Three Research Runs

Three research runs

Reports written by the exhaustive research skill on three questions. The claims are the skill's own; each report links its sources and says how the search was done.

Asked Which language model is the best writer right now, and is it available on OpenRouter at a reasonable price?

No model is the clear best writer, but Claude Opus 5.5 is the safest pick, and it and every rival are on OpenRouter from $0.50 to $40 per million output tokens

Report from a first pass by 15 researchers. A second pass was stopped before it rewrote the report. The totals below include what that pass had already found. The claims have not been independently checked.

Sources found
1,668
Opened and read
1,190
Searches and lookups
1,137
Researchers
20
Leads still open
351

As of 15 November 2026 there is no single best writer, because human voters, blind readers, LLM judges and slop measures rank the models differently. The pick that holds up across the most kinds of evidence is Claude Opus 5.5, on OpenRouter at $4 input / $20 output per million tokens: it is in a statistical tie for first with human voters, at or near the top of most LLM-judged boards, and the most common choice of reviewers. Gemini 4 Argon ties it with human voters and is the favourite of many fiction and roleplay users, at $2 / $10 until 30 November and $4 / $20 from 1 December, but it scores worst of the frontier models on every measure of AI-sounding prose and it invents details. Claude Fable 5.2 ($8 / $40) gets the best prose scores from LLM judges but loses blind preference tests, and reviewers do not think it is worth double the price for drafting. Every model named as a strong writer is live on OpenRouter except one small writing fine-tune, and the prices are reasonable for an individual writer: the output of a 100,000-word draft costs about $2.70 at Opus 5.5's list price and under $0.10 on the cheapest capable models, before hidden reasoning tokens (arithmetic, explained below).

Statements marked (inference) or (arithmetic) are a researcher's or this report's own reading or calculation, not something a source states. All prices are US dollars per million tokens, input / output, checked against OpenRouter's live endpoints API on 15 November 2026.

Short pick list by budget

BudgetPickOpenRouter idPrice in / outWhyWatch out for
Best overallClaude Opus 5.5anthropic/claude-opus-5.5$4 / $20Top group with human voters and with LLM judges; reviewers' defaultLong-winded; "buries the point"; hidden reasoning roughly doubles the bill per visible word at default settings
Best overall, fiction with flairGemini 4 Argongoogle/gemini-4-argon$2 / $10, then $4 / $20 from 1 Dec 2026Tied first with human voters; fiction users prefer its proseHighest slop scores of the frontier group; adds facts that are not in the brief; content filter
Middle (about $10 output)Claude Sonnet 5.5anthropic/claude-sonnet-5.5$2 / $10Most of Opus 5.5's writing gains at half the priceWeaker on human-vote boards than Opus 5.5
Middle, clear non-fiction and editingGPT-6.1 Sol (or GPT-6 Sol)openai/gpt-6.1-sol$2 / $10Cleanest, plainest prose; best value for proofreadingFiction readers and voters rate it low; refuses explicit scenes
Low ($5 output)GPT-6.1 Terraopenai/gpt-6.1-terra$1 / $5First with blind fiction readers on one boardEvidence is thin and mixed
Low, open-weightGLM-5.3z-ai/glm-5.3$1.40 / $4.40Best open-weight model on several judged boardsHeavy hidden reasoning can make it cost as much per word as Opus 5.5
Very cheap (under $1 output)GLM-5.3 Flash or GPT-6 Lunaz-ai/glm-5.3-flash, openai/gpt-6-luna$0.15 / $0.50 and $0.10 / $0.50Hold most of the flagship score on judged boards for centsDrafts need editing; weak with human voters
Only for the hardest workClaude Fable 5.2anthropic/claude-fable-5.2$8 / $40Best-judged prose, least detectable as AILoses blind preference tests; dense; twice Opus 5.5's price

