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.
npx skills add ychampion/cskill-agents --skill shared-system-init-shape-paritygit clone --depth 1 https://github.com/ychampion/cskill-agentsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/ychampion/cskill-agents/shared-system-init-shape-parity)<a href="https://agentmods.dev/skills/ychampion/cskill-agents/shared-system-init-shape-parity"><img src="https://agentmods.dev/badge/skills/ychampion/cskill-agents/shared-system-init-shape-parity/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ychampion/cskill-agents/shared-system-init-shape-parity"><img src="https://agentmods.dev/badge/skills/ychampion/cskill-agents/shared-system-init-shape-parity.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00032 | $0.00611 |
| Opus 5 | $0.00016 | $0.00305 |
| Sonnet 5 | $0.00006 | $0.00122 |
| Haiku 4.5 | $0.00003 | $0.00061 |
Grade A, and why
shared-system-init-shape-parity 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 8d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 31 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Shared System Init Shape Parity
Domain: transport-architecture Trigger: Use when the same system init or capability-announcement payload is emitted from multiple entrypoints or transports and downstream clients depend on one stable schema. Source Pattern: Distilled from reviewed remote-control, bridge transport, and capability-advertising implementations.
Core Method
Define one canonical builder for the init payload and make every entrypoint call it. Put field names, defaults, derived state, feature-gated fields, and final key shaping inside that builder, not in the callers. Each transport path should do only path-local work: gather inputs, prefilter or redact collections when policy requires it, and choose when to send the message. This keeps the wire schema identical across stream, bridge, headless, or future transports so clients and tests do not drift between supposedly equivalent init events.
Key Rules
- Make the shared builder own the full schema contract, including optional and feature-gated fields plus derived values such as session identifiers or fast-mode state.
- Let callers vary only inputs and delivery mechanics. They may filter commands, redact sensitive inventories, or load metadata asynchronously, but they should not hand-assemble sibling init objects.
- If two paths describe the same conceptual event, route both through the same builder even when one yields into a stream and another pushes via a bridge writer.
- Add new init fields once in the builder, then update callers only enough to supply the new inputs; never patch a field into one transport and plan to mirror it later.
- Keep transport-specific policy outside the builder when it truly differs by caller. The builder should serialize the canonical shape from supplied inputs, not decide privacy, bridge safety, or connection timing on its own.
- Review and test parity at the schema level, not just field-by-field intent, because drift usually appears as omitted, renamed, or differently defaulted keys.
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.
- 8d ago First seen · 31 lines · 32 tokens per session scan A e12634a3bc4c
shared-system-init-shape-parity is a skill published in the GitHub repository ychampion/cskill-agents (36 stars, last pushed 5mo ago), licensed MIT. It adds 32 tokens to every session and 611 once invoked, about $0.0002 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 2026-09-03.
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