Opened 21-05-2026 by hythloda, last activity 5mo ago
Proposal file:
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Author: Denend | FTP
Status: Submitted
Created: 2026-03-12
x402 is an open HTTP payment protocol that has already processed 75M+ transactions across $24M+ in volume. It allows any server to require payment for any API response using a single middleware line, with no accounts, API keys, or manual billing flows. It is purpose-built for autonomous AI agents. Every major EVM chain, Solana, and several others already have live x402 facilitators. Canton does not.
This proposal delivers:
A Canton x402 Facilitator — the /verify and /settle service, accompanied by a formal scheme specification submitted upstream to the x402 repository, enabling Canton Coin to appear as a selectable payment scheme in any x402 accepts array
A Canton x402 Client SDK - a library for the payer side (developers and autonomous agents) to interact with Canton-settled x402 endpoints.
A Canton x402 Resource Server Middleware - drop-in server-side middleware so Canton builders can gate any API endpoint behind Canton Coin payment in minutes.
CanTrustAI as the canonical reference implementation - a live, production deployment of a Canton-settled x402 resource server, demonstrating the full stack end-to-end.
CanTrustAI's infrastructure was already deployed (smart contracts, on-chain payment settlement, production UI), which serves as the empirical foundation for this proposal. Forward development is funded across four milestones at 150,000 CC / 250,000 CC / 300,000 CC / 400,000 CC, for a total of 1,100,000 CC.
x402 reuses HTTP's dormant 402 Payment Required status code to embed payment flows natively into API requests. A server that wants to charge per request responds with a 402 containing payment requirements; the client pays and retries; the server verifies and fulfills. No accounts. No API keys. No billing relationships. The entire flow is stateless and machine-readable by design — which is why it is rapidly becoming the default payment layer for autonomous AI agents.
The protocol is already live at scale. It is chain-agnostic by specification: the accepts field in a 402 response can enumerate any number of networks and payment schemes. The facilitator architecture means a new chain does not require changes to the core protocol — it requires only a new facilitator implementation that speaks to the target chain's settlement layer.
Canton Coin is not listed among x402's supported networks. This means:
This is a concrete, remediable gap. The x402 facilitator interface is well-specified. The Canton ledger API is well-specified. The integration work is tractable and has a clear output: Canton Coin becomes a selectable payment scheme in any x402 accepts array.
CIP-0082 names "dev tools, reference implementations, and critical infra" as explicit targets for the development fund. A Canton x402 facilitator is squarely in all three categories:
Problem: Canton Coin has no x402 facilitator. As x402 becomes the default payment protocol for AI agent infrastructure and API monetisation, Canton's absence means:
Outcome: A complete, maintained Canton x402 integration stack — facilitator, client SDK, resource server middleware — that is protocol-compliant with the x402 spec, listed in the x402 ecosystem directory, and demonstrably functional via CanTrustAI in production.
Success looks like:
Before this grant program existed, the following was built and deployed:
On-chain payment settlement: Smart contracts deployed on Canton mainnet handling payment authorisation and settlement in Canton Coin and supported stablecoins. Each inference request is a settled Canton ledger transaction.
Unified AI gateway: A production API gateway routing inference requests to Claude (Anthropic), Gemini (Google), and GPT-4/OpenAI, with per-provider authentication, billing, and response normalisation.
Production frontend: A working user interface for developers and end users to manage balances, submit inference requests, and monitor usage.
Visualization of the architecture - https://cdn.ftptech.xyz/cantrustai_architecture.html
This deployment is the empirical proof that Canton Coin can function as a payment settlement layer for per-request API access — the exact model x402 formalises at the protocol level.
The facilitator is the server-side service that sits between a resource server and the Canton ledger. It exposes two endpoints per the x402 spec:
POST /verify — validates a client's payment payload against the resource server's declared payment requirements, without yet settling.
POST /settle — submits the validated payment payload to the Canton ledger and returns a settlement response.
By running this facilitator, any resource server can accept Canton Coin payments without maintaining its own Canton node, implementing Canton gRPC client logic, or handling ledger-level payment verification.
Key design decisions:
Alongside the facilitator implementation, we will produce a formal scheme specification (scheme_exact_canton.md) following the structure established by the SVM integration, and submit it upstream to the x402 repository as the canonical description of Canton's payment scheme.