Opus 5.5 is the only model near the top with both human voters and LLM judges

  • Human votes. On Arena's creative-writing board of 11 November, Gemini 4 Argon is first at 1522.5 (4,928 votes), Claude Opus 5.5 second at 1517.1 (3,800 votes) and Gemini 4 Carbon third at 1516.1 (1,007 votes). Their 95% intervals overlap, and the lead has changed hands between Opus 5.5 and Argon four times since late September (Arena leaderboard dataset).
  • LLM judges. Opus 5.5 is in the top group on Lech Mazur's story benchmark (3.555, where the top four overlap) (lechmazur/writing), first on ToneBench at 2,704 Elo with Fable 5.2 inside its interval (ToneBench data), first overall on Novelcrafter's NC Bench at 96.43% (NC Bench), third on EQ-Bench Longform at 84.6 (EQ-Bench longform data) and fifth on Caliper Bench at 85.96 (Caliper Bench).
  • Blind readers plus judges. It is second overall on Fiction Bench (66.7), which combines blind reader votes with AI judges (Fiction Bench data).
  • Reviewers. Chapter calls Claude "the best LLM for creative writing in November 2026" (Chapter); BenchLM calls it "a tie between Claude Opus 5.5 and Gemini 4 Argon" (BenchLM); Layer3 Labs and Ryan Doser both pick Opus 5.5 (Layer3 Labs; Ryan Doser). Five cost reviews agree that Opus 5.5 is the default Claude for writing and Fable the exception (Lindy; FullStack).
  • Usage. Through OpenRouter, the novel-writing tool novelcrafter sent the most tokens this month to Gemini 4 Argon (5.34B) and Claude Opus 5.5 (3.95B), and Opus 5.5 has the largest share of content-writing spend at 12.8% (novelcrafter app page; OpenRouter rankings). OpenRouter says its rankings "reflect adoption, not model quality" (OpenRouter roleplay collection).

The praise is qualified. Every found "the most readable prose we've seen from an Anthropic or OpenAI model" but said "It still buries the point" (Every). Arize measured em dashes falling from 12.9 to 0.05 per 1,000 words against Opus 5 while new habits appeared, and concluded "better, but not fixed" (Arize). EQ-Bench's short-fiction board puts Opus 5.5 only eighth, behind the older Opus 5 (EQ-Bench data).

A sizeable minority prefers the older Claude Opus 4.6 for voice. An Anthropic fine-tuning engineer said he has not been as happy with a model's writing since Opus 4.6 (The Decoder), and one nine-test comparison scored Opus 4.6 ahead of Opus 5.5 by 6 to 4 (Why Try AI). Opus 4.6 is still on OpenRouter at $5 / $25 and Anthropic will not retire it before 5 February 2027 (Opus 4.6 endpoints; Anthropic deprecations).

Gemini 4 Argon wins human votes and loses every slop measure

"Slop" here means the filler, stock phrasing and templated structure that make text read as machine-written.

Argon leads Arena's human vote and the UGI leaderboard's Writing metric (79.7) (Arena dataset; UGI leaderboard), and blind readers on Fiction Bench prefer it 59.4% of the time, second only to GPT-6.1 Terra (Fiction Bench data). Fiction users are direct about it: "I'm a big fan of Opus 5.5 but Argon just flat out writes better" (Hacker News). The most upvoted roleplay answer says the choice between Opus 5.5 and Argon "comes down to mostly taste" (r/SillyTavernAI).

Measures that look for AI-sounding prose put it at or near the bottom of the frontier group:

MeasureGemini 4 ArgonClaude Opus 5.5Source
EQ-Bench creative Elo and slop score (lower slop is better)1757.8, slop 22.702050.9, slop 10.43EQ-Bench data
Mazur story benchmark0.5513.555lechmazur/writing
ToneBench Writing Elo15642704ToneBench data
Caliper Bench creative-writing score and slop82.02, slop 32.285.96, slop 21.3Caliper Bench
NC Bench "AI-isms" (higher is better)86.48% (#90)92.05% (#33)NC Bench AI-isms
Stop Slop Studio blind fiction score out of 8037.6 (17th of 21)61.6 (4th)Stop Slop benchmark
Graphite "mannered prose" (human text 6.65)19.4810.57Graphite Argon update
Artificial Analysis slop percentile (lower is better)6820AA-PersonalityBench

Argon also embellishes. In a vendor test of cited research writing, 31% of its claims were fully supported by the sources against 75% for Opus 5.5 and 85% for GPT-6.1 Sol (Agent Bayes). In a small marketing-copy test it invented six product specifications in four briefs (Skryvo). The positive reports are about fiction and the negative ones about writing bound to a source or brief, so both can be true: inventive, and unfaithful to a brief (inference).

The position this supports: choose Argon for fiction when you like its voice and will edit, and Opus 5.5 for structure, long projects and anything that must stay faithful to source material. From 1 December the two cost the same.

