Spanda

Continuity Policies

Continuity policies declare takeover, delegation, and succession behavior when robots or fleet members fail mid-mission.

Syntax

continuity_policy WarehouseContinuity {
    on robot.failed {
        resume from checkpoint;
        reassign mission;
    }
    on battery.critical {
        hot takeover;
    }
    on fleet.failed {
        reassign mission;
    }
}

Declared actions influence takeover mode inference (resume, hot takeover, restart, human takeover, etc.).

Triggers

Common on conditions:

Trigger	Meaning
`robot.failed`	Primary robot offline or faulted
`robot.degraded`	Robot degraded but partially operational
`battery.critical`	Battery below safe threshold
`fleet.failed` / `swarm.failed`	Fleet or swarm member lost
`communication.interrupted`	Link loss between coordinator and agent
`hardware.capability_lost`	Required sensor or actuator unavailable

Pair fleet triggers with a fleet declaration. Diagnostics emit continuity:fleet when fleet/swarm triggers appear without a fleet block.

Actions

Action	Typical takeover mode
`resume from checkpoint`	Resume at last checkpoint
`reassign mission`	Hand off to ranked successor
`hot takeover`	Immediate replacement
`cold takeover`	Initialize successor after failure
`shadow takeover`	Pre-synchronized backup takes over
`human takeover`	Operator assumes control
`restart` / `partial restart`	Full or stage-level restart

Hot, cold, and human takeover are high-risk. Declare an Approval topic or operator path; diagnostics emit continuity:approval when missing.

Mission plans and checkpoints

Resume and checkpoint actions work best with a mission_plan:

mission_plan WarehouseInventoryScan {
    step navigate_aisles;
    step scan_shelves;
    step report_inventory;
}

continuity_policy WarehouseContinuity {
    on robot.failed {
        resume from checkpoint;
        reassign mission;
    }
}

Without a mission_plan, the continuity engine synthesizes progress from context; diagnostics warn with continuity:mission when resume/checkpoint actions are declared without a plan.

Fleet programs

Declare a fleet and continuity policy together:

fleet PatrolFleet {
    RoverAlpha;
    RoverBeta;
}

continuity_policy PatrolContinuity {
    on robot.failed {
        resume from checkpoint;
        reassign mission;
    }
}

Diagnostics emit continuity:policy when a multi-member fleet lacks continuity_policy. Pair recovery_policy reassign actions with continuity_policy for takeover mode — continuity:handoff hints when recovery reassigns without continuity.

Runtime dispatch

When SPANDA_FLEET_MESH_URL is set, recovery handoff and continuity CLI commands relay through the mesh:

Coordinator: POST /v1/fleet/continuity
Agent: POST /v1/continuity/execute, POST /v1/continuity/ack
Peer topic: fleet_takeover

See fleet-distributed.md and mission-continuity.md.

CLI

spanda continuity examples/showcase/continuity/warehouse.sd \
  --failed ScannerAlpha --progress 72 --trigger robot_failed
spanda takeover examples/showcase/takeover/patrol.sd --failed RoverA
spanda delegate examples/showcase/delegation/survey.sd --failed SurveyBot --to RelayBot
spanda succession examples/showcase/fleet_succession/delivery.sd --scope fleet
spanda check examples/showcase/continuity/warehouse.sd --readiness-json
spanda demo continuity

Package

Official scaffold: spanda-mission-continuity (assurance.continuity).

Examples

Example	Focus
`examples/showcase/continuity/warehouse.sd`	Checkpoint resume
`examples/showcase/takeover/patrol.sd`	Hot takeover
`examples/showcase/delegation/survey.sd`	Delegation
`examples/showcase/fleet_succession/delivery.sd`	Fleet succession

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