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docs: Cardano x402 open standard specification#3

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adacapo21 wants to merge 6 commits into
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feat/cardano-x402-open-standard
Open

docs: Cardano x402 open standard specification#3
adacapo21 wants to merge 6 commits into
mainfrom
feat/cardano-x402-open-standard

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Summary

  • Adds specs/cardano-x402.md — a formal RFC-style specification for the Cardano payment scheme in x402
  • Covers wire format (exact_cardano scheme), token registry (ADA + 4 stablecoins), transaction structure (Lucid Evolution + CML), structural verification rules, and Blockfrost settlement flow
  • Enables third-party implementations of compatible Cardano x402 clients and servers without depending on @qbtlabs/x402

What's in the spec

  • Wire format: 402 response requirements + X-PAYMENT header payload
  • Token registry: ADA, iUSD, USDM, DJED, USDCx with policy IDs and asset name hex
  • Transaction construction rules (client-side, BIP-39 seed, Lucid Evolution)
  • Structural verification algorithm (server-side, CML CBOR parsing, no on-chain calls)
  • Settlement via Blockfrost REST API
  • Security considerations (replay protection via eUTXO, min-ADA enforcement, no smart contracts)
  • Comparison with EVM and Solana x402 schemes

Test plan

  • Review spec accuracy against reference implementation in src/chains/cardano.ts
  • Verify token policy IDs match src/types/cardano.types.ts
  • Confirm wire format examples match actual 402 response structure
  • Cross-reference with existing Cardano docs at docs.qbtlabs.io/chains/cardano.mdx

adacapo21 added 6 commits May 2, 2026 16:16
Formalises the Cardano payment scheme as an RFC-style spec covering wire
format, token registry, transaction structure, verification rules, and
settlement flow. Enables third-party implementations of compatible
Cardano x402 clients and servers.
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