[ccashwell]

Fixes for four of the eight contest findings filed against dev-2.3.0 at 26f89e6, one commit each with a regression test that fails on the unfixed code, plus README text for the new behavior and regenerated Hardhat gas snapshots. The OZ findings were already resolved on the base. The other four findings are covered at the end: three acknowledged without code changes, one a comment fix in v4-periphery.

What's in it

Finding	Commit	Change
7	9108e53	V4_POSITION_MANAGER_CALL refuses to run inside a foreign PoolManager unlock. The command only admits modifyLiquidities, which opens its own unlock, so inside an unlock someone else opened it could only fail with AlreadyUnlocked. That failure fell under FLAG_ALLOW_REVERT, so a plan built with the flag completed with the leg skipped and the route's funds left in the position manager: the L-01 shape, which the 2.3.0 gate closed for V4_SWAP but not here. The branch now reads poolManager.isUnlocked() after the calldata check and reverts NestedExecutionNotPermitted in the router's own frame, where the flag does not reach. The existing EXECUTE_SUB_PLAN re-throw carries it out of nested plans.
11	69ebd2b	PERMIT2_TRANSFER_FROM_BATCH maps each detail's to through _mapRecipient. The batch passed recipients straight to Permit2, so the MSG_SENDER and ADDRESS_THIS sentinels every other recipient field honors sent tokens to address 1 and address 2 instead. Permit2Payments sits below the contract that defines the mapper, so the per-detail loop moves into the Dispatcher branch beside the single-transfer command, and the batch overload in Permit2Payments is removed with its imports.
8	669b869	A gas-starved command failure is fatal regardless of FLAG_ALLOW_REVERT. A call-based command fails with no returndata when its callee runs out of gas, and the flag tolerated that like any other failure, even though the gas limit is the one input a route's submitter controls. The execute loop snapshots gasleft() before dispatch and, on failure, reverts InsufficientGas when the frame holds under 1/64 of it, the share EIP-150 leaves behind a callee that ran dry (the check OpenZeppelin's forwarder uses). It runs before the required-command check on purpose: after it, a starved required command inside an allow-revert sub-plan would surface as a plain ExecutionFailed that the parent frame, still holding about 2/64 of its own gas, would swallow. EXECUTE_SUB_PLAN re-throws InsufficientGas the same way it re-throws the nested-execution gate. Pre-existing since v1.
1	6247453	_v2Swap measures delivery across the final hop only. The recipient's balance was snapshotted before the first hop, so when the recipient is itself a pair the path passes through, the tokens an earlier hop routed into it counted toward amountOutMinimum. The snapshot now happens inside the loop at the penultimate pair, right before the final swap; the check after the loop is unchanged. Pre-existing since v1.
	2a9bdac	Regenerated Hardhat gas snapshots.

The README documents the failures the flag never swallows, the batch recipient sentinels, and the final-hop measurement.

Alternatives considered

• 7. Decoding the returned AlreadyUnlocked selector and re-throwing costs more bytes and ties the router to the position manager's error. Making the command ignore the flag altogether breaks plans that legitimately tolerate a failed mint at top level. Gating on the nested opt-in instead of the unlock state is wrong, since an opted-in route still cannot run it. The gate sits after the calldata check so a malformed input still reports the slice error first, and a chain without a pool manager never reads one before validating the input.
• 11. Copying the array to memory and rewriting recipients before calling Permit2's own batch function costs a memory copy and more bytes. Redefining the mapper lower in the hierarchy clashes with the periphery's definition on linearization.
• 8. Reverting with invalid() saves 12 bytes and burns the submitter's remaining gas, which is what OpenZeppelin does, but gives integrators nothing to decode. Checking only on the tolerated path leaves the sub-plan hole above. A per-command gas stipend or a minimum-gas field in the plan changes the format and the SDK.
• 1. Rejecting recipients that are pairs on the path needs a scan per hop and blocks legitimate pair-delivery composition. Trusting the pair-computed output instead of the balance delta reopens the fee-on-transfer gap the delivery check exists to close.

Not in this branch

• 5, a permissioned fee-on-transfer underlying consuming the fee adapter's verification surplus. Acknowledged: the token and the surplus are the adapter owner's own, fee-on-transfer tokens are unsupported, and any fix belongs in the adapter.
• 6, a buy-tax intermediate in a v3 multi-hop spending other router-held balance. Acknowledged: pre-existing since v1 and shared with SwapRouter02, and fee-on-transfer tokens are unsupported.
• 10, aggregate v4 deltas at or above 2^127 reverting SafeCastOverflow. Acknowledged: core bounds each operation to int128, the amounts exceed any supply, and a plan can split.
• 4, the PositionInfoLibrary field list naming tickUpper before tickLower while claiming LSB order. Fixed in v4-periphery as a comment-only commit, a14b2e80 on fix/position-info-layout-comment off periphery main. The file is identical on the 7ed84398 pin, so the submodule pointer here is unchanged.

Bytecode

UniversalRouter runtime, from snapshots/UniversalRouterTest.json at each commit:

	Runtime	Free under 24,576
dev-2.3.0 (26f89e6)	24,121	455
this branch	24,065	511

Gas

66 Hardhat snapshot entries changed, median 13 gas lower. PositionManager mint paths pay about 1.0k to 1.3k more for the isUnlocked read; long multi-swap plans are down by as much as 1.7k.

Testing

New Foundry tests, each run against the unfixed code first and failing there:

• V4PositionManagerCallWithinUnlock.t.sol: deploys a real PositionManager from its artifact, since importing it clashes with the per-file optimizer_runs restrictions in foundry.toml. A top-level mint succeeds as a control; inside a foreign unlock the command reverts with the flag clear, with the flag set, and with the flag set on an enclosing sub-plan.
• Permit2TransferFromBatch.t.sol: ADDRESS_THIS delivers to the router, MSG_SENDER to the caller, and a detail whose from is not the caller reverts FromAddressIsNotOwner.
• GasStarvation.t.sol: a RESOLVE against a resolver that burns all forwarded gas, under a 1M gas limit, reverts InsufficientGas as a required command, as an allow-revert command, and as either inside an allow-revert sub-plan. Two controls show ordinary failures still follow the flag.
• V2RecipientPairAlias.t.sol: fork test at block 20010000 against the real v2 factory with four mock tokens, path A, B, C, D, B, delivering to the B-C pair. A minimum one wei above the final hop's output reverts V2TooLittleReceived; the exact final-hop output passes; an ordinary recipient receives the final hop's output.

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