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 agentmods add skills/borhen68/skillengine/deprecation-and-migrationnpx skills add borhen68/SkillEngine --skill deprecation-and-migrationgit clone --depth 1 https://github.com/borhen68/SkillEngineWrote 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/borhen68/skillengine/deprecation-and-migration)<a href="https://agentmods.dev/skills/borhen68/skillengine/deprecation-and-migration"><img src="https://agentmods.dev/badge/skills/borhen68/skillengine/deprecation-and-migration.svg" alt="Measured on agentmods" 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 | $0.00045 | $0.02158 |
| Opus 5 | $0.00023 | $0.01079 |
| Sonnet 5 | $0.00009 | $0.00432 |
| Haiku 4.5 | $0.00005 | $0.00216 |
Grade A, and why
deprecation-and-migration 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 6d 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.
This is a copy
84% identical to deprecation-and-migration — 92 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 234 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Deprecation and Migration
Overview
Engineering teams celebrate launches. They rarely celebrate removals. Yet every line of code is a liability — it needs testing, updating, documenting, and securing. Code that no longer earns its keep is not neutral; it's actively harmful because it obscures what matters, consumes attention, and accumulates risk.
The deprecation contract: Every system should be designed with its removal in mind. When deprecation is necessary, provide a replacement, migration tooling, and a clear timeline. Never leave users stranded. Removing code is as important as writing it — and deserves the same rigor.
Real-world impact: Organizations that actively remove dead code have 30% lower maintenance costs and 40% faster onboarding for new engineers. Zombie code (unused but depended upon) is the single biggest source of "don't touch that" fear in legacy systems. Removing it isn't risky — keeping it is.
When to Use
- Replacing an old system, API, or library with a new one
- Sunsetting a feature that's no longer needed
- Consolidating duplicate implementations
- Removing dead code that nobody owns but everybody depends on
- Planning the lifecycle of a new system (deprecation planning starts at design time)
- Deciding whether to maintain a legacy system or invest in migration
Core Principles
Code Is a Liability
Every line of code has ongoing cost: it needs tests, documentation, security patches, dependency updates, and mental overhead for anyone working nearby. The value of code is the functionality it provides, not the code itself. When the same functionality can be provided with less code, less complexity, or better abstractions — the old code should go.
Hyrum's Law Makes Removal Hard
With enough users, every observable behavior becomes depended on — including bugs, timing quirks, and undocumented side effects. This is why deprecation requires active migration, not just announcement. Users can't "just switch" when they depend on behaviors the replacement doesn't replicate.
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.
- 6d ago First seen · 234 lines · 45 tokens per session scan A 1442244b9f81
deprecation-and-migration is a skill published in the GitHub repository borhen68/SkillEngine (17 stars, last pushed 2mo ago), licensed MIT. It adds 45 tokens to every session and 2,158 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 84% identical to deprecation-and-migration, differing in 92 lines, and is treated as a copy.
Other skills, from other repositories
doubt-driven-development
在每个非平凡决策成立前，用全新上下文进行对抗式审查。当正确性比速度更重要、处理不熟悉代码、风险较高（生产、安全敏感逻辑、不可逆操作），或任何自信输出现在验证比之后调试更便宜时使用。.
code-review-and-quality
执行多维度代码审查。用于合并任何变更之前；用于审查自己、其他 agent 或人类编写的代码；用于在代码进入主分支前从多个维度评估代码质量。.
code-simplification
为清晰度简化代码。用于在不改变行为的前提下重构代码以提升清晰度；用于代码能运行但比应有状态更难阅读、维护或扩展时；用于审查已累积不必要复杂度的代码时。.
test-driven-development
用测试驱动开发。用于实现任何逻辑、修复任何 bug，或改变任何行为。用于需要证明代码能工作、收到 bug 报告，或即将修改现有功能时。.
api-and-interface-design
指导稳定的 API 和接口设计。设计 API、模块边界或任何公共接口时使用。创建 REST 或 GraphQL endpoint、定义模块之间的类型契约，或建立前后端边界时使用。.
ci-cd-and-automation
自动化 CI/CD pipeline 设置。用于设置或修改构建和部署 pipeline 时；用于需要自动化质量门禁、在 CI 中配置 test runners，或建立部署策略时。.