Legacy modernisation, proven

Modernise legacy
systems. Prove
nothing broke.

LegacyLift turns decades-old code into modern, tested software. It learns every business rule, migrates one piece at a time with a person approving each change, and proves the new system behaves exactly like the old one.

Understand/Migrate/Prove/Human-approved
Replay ACCTINT.cbl against the legacy reference
Fidelity Replay Replaying
Vector · legacy = migratedΔ
ACC001standard1,201.50·
ACC004senior tier5,006.25·
ACC005dormant790.00·
ACC007premium25,041.67·
ACC010closed0.00·
ValueSequenceStoreDeterminismAttested

Built for banks, government, and the systems that can't go down

Sandboxed execution
zero network egress
Independent proof
held out from training
Signed & reproducible
Ed25519, verifiable
Human-approved
every change
How it works

Understand it. Migrate it. Prove it.

Most migrations start with guesswork and end with a leap of faith. LegacyLift replaces both.

Codebase map · ACCTINT
Business rules found
Interest tiers by balance bandFinance
Senior bonus over age 65Finance
Dormant after 12 months inactiveOps
ACCTINTcalls INTCALC, DATEUTIL · reads ACCTREC
risk profile42 programs
The independence rule

Replay can teach the migrator, or certify the result. Never both in the same lineage.

A validator that grades a rewrite against the same data that produced it is marking its own homework. LegacyLift keeps the two apart, so a passing score means something to your model-risk team and to an auditor.

Why LegacyLift

Not a translator. A system you can trust.

Rewriting old code is the easy part. Doing it without losing the rules, without a risky cutover, and with proof it still works. That is what a serious migration actually needs.

The business rules survive.

Generic translators convert syntax and quietly lose the intent. LegacyLift carries every rule across (fees, eligibility, the awkward edge cases), each traced back to the decision that set it.

Late-payment fee: cap at £25Finance
set in 2019 · regulatory cap · carried across unchanged

A human signs off, every time.

No big-bang cutover, no black box. The work stops at every piece for a person to approve, edit, or reject. You stay in control of your own system.

ApproveEditReject
every change · no exceptions

Proof, not promises.

Fidelity Replay shows the new system behaves exactly like the old, field by field, and signs the result. Something you can hand to risk and audit that actually holds up.

behavioural equivalence100.0% ✓
signed ed25519· verifiable by anyone
every rule
carried across, traced to a decision
human
approval before anything ships
byte-exact
behaviour comparison, no fudge
signed
attestation on every result
The honest math

Months of consultants, or weeks with proof.

Modernising a core system usually means paying specialists to relearn code nobody documented, then hoping the rewrite behaves. LegacyLift does the reading and the proving. Your team does the deciding.

The consultant route
6 months≈ £480k
  • A team of specialists reading COBOL line by line
  • Business logic locked in people's heads
  • Big-bang cutover, fingers crossed
With LegacyLift
~2 weekssigned & approved
  • Every rule traced back to the commit that set it
  • Risk-scored and migrated chunk by chunk
  • Behaviour proven, every merge human-approved

For regulated institutions · independent · fully auditable