Fable 5.2 has the best-judged prose, but it loses blind tests and costs double

Claude Fable 5.2 was released on 9 November, so only a few boards have it. Where it is tested by LLM judges it is first or tied first: Mazur 3.687 (lechmazur/writing), Caliper Bench 87.62 (Caliper Bench), and Fiction Bench's AI judges at 87.6, top in 19 of 20 genres (Fiction Bench data). On HumanBench its everyday writing passed an AI-text detector 23.1% of the time, about double any other model (HumanBench paper).

Preference tests go the other way. Fiction Bench readers chose it 45% of the time, on only 42 votes (Fiction Bench data). In a blind essay test judged by GPT-6.1 Sol it "wrote the cleanest prose and almost never won" (1 of 12 rounds) (My Life in the Stack), though Peter Yang, judging by hand, picked it over Opus 5.5 in four of five essays (write-up). Ethan Mollick found its drafts could be "accurate and joyless" (One Useful Thing). A working author's advice is "Use Fable like a specialist, not a typist": Opus 5.5 or Sonnet 5.5 for drafting and line edits, Fable for structure and diagnosis (Writing Secrets). Fable 5.2 is not yet on Arena, EQ-Bench, NC Bench or Hemingway-bench (Arena dataset).

GPT-6 models write the cleanest, plainest prose and are the least liked for fiction

  • LLM judges like GPT-6 Astra. It is first on EQ-Bench creative writing (2176.9) and second on Caliper Bench (87.42) (EQ-Bench data; Caliper Bench).
  • Human voters do not. Astra is 40th on Arena creative writing and GPT-6.1 Sol 43rd; without Arena's style control they fall to 70th and 72nd (Arena dataset). Fiction communities describe GPT prose as staccato and same-voiced (r/WritingWithAI).
  • Astra is not worth $10 / $50 for writing. GPT-6 Sol at $2 / $10 has the lowest slop on three boards and scores 82.5 on ToneBench at $0.056 per script against Opus 5.5's 85.8 at $1.00 (ToneBench data; AA-PersonalityBench). A vendor guide's answer on Astra for writers is "For most writers, no" (Inkfluence AI).
  • For clear business and technical prose GPT leads. In one blind test OpenAI models "consistently produced writing that I found clearer and easier to read" (How I AI). On a German book-writing benchmark GPT-6.1 Sol rated 1382 on literary prose against Opus 5.5's 1325, with overlapping intervals and LLM judges (hermes3000 report).
  • GPT-6.1 Terra ($1 / $5) is the open question. It is first on Fiction Bench with the best blind-reader rating (63.5% win rate), and OpenAI describes it as built for "clear, natural writing" (Fiction Bench data; OpenAI model page). But it is 23rd of 87 models on ToneBench (ToneBench data), Every says it "still needs a lot of human steering" (Every), and it is not on Arena. Its Fiction Bench lead overlaps about 30 other models' intervals (arithmetic).

What holds up among the cheaper models

ModelOpenRouter idPrice in / outEvidence forEvidence against
Claude Sonnet 5.5anthropic/claude-sonnet-5.5$2 / $10Fiction Bench #4; ToneBench 84.6 at max effort; second by spend for content writing on OpenRouter (Fiction Bench; ToneBench; rankings)Arena #29 (Arena dataset)
Kimi K3.1 Promoonshotai/kimi-k3.1-pro$2 / $10NC Bench creative #1 (92.62%), EQ-Bench #2, Caliper #4 (NC Bench; EQ-Bench)Users call it "robotic" and censored, and say the older Kimi K3 wrote better (r/SillyTavernAI); Arena #36 on 869 votes
GLM-5.3z-ai/glm-5.3$1.40 / $4.40Mazur #7, EQ-Bench #7, best open-weight on ToneBench (lechmazur/writing; Bouchard)Fiction Bench readers prefer it only 39% of the time; about double the literal-error rate of Opus 5.5 (Fiction Bench; Caliper Bench)
GLM-5.3 Flashz-ai/glm-5.3-flash$0.15 / $0.50ToneBench 81.8 at $0.022 per script; proofreading 90.1% (ToneBench; ErrataBench results)Arena #67; users report rising "slopism" (megathread)
GPT-6 Lunaopenai/gpt-6-luna$0.10 / $0.50Fiction Bench reader rating 5th; NC Bench creative 90.86% (Fiction Bench; NC Bench models)Arena #98; ToneBench 78.2
DeepSeek V4.1 Flashdeepseek/deepseek-v4.1-flash-1017$0.15 / $0.60 off-peak, $0.30 / $1.20 peakToneBench 81.6 at $0.014 per script; the most-used model for roleplay by tokens (ToneBench; rankings)Mazur -0.697; OpenRouter itself reports "lower satisfaction on writing and tone" for DeepSeek V4 Flash (OpenRouter blog)
MiMo-V2.6-Proxiaomi/mimo-v2.6-pro$0.435 / $0.87The roleplay community's cheap favourite: "still writes great prose and solid character dialogue" (Sukino's Findings)Others call the prose "mid"; quality varies by host (r/SillyTavernAI)
Gemini 3.8 Flashgoogle/gemini-3.8-flash$0.75 / $3.75, then $1.50 / $7.50 from 1 Jan 2027Arena #10; fourth with expert writers on Hemingway-bench (Arena dataset; Hemingway-bench)ToneBench 70.2; among the highest slop scores everywhere
Claude Haiku 5.5anthropic/claude-haiku-5.5$0.10 / $0.50 (prompts up to 100K tokens)Caliper 82.49Arena #170; last on literary prose and copy-editing in hermes3000, where GPT-6 Luna beat it at the same price class (hermes3000 report)

