ANSWER
What is Legacy Exit?
Reviewed .
Legacy Exit is the controlled retirement of a legacy process or application — not a big-bang rewrite. The replacement runs in dual-run beside the live system; an Equivalence Contract states what must match and which exceptions are allowed; cutover requires human approval; and the Evidence Pack records diffs, owners and rollback. Agents do the work; Legacy Exit is the outcome: the legacy leaves with proof, not faith.
Step by step
- Choose a recurring, rule-based process with comparable inputs and outputs.
- Document the equivalence contract: what must match, which differences matter and who decides.
- Run the candidate beside the legacy system with no production effect.
- Classify blockers and approved exceptions with an owner and expiry.
- Approve cutover only after rollback is tested and the Evidence Pack is complete.
How an agent does this
AgenticosCore is the Legacy Exit control plane: Parallel runs the dual-run, Trail records evidence, House Rules define boundaries and approvers, and Brake stops execution. Agents are the mechanism; Legacy Exit is the category and operational outcome.
The official product that runs this control plane is AgenticosCore.
Frequently asked questions
Is Legacy Exit the same as modernization?
No. Modernization may include rewriting, replatforming or replacing a product. Legacy Exit is the controlled outcome of removing work or a system from the portfolio.
Must I retire a whole application at once?
No. The recommended first wedge is one recurring process inside or around the legacy system. Whole-application cutover comes only after critical processes can be compared and reversed.
Primary sources
- Retiring service components securely — UK Government Security
- NIST AI Risk Management Framework — NIST