Argument-Order Bug Silently Breaks LaunchDarkly-to-OpenFeature Migrations

When teams migrate from LaunchDarkly to OpenFeature, a subtle but critical difference in argument order between the two SDKs can cause production bugs that are hard to detect. Both libraries share similar method names, but LaunchDarkly's boolVariation places the evaluation context before the fallback value, while OpenFeature's getBooleanValue reverses that order. A simple search-and-replace migration correctly renames methods but silently swaps the arguments, causing users to receive fallback values instead of evaluated flag results. An open-source tool called FlagLint addresses this by using Abstract Syntax Tree analysis to understand argument semantics, not just method names, enabling safe automated rewrites. FlagLint also flags cases it cannot safely automate — such as dynamic flag keys or bulk state calls — and can be integrated into CI pipelines to prevent developers from reintroducing direct LaunchDarkly calls after migration.