Base/EVM canonical: port Phases 5–7 (disputes/slashing/refunds) + fix Lane B F-1

[dirtybits]

Tracking issue for the engineering work that has to land before Base/EVM can be called the canonical AgentVouch chain. Context: the gas-free UI + live x402 agent purchase (#53) settled the UX question, but the deployed AgentVouchEvm (Base Sepolia 0x5D90…913E) is Phases 0–4 only — the trust-enforcement half of the protocol does not exist in Solidity yet. Decision framing in docs/KORA_VS_BASE_X402.md (#54) and docs/BASE_POC_INTERIM.md.

This issue makes the "fund the bet" sequence actionable. It is gated on an explicit decision (item 0) — none of the build work below should start until the x402/agent-commerce distribution bet is committed.

0 · Decision gate (blocks everything below)

• Founder commits the x402 distribution bet in writing: "AgentVouch is an agent-commerce protocol; native x402/EIP-3009 presence is worth a protocol re-implementation + second audit." Without this, ship Kora on Solana and keep Solana canonical (see .agents/plans/kora-usdc-fee-abstraction.plan.md).

1 · Port Phases 5–7 to the EVM contract (parity with Solana)

The Solana program has these; the EVM contract does not. Port by spec, not transpilation, matching the Solana semantics.

• Disputes — openDispute / resolveDispute, dispute statuses (Open/Resolved/SlashingVouchers), and the bond/listing locks (the EVM contract already has DisputeLocked/BondExposureLocked errors + openDisputes counters wired as no-op guards — fill in the lifecycle that sets them).
• Voucher slashing — liability scopes (AuthorBondOnly, AuthorBondThenVouchers), the VouchStatus.Slashed transition (Phase 5 residual rules referenced at AgentVouchEvm.sol vouch), and stake reduction accounting.
• Refunds — buyer refund claims against slashed/disputed purchases, preserving the reward-index + proceeds accounting invariants.
• Foundry test parity: replicate the Solana dispute/slash/refund test surface; reach green with the existing 66 tests still passing.
• Adversarial re-audit pass (parity / insolvency / solidity-security) as was done for Phases 0–4.

2 · Fix Lane B F-1 (EIP-3009 fund-stranding)

The signed authorization names the contract as to, so it can be replayed straight to USDC — funds land in the contract with no purchase receipt, stranded (test_laneB_frontRunStrandsFundsNoReceipt). Re-surfaced in #53.

• Adopt receiveWithAuthorization (binds msg.sender == to) or a documented reconciliation/sweep path. Note: a sweep tends to reintroduce some settlement-authority trust — weigh against Lane B's trust-minimization, the whole reason it exists.
• Test the chosen fix closes the stranding edge; update the harness (agent-x402-demo.ts) + UI accordingly.

3 · Production hardening (before any hosted/mainnet surface)

• Lock the CDP paymaster policy — the bundler URL is browser-exposed (VITE_CDP_RPC_URL in feat(base-poc): Base Sepolia gas-free UI + x402 agent purchase flow #53's UI); a hosted UI makes it a drainable sponsorship endpoint. Allowlist the contract + USDC approve/transfer calls and rate-limit.
• Bring contracts/base-poc/ui + harness into CI typecheck (currently outside the repo's scoped typecheck — tsc --noEmit is a local-only claim).
• Second external audit of the full EVM surface (Phases 0–7).
• Live-USDC Base mainnet deploy + config init.

4 · Migration & operations

• State-migration plan for existing Solana reputation / vouches / author bonds → Base.
• Explicit decision: dual-chain operation vs. Solana sunset, with a cutover plan (see docs/DATABASE_CUTOVER.md for prior cutover shape).
• Web/API/CLI adapter swap (web/lib/chains.ts already carries eip155:8453).

Parallel track (not blocked by item 0)

• Ship the Kora fee-only spike on the Solana RC path (.agents/plans/kora-usdc-fee-abstraction.plan.md). Removes live "you need SOL" friction now, keeps Solana usable through any migration window, and is not wasted if Base wins.

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Refs: #53 (UX + x402 POC), #54 (decision doc), docs/BASE_POC_INTERIM.md (Phase 4.5 gate).