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SPECIFICTION
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Halcyon

halcyon.tel

Free plan LinuxAndroid
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Spec score 7.8 #15 of 33 in Softphone Software

What it is

Halcyon is a free, pre-1.0 Android softphone built on PJSIP and integrated with Android Telecom. It registers with a PBX over UDP, TCP, or TLS, advertises RFC 8599 push parameters, and supports several SIP identities with an account selected for each call. When server-side push is configured, the registrar sends a data-only FCM message before an incoming INVITE to wake the device. Without push, Halcyon uses a foreground SIP service with permanent TLS registration and the associated battery cost. Its Android ConnectionService handles tel: and sip: calls, including from the lock screen, while Telecom-native routing supports Bluetooth headsets and Android Auto. Listed audio codecs are Opus, G.722, AMR-WB, and G.729; video codecs include VP8, VP9, and arm64 MediaCodec H.264. Media uses SRTP encryption, with ZRTP on the roadmap. Android 8.0 or newer is required; signed APKs are available from GitHub Releases.

Spec sheet

Product
Halcyon is a low-latency Android softphone built on PJSIP and integrated with Android Telecom.Read 9 Oct 2026 · halcyon.tel
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.Read 9 Oct 2026 · halcyon.tel
Audio routing
Halcyon supports Telecom-native audio routing for Bluetooth headsets and Android Auto.Read 9 Oct 2026 · halcyon.tel
Audio security
The feature list describes SRTP encrypted media and says ZRTP support is on the roadmap.Read 9 Oct 2026 · halcyon.tel
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.Read 9 Oct 2026 · halcyon.tel
Call handling
Its self-managed Android ConnectionService handles tel: and sip: calls and supports the lock screen.Read 9 Oct 2026 · halcyon.tel
Codecs
Listed audio codecs are Opus, G.722, AMR-WB, and G.729; listed video codecs are VP8, VP9, and arm64 MediaCodec H.264.Read 9 Oct 2026 · halcyon.tel
Development status
The site labels Halcyon pre-1.0 and in active development.Read 9 Oct 2026 · halcyon.tel
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.Read 9 Oct 2026 · halcyon.tel
Multiple accounts
Users can run several SIP identities side by side and select an account per call.Read 9 Oct 2026 · halcyon.tel
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.Read 9 Oct 2026 · halcyon.tel
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.Read 9 Oct 2026 · halcyon.tel
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.Read 9 Oct 2026 · halcyon.tel
SIP transports
Halcyon registers with a PBX over UDP, TCP, or TLS and advertises RFC 8599 push parameters.Read 9 Oct 2026 · halcyon.tel

Plans and prices

Pre-1.0 free Free Free to install and use; pricing and licensing for 1.0 will be announced before launch. Active pre-1.0 development Read 9 Oct 2026 · halcyon.tel

Every Halcyon plan and price →

Strong points and limits

Strong points

  • Free to install and use during pre-1.0
  • Supports UDP, TCP, and TLS SIP transport
  • Multiple SIP identities selectable per call
  • Bluetooth headset and Android Auto routing
  • Self-hostable with direct PBX-to-FCM connection

Limits

  • No iOS version
  • Without push, permanent TLS registration uses more battery
  • Pre-1.0 active development status
  • Play Store listing planned for stable release

Who it suits

It suits Android users or PBX administrators wanting a self-hosted SIP softphone with push calling, multiple identities, and Telecom integration. It requires Android 8.0 or newer and PBX-side FCM configuration for push behavior.

Verdict

Halcyon provides a focused Android SIP client with push support, native call handling, and several codecs. Its pre-1.0 status, Android-only availability, and push setup requirements define the practical boundaries.

Where Specifiction places it

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