Application matrix

The AlgoVoi stack is organised in four layers: a canonicalisation substrate at the base, receipt formats above it, verifiers that validate those receipts, and platform services and integrations that produce and consume them. Every arrow in the diagram below is a verifiable, production-deployed dependency.

Architecture layers

1 — Package dependency stack

How the open-source packages depend on each other, from substrate up to the top-of-stack aggregator.

2 — Platform services

How the gateway uses the package layer and feeds the platform services.

3 — Integration layer

What calls the gateway and what the Agent Trust Bench exercises.

Interaction cross-reference

Rows = producer / source. Columns = what it depends on, calls, or feeds.

Package / Service	Depends on	Calls / feeds	Verified by
algovoi-substrate	—	Receipt formats, platform gateway, verifiers	jcs-conformance-vectors (1226/1226)
algovoi-substrate-pqc	algovoi-substrate (extends)	Future PQC receipt formats	PQC cross-product matrix (48/48)
algovoi-jcs-conformance-vectors	—	Tests substrate across 10 languages	—
algovoi-settlement-attestation	algovoi-substrate	algovoi-pef, composite-trust-query, gateway	substrate conformance vectors
algovoi-refund-receipt	algovoi-substrate	algovoi-pef, gateway	substrate conformance vectors
algovoi-cancellation-receipt	algovoi-substrate	algovoi-pef, gateway (via Recurr)	substrate conformance vectors
algovoi-pef	settlement-attestation, refund-receipt, cancellation-receipt	Top-level receipt container	—
algovoi-receipt-verifier	algovoi-substrate (JCS, canon_version)	composite-trust-query, gateway `/v1/receipt/verify`	13/13 cross-validation vectors, Python 41/41, TypeScript 19/19
algovoi-webhook-verifier	—	Tenant webhook consumer (validates `X-AlgoVoi-Signature`)	104/104 cross-validation (8 langs × 13 vectors), Python 47/47, TypeScript 45/45
algovoi-receipt-sentinel	webhook-verifier + receipt-verifier error streams	Sliding-window tamper/replay/scan monitor — fires `TAMPER_DETECTED`, `REPLAY_DETECTED`, `SCAN_DETECTED`, `BURST_FAILURE`	104/104 cross-validation (8 langs × 13 vectors), Python 36/36, TypeScript 35/35
algovoi-audit-verifier	algovoi-substrate (JCS + SHA-256)	Standalone offline audit	103 tests (Python 65, TypeScript 38)
algovoi-rfc9421-verifier	—	Inbound request verification (gateway)	24/24 cross-implementation agreements
algovoi-rfc9421-signer	—	Outbound signed request creation	24/24 cross-implementation agreements
algovoi-composite-trust-query	receipt-verifier signal, settlement-attestation	Top-of-stack `TRUSTED` / `PROVISIONAL` / `UNTRUSTED` verdict	—
AlgoVoi Gateway	substrate, receipt-verifier, rfc9421-verifier, compliance-engine	Audit chain, settlement-attestation, refund-receipt, cancellation-receipt	ATB 128/138, E2E 88/88
Audit Chain	Gateway feed	algovoi-audit-verifier	B2 Object Lock COMPLIANCE 7-year retention
Compliance Engine	Gateway enforces	Wallet screening, KYC/KYB	OFSI, OFAC SDN, EU Consolidated + 7 URL/IP threat feeds
Recurr Engine	Gateway delegates	Cancellation receipts, pull executor (7 chains)	—
Agent Trust Bench	—	Probes gateway + mcp-server	187 profiles / 42 categories
algovoi-mcp-server	—	Gateway HTTP API (29 tools)	ATB 128/138 pass rate
algovoi-reference-agent	algovoi-substrate	Gateway (A2A), settlement-attestation	End-to-end Base chain worked example
algovoi-shopify-app	—	Gateway HTTP API	Gateway E2E 88/88 (scripts/e2e_external.sh, commit 59ff40f8) — all consumed API endpoints route-tested
algovoi-x402-widget	—	Gateway (x402 protocol)	x402 v2 live: all 7 chain test resources return correct 402 envelopes (health-check 2026-05-16) · ATB Phase 8 receipt probes
algovoi-xchain-runtime	—	Gateway + Allbridge + CCTP V2	CCTP V2 Solana live (~50s settlement) · Allbridge EVM→Stellar live · both production-deployed
recurr.algovoi.co.uk	—	Gateway (MPP subscriptions, Tier 1 + Tier 2 pull executor, 7 chains)	MPP subscription external validation 2026-05-16: dual-envelope 402 verified + 4/4 negative-path tests pass (bogus credential → 400, nonexistent resource → 404, wrong tenant → 404, non-subscription via subscription endpoint → 404). Public fixture: api.algovoi.co.uk/mpp/sub/demo/mpp-sub-test-daily-base
AP2 mandate client	—	Gateway (mandate authorisation + on-chain settlement across 7 chains)	AP2 `open_mandate_hash` v0 — 7/7 PASS (confirmed 2026-05-26)
External A2A agents	—	Gateway (A2A agent card, 3 skills: verify-payment, create-checkout, check-status) — only live A2A payment agent	Agent card live at api.algovoi.co.uk/.well-known/agent.json · ATB 187 profiles · AlgoVoi-authored RFC 9421 proxy-chain fixture 4/4 OK (submitted to aps-conformance-suite, withdrawn 2026-05-24) · AlgoVoi-authored multi-chain Ed25519 fixture 3/3 OK · cross-extension v0 5/5 PASS (dogfood-B 2026-05-19) · only confirmed live A2A payment agent (2026-04-22)

Data-flow by receipt lifecycle

Each payment event produces a structured receipt chain. All receipts share canon_version: jcs-rfc8785-v1 from the substrate.

