[P0] Complete and confirm one autonomous x402 Solana devnet payment

[TFT444]

Objective

Complete one genuine x402 payment on Solana devnet through the autonomous SolGuard security path and independently confirm its transaction on-chain.

Dependencies

Blocked by #32 and #33.

Scope

• Use the official x402 client and SVM support already introduced in the repository.
• Request a real paid test resource and validate the returned x402 v2 payment requirements.
• Canonicalize the selected recipient, amount, token mint, network, and expiry before policy evaluation.
• Route the payment through the autonomous decision API and isolated wallet signer.
• Submit settlement through the configured x402 facilitator only after ALLOW.
• Capture the returned Solana transaction signature.
• Confirm the signature through Solana RPC and record confirmation status, slot, mint, source, destination, and actual balance delta.
• Return the paid resource to the autonomous agent only after the expected payment flow succeeds.
• Preserve the deterministic simulated settlement path as the network-independent fallback.

Security invariants

• The x402 response cannot override a hard mandate or SolGuard decision.
• Unsupported networks, mints, schemes, facilitators, or recipients fail closed.
• No transaction is signed or submitted before ALLOW and authorization verification.
• A facilitator response alone is not presented as on-chain confirmation.
• Duplicate settlement protection remains active.
• Credentials and wallet secrets never enter the repository, frontend, logs, or evidence package.

Acceptance criteria

• An autonomous allowed request obtains the paid resource without payment-by-payment human interaction.
• The returned transaction signature is independently visible through Solana devnet RPC or Explorer.
• The recorded transaction fields match the canonical request and SolGuard authorization.
• Before/after devnet balances are queried rather than hardcoded.
• The evidence explicitly labels devnet tokens as having no real monetary value.
• Network, RPC, facilitator, and settlement failures stop safely without manufacturing a signature or success state.
• The local simulated fallback remains deterministic and fully tested.
• Integration tests use injected transports; the credentialed live exercise remains opt-in.

Evidence required before closure

• Transaction signature
• RPC confirmation response
• Explorer URL using the devnet cluster
• Sanitized SolGuard authorization receipt
• Paid-resource response
• Exact command and source commit used

Keywords

x402-v2 solana-devnet on-chain-confirmation autonomous-payment facilitator usdc cryptographic-proof

Real-evidence contract

• The devnet transaction demonstrates that legitimate autonomous commerce still works after SolGuard authorizes it; it is not a claim of real monetary settlement.
• Treat RPC confirmation as authoritative and use Explorer only as an independently inspectable presentation link.
• Display only RPC-derived wallet addresses, transaction signatures, slots, token mints, confirmation states, and balance changes.
• Keep any large treasury or pound-denominated scenario in a separately labelled simulated ledger. Devnet tokens must never be assigned a real GBP value.
• The transaction and authorization proofs may be displayed; private keys, seed phrases, and raw secret material may not.
• The real path must remain optional so an external outage cannot force the deterministic security proof to fabricate settlement evidence.