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This is the normative specification. RFC-2119 keywords (MUST, SHOULD, MAY) apply. For a gentler introduction, read the whitepaper. This page is for implementers.

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1. SintCapabilityToken

The SintCapabilityToken is the primitive identity and authorization unit. An implementation MUST serialize it as JSON conforming to https://schema.sint.gg/v1/capability-token. 
{
  "$schema":   "https://schema.sint.gg/v1/capability-token",
  "tokenId":   "uuid-v4",
  "agentDID":  "did:sint:agent:<sha256-fingerprint>",
  "issuerId":  "did:sint:gateway:<installation-id>",
  "issuedAt":  "ISO-8601",
  "expiresAt": "ISO-8601",
  "tier":      "0 | 1 | 2 | 3",
  "scope": {
    "allowedTools":    ["string"],
    "allowedTopics":   ["string"],
    "allowedActions":  ["string"],
    "deniedPatterns":  ["glob-string"]
  },
  "physicalConstraints": {
    "maxLinearVelocity_ms":  "float",
    "maxAngularVelocity_rads": "float",
    "maxForce_N":            "float | null",
    "geofence":              "GeoJSON FeatureCollection",
    "proximityGuard_m":      "float",
    "eStopBinding":          "topic | service | action"
  },
  "humanSponsor": {
    "sponsorDID":          "did:sint:human:<id>",
    "escalationContact":   "uri",
    "maxAutonomousDuration_s": "int"
  },
  "modelBinding": {
    "foundationModelId":  "string",
    "allowedBackends":    ["string"],
    "rosclaw_audit_ref":  "string | null"
  },
  "proofReceipt": {
    "teeAttestation": "base64-cbor",
    "ledgerHash":     "sha256-hex",
    "signature":      "Ed25519-hex"
  }
}

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1.1 MUST requirements

  • MUST use W3C DID Core 1.0 for agentDID, issuerId, and humanSponsor.sponsorDID.
  • MUST sign the token body with Ed25519; proofReceipt.signature MUST verify against the issuer’s public key.
  • MUST reject tokens with tier ≥ 1 and physicalConstraints.eStopBinding == null.
  • MUST enforce expiresAt strictly; tokens past expiry MUST NOT authorize any action.

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1.2 SHOULD requirements

  • SHOULD include proofReceipt.teeAttestation for production deployments on hardware with TEE support.
  • SHOULD link modelBinding.rosclaw_audit_ref to an external empirical safety study when available.

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2. Wire messages

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2.1 SintRequest

{
  "$schema":   "https://schema.sint.gg/v1/request",
  "requestId": "uuid-v4",
  "timestamp": "ISO-8601",
  "agentDID":  "string",
  "tokenRef":  "tokenId",
  "requestedAction": {
    "toolName":   "string",
    "parameters": "object",
    "estimatedPhysicalImpact": {
      "affectedJoints":  ["string"],
      "peakForce_N":     "float | null",
      "duration_ms":     "int",
      "reversible":      "boolean"
    }
  },
  "contextSnapshot": {
    "environmentClass": "indoor_structured | outdoor | shared_human | unknown",
    "nearbyHumans":     "boolean",
    "sensorHealth":     "nominal | degraded | failed",
    "rosclaw_session_id": "string | null"
  }
}

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2.2 PolicyDecision

{
  "$schema":    "https://schema.sint.gg/v1/policy-decision",
  "decisionId": "uuid-v4",
  "requestId":  "string",
  "timestamp":  "ISO-8601",
  "decision":   "ALLOW | BLOCK | ESCALATE | DEFER",
  "tier":       "0 | 1 | 2 | 3",
  "rationale": {
    "matchedRule":       "string",
    "blockedField":      "string | null",
    "escalationReason":  "string | null"
  },
  "executionBudget": {
    "maxDuration_ms":  "int",
    "interruptible":   "boolean"
  }
}

