Branch by abstraction is a software development technique that facilitates continuous deployment by allowing large code changes to be made gradually and safely through an abstraction layer. This pattern is crucial for trunk-based development and continuous integration and continuous delivery (CI/CD) pipelines, as it ensures that code alterations can coexist with ongoing development and that the entire codebase remains releasable at any time. The process involves creating an abstraction layer that enables communication between new and old systems, allowing for incremental updates without disrupting existing functionality. Feature flags can enhance this process by allowing developers to toggle access to new code, conduct limited releases, and safely test in production environments. This method reduces merge conflicts and allows for easy pausing and resuming of changes, although it may not be suitable for scenarios where customers choose their own upgrade timelines. Tools like Harness can further streamline this process by offering AI-driven automation and feature management capabilities, enabling faster and safer code deployments.