Argumentation-based consensus for multi-agent AI · A2A + MCP native · open source

Every decision
deserves a proof.

Deliberatic extends Dung's argumentation framework into a weighted bipolar system with Byzantine fault tolerance, constitutional guardrails, and Merkle-chained evidence — giving your agent clusters auditable, principled decisions instead of opaque confidence scores.

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Core Formalism — Deliberatic Argumentation Framework (DAF)
DAF = A, R⁻, R⁺, w:A[0,1], α:AAgents, C, ρ:Agentsℝ⁺
A=arguments · R⁻=attacks · R⁺=supports · w=evidence weights · α=authorship · C=constitution · ρ=reputation

σ(a) = w(a) · ρ(α(a)) + Σ[s Sup(a)] σ(s)·γ⁺ Σ[t Att(a)] σ(t)·γ⁻
Graded semantics — converges when max|σₙ(a) − σₙ₋₁(a)| < ε (Potyka 2019)

Why Multi-Agent Debate isn't enough

Three fatal gaps in current MAD frameworks that Deliberatic solves.

01
No formal semantics
Agents exchange natural language opinions and opaque confidence scores. There's no structured way to compare, attack, or support positions. When Agent A says "87% confident" and Agent B says "91%," those numbers are unverifiable and incomparable.
Du et al. 2023 · Wu et al. 2025: "simple majority voting already achieves most performance gains"
02
No fault tolerance
If one agent is compromised, hallucinating, or adversarial, no mechanism detects it. Most frameworks use majority voting, which Wu et al. showed cannot exceed the accuracy of the strongest single agent — and over-confident agents actively degrade team output.
Wu et al. 2025: "MAD cannot exceed the accuracy of its strongest participant"
03
No audit trail
Enterprise deployments in finance, healthcare, and government require explainable decision chains. Current frameworks produce conversation logs — not verifiable evidence. When regulators ask "why did the system decide X?", there's no proof.
AI Governance market: $309M → $4.8B by 2034 (Precedence Research)

Six layers of principled reasoning

Each maps to established research in argumentation theory, distributed consensus, and agent communication.

Layer 1
Argumentation
Weighted Bipolar AF (wBAF) Graded Semantics
Agent positions modeled as nodes in a weighted bipolar argumentation graph. Attacks and supports form directed edges. Acceptability computed via iterative propagation — σ(a) = w(a)·ρ(α(a)) + Σ supports − Σ attacks — converging under contraction when γ⁺ + γ⁻ < 1. Not binary accept/reject. Degrees.
Dung 1995 · Amgoud & Cayrol 1998 · Potyka 2019 wBAF modular semantics
Layer 2
Consensus
Adaptive Two-Phase Raft → PBFT
Clear winner (gap > τ=0.15)? Raft fast-path — leader proposes, majority quorum commits in ~50ms. Close call? PBFT conflict-path — Pre-Prepare → Prepare → Commit with 3f+1 Byzantine tolerance. New evidence allowed during Prepare. ~200ms but provably correct.
Ongaro & Ousterhout 2014 (Raft) · Castro & Liskov 1999 (PBFT) · Zhu et al. 2025
Layer 3
Constitution
Normative DSL YAML + Predicate Logic
Hard boundaries (violations → instant rejection), soft preferences (adjust acceptability ±delta), amendment rules (3 vindicated dissents trigger constitutional review). Pre-commit validator ensures every verdict is constitutionally compliant.
Anthropic Constitutional AI · OpenAI Deliberative Alignment · Public Constitutional AI (Abiri 2024)
Layer 4
Transport
A2A v0.3 + MCP Linux Foundation / AAIF
Deliberation rounds are A2A Tasks. Positions are A2A Messages with structured Parts. Verdicts emit as A2A Artifacts. Also ships as an MCP server with 7 tools. Agent Cards advertise deliberation/v1 skill. JSON-RPC 2.0 / SSE / gRPC.
A2A v0.3 (150+ orgs) · MCP Nov 2025 spec (97M+ SDK downloads) · AAIF, Linux Foundation
Layer 5
Evidence
Merkle Evidence Chains SHA-256 · Append-Only
Every round produces a Merkle tree: Hash(positions) → Hash(challenges) → Hash(constitutional checks) → Hash(verdict). Merkle root published with verdict. Any party can verify integrity, trace reasoning, audit compliance. Export: JSON, PDF, OTEL spans.
Merkle 1979 · OpenTelemetry trace correlation · Append-only audit log pattern
Layer 6
Reputation
Dissent-Weighted ELO ρ ∈ [800, 2400]
Modified ELO: ρ_new = ρ_old + K·(S − E). Vindicated dissenters get 1.5× K bonus. Reputation feeds back into wBAF weights — experienced agents' arguments carry more initial mass. Creates systemic incentive against groupthink.
Elo 1978 · Wu et al. 2025: "majority pressure suppresses independent correction"

Anatomy of a deliberation

What happens when agents disagree — in 200ms.

