PROVENANCE.md records the vendored Math.sol SHA-256 as a6ee779fc42e6bf01b5e6a963065706e882b016affbedfd8be19a71ea48e6e15 and states 'The dependency is unchanged'. docs/REVIEW.md line 38 states 'Vendored source/license checksums matched the provenance record.' The committed file hashes to 370229dde74ae1e02df304c97851ac561c632c6c9985c3c2d816a98d711751e0.

Diffing against upstream v5.0.2 shows the only change is a forge-fmt line wrap of the four-argument mulDiv signature (line 207), so the code is semantically identical and no arithmetic behaviour is affected. The defect is that the provenance record and the review's verification statement cannot both be true of the committed tree, so anyone re-running the documented integrity check gets a mismatch and cannot distinguish a formatting change from a tampered dependency.

Fix: either restore the byte-exact upstream file (and exclude lib/ from forge fmt) or update the recorded hash and the 'unchanged' wording.

The only tests that reach the 32-fill cap (testFuzzFillCapReleasesCrossingRemainder, testFuzzFillCapMayRestUncrossedRemainder) put all resting makers on a single price level, so the branch where the cap is hit while levels are being emptied and unlinked mid-loop (bestBid/bestAsk advancing through _unlink, then the crossing remainder released against a still-crossing 33rd level) is never exercised.

The case where the remainder after exactly 32 fills is below minBaseAmount (dust released rather than cap release) is also untested.

Instrumenting BookHandler._compareTrades with require(seen < N) shows the OrderBookInvariant campaign (256 runs x 100 actions) fails at N=4 but passes at N=6 and N=8, i.e. no random placement ever touched more than 5 makers; the 32-cap and 64-walk paths are therefore covered only by deterministic single-level tests, as ORDERBOOK_REVIEW.md acknowledges.

I reproduced the untested scenarios in a scratch harness and the implementation behaves correctly (32 fills across 32 one-tick levels cost 2,375,852 gas; remainder released; bestAsk equals the 33rd level; conservation exact), so this is a coverage gap, not a defect.

The TooDeep bound is the requested design ('bounded gas, no hints') and README documents that the walk cap can prevent deep insertion, so this is recorded as an operational observation rather than a defect.

The concrete cost is worth stating: with the test parameters (tick 1e16, minBaseAmount 100) an attacker who rests 64 minimum-size bids at consecutive ticks just below the best bid locks only 4,320 quote wei in total, all recoverable by cancel, and thereafter any bid more than 64 ticks below the best reverts TooDeep for every user until the attacker cancels or is filled. The same holds for asks placed just above the best ask.

Inserting at a better price than the spam is unaffected (walk length 0), and appending to an existing deep level needs no walk. A 64-level walk costs 405,077 gas for the inserter, which is bounded as specified. Any mitigation (price hints, larger minBaseAmount, coarser tick) is a design or parameter decision outside this review's scope.