← All models Claude Sonnet 5.5 editing test Anthropic · Tested Oct 27, 2026 · 50s · $0.33
Four checks All in one 73/90 caught
Grammar & spelling 38/45 Repetitions 12/15 Redundancy 10/15 Consistency 13/15 96 comments · 3 extra flags
Claude Sonnet 5.5 caught 73 of 90 planted mistakes, 10th of 16 models tested. It was strongest on contradictions (13 of 15) and missed most on redundancies (10 of 15). The 4 checks took 50s and cost $0.33; asked for all of them in one prompt, it caught 73.
Every comment Claude Sonnet 5.5 left on our 6,000-word test story, where it left it. Click a missed mistake to find it in the text. The checks come from icanwrite , a markdown editor for writers.
Missed · 17
who, not whom: subject of 'was' “whom she guessed was the owner” Misplaced modifier: bound nearly every “he had nearly bound every family Bible” any other shop: the bakery is on Wharf Street “longer than any shop on Wharf Street” Fragment: the survey has no verb “The survey from twelve years ago, which an engineer from the county” Restrictive clause, no commas: the entries that held “The entries, which held only a single word, were” in to, not into “turned his uniform into the quartermaster” 'one of those who' takes a plural verb: were “one of the last binders in New England who was still” Distinctive, chapters apart: gleaming “a gleaming pair of shoes” Distinctive, chapters apart: brittle “a short, brittle sound” Close: remembered … memory “her hands remembered” twins are two “the two twins” an agreement is mutual “By mutual agreement” finished is complete “completely finished the wine” a haven is safe “a safe haven” began is first “the week we first began” The bakery has three tables; she sits at the fourth “three small tables” Tomas beside him: two decades, then thirty years “for most of two decades”