---
id: "question-legacy-brownfield-migration"
type: "open-question"
source_timestamps: ["00:23:00"]
tags: ["enterprise", "legacy-systems"]
related: ["concept-dark-factory"]
resolution_path: "Case studies of Fortune 500 companies successfully retrofitting Level 4/5 vibe coding onto legacy monoliths."
sources: ["s01-5-levels-ai-coding"]
sourceVaultSlug: "s01-5-levels-ai-coding"
originDay: 1
---
# How do enterprises migrate legacy codebases to agentic workflows?

## The Question
While [[concept-dark-factory|Dark Factories]] work exceptionally well for **greenfield** projects or highly controlled environments (like [[entity-strongdm|StrongDM]]), it remains unclear how massive enterprises with **decades of undocumented, brownfield legacy code** can safely transition to autonomous agentic workflows without catastrophic failures.

## Why It Matters
- The vast majority of enterprise value sits in legacy systems.
- These systems often lack specs, scenario tests, or documented integration boundaries — exactly what Level 4/5 workflows require.
- Organizations that solve brownfield migration unlock the actual prize.

## Possible Resolution Paths
1. **Spec-mining from running systems**: agents reverse-engineer specs from observed behavior.
2. **Strangler-fig with twins**: build [[concept-digital-twin-universe|digital twins]] of legacy services, replace behind them piece by piece.
3. **Fortune 500 case studies**: track which incumbents successfully retrofit Level 4/5 workflows onto monoliths.

## Connection
Unresolved — currently the single largest practical risk to the speaker's thesis.