x402 Protocol Integration for Canton #78 - Milestone 1: Canton x402 Facilitator

OPENIssue
by pedrodneves17-06-2026
150K CC requested
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Milestone 1.1: Canton x402 Facilitator

Estimated Delivery: 2026-06-15 Funding: 0,00 CC upon committee acceptance of delivery

Deliverables:

  • Canton x402 facilitator live at a public endpoint, with /verify and /settle compliant with the x402 facilitator spec.
  • Open-source facilitator repository with deployment documentation.
  • Compatibility matrix: tested against current Canton ledger API version and documented supported Canton Coin denominations.
  • Canton x402 payment scheme specification (specs/schemes/exact/scheme_exact_canton.md) covering Canton's payment model and transaction semantics, payload structure, signing and verification flow, and how Canton maps to the x402 scheme/network abstraction — submitted as part of an upstream PR to the x402 repository.
  • General submission to the x402 ecosystem directory for inclusion as a supported Canton network facilitator.

Acceptance criteria:

  • /verify and /settle endpoints behave per the x402 facilitator spec under normal and error conditions.
  • A committee member or delegate can send a test payment payload to the live facilitator and receive a valid verification and settlement response.

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Milestone 1.2: Canton x402 Client SDK + Resource Server Middleware

Estimated Delivery: 2026-07-30 Funding: 0,00 CC upon committee acceptance of delivery

Deliverables:

  • Canton x402 client SDK published to a public package registry.
  • Canton x402 resource server middleware published.
  • Developer tutorial.
  • End-to-end integration test.

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Milestone 1.3: CanTrustAI Reference Implementation + Ecosystem Close-out

Estimated Delivery: 2026-08-15 Funding: 150,000 CC upon committee acceptance of delivery

Deliverables:

  • CanTrustAI migrated to use the Canton x402 facilitator and middleware.
  • Public reference guide.
  • Mainnet transaction demonstrating end-to-end x402 payment flow.
  • Maintenance playbook.

| Milestone | CC Amount | Payment Trigger | | :---- | :---- | :---- | |Milestone 1.1| 0,00 CC|Canton x402 Facilitator| |Milestone 1.2| 0,00 CC|Client SDK + Resource Server Middleware | |Milestone 1.3| 150,000 CC|CanTrustAI Reference Implementation + Ecosystem Close-out |

_Originally posted by @pedrodneves in https://github.com/canton-foundation/canton-dev-fund/issues/78#issuecomment-4729761806_