I built a browser-only Git diff viewer using File System Access API — no server needed

A developer built Duff, a browser-only Git diff viewer that combines the File System Access API with isomorphic-git to let users view diffs across multiple local repositories without any server or CLI. Key technical challenges included handling instanceof inconsistencies in test environments, unexpected write operations from read-only Git commands, significant performance overhead from the browser's security layer requiring multi-layer caching, and persistence quirks with IndexedDB-stored directory handles.