Skill · AI & Development

Code Migration Planner

Design zero-downtime migrations with risk-first sequencing, rollback gates, and Strangler Fig patterns. Install in 30 seconds.

Category: AI & Development
Deliverable: 1 .skill bundle
Outputs: —
Last updated: 13 Jun 2026

$9.99 One-time · lifetime updates

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Overview

What Code Migration Planner does.

Code Migration Planner installs as a Claude skill and acts as an architect-level advisor for any codebase transition you describe. It opens by asking four focused questions — your stack, target state, constraints, and audience — then generates a sequenced plan that ships continuously to main. Every phase gets a rollback gate; any step that cannot be reversed is flagged explicitly rather than buried. The skill applies Strangler Fig boundaries, dual-write verification, and feature-flag routing as structural tools, not suggestions.

A typical session starts with input like: 'We have a 200k-line Django 2.2 monolith, four backend engineers, a hard freeze in eight weeks, and we need to extract the billing service first because it blocks a compliance audit.' The skill identifies the riskiest assumption — usually data consistency between the old and new billing paths — designs phase one as the smallest real test of that assumption, and builds the rest of the sequence from there.

The output is a structured migration plan. Example excerpt — Phase 1 Rollback Gate: 'If dual-write divergence exceeds 0.1% over 48 hours in canary traffic, revert feature flag to legacy path. Exit criteria: zero divergence for 72 hours, audit log parity confirmed, no P1 alerts. Estimated effort: 1 engineer, 5 days. Phase 2 prerequisite: Phase 1 gate passed and compliance sign-off received.'

Who it's for

Backend engineers and tech leads planning a major version upgrade, framework swap, or monolith decomposition who need a defensible, incremental plan — not a rewrite ticket. Particularly useful when a migration must stay shippable throughout and involve more than one engineer.

How it works

Three steps. About two minutes.

Install

Add the .skill file to your Claude app. ~10 seconds.

Run it on your work

Invoke the skill and paste in your material.

Apply the output

Review, keep what works, and use it.

In depth

Why a Claude skill beats a prompt template.

A copy-paste prompt runs one static pass and stops. A skill is a bundled program — instructions, examples, and a workflow Claude runs as a unit: it asks for the right input, applies the same pattern every time, and returns the structured outputs above.

FAQ

Common questions.

What information do I need to provide before the skill can generate a plan?

At minimum: your source and target (e.g. Python 2 to 3, monolith to microservices), approximate codebase size, team size, and any hard constraints like deadlines or compliance requirements. The skill asks these conversationally and accepts 'decide for me' if you want it to proceed with defaults.

Does the skill prescribe a specific migration pattern, or does it adapt to my stack?

It adapts. Strangler Fig, dual-write, and feature-flag routing are applied where they fit your described architecture. If your situation calls for a different boundary strategy, the skill will say so and explain why.

What format does the output take?

By default, complex migrations produce a structured document with phases, rollback gates, exit criteria, and effort estimates. For quick questions it returns direct bullets. You can request a checklist or copy-paste spec instead.

Will this work for library replacements or just large-scale replatforms?

It works across the scale spectrum — swapping a single ORM, porting a frontend build tool, or decomposing a full monolith. The risk-first sequencing and rollback gates are just as useful for a focused library replacement as for a multi-quarter replatform.

Does the skill write migration code, or does it produce plans only?

It produces plans, phase definitions, rollback criteria, and verification logic descriptions — not executable code. The output is designed to be handed to engineers as a spec or used to structure sprint planning.