Borrowing it
Nothing to install: this file belongs to stevesolun/ctx. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/stevesolun/ctx/main/.agents/skills/codebase-design/SKILL.mdgit clone --depth 1 https://github.com/stevesolun/ctxWrote 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/stevesolun/ctx/codebase-design)<a href="https://agentmods.dev/skills/stevesolun/ctx/codebase-design"><img src="https://agentmods.dev/badge/skills/stevesolun/ctx/codebase-design/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/stevesolun/ctx/codebase-design"><img src="https://agentmods.dev/badge/skills/stevesolun/ctx/codebase-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00040 | $0.00525 |
| Opus 5.5 | $0.00016 | $0.00210 |
| Sonnet 5.5 | $0.00008 | $0.00105 |
| Haiku 4.5 | $0.00004 | $0.00052 |
Grade A, and why
codebase-design 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 1mo 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 — 55 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Codebase Design
Seek deep modules: substantial useful behavior behind a small, stable interface. Use the concepts below as design lenses, while matching the repository's established domain language.
Working vocabulary
- Module: a coherent unit with an interface and implementation, at any scale.
- Interface: everything callers must know, including invariants and failure modes—not just a type signature.
- Seam: a location where behavior can vary without editing its callers.
- Adapter: an implementation that connects at a seam.
- Depth: useful capability relative to interface complexity.
- Leverage: capability gained by callers; locality: change and knowledge concentrated for maintainers.
Translate these terms to the project's vocabulary when that makes the design clearer. Consistency with the codebase is more valuable than enforcing a private lexicon.
Design workflow
- Map representative callers, responsibilities, dependencies, and existing contracts.
- Look for coordination or policy that can move behind a smaller interface.
- Place seams where variation, ownership, or test isolation justifies them.
- Compare alternatives when the choice is consequential.
- Validate the candidate with representative caller code and tests.
Heuristics, not laws
- Reduce methods, parameters, ordering constraints, and configuration callers must understand.
- Use the deletion test: if removing a module merely spreads its complexity across callers, it was likely earning its keep.
- Treat pass-through layers skeptically, but keep them when they provide a real compatibility, ownership, policy, or navigation boundary.
- Introduce dependency seams when actual variation or test isolation repays the indirection; avoid interfaces justified only by hypothetical futures.
- Prefer tests through observable interfaces, while allowing focused internal tests when they provide cheaper or more precise feedback.
- Favor explicit dependencies and returned results when they improve control and testability; side effects and internally created dependencies can still be appropriate at well-defined boundaries.
What ships with it
3 files 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.
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.
- 1mo ago First seen · 55 lines · 40 tokens per session scan A f8bdd1b33e97
codebase-design is a skill published in the GitHub repository stevesolun/ctx (589 stars, last pushed 11d ago), licensed MIT. It adds 40 tokens to every session and 525 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-30.
Other skills, from other repositories
vuln-scanner
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fork-fleet
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pack-submit
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shiplog
Recap of everything shipped since the last run - cross-repo PRs, security fixes, star deltas, and X traction, synthesized into a digest article and a ready-to-post shiplog in your voice.
token-pick
One token recommendation and one prediction market pick - scored, quantified, with a skip branch when signals are weak.
autoresearch
Evolve a skill by generating variations, evaluating them, and updating the best version.