concordia-protocol

Concordia v0.6 Predicate Primitive

The v0.6 predicate primitive is a standalone signed artifact for authority, scope, policy, eligibility, or bounds evaluations. It does not replace mandates, attestations, or ApprovalReceipts. Those primitives remain authoritative for their own domains; predicates package a typed condition into a portable artifact.

Artifact Shape

New emissions write type as the predicate-type field. Readers accept legacy predicate_type only when type is absent.

Required fields:

• predicate_id: urn:concordia:predicate:<id>
• type: predicate type profile URN
• authority: authority namespace
• issuer: DID or service id
• subject: subject identifier
• condition: profile-defined object
• issued_at, expires_at: ISO 8601 timestamps
• references: attestation-style references
• algorithm: EdDSA or ES256
• status: active, expired, revoked, or suspended
• signature: base64url signature

Optional fields: validity, constraints, delegation_chain, revocation_endpoint, revoked_at, and metadata.

Signing

Predicate signatures cover RFC 8785 JCS canonical JSON bytes with signature removed. The reference signer emits Ed25519 through algorithm: "EdDSA". ES256 is accepted by the schema but not emitted by the v0.6 reference signer.

condition.result is allowed only when the predicate type profile declares deterministic semantics. Non-deterministic profiles with condition.result fail at sign time and verify time with schema_invalid.

Verifier Surface

concordia.predicate.verify_predicate(predicate, *, resolver=None) returns PredicateVerificationResult with stable failure reasons:

• schema_invalid
• bad_signature
• expired
• revoked
• unknown_authority
• ref_mismatch
• wrong_subject
• resolver_miss

The verifier validates schema, profile semantics, resolver bindings, signature, lifecycle, subject binding, references, revocation, and ApprovalReceipt composition warnings.

Resolver

concordia.predicate_resolver.BasicHttpsResolver resolves signed predicates from HTTPS or a local mirror. It caches by predicate id with ETag and canonical SHA-256 metadata, validates parseability and signature, and returns None for soft misses. Transport and parse failures raise ResolverProtocolError.

CTEF

Authority predicates map to:

{
  "claim_type": "authority",
  "claim_subtype": "predicate_evaluation",
  "artifact_ref": "urn:concordia:predicate:pred_001",
  "issuer": "did:web:operator.example#policy",
  "subject": "urn:sanctuary:action:tool_call_9d4e8f01",
  "authority": "urn:concordia:authority:policy",
  "verified_at": "2026-05-14T00:00:00Z",
  "result": "satisfied"
}

Composition

Predicate references preserve unknown type and relationship strings as opaque read-side values. A reference with type: "receipt" and relationship: "fulfills" composes with ApprovalReceipt verification when that verifier is importable. If not, predicate verification records approval_receipt_verifier_unavailable as a warning and continues.

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