Our summary lists: Python 3.

Does Cyphal Parity Guard access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Cyphal Parity Guard safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Cyphal Parity Guard use?

Cyphal Parity Guard is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Cyphal Parity Guard use?

About 1.2k tokens (SKILL.md is roughly 4.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 351 tokens, read only when the agent opens those files.

What are the alternatives to Cyphal Parity Guard?

Skills that share tags, products or a category with Cyphal Parity Guard: Apple Container Test Runner (RustPython/RustPython, 22k stars), Cross Platform Paths (microsoft/vscode-python-environments, 141 stars), Xhs Auto Publisher (DjangoPeng/agentic-ai, 152 stars) and CCC Dashboard Runtime Testing (amirfish1/claude-command-center, 178 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Cyphal Parity Guard?

OpenCyphal (a GitHub organization) maintains it in OpenCyphal/pycyphal, which has 142 GitHub stars. The repository holds 3 skills in this directory. The repository was last updated on July 24, 2026.

Source: OpenCyphal/pycyphal on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.