A client-side library for developers and autonomous agents that want to pay for x402-gated services using Canton Coin. The client handles:
The SDK is designed to be usable both by human developers (standard async library) and by autonomous AI agents (no interactive steps, fully programmatic).
A drop-in middleware package for Canton builders to add x402 payment gating to any HTTP API endpoint. Mirrors the ergonomics of the existing x402 TypeScript middleware:
app.use(
cantonPaymentMiddleware({
"GET /api/data": {
accepts: [cantonCoinScheme],
price: "1.0",
description: "Access to dataset endpoint",
},
})
);
The middleware handles the full x402 flow server-side: emitting 402 responses with correct PAYMENT-REQUIRED headers, delegating verification and settlement to the Canton facilitator, and releasing the response on successful payment.
CanTrustAI is refactored and documented as the canonical end-to-end reference implementation of the Canton x402 stack.
Estimated Delivery: 2026-06-15
Funding: 0,00 CC upon committee acceptance of delivery
Deliverables:
Acceptance criteria:
Estimated Delivery: 2026-07-30
Funding: 0,00 CC upon committee acceptance of delivery
Deliverables:
Estimated Delivery: 2026-08-15
Funding: 150,000 CC upon committee acceptance of delivery
Deliverables:
850 MB of total network traffic burned on the Canton Network. At current network conditions, this is estimated to correspond to approximately 380,000 $CC burned, though the actual amount of $CC required may vary over time. Traffic counted toward this milestone must originate from real usage by users/companies not affiliated with the FTP team.
250,000 CC upon committee acceptance of delivery.
1.85 GB of total network traffic burned on the Canton Network. At current network conditions, this is estimated to correspond to approximately 820,000 $CC burned, though the actual amount of $CC required may vary over time. Traffic counted toward this milestone must originate from real usage by users/companies not affiliated with the FTP team.
300,000 CC upon committee acceptance of delivery.
3.1 GB of total network traffic burned on the Canton Network. At current network conditions, this is estimated to correspond to approximately 1,370,000 $CC burned, though the actual amount of $CC required may vary over time. Traffic counted toward this milestone must originate from real usage by users/companies not affiliated with the FTP team.
400,000 CC upon committee acceptance of delivery.
For all performance-based milestones, PPS metrics are calculated using only successfully finalized x402 payment flows executed through the Canton x402 facilitator infrastructure.
A qualifying payment flow must include:
Excluded activity includes:
Performance verification may use:
The committee or its delegates may request:
All performance-based milestones must be achieved within 18 months of approval of the proposal.
The Canton x402 stack aligns with Canton architecture at several levels.
Ledger settlement as the source of truth.
Privacy-preserving payment flows.
Agent compatibility.
Open standard, not vendor lock-in.
The Canton x402 facilitator is additive to the Canton ecosystem. It does not require changes to Canton core, Splice, or Daml.
Total Funding Request: 1,100,000 CC
Milestone 1.1 — Canton x402 Facilitator
0,00 CC
Milestone 1.2 — Client SDK + Resource Server Middleware
0,00 CC
Milestone 1.3 — CanTrustAI Reference Implementation + Ecosystem Close-out
150,000 CC
Milestone 2 (Performance based):
250000 $CC
Milestone 3 (Performance based):
300000 $CC
Milestone 4 (Performance based):
400000 $CC
Given the use of escrow and on-ledger settlement, a formal external security audit is planned prior to broader production scaling.
Budget Allocation:
Per CIP-0100:
Upon each milestone delivery, FTP will collaborate with the Canton Foundation.
Milestone 1.3 announcement & developer tutorial promotion.
Milestone 4 announcement
Why x402 specifically?
x402 is the credibly neutral, open-source standard for machine-to-machine HTTP payments.
Why a facilitator rather than a Canton-specific payment protocol?
The facilitator pattern is precisely designed for new chain integrations.
Why is CanTrustAI the right reference implementation?
Because it is already live.
Why does this serve the broader Canton ecosystem, not just FTP?
The facilitator, client SDK, and middleware are open-source general-purpose infrastructure.
Rebuilt from the recorded board moves (complete history). get_dev_fund_lifecycle(number) gives the same in the MCP.