Two points follow. Benchmark-only cases (Kimi K3.1 Pro, GLM-5.3) are weaker than they look, because users and blind readers do not confirm them. And the cheap tier is good enough for drafts a person will edit: on ToneBench "the last five points cost about 175× more" (Bouchard). Open-weight vendors concede that "Open weights lose at the top of the range" (Featherless).

For editing and proofreading, cheap models are close to the flagships

ErrataBench runs every model through OpenRouter on documents seeded with errors. Fix rate and the cost of the model per document, from the raw results file (ErrataBench results):

Model (reasoning effort)Fix rateCost per document
GPT-6 Sol (none)95.4%$0.31
Claude Fable 5.2 (high)94.9%$0.88
Claude Opus 5.5 (high)94.7%$0.42
Gemini 4 Argon (low)93.2%$0.066
GPT-6 Luna (high)90.9%$0.028
Claude Sonnet 5.5 (high)90.8%$0.27
GLM-5.3 Flash (high)90.1%$0.008

Argon at low effort is the cheapest route above 93%, and stays so after its price doubles (arithmetic). Revise, which runs the benchmark and sells a proofreading product, names GPT-6 Sol without reasoning as the best value (Revise). A Reddit user's test with 90 planted errors agrees on the order: Opus 5.5 98%, GPT-6.1 Sol 97% and "up to 4x cheaper", Argon 93% (r/WritingWithAI). These tests measure error-catching. For developmental and line editing there is no benchmark on current models, and reviewers split between Fable, Opus 5.5 and the GPT models (Zvi Mowshowitz; Every).

Availability and verified prices on OpenRouter

All 134 current model ids that the research checked are live; the only strong writers missing are the Hemmingway-1 / 1.5 fine-tune and a demo-only model (OpenRouter models API; Hemmingway model card). No leading writer has a free variant. Prices below are the lab's own endpoint on OpenRouter, from the endpoints API (https://openrouter.ai/api/v1/models/<id>/endpoints), which matches each lab's pricing page (Anthropic pricing; OpenAI pricing; Gemini pricing). "Draft" is output price times 135,000 tokens, the output of one 100,000-word draft before input and reasoning tokens (arithmetic).

