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Castor Credits

Idle Compute Contribution Protocol · Status: Draft · RCAN v1.7

1. Overview

Castor Credits are earned by robots contributing idle compute capacity to harness research tasks — such as neural architecture search and model evaluation. The protocol is defined as part of RCAN v1.7 under the contribute scope (level 2.5).

Key properties:

  • 1 credit ≈ 1 evaluated candidate. Each accepted CONTRIBUTE_RESULT submission earns the robot's owner exactly one credit (subject to validation).
  • Tracked per owner, not per device. Credits accumulate on the owner_uid, so a fleet of robots contributes to a shared pool.
  • Transferable within a fleet. Credits may be moved between robots registered under the same owner_uid.
  • Non-transferable across owners. Inter-owner credit transfer is not supported in v1.7.

Scope requirement: All three contribution message types require the contribute scope (level 2.5). Robots without this scope MUST reject contribution requests with an ERROR response (code: SCOPE_INSUFFICIENT).

2. Message Types

The contribute protocol uses three dedicated §3 MessageTypes. All three require the contribute scope.

Value Name Direction Description
33 CONTRIBUTE_REQUEST Coordinator → Robot Deliver a work unit for evaluation. Carries model format, input data, and timeout.
34 CONTRIBUTE_RESULT Robot → Coordinator Return evaluation results. Response payload includes a credit_grant object when the submission is accepted.
35 CONTRIBUTE_CANCEL Robot → Coordinator Cancel an active contribution (preempted by higher-priority command, battery low, etc.).

CONTRIBUTE_REQUEST (33)

Sent by the coordinator to a robot that has advertised idle compute capacity. The robot MUST respond with either a CONTRIBUTE_RESULT or CONTRIBUTE_CANCEL before the timeout_s expires.

{
  "version": "1.7.0",
  "message_id": "550e8400-e29b-41d4-a716-446655440000",
  "source_ruri": "rcan://coordinator.castor.ai/prod",
  "target_ruri": "rcan://owner.example.com/robot-arm-7",
  "type": 33,
  "priority": 1,
  "payload": {
    "work_unit_id": "wu_2026031_0042",
    "project": "castor-architecture-search",
    "model_format": "onnx",
    "input_data": "...",
    "timeout_s": 120
  }
}

CONTRIBUTE_RESULT (34)

Sent by the robot upon completing the work unit. When the coordinator validates the result, a credit_grant object is embedded in the acknowledgement payload. If validation fails, no credit is issued and an ERROR is returned.

{
  "version": "1.7.0",
  "message_id": "660f9511-f30c-52e5-b827-557766551111",
  "source_ruri": "rcan://owner.example.com/robot-arm-7",
  "target_ruri": "rcan://coordinator.castor.ai/prod",
  "type": 34,
  "priority": 1,
  "payload": {
    "work_unit_id": "wu_2026031_0042",
    "output": { "loss": 0.0421, "accuracy": 0.9734 },
    "latency_ms": 8204,
    "hw_profile": { "npu_tops": 26, "tier": "silver" },
    "status": "complete",
    "credit_grant": {
      "owner_uid": "uid_abc123",
      "robot_rrn": "RRN-A1B2C3D4E5F6G7H8",
      "credits_earned": 1,
      "candidate_id": "wu_2026031_0042",
      "hardware_tier": "silver",
      "score": 0.9734,
      "timestamp": "2026-03-20T14:30:00Z"
    }
  }
}

CONTRIBUTE_CANCEL (35)

Sent by the robot to abort an active contribution. Common reasons include P66 preemption (see §5 below), low battery, thermal throttle, or operator override. The partial_result field is optional; if present, the coordinator MAY use it for scoring even without a full result. No credit is issued for a cancelled work unit.

3. Credit Grant Schema

The credit_grant object is attached to the coordinator's CONTRIBUTE_RESULT acknowledgement when a submission is accepted. Implementations MUST validate all fields before persisting credits.

{
  "owner_uid": "string",
  "robot_rrn": "string (RRN-XXXXXXXXXXXXXXXXX)",
  "credits_earned": "integer",
  "candidate_id": "string",
  "hardware_tier": "string",
  "score": "number (0.0–1.0)",
  "timestamp": "ISO-8601"
}
Field Type Notes
owner_uid string Identity of the robot's registered owner. Credits are applied to this account.
robot_rrn string Canonical RRN of the contributing robot (format: RRN-XXXXXXXXXXXXXXXXX).
credits_earned integer Number of credits granted. Always 1 in v1.7; reserved for future batch work units.
candidate_id string Opaque identifier for the evaluated model candidate. Matches work_unit_id.
hardware_tier string Hardware capability tier of the contributing robot at evaluation time.
score number Validation score for the submitted result (0.0–1.0). Scores below 0.5 may result in credit withholding.
timestamp string ISO-8601 UTC timestamp when the credit was granted by the coordinator.

4. Badge Tiers

Owners accumulate credits across their entire fleet. Badge tier is determined by the total lifetime credits earned by the owner_uid. Badges are displayed in the leaderboard and may be embedded in conformance reports.

Badge Credits Description
Bronze 100–499 Entry contributor
Silver 500–1,999 Active contributor
Gold 2,000–9,999 Major contributor
Diamond 10,000+ Elite contributor

Tier downgrade: Tiers are based on lifetime credits and never decrease. An owner who reaches Silver cannot fall back to Bronze regardless of future inactivity.

5. P66 Preemption

Contribution work runs at the lowest priority level (P1 — LOW). Any active robot command arriving at priority P66 or higher (i.e. NORMAL, HIGH, or SAFETY) immediately preempts an active contribution session.

The robot MUST send a CONTRIBUTE_CANCEL message to the coordinator within 500 ms of receiving the preempting command. The cancel reason SHOULD be set to "preempted".

Safety invariant: Contribution MUST NOT delay, buffer, or rate-limit any command at priority NORMAL or above. The contribute scope (level 2.5) is explicitly subordinate to all operational scopes. A robot MUST NOT enter a contribution session while a SAFETY-priority message is pending.

Non-compliance: Failing to cancel within 500 ms of preemption is a conformance violation. Coordinators MUST treat late cancellations as an implicit cancel and MUST NOT issue credit for the work unit.

6. References