Halcyon Sync v3.4.0

Date: 2026-09-30

Highlights

• Selective sync lets you choose which folders sync to each device, so laptops with small disks stop filling up.
• Conflict copies are gone for text files: edits from two devices now merge line by line.
• Uploads of large files are up to 2.3x faster on connections over 100 Mbps.

New

• Selective sync per device, under Settings, Folders. Unchecked folders stay in the cloud and remain shareable.
• halcyon status --json prints sync state in a machine-readable form for scripts and monitoring.
• Admins can set a workspace-wide bandwidth cap from the admin console.

Improved

• Large uploads now use parallel chunks (4 by default, configurable with upload.parallelism).
• The tray icon shows the number of files still syncing, not just a spinner.
• Startup on folders with over 200,000 files is about 40% faster thanks to a cached index.

Fixed

• Files renamed only by letter case (Report.pdf to report.pdf) on macOS now sync correctly (#2214).
• Sync no longer stalls after the laptop wakes from sleep on a different Wi-Fi network (#2190).
• Shared links created from the mobile app now respect the workspace's link expiry policy (#2231).

Breaking changes

• What changed: The sync.ignore file now uses gitignore syntax instead of plain glob lines. Patterns like *.tmp still work, but a leading / now anchors to the sync root. Migration: Run halcyon ignore --check to list any pattern whose meaning changed, then edit those lines. Most users need no changes.
• What changed: The minimum supported version of Windows is now Windows 10 21H2. Migration: Upgrade the OS, or stay on v3.3.x, which receives security fixes until 2027-03-31.

Deprecations

• The --legacy-auth CLI flag is deprecated. Use halcyon login --device instead. The flag will be removed in v4.0, planned for Q2 2027.

Known issues

• Selective sync settings do not yet transfer when you replace a device; set them again after signing in. A fix is planned for v3.4.1.
• On Linux with Btrfs, the first scan after upgrade can take several minutes.

Contributors

Thanks to Ana Lima, Dmitri Sokolov, Hana Ito and Tomas Berg, and to first-time contributors @kwame-codes (the case-rename fix) and @lucia-r (the JSON status output).