ModelOpenRouter idIn / outDraftSurcharges and scheduled changes
Claude Fable 5.2anthropic/claude-fable-5.2$8 / $40$5.40None
Claude Fable 5.1anthropic/claude-fable-5.1$10 / $50$6.75Dearer than 5.2
Claude Opus 5.5anthropic/claude-opus-5.5$4 / $20$2.70None; flat across the 1M window
Claude Opus 4.6anthropic/claude-opus-4.6$5 / $25$3.38Not retired before 5 Feb 2027
Claude Sonnet 5.5anthropic/claude-sonnet-5.5$2 / $10$1.35None
Claude Sonnet 4.5anthropic/claude-sonnet-4.5$3 / $15$2.03Retires at Anthropic 30 Nov 2026; $6 / $22.50 above 200K prompt tokens
Claude Haiku 5.5anthropic/claude-haiku-5.5$0.10 / $0.50$0.07$0.50 / $2.50 above 100K prompt tokens
GPT-6 Astraopenai/gpt-6-astra$10 / $50$6.75$20 / $75 above 272K prompt tokens
GPT-6.1 Sol, GPT-6 Solopenai/gpt-6.1-sol, openai/gpt-6-sol$2 / $10$1.35$4 / $15 above 272K
GPT-6.1 Terraopenai/gpt-6.1-terra$1 / $5$0.68$2 / $7.50 above 272K
GPT-6 Lunaopenai/gpt-6-luna$0.10 / $0.50$0.07$0.20 / $0.75 above 272K
Gemini 4 Argon, Gemini 4 Carbongoogle/gemini-4-argon, google/gemini-4-carbon$2 / $10$1.35$4 / $20 from 1 Dec 2026 (draft $2.70)
Gemini 4 Hydrogengoogle/gemini-4-hydrogen$1.50 / $7.50$1.01None
Gemini 3.8 Flashgoogle/gemini-3.8-flash$0.75 / $3.75$0.51$1.50 / $7.50 from 1 Jan 2027; catalogue shows the US price $0.825 / $4.125
Muse Wondermeta/muse-wonder$4 / $20$2.70None
Grok 4.7x-ai/grok-4.7$2 / $6$0.81$4 / $12 above 200K
Kimi K3.1 Promoonshotai/kimi-k3.1-pro$2 / $10$1.35Other hosts $1.22 / $6.10 to $2.70 / $13.50
GLM-5.3z-ai/glm-5.3$1.40 / $4.40$0.59Other hosts $0.07 / $1.40 to $1.68 / $5.28
GLM-5.3 Flashz-ai/glm-5.3-flash$0.15 / $0.50$0.07Other hosts $0.04 / $0.078 to $0.225 / $0.75
DeepSeek V4.1 Flashdeepseek/deepseek-v4.1-flash-1017$0.15 / $0.60$0.08Doubles to $0.30 / $1.20 on weekdays 01:00-04:00 and 06:00-10:00 UTC
MiMo-V2.6-Proxiaomi/mimo-v2.6-pro$0.435 / $0.87$0.12One host charges $4 / $8
Tencent Hy4tencent/hy4$0.417 / $1.25$0.17$0.834 / $2.50 from 1 Jan 2027

Scheduled changes, in date order:

DateModelChangeSource
30 Nov 2026Claude Sonnet 4.5Retired by Anthropic; OpenRouter shows no expiryAnthropic deprecations
30 Nov 2026GPT-5.6 SolPromotional $4 / $20 ends; new price not statedOpenAI pricing
1 Dec 2026Gemini 4 Argon and Carbon$2 / $10 becomes $4 / $20Gemini pricing
End Dec 2026Kimi K2 seriesRetired by MoonshotKimi pricing
1 Jan 2027Tencent Hy450% discount ends: $0.417 / $1.25 becomes $0.834 / $2.50Tencent TokenHub pricing
1 Jan 2027Gemini 3.8 Flash$0.75 / $3.75 becomes $1.50 / $7.50Gemini pricing

OpenRouter's pages show a 50% discount flag on these Gemini and Hy4 endpoints but no end date (Gemini 4 Argon endpoints). Claude Sonnet 4.5 matters because it still has the largest share of roleplay and fiction spend on OpenRouter (10.1%) (OpenRouter rankings). After 30 November it may stay callable through Bedrock or Vertex for a while, as Opus 4.1 has, and then disappear (inference from two earlier retirements) (Opus 4.1 endpoints).

What you pay per word differs from the list price

Hidden reasoning bills as output. At maximum effort, 70% to 86% of the output tokens of every model measured on Artificial Analysis's general test suite are reasoning that the writer never sees. For Opus 5.5 the share falls from 79% at maximum effort to 31% at low (Artificial Analysis: Opus 5.5). That is a general suite, not a writing test. On real short writing tasks run through OpenRouter at default settings, billed output tokens per visible word and the resulting output cost per 1,000 visible words were (researcher's arithmetic on the Slop Index output data) (Slop Index dataset):

ModelBilled tokens per visible wordOutput cost per 1,000 visible words
GPT-6 Luna2.07$0.0010
Claude Haiku 5.52.70$0.0013
Gemini 4 Argon1.32$0.013 (about $0.026 from 1 Dec)
GPT-6.1 Sol1.47$0.015
Gemini 3.8 Flash4.65$0.017
Claude Sonnet 5.52.49$0.025
Claude Opus 5.52.50$0.050
GLM-5.311.54$0.051
GPT-6 Astra1.44$0.072
Kimi K37.38$0.111

