Legacy Modernization Pattern — Failures

Pattern: Legacy Modernization
Component: failures.md
Version: 1.2 | Updated: 2026-07-29

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Purpose

Recover when the Legacy Modernization pattern is misapplied — without abandoning the gate.

Failure → detection → recovery

Failure	Detection	Recovery
No golden tests	Parity bugs in prod	Stop rewrite; build characterization first
Orphan seam	Dual-run confusion	Assign boundary owner; redraw map
Dump context	Agent reimplements myths	Rebuild legacy pack with ranking
Flag day	Rollback impossible	Reintroduce incremental slices

Escalation from Legacy Modernization failures

• Security-class impact during Legacy Modernization → Security skill + human security owner
• Production SEV while misusing Legacy Modernization → Hotfix containment first
• Learning after Legacy Modernization containment → Root Cause

Do not

• Skip the Legacy Modernization human gate “just this once” after a failure
• Delete Legacy Modernization evidence to hide a bad run
• Replace Legacy Modernization with unstructured chat under pressure

Related

• Checklist
• Enterprise notes
• Example

Changelog

• 1.2 (2026-07-29): Legacy Modernization failure recovery table and escalation paths expanded.