Betaflight vs SUNDIALS

Betaflight runs two lines at once. The 2025.12.x branch is pure maintenance — UART interrupt handling, MSP race conditions, failsafe clamping, and periodic board-target refreshes — while the 2026.6 line, which reached 2026.6.1 in August, carries the largest feature set in this window by a wide margin. That feature set is dominated by one thread: an AUTOPILOT mode with flight-plan configuration, CLI waypoint commands, in-flight waypoint capture on a switch, geofence return-to-home, LAND loiter and TAKEOFF patterns, plus OSD waypoint elements and a navigation minimap. Alongside it sits a DroneCAN protocol stack with ESC and GNSS providers, CAN peripheral support on three MCU families, MAVLink mission upload and download, and STM32N6 platform bring-up.

The autopilot work is not a single feature but a rebuild of how the firmware handles position: the release notes show position control unified on a velocity primitive and the existing GPS rescue reimplemented as a flight-plan mission rather than a special case. That direction pulls hardware integration along with it — DroneCAN node allocation, GNSS Fix2, ESC telemetry and MAVLink ground-station handshaking are all things a manually flown craft does not need. The SITL harness gained fidelity and per-run session ids in the same releases, which is what you build when autonomous behaviour has to be regression-tested rather than test-flown.

With GPS rescue now running through the mission engine, the next releases on this line should concentrate on hardening that path — the release candidates already added an rx-loss policy, sanity checks and an arming gate for flight plans, and safety scaffolding of that kind usually keeps accumulating after the feature ships.