← All models GPT-6 Luna editing test OpenAI · Tested Oct 27, 2026 · 1m 20s · $0.02
Four checks All in one 59/90 caught
Grammar & spelling 35/45 Repetitions 11/15 Redundancy 5/15 Consistency 8/15 67 comments · 3 extra flags
GPT-6 Luna caught 59 of 90 planted mistakes, 14th of 16 models tested. It was strongest on grammar and spelling (35 of 45) and missed most on redundancies (5 of 15). The 4 checks took 1m 20s and cost $0.02; asked for all of them in one prompt, it caught 60.
Every comment GPT-6 Luna 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 · 31
Dangling modifier: the door didn't turn the key “Turning the key at last, the door opened” who, not whom: subject of 'was' “whom she guessed was the owner” Misplaced modifier: bound nearly every “he had nearly bound every family Bible” 'along with' adds no subject: Mr. Pell … was “along with a secretary in a lace collar, were” Past habit: used to “the way he use to hold it up” 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” Close: careful … careful “his careful hands” Close: neatly … neat “neatly labeled” Distinctive, chapters apart: gleaming “a gleaming pair of shoes” Close: remembered … memory “her hands remembered” twins are two “the two twins” the reason … was because “was because he had never paid himself” a sum is a total “The sum total” an agreement is mutual “By mutual agreement” finished is complete “completely finished the wine” planning is in advance “no advance planning” a haven is safe “a safe haven” began is first “the week we first began” join together “wants them to join together” an outcome is final “The final outcome” The bakery has three tables; she sits at the fourth “three small tables” Grandfather's eyes: grey, then blue “the same gray eyes as her grandfather” The ledger: green, then red “a ledger bound in green leather” Tea becomes coffee “poured her a mug of tea” Tomas beside him: two decades, then thirty years “for most of two decades” The bakery: two doors down, then a ten-minute walk “BAKERY TWO DOORS DOWN” Nora's home: Chicago, then Boston “the firm in Chicago”