Multi-Agent Coordination Protocol (MACP) - Quorum Mode

Document: RFC-MACP-0011 Version: 1.0.0-draft Status: Community Standards Track Updates: RFC-MACP-0002

Abstract

This document defines macp.mode.quorum.v1, the standards-track MACP primitive for threshold approval or rejection. Quorum Mode is narrower than Decision Mode: it standardizes one approval request, participant ballots, and a commitment once the threshold is satisfied or becomes impossible to satisfy.

1. Purpose

Quorum Mode is appropriate when one bounded action requires N-of-M approval rather than open-ended proposal comparison.

2. Identifier and participant model

• Mode identifier: macp.mode.quorum.v1
• Participant model: quorum

The participant set MUST be declared at SessionStart, but resolution is based on a threshold rather than unanimity.

3. SessionStart requirements

A Quorum Mode Session MUST bind:

• participants - eligible approvers,
• mode_version - quorum-mode semantic profile,
• configuration_version - approval threshold profile,
• policy_version - governance profile,
• ttl_ms - approval deadline,
• context - optional approval context.

Base Quorum Mode v1 assumes exactly one approval request per Session.

4. Message types

Quorum Mode defines the following mode-specific message types:

• ApprovalRequest - opens the approval request and states the threshold.
• Approve - records an approval ballot.
• Reject - records a rejection ballot.
• Abstain - records a neutral ballot.
• Commitment - authoritative terminal outcome.

5. Validation rules

Implementations MUST enforce the following:

1. A Session MUST accept at most one ApprovalRequest in base v1.
2. required_approvals MUST be greater than zero and MUST NOT exceed the count of eligible participants.
3. Each eligible participant MAY cast at most one ballot across Approve, Reject, or Abstain.
4. A Session becomes eligible for Commitment when approvals reach the required threshold, or when the remaining possible approvals can no longer reach that threshold.
5. Only an authorized coordinator may emit the final Commitment.

6. Terminal semantics

Quorum Mode resolves only when an authorized Commitment is accepted.

Recommended CommitmentPayload.action values include:

• quorum.approved
• quorum.rejected

The commitment SHOULD bind the approval request identifier and the threshold profile used.

7. Determinism class

Quorum Mode claims semantic-deterministic determinism.

Given the same participant set, the same approval threshold, the same accepted ballots, and the same bound versions, implementations MUST derive the same quorum state and the same commitment eligibility.

8. Security considerations

Implementations MUST address all of the following:

• authenticate each ballot sender,
• reject ballots from ineligible participants,
• ensure ballots cannot be counted twice,
• protect confidential approval context where necessary,
• preserve the exact accepted ballot history for audit and replay.

9. Canonical schemas and examples

Canonical schemas:

• schemas/proto/macp/modes/quorum/v1/quorum.proto
• schemas/modes/quorum.proto

Example transcript:

• examples/quorum-mode-session.json