So GLM-5.3, at under a quarter of Opus 5.5's list output price, cost the same per visible word in that data, and Kimi K3 cost more than GPT-6 Astra. Lowering reasoning effort would cut the GLM and Kimi figures. On these numbers a 100,000-word draft on Opus 5.5 costs about $5 in output, not $2.70 (arithmetic). Higher effort does buy some quality on ToneBench (median +231 Elo for 4.6 times the cost), but Opus 5.5 scores the same at "xhigh" for $1.00 a script as at maximum for $2.58 (ToneBench thinking page; ToneBench data).

Newer Claude models count more tokens. Anthropic says Claude 4.7 and later use a tokenizer that "produces approximately 30% more tokens for the same text" (Anthropic pricing). So moving from Opus 4.6 ($5 / $25) to Opus 5.5 ($4 / $20) is roughly cost-neutral per word, and moving from Sonnet 4.x ($3 / $15) to Sonnet 5.5 ($2 / $10) saves about 13%, not 33% (arithmetic). Token counts are not comparable across labs either (OpenRouter datasets doc).

The catalogue price of an open-weight model is not the price to budget. OpenRouter's headline figure is one cheap host: Kimi K3 shows $0.192 / $16 while Moonshot's own endpoint is $3 / $15 (Kimi K3 endpoints). The cheapest hosts are often compressed versions of the model, and on one model the same weights scored 90% at the lab's host and 75% at another (So you want to use OpenRouter?). Users advise pinning the lab's own host for open-weight models.

Other costs. OpenRouter says it adds no markup to provider prices (OpenRouter SillyTavern guide); a user guide reports a 5.5% fee on credit purchases (RoboRhythms). Prompt caching cuts the cost of resending a manuscript: 50 replies at a 32K prompt cost $8.84 on Opus 5.5 uncached and $1.32 cached in that guide. Writers on Google's forum report that responses blocked by Gemini's safety filter are still billed, including through OpenRouter (Google AI Developers Forum).

No model sounds human by default

  • Every model that the Slop Index ran through the Pangram detector scored 100% AI (Slop Index). On HumanBench no output beat its human reference (HumanBench paper).
  • Graphite finds that Opus 5.5 has the word distribution closest to human text (divergence 0.052 against 0.109 for GPT-6 Astra) and still has 2,548 measurable tells: "AI tells change between models and versions, but do not go away" (Graphite Opus 5.5 update).
  • A study of nine frontier models found that all use more hard-to-process constructions than human writers, and that Opus 5.5 improved on Opus 5 on 19 of 21 measures (arXiv 2610.29162).
  • Prompting moves the result more than the model choice within a tier. One page of style rules made all 21 models in one blind test sound more human, with Argon gaining most (Stop Slop benchmark).
  • Claude output carries a statistical text watermark on every platform, which customers cannot turn off on current models (Anthropic watermark docs). OpenAI's watermark is opt-in for API users (The Decoder). Whether Gemini API text is watermarked was not checked.

Where sources disagree

The four kinds of evidence rank the same models in different orders.

EvidenceWhat it favoursExample
Human crowd votes (Arena)Gemini 4 and Claude Opus/Fable; penalises GPT-6Argon #1, Opus 5.5 #2, Astra #40 (Arena dataset)
Blind fiction readers (Fiction Bench)Cheap, plain or vivid modelsGPT-6.1 Terra, Argon, Gemini 3.7 Flash and GPT-6 Luna in the top five; Fable 5.2 32nd on 42 votes (Fiction Bench data)
LLM judges (Mazur, EQ-Bench, ToneBench, Caliper, Fiction Bench judges)Claude Fable and Opus, GPT-6 Astra, Kimi, GLM; penalise GeminiFable 5.2 first on Mazur and Caliper; Argon 25th on Mazur (lechmazur/writing)
Mechanical slop measuresGPT-6 Sol and cheap open models; penalise Gemini, and on workplace writing also ClaudeOpus 5.5 and Sonnet 5.5 among the four sloppiest of 58 on the Slop Index's mechanical score (Slop Index)

None of the four is a clean measure:

