Modernize one legacy workflow without a wholesale rewrite

A critical application is difficult to change. Documentation is incomplete, and the business cannot pause operations while a new system is built from scratch. Source code describes implementation, but business rules may live in scheduled jobs, database behavior and staff practice. AI-generated documentation and code can repeat those misunderstandings with confidence.

We modernize one capability at a time, with the old behavior captured as the standard to match.

• We map the selected workflow and its dependencies from authorized source code, a dependency inventory, sanitized transactions and known business rules.
• AI drafts explanations and candidate changes with source references, so engineers can check every claim.
• Existing behavior is captured in characterization tests. A bounded interface is introduced, and old and new behavior are compared on the same inputs. Only the accepted capability moves, through a controlled routing layer.
• Unexpected differences stop the migration. Traffic routes back to the legacy capability where supported, preserving transaction state. Data already changed may need separate reconciliation.
• Proprietary source and production data stay within approved tooling. Code-generation tool permissions are restricted, and the boundary includes developer tooling, source storage and logs.

• A workflow and dependency map. The selected workflow, its dependencies and the business-rule questions still open.
• Candidate implementation. AI-drafted changes with source references, characterization tests and review evidence.
• A migration plan. How the accepted capability moves, how parity is verified and how traffic routes back if needed.

• Domain experts confirm business rules.
• Engineers review generated code before an authorized release owner moves traffic.
• Material data or schema changes need explicit review beyond a passing test run.

An ordinary integration, vendor upgrade or manual documentation may be enough. Avoid AI-driven rewriting where there is no reliable behavioral baseline or owner for the rules.

• Legacy technology decisions: what to measure before replacing a system