T+0ms · A2A tasks/send
Round opens
Task arrives via A2A. Engine opens round with topic, constitution reference, deadline (30s), and quorum (3). All agents matching the Agent Card skill filter deliberation/v1 are invited. Moderator elected: highest-reputation non-participant.
T+50ms · Position submission
wBAF graph constructed
Each agent submits a Position — structured argument with typed evidence (performance, resource, latency, schema). Parsed into wBAF nodes. Initial weights = evidence strength × agent reputation ρ(α(a)). Agents can challenge() — adding attack edges — or support() — adding support edges.
T+120ms · Graded semantics
Acceptability computed
Iterative propagation: σ(a) = w(a)·ρ(α(a)) + Σ γ⁺·σ(supporters) − Σ γ⁻·σ(attackers). Converges when max delta < ε=0.001. Typically 3-7 iterations. Result: every position has a continuous acceptability degree in [0,1].
T+140ms · Constitutional check
Normative validation
Constitution Interpreter validates all surviving positions. Hard boundary violations → instant rejection. Soft preferences → acceptability adjusted ±delta. If all positions rejected, round escalates to human review via A2A push notification.
T+200ms · Consensus commit
Verdict + evidence chain
Gap > τ? Raft fast-path commits. Close? PBFT conflict-path with new evidence window. Winning position → verdict. All data → Merkle chain (SHA-256). Dissents recorded. Reputation scores updated. Verdict emitted as A2A Artifact. Evidence chain: merkle://0x...

The API

TypeScript SDK · Python SDK · Rust core engine · MCP server

deliberate.ts
constitution.yaml
evidence.ts
TypeScript
// Open a deliberation round over A2A v0.3 const round = await deliberatic.open({ topic: "Which agent handles user onboarding?", constitution: "cluster://production-alpha", deadline: "30s", quorum: 3, transport: "a2a", // or "mcp", "http" consensus: "adaptive" // raft fast-path → pbft conflict-path }); // Submit a position (becomes a wBAF node) await round.submit({ agent: "onboarding-specialist", position: { claim: "Domain context yields 94% accuracy over 1,847 tasks", evidence: [ { type: "performance", value: 0.94, n: 1847, confidence: 0.03 }, { type: "resource", tokens: 1200, latency_ms: 340 }, { type: "schema", output: OnboardingResult } ], fallback: "general-agent" } }); // Challenge (adds an attack edge to the wBAF graph) await round.challenge({ agent: "general-agent", target: "onboarding-specialist", grounds: "resource_efficiency", evidence: [ { type: "resource", tokens: 380, latency_ms: 95 }, { type: "performance", value: 0.89, n: 3200, confidence: 0.02 } ], claim: "3x cheaper at p=0.89 — within soft preference delta" }); // Resolve: wBAF semantics → constitutional check → consensus const verdict = await round.resolve(); // { // winner: "general-agent", // acceptability: 0.82, // consensus_path: "raft", // gap was > τ // constitutional: { hard: "all_pass", soft_delta: +0.08 }, // dissents: [{ agent: "onboarding-specialist", σ: 0.71 }], // evidence_chain: "merkle://0xab3f...c912", // latency_ms: 142 // }

Two halves of one mind

Deliberatic decides. AgenTroMatic executes. Connected by A2A.

Decisions · deliberatic.com
Deliberatic
The prefrontal cortex
  • Weighted Bipolar AF (Dung + Potyka)
  • Adaptive consensus (Raft / PBFT)
  • Constitutional normative DSL
  • Merkle evidence chains (SHA-256)
  • Dissent-weighted ELO reputation
  • A2A + MCP dual transport
Execution · agentromatic.com
AgenTroMatic
The autonomous nervous system
  • Spec-driven task execution
  • Self-healing agent workflows
  • Automatic scaling & retry
  • Fault-tolerant pipelines
  • Real-time telemetry (OTEL)
  • A2A Artifact streaming

Part of the [&] stack

Eight domains. One agent infrastructure.

Compute
fleetprompt.com Runtime & Skills
Contracts
specprompt.com Specifications
Orchestrate
delegatic.com Task Routing
Decisions
deliberatic.com Argumentation & Consensus
Execution
agentromatic.com Autonomous Automation
Infra
webhost.systems Hosting
Spatial
geofleetic.com Location Awareness
Temporal
ticktickclock.com Scheduling & Deadlines

Agents that prove
before they act.

Open-source argumentation engine for multi-agent AI. Dung's framework + BFT consensus + Merkle chains. A2A and MCP native. Apache 2.0.

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