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 mickeyyaya/refactoring-skills --skill migration-patternsgit clone --depth 1 https://github.com/mickeyyaya/refactoring-skillsWrote 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/mickeyyaya/refactoring-skills/migration-patterns)<a href="https://agentmods.dev/skills/mickeyyaya/refactoring-skills/migration-patterns"><img src="https://agentmods.dev/badge/skills/mickeyyaya/refactoring-skills/migration-patterns.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 | $0.00072 | $0.04790 |
| Opus 5 | $0.00036 | $0.02395 |
| Sonnet 5 | $0.00014 | $0.00958 |
| Haiku 4.5 | $0.00007 | $0.00479 |
Grade A, and why
migration-patterns 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 7d 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 — 516 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Migration Patterns
Overview
Migrating a monolith to services, or moving a legacy database to a new schema, is one of the highest-risk engineering activities. Done wrong it causes data loss, extended downtime, and introduces coupling that is worse than the monolith it replaced. The patterns here provide incremental, reversible migration paths — each one shifts traffic or data gradually, allowing rollback at any step.
When to use: Planning service extraction from a monolith; replacing a legacy component; migrating databases without downtime; reviewing a migration PR for hidden risks.
Quick Reference
| Pattern | Core Idea | When to Use |
|---|---|---|
| Strangler Fig | Proxy routes traffic; new service replaces old routes incrementally | Extracting services from a running monolith |
| Anti-Corruption Layer | Adapter translates between old and new domain models | Integrating two bounded contexts with conflicting models |
| Branch by Abstraction | Abstract interface first, swap implementation behind it | Replacing an internal library or module in-place |
| Expand-Contract | Widen schema before migrating data, narrow after | Database column renames, type changes, normalisation |
| Dual-Write | Write to both old and new stores in parallel | Migrating a live database with zero downtime |
| CDC Bridge | Capture database change events and replay to new store | Backfilling a new service's datastore from a legacy DB |
| Change Data Capture | Stream row-level changes via Debezium or AWS DMS | Event-driven migration, read-model population |
Patterns in Detail
1. Strangler Fig
The Strangler Fig pattern (named after the tree that grows around a host) routes all traffic through a proxy. New functionality is built in the new service; the proxy redirects matching routes there. The monolith shrinks as routes migrate until it can be deleted.
Key phases:
- Deploy a routing proxy in front of the monolith (no traffic change yet)
- Build the replacement service endpoint
- Shadow-test: send traffic to both, compare responses, route users to new service
- Remove the monolith code path when confidence is high
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.
- 7d ago First seen · 516 lines · 72 tokens per session scan A 6f43c2e3a409
migration-patterns is a skill published in the GitHub repository mickeyyaya/refactoring-skills (6 stars, last pushed 5mo ago), licensed MIT. It adds 72 tokens to every session and 4,790 once invoked, about $0.0004 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.
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