  • LLM judges changed their verdict in 43% of story pairs when the order was swapped (lechmazur/position_bias), and favoured their own lab's models by up to 7.5 points on ToneBench (ToneBench judges page).
  • EQ-Bench is judged by a Claude model and, according to Surge, agreed with expert writers as little as 43% of the time (Surge).
  • Arena voters reward length and formatting (Surge on LMArena), and new models' scores fall as votes arrive: GPT-6 Astra went from 22nd to 40th in two months (Arena dataset). Carbon, on about 1,000 votes, may also settle lower (inference).
  • Academic work finds lay readers prefer AI prose while trained writers prefer human prose, which places crowd and LLM-judged boards closer to lay taste (arXiv 2510.13939).
  • The one expert-writer board, Hemingway-bench, has no GPT-6, Opus 5.5, Fable 5.2 or Gemini 4 rows (Hemingway-bench).

Other open disagreements.

  • Whether Claude 5.x writes better or worse than Claude 4.6: writers who want structure and obedience praise 5.5, and those who care about voice call 5.x "hollow" (r/SillyTavernAI).
  • Whether Claude sounds human: Graphite says Opus 5.5 is closest to human word use, the Slop Index says it is among the most templated. They measure different things on different kinds of text.
  • A widely repeated line that Every's Dan Shipper called Argon "by far better" at writing appears only in a second-hand report and could not be confirmed at source (BigGo). Every's own free text says Argon should be used as an editor, not a ghostwriter (Every).
  • Fiction Bench's price column shows cheapest-host prices for Kimi K3.1 Pro, GLM-5.3 and DeepSeek V4.1 Flash, not the lab prices given above (Kimi K3.1 Pro endpoints).

Single-origin and unverified. Fable 5.2's standing rests on six days of data. GPT-6.1 Terra's first place rests on one board with about 120 votes per model. Stop Slop Studio does not say whether its "anonymous" judges are people or models (Stop Slop benchmark). Most "best AI for writing" articles are vendor or affiliate content, and one states that it ran no prose tests (Inkfluence AI).

Unknown. No study has expert human judges ranking the current models against each other on fiction. No benchmark covers developmental or line editing. No independent hands-on prose review of GLM-5.3 or Gemini 4 Carbon was found.

How the search was done

Scale. 15 researchers ran 710 probes and recorded 1,123 sources, of which 784 were opened and read and 339 were seen only in a listing. The run was one leg and stopped at its cap of 15 researchers.

Surfaces and moves. General web search (170 probes); OpenRouter's catalogue, endpoints API, rankings and blog (54); arXiv, Semantic Scholar and OpenReview (51 search probes and 16 citation walks); Reddit through an archive API and Hacker News (48); GitHub (34); Hugging Face datasets (21); YouTube and podcast listings (21); Chinese-language pages (14); and direct walks of benchmark sites. Later researchers switched from searching to opposition search, time slicing to October and November, raw dataset parsing, author pivots, and direct price verification against 148 OpenRouter ids and the labs' pricing pages.

What was not covered.

  • The shared web-search budget ran out partway through. Researchers 10 and 12 to 15 worked almost entirely by direct fetch, so angles that depend on search are under-covered.
  • Chinese-language sources: price pages and news were read, but no Chinese test of prose quality was found, and Zhihu, Bilibili, 少数派 and most mainland sites refused connections. The case for Kimi, GLM, DeepSeek and Qwen as writers rests on English-language benchmarks.
  • Video transcripts: YouTube refused unauthenticated access, so every video (including the Nerdy Novelist's model reviews) was read by title, description and chapter list only.
  • X posts were not fetchable and are known only through summaries.
  • Also not reached: Every's paywalled reviews, novelist Discords, fan-fiction forums, and arena.ai's live pages (its official dataset was read instead).

Searched and found empty. An OpenRouter guide or category for writing quality; cost columns on Mazur, EQ-Bench, Hemingway-bench, Vulsar and Caliper; a post-launch critique of Argon's prose in the press; major general-press comparisons of current models for writing; current-model benchmarks for poetry, screenwriting or translation.

Saturation. The search is not saturated. The last five researchers still found 49% to 86% new sources among their results, and 224 recorded leads remain open. The most useful next steps are transcripts of the novelist videos, Chinese-language prose tests, a re-read of Arena and Fiction Bench once Fable 5.2, Carbon and Terra have more votes, and a price re-check after 1 December.

Full source catalogue: sources.md in this folder.