Solution
Modernize legacy code without guessing which behavior must survive.
The system handles real transactions, nobody remembers why it works, and the team needs to preserve behavior while changing it. Inspect a seam, confirm uncertain intent, and move one bounded package with evidence.
01
Surgery on a patient running a marathon
Legacy code accumulates risk quietly: undocumented decisions, untested edges, and a growing cost of change. The people who knew why it works have moved on; the documentation stopped matching the code years ago; and the system still handles real transactions every day, so touching it feels like surgery on a patient running a marathon. Meanwhile the modernisation backlog grows faster than it shrinks, and every quarter of leaving it alone costs more than the last.
02
Why the rewrite never ships
A full rewrite is slow and risky in its own right. The requirements that shaped the original system rarely survive as anything more than tribal memory, so a rewrite team re-derives them under time pressure and gets them subtly wrong. The old system keeps changing while the new one is built. And a rewrite has one delivery moment — it either works on cutover day or it doesn’t — which is why so many are quietly abandoned after the first ninety days of excitement. Pointing an AI assistant at the codebase does not change any of that: it writes new code faster, against the same missing requirements.
03
What Praxis Legacy Upgrade does
Begin with inspected code behavior and known constraints. A person confirms the business intent that legacy code alone cannot reveal. BA records the accepted requirement and creates an initial WP; Architect enriches the affected technical scope; Developer makes one bounded modernization change and records evidence for review. Source-internal scanning tools should not be assumed to ship in every installed role package.
04
How it works
- Inspect a seam — use code behavior, tests and operational constraints as evidence, and mark uncertain business intent for human confirmation.
- Prepare one WP — preserve accepted scope while Architect designs a bounded replacement or adaptation.
- Implement and check — change only the selected seam and show checks run, failed or skipped.
- Review and deliver — Quality Harness can inspect the result; Git publication and merge remain separate decisions. Incremental work reduces scope, but it does not guarantee uninterrupted production.
05
What’s included
- Current-state map — the relevant behavior and constraints, with uncertainties named.
- Bounded package — accepted requirement, technical choice and implementation boundary.
- Evidence — tests and observations actually performed for the change, plus remaining risks.
Move your legacy system forward
Book a walkthrough of Legacy Upgrade against your own system.