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2.3 EvidenceLedgerEvent

See conformance for the full EventTypeEnum. Core fields: 
{
  "$schema":         "https://schema.sint.gg/v1/ledger-event",
  "eventId":         "uuid-v4",
  "sessionId":       "string",
  "sequenceNumber":  "uint64",
  "timestamp":       "ISO-8601",
  "eventType":       "EventTypeEnum",
  "agentDID":        "string",
  "tokenRef":        "string",
  "tier":            "0 | 1 | 2 | 3",
  "prevHash":        "sha256-hex",
  "eventHash":       "sha256-hex",
  "teeSignature":    "Ed25519-hex | null"
}

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3. DFA

An implementation MUST model every request as a deterministic finite automaton: 
𝓜 = (Q, Σ, δ, q₀, F)

Q  = { IDLE, PENDING, POLICY_EVAL, ESCALATING, PLANNING,
       OBSERVING, PREPARING, ACTING, COMMITTING,
       COMPLETED, FAILED, ROLLEDBACK }

q₀ = IDLE
F  = { COMPLETED, FAILED, ROLLEDBACK }
The transition function δ is given by the table in conformance §State machine coverage. An implementation MUST reject any transition not in δ. Unreachable states MUST NOT be enterable.

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4. Tier escalation

An implementation MUST compute effective tier as: 
Tier(r) = max( BaseTier(r), Δ_human(r), Δ_trust(r), Δ_env(r), Δ_novelty(r) )
See tiers for the Δ-factor formulas. Weights MAY be tuned per deployment; the defaults MUST be provided.

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5. CSML

An implementation MUST compute CSML as: 
CSML(m, P, t) = α · AR̄_m + β · BP̄_m + γ · SV̄_m − δ · CR̄_m + ε · 𝟙[ledger_intact(t)]
Default weights: α=0.30, β=0.25, γ=0.20, δ=0.15, ε=0.10. CSML updates MUST emit CSML_UPDATE events to the ledger.

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6. Ledger requirements

  • MUST be append-only. Deletion or modification of past entries MUST be detectable.
  • MUST chain each event via prevHash = SHA-256(canonicalize_cbor(previous_event)).
  • MUST provide verifyChain(from, to) that returns { valid: bool, brokenAt?: int }.
  • SHOULD TEE-sign events for tier ≥ 1.
  • MUST retain events per tier per the retention table in conformance.

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7. API endpoints

Implementations SHOULD expose the following endpoints. URL paths MAY differ; semantics MUST match.
MethodPathPurpose
GET/.well-known/sint.jsonProtocol discovery
GET/v1/healthHealth check
POST/v1/interceptEvaluate a single request
POST/v1/intercept/batchEvaluate multiple requests (207 Multi-Status)
POST/v1/tokensIssue capability token
POST/v1/tokens/delegateDelegate (attenuate) a token
POST/v1/tokens/revokeRevoke a token
GET/v1/ledgerQuery audit ledger events
POST/v1/ledger/verifyVerify hash-chain integrity
GET/v1/approvals/pendingList pending approval requests
POST/v1/approvals/:id/resolveApprove or deny (M-of-N quorum supported)
GET/v1/approvals/eventsSSE stream for real-time approval events
GET/v1/metricsPrometheus metrics
GET/v1/openapi.jsonOpenAPI surface
GET/v1/compliance/tier-crosswalkTier → NIST / ISO / EU AI Act mapping

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8. Versioning

The spec follows semantic versioning. Breaking changes to schemas or endpoints increment the major version and are published to schema.sint.gg/v{N}/. Deprecation policy:
  • Deprecation MUST be announced in the changelog at least one minor version before removal.
  • Deprecated endpoints MUST continue to work for at least one minor version.
  • The /v1/openapi.json surface MUST document deprecated endpoints with deprecated: true.

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9. SINT Improvement Proposals (SIPs)

Changes to this specification follow a formal SIP process. Substantive changes MUST have an associated SIP. Editorial fixes MAY be made directly.

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10. References

Normative:
  • W3C DID Core 1.0
  • RFC 8032 (Ed25519)
  • RFC 8949 (CBOR)
  • RFC 4634 (SHA-256)
  • RFC 2119 (MUST/SHOULD/MAY)
Informative:
  • IEC PAS 62443-1-6:2025
  • EU AI Act Regulation (EU) 2024/1689
  • NIST AI RMF 1.0
  • ISO/IEC 42001:2023