Proposal: Canton x402 integration

[piotrswierzy]

Development Fund Proposal Submission

Proposal file:
/proposals/canton-x402.md

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Summary

This PR adds a proposal to bring Canton Coin support to the x402 ecosystem through the full upstream contribution path: a Canton x402 payment scheme specification followed by a reference implementation after upstream acceptance. It also includes integrating Canton into the open-source Blocky402 facilitator platform, operating a public Canton-compatible facilitator for 12 months, and allocating a dedicated 100,000 CC subsidy pool to offset qualifying Canton-side transaction costs. The proposal is intended to make Canton usable for API-native, agent-native, and machine-to-machine payments via HTTP 402 flows.

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Checklist

• Proposal file added under /proposals/
• Milestones and funding amounts defined
• Acceptance criteria included
• Alignment with Canton priorities described

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Notes for Reviewers

Please pay close attention to the dependency between the two upstream workstreams: the reference implementation is intentionally scoped to begin only after the Canton x402 specification is accepted by x402 maintainers. The proposal is designed around x402’s actual contribution model rather than assuming Canton support can be delivered as an isolated implementation.

It may also be useful to review the balance between protocol contribution, operated infrastructure, and ecosystem enablement. In addition to the code and specification work, this proposal includes a 12-month operated public facilitator commitment via Blocky402 and a restricted 100,000 CC subsidy pool that can only be used for qualifying Canton-side transaction costs on the public Canton facilitator. Total funding requested is 760,000 CC.