kaptan/docs/src/mavlink.md

MAVLink and telemetry

Kaptan emits telemetry using MAVLink 2 framing. The production receiver does not promote inbound MAVLink frames to authority records:

• MAVLink 1 is discarded.
• CRC-invalid MAVLink 2 frames are discarded.
• Signed frames are discarded because no signature verifier or persistent replay state exists.
• Unsigned MAVLink 2 frames are also discarded; a V2 CRC detects corruption, not authentication.

TODO(signing): any future inbound authority requires verified MAVLink 2 signing, configured source/target binding, persistent anti-replay state, and a provisioning/key-rotation policy as one reviewed feature.

Telemetry transmission uses bounded frame classes. A critical frame may replace pending best-effort traffic, but never the DMA-owned active buffer. Completion retries preserve ordering and retain a transiently busy frame for a later service turn.