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Halcyon
What it is
Halcyon is a free, pre-1.0 Android softphone built on PJSIP and Android Telecom for SIP calling through a PBX. It registers over UDP, TCP, or TLS and supports several SIP identities, with an account selectable for each call. With server-side push configured, the registrar sends a data-only FCM message before an incoming call to wake the device. Without push, Halcyon keeps a foreground SIP service and permanent TLS registration, which has the usual battery cost. Its Android ConnectionService handles tel: and sip: calls from the lock screen, while Telecom-native routing supports Bluetooth headsets and Android Auto. Listed audio codecs include Opus, G.722, AMR-WB, and G.729; video codecs include VP8, VP9, and arm64 MediaCodec H.264. Media uses SRTP encryption. The project is self-hostable, with the PBX connecting directly to FCM and no third-party push relay in the call path.
For and against
For
- Free during pre-1.0 development
- UDP, TCP, and TLS SIP registration
- Multiple SIP identities
- Lock-screen calling through Android Telecom
- Bluetooth and Android Auto audio routing
Against
- Pre-1.0 and actively developing
- No iOS version
- Without push, foreground service uses battery
- Play Store release planned for stable version
The verdict
Halcyon provides a self-hostable Android SIP client with push calling, multiple accounts, and Telecom integration. Its current pre-1.0 status, Android-only availability, and push setup requirements are important considerations.
Who it suits
It suits Android users and self-hosted PBX operators needing SIP calling. Android 8.0 or newer is required; there is no iOS version.
Plans and prices
Pre-1.0 free
Active pre-1.0 development
Read 9 Oct 2026 · halcyon.tel
On the record
- Android requirements
- The FAQ specifies Android 8.0 (API 26) or newer on arm64-v8a, armeabi-v7a, or x86_64; video codecs are currently only compiled into the arm64-v8a build.halcyon.tel · read 9 Oct 2026
- Audio routing
- Halcyon supports Telecom-native audio routing for Bluetooth headsets and Android Auto.halcyon.tel · read 9 Oct 2026
- Audio security
- The feature list describes SRTP encrypted media and says ZRTP support is on the roadmap.halcyon.tel · read 9 Oct 2026
- Availability
- The site says pre-1.0 signed APK builds are available from GitHub Releases, while the Play Store listing is planned for the first stable release.halcyon.tel · read 9 Oct 2026
- Call handling
- Its self-managed Android ConnectionService handles tel: and sip: calls and supports the lock screen.halcyon.tel · read 9 Oct 2026
- Codecs
- Listed audio codecs are Opus, G.722, AMR-WB, and G.729; listed video codecs are VP8, VP9, and arm64 MediaCodec H.264.halcyon.tel · read 9 Oct 2026
- Development status
- The site labels Halcyon pre-1.0 and in active development.halcyon.tel · read 9 Oct 2026
- iOS and desktop
- The site says there is no iOS version and mentions a desktop build in the repository for testing the SIP stack on Linux.halcyon.tel · read 9 Oct 2026
- Multiple accounts
- Users can run several SIP identities side by side and select an account per call.halcyon.tel · read 9 Oct 2026
- PBX and FCM setup
- Halcyon is described as self-hostable, with the user's PBX talking directly to FCM and no third-party push relay in the call path.halcyon.tel · read 9 Oct 2026
- Product
- Halcyon is a low-latency Android softphone built on PJSIP and integrated with Android Telecom.halcyon.tel · read 9 Oct 2026
- Push calling
- With server-side push configured, the registrar sends a data-only FCM before the INVITE to wake the device for an incoming call.halcyon.tel · read 9 Oct 2026
- Push limitation
- Without server-side push, Halcyon falls back to a foreground SIP service that uses a permanent TLS registration and has the usual battery cost.halcyon.tel · read 9 Oct 2026
- SIP transports
- Halcyon registers with a PBX over UDP, TCP, or TLS and advertises RFC 8599 push parameters.halcyon.tel · read 9 Oct 2026
