AI-native legacy software replacement

Make legacy
new again.

Your business has moved forward. Your software should too. We help you understand, rebuild and progressively replace legacy applications, with evidence at every step.

Start with an assessment → Explore Renew Factory →
Funding Modernization designed around the maintenance budget you already spend. An assessment sets scope, risk and commercial terms before anything is replaced.
freight-billing · illustrative architecture
UnderstandRecover the rules
VerifyReview differences
ReplaceRetire in stages
Concept illustration. Not a customer system or a live product view.
Keep the business knowledge. Renew the software.
  1. Understand first
  2. Verify before replace
  3. Retire progressively
Evidence before confidence

The rule survives.
The old code doesn't have to.

A replacement is only useful if it preserves the behavior your business depends on. We trace each important rule to its sources, compare outcomes on both systems, and put every unresolved difference in front of the people who own the process.

Approved improvements can change old behavior. Each intentional change is recorded with the decision behind it.

FREIGHT-014 · remote-zone surchargeIllustrative
LegacyFRTCALC.cbl · COBOL
IF WS-ZONE = 'R'
    ADD 12.50 TO WS-FREIGHT
END-IF.
Rule

Shipments to a remote zone carry the approved surcharge from the current rate card.

Derived3 / 3 scenarios matchsources: FRTCALC.cbl · rate card
Renewedfreight.ts · TypeScript
if (shipment.zone === "REMOTE") {
  fee = fee.plus(rateCard.remoteSurcharge);
}
Evidence → business review → approved specificationConcept example. No customer results shown.
Renew Factory

One lifecycle. A shared foundation of evidence.

Renew Factory is the platform we are building to connect system understanding, reconstruction, verification and migration. The knowledge core keeps business rules and their evidence connected throughout the work.

01 / 04

Discover

Map what the legacy system really does from code, schema, logs, UI and documents.

  • Source & schema analysis
  • Dependency graph
  • Business rule extraction
System model
02 / 04

Rebuild

Rebuild against a reviewed business specification.

  • Executable specification
  • Architecture & coding agents
  • Security review
Candidate application
03 / 04

Verify

Compare agreed scenarios and resolve differences against approved business rules.

  • Golden test scenarios
  • Difference engine
  • Business sign-off
Evidence report
04 / 04

Migrate

Shadow production, cut over in steps, then retire the old system.

  • Data mapping & reconciliation
  • Shadow traffic
  • Progressive cutover
Decommission plan
Renew Knowledge Coreshared by every stage · knowledge and evidence stay scoped to each project

Knowledge Graph

Business processes and rules, linked to the code, tables and documents they come from.

Evidence Ledger

Every rule carries a provenance (observed, derived, inferred, unknown), its sources and its review status.

Golden Test Corpus

The scenarios that define correct behavior, replayed against both systems.

Renew ManagedMonitoring, security updates, SLA and ongoing changes after cutover.
How replacement earns approval

A controlled transition. Clear decisions at each step.

Six stages, three gates. Production changes follow agreed acceptance criteria and a rehearsed rollback plan. Nothing passes a gate on assumption.

  1. ObserveRead the legacy system. No change to production.
  2. Gate 1 ReconstructRebuild the module in an isolated environment.
  3. CompareReplay agreed scenarios on both systems and diff results.
  4. ShadowRun production inputs against the new system, with side effects contained.
  5. Gate 2 Progressive cutoverSwitch by module, user group or traffic share.
  6. Gate 3 DecommissionRetire the legacy system once nothing depends on it.
Gate 1Before rebuilding

Confirm system boundaries, critical rules, access rights and the unknowns that remain open.

Gate 2Before cutover

Resolve material differences, reconcile data and approve operational readiness and rollback.

Gate 3Before retirement

Confirm remaining dependencies, retention needs and handover responsibilities.

Where to start

Start with a bounded system. Prove the path forward.

An initial assessment determines whether replacement makes technical and economic sense. These are our focus areas, not claims of completed customer work.

Logistics & supply chain

Billing, rating and reconciliation

Freight rating, settlement, order workflows and billing modules with testable business boundaries.

  • TMS
  • WMS
  • Rate engines
  • Settlement
Manufacturing operations

Plant and back-office systems

Inventory, procurement and internal reporting. Integrations and production dependencies are scoped before a module is replaced.

  • Inventory
  • Procurement
  • Reporting
  • Non-core MES
Enterprise workflows

Internal applications

Approval systems, internal CRM and database-driven applications where the cost of change keeps rising.

  • Approvals
  • Internal CRM
  • HR & admin
  • Admin back ends
Why Renew

Your maintenance budget. A path to something better.

Most organizations pay twice: for keeping the old system alive and, eventually, for a large one-off rewrite. A Renew agreement moves transferable maintenance spend into phased replacement and managed operation. Scope, parallel-running costs and commercial terms are set in the assessment.

  • Maintenance-fundedModernization paid from a budget line that already exists, under one multi-year agreement.
  • Verified replacementThe deliverable is a system that passes agreed acceptance and a legacy system that can be retired, not just new code.
  • Factory economicsReusable analysis, tests and components lower the cost of each successive module.

Today

Legacy maintenancerecurring · rising
Rewrite projectone-off · large · high risk

Two budgets. The old system keeps running while the new one is funded separately, often for years.

With Renew

Renew Modernization Agreementmulti-year
AssessReplace in phasesOperate

One agreement, scoped by assessment. Legacy spend falls as each module is retired.

The standard deliverable

Every project ends with a Modernization Evidence Report.

Not a slide deck. A document your auditors, your process owners and your next engineering team can read: what was recovered, how it was verified, what changed on purpose, and what still needs a decision.

The report is produced from the same knowledge core the work runs on, so it cannot drift from what was actually built and tested.

Modernization Evidence Report · contents

Freight billing · module 3 of 7 · illustrative

  1. Recovered business rules186 rules · provenance per rule
  2. Rule evidencesources, traces, documents
  3. Scenario coveragegolden corpus · both systems
  4. Differences and decisionsmatched · corrected · open
  5. Data integrityreconciliation results
  6. Migration risk and rollbackper gate
  7. Open questionsowner · due date
  8. Acceptance conclusionsigned by process owners
Generated from the knowledge core · figures are placeholders for layout
Company

Six principles we won't trade for speed.

Renew Software is building an AI-native way to modernize enterprise software. These principles shape the platform, the delivery method and the contracts we sign.

  1. 01Understand before rebuild

    No full reconstruction until the legacy system is sufficiently understood.

  2. 02Evidence over assumptions

    Every important business rule carries its sources and verification status.

  3. 03Verify before replace

    No production replacement before critical business verification is complete.

  4. 04Incremental over big bang

    Progressive migration by default. Critical systems are never swapped in one step.

  5. 05Productize every delivery

    Each project leaves reusable capability in the platform, never customer data.

  6. 06Retire the legacy

    Every modernization has a decommission target. Two systems forever is a failure.

Mission Turn legacy software maintenance spending into continuous software modernization. Group A Runworld company
Start with the system you know

What is your legacy holding back?

Tell us its business role, its current maintenance burden and the module you would change first. We reply with whether an assessment makes sense and what it would cover.

What an assessment brief covers
  1. What the system does, and who relies on it.
  2. Which module creates the most maintenance pain.
  3. What code, schema and test environments are available.
  4. What must be preserved, and what should change.
  5. Budget, timing and migration constraints.

Send the brief, or just the system name, to hello@renew.software. We reply within two business days.