Payer initiates payment
        │
        ▼
AlgoVoi Gateway
  ├─► Compliance Engine — screens wallet + URL (OFSI, OFAC, 7 feeds)
  ├─► build_compliance_receipt() [substrate] → compact JWS → Payer
  ├─► Facilitator — on-chain verification (7 chain families)
  ├─► build_settlement_attestation() [substrate] → stored + returned
  ├─► Audit Chain — JCS hash-chained row appended (B2 WORM)
  └─► (on refund) build_refund_receipt() [substrate]
      (on cancellation) build_cancellation_receipt() [substrate]

Recipient verifies receipt
  └─► algovoi-receipt-verifier
        ├─ JWS decode + Ed25519 verify
        ├─ JCS re-canonicalisation check
        └─ Result → algovoi-composite-trust-query → TRUSTED / PROVISIONAL

Auditor verifies chain
  └─► algovoi-audit-verifier
        ├─ Per-row content_hash check
        ├─ hash-chain continuity
        └─ HMAC-SHA256 bundle signature

AI agent calls gateway
  └─► algovoi-mcp-server (29 tools)
        └─► gateway HTTP API
              └─► receipts / compliance / screening

Tenant receives webhook
  └─► algovoi-webhook-verifier
        ├─ Header parse + timestamp check
        ├─ HMAC-SHA256 v1 verify
        ├─ HKDF-SHA256 key derive + HMAC-SHA384 v2 verify
        └─ JSON parse + event-type check → event dict
              │ error_code (on failure)
              ▼
        algovoi-receipt-sentinel
              ├─ sliding window per source
              ├─ matches TAMPER / REPLAY / SCAN / BURST rules
              └─ SentinelAlert → notify security team (or null)

Package dependency graph (compact)

Dependencies flow upward. Packages at each row depend only on packages at rows below them.

Layer	Packages	Depends on
0	substrate	—
0	substrate-pqc	substrate
0	jcs-conformance-vectors	— (tests substrate)
1	settlement-attestation, refund-receipt, cancellation-receipt	substrate
1	pef	settlement-attestation, refund-receipt, cancellation-receipt
1	policy-binding, compliance-gate-lite, spend-guardrail-lite, substrate-guard	substrate (additive, pinned refs)
2	receipt-verifier	substrate
2	audit-verifier	substrate
2	rfc9421-verifier, rfc9421-signer	—
2	composite-trust-query	receipt-verifier signal, settlement-attestation
3	Gateway	substrate, receipt-verifier, rfc9421-verifier
3	Audit Chain	Gateway feed
3	Recurr Engine	Gateway
3	Agent Trust Bench	Gateway, mcp-server
4	mcp-server, shopify-app, x402-widget, xchain-runtime, reference-agent	Gateway HTTP API
4	webhook-verifier	Gateway webhook output (`X-AlgoVoi-Signature`)
4	receipt-sentinel	webhook-verifier + receipt-verifier error streams
4	recurr.algovoi.co.uk	Gateway (MPP subscriptions + pull executor)
4	AP2 mandate client	Gateway (mandate flow + settlement)
4	External A2A agents	Gateway (A2A v0.3 — agent card + 3 skills)

IETF I-D coverage

Eight Internet-Drafts anchor the formats this stack implements. Each I-D maps to one or more packages.

Draft	Packages
`draft-hopley-x402-canonicalisation-jcs-v1`	substrate, substrate-pqc, jcs-conformance-vectors
`draft-hopley-x402-compliance-receipt`	substrate (emitter), receipt-verifier
`draft-hopley-x402-settlement-attestation`	settlement-attestation
`draft-hopley-x402-refund-receipt`	refund-receipt
`draft-hopley-x402-cancellation-receipt`	cancellation-receipt
`draft-hopley-x402-composite-trust-query`	composite-trust-query
`draft-hopley-x402-payment-evidence-frame`	pef
`draft-hopley-x402-retention-chain`	policy-binding, compliance-gate-lite, spend-guardrail-lite, substrate-guard

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Platform

Concepts

Keystone

Substrate 2

Commercial

Open substrate

Payment protocols

Chains

Integrations

Help

Company

Architecture layers

1 — Package dependency stack

2 — Platform services

3 — Integration layer

Interaction cross-reference

Data-flow by receipt lifecycle

Package dependency graph (compact)

IETF I-D coverage

See also

​Architecture layers

​1 — Package dependency stack

​2 — Platform services

​3 — Integration layer

​Interaction cross-reference

​Data-flow by receipt lifecycle

​Package dependency graph (compact)

​IETF I-D coverage

​See also

Architecture layers

1 — Package dependency stack

2 — Platform services

3 — Integration layer

Interaction cross-reference

Data-flow by receipt lifecycle

Package dependency graph (compact)

IETF I-D coverage

See also