Open Source in Finance Forum London 2026

Financial institutions maintain vast codebases where critical domain logic is embedded in implementation details and scattered across services. Documentation drifts and tests verify the code as written rather than as intended. AI tools generate new code quickly, but understanding whether existing systems behave correctly, remains slow and expensive.

This session shows how specifications can be captured from existing codebases, creating a formal reference for what a system does that is independent of how it does it. We've applied this to significant projects and surfaced latent defects encoded in both implementation and test suites, where code and tests reinforced the same wrong behaviour. Henry will demonstrate the open source tooling and workflows involved, and show how specifications make codebases more fluid: once behaviour is captured, AI agents can refactor, re-platform or modernise the implementation with a verification gate, turning legacy code into a foundation for new development.

Attendees will gain practical techniques for distilling specifications from existing code and applying them to quality assurance, legacy modernisation and resilient open source contributions.