025What does Fable 5.2 do to the price of the frontier?

One full day in

Fable 5.2’s first full day on OpenRouter was the biggest of any launch we track in dollars, and ordinary as a share of Anthropic. It was listed on November 9 at about 19:00 UTC. On November 10, its first full day, it processed 179 billion tokens, which at list price is an estimated $1.37M: 9.1% of everything spent on OpenRouter that day, from 0.6% of the tokens. Only Opus 5.5 took more.

That is 2.1 times Fable 5.1’s first day in dollars and 2.6 times in tokens. But OpenRouter is 1.6 times the size it was at the start of September, and Fable 5.2 took 20.6% of Anthropic’s own spend there, a little less than Fable 5 (23.6%) and Fable 5.1 (22.4%) did. The launch is bigger because the market is, not because Fable took more of Anthropic.

Nothing was taken from Opus 5.5 on day one: it processed 1,113 billion tokens, against 1,098 billion the Tuesday before. Fable 5.1 had already faded. Its last day in OpenRouter’s daily top 50 was October 28; the cut-off for that list has been 45 to 63 billion tokens a day since. And the traffic is mostly one product: OpenRouter’s page for the model attributes 111 billion tokens to Claude Code, 83% of what it lists by app (it gives no time window).

OpenRouter is a small window on Anthropic. Its spend there annualizes to about $2.4B, 3% of the roughly $81B run-rate in its IPO filing. What the window shows clearly is the split between tokens and dollars.

One day settles nothing. Every premium launch on the tracker has run the same course: a few weeks as the most capable model on sale, then a cheaper model that is nearly as good, usually from the same lab, takes the volume. Fable 5’s best week was 8.0% of OpenRouter spend and Fable 5.1’s 8.9%; Opus 5.5, at 40% of the price, reached 33.4%. The tracker’s bar for a game-changer is 15% in the best of the first four weeks with 60% of that kept in week six, and its verdict comes in December.

What is different this time is the distance to the tier below. Fable 5 launched 4.3 points ahead of the best Opus on Epoch’s index and Fable 5.1 2.6 ahead; Opus 5.5 passed it three weeks later. Fable 5.2 is 5.6 points ahead of Opus 5.5, more than any single Opus update has added (the most is 4.6).

A cut at the top of the list

Fable 5.2 is the first cut to a Fable list price, and it completes a repricing of every Claude tier in under five months. Haiku fell 90%, Sonnet 33%, Opus 20% and now Fable 20%. The cuts are deepest at the bottom, where open-weight models compete, and shallowest at the top, where nothing does.

The list is now a ladder that doubles at each rung: $2 / $10 for Sonnet, $4 / $20 for Opus, $8 / $40 for Fable, and fast mode doubles Fable again to $16 / $80. Cached input is the exception, at $0.20 per million tokens on both Opus 5.5 and Fable 5.2.

The top rung is not getting cheaper year on year. Anthropic’s most expensive model cost $75 per million output tokens in May 2025, $25 after Opus 4.5 that November, $50 when Fable 5 added a tier above Opus in June, and $40 now: 60% more than a year ago. The sticker at the frontier fell with a price cut and rose with a new tier, and the new tier was the bigger move.

Against rivals, $8 / $40 sits 20% under GPT-6 Astra’s $10 / $50. Google answered within a day: Gemini 4 Carbon became generally available on November 10 at $2 / $10 until November 30 and $4 / $20 after, which is Opus 5.5’s price.

Five strengths at one price

The token price is no longer the price. Fable 5.2 is sold at five effort levels, and what a task costs depends more on the level than on the list. On Artificial Analysis’s index the same model costs $3.10 a task at low effort and $26.54 at max, 8.6 times as much, for 54 points and 65. On Cognition’s FrontierCode 2.0, as published in Anthropic’s system card, the range is $2.10 to $44.70: 21 times.

Above about $3 a task, Fable 5.2 is nearly always the better buy than Opus 5.5 on that index, at twice the price per token. Fable at low effort scores 54 for $3.10; Opus at high scores 52 for $3.46. Fable at high scores 62 for $9.08; Opus at max scores 59 for $10.04. Only Opus at xhigh (57 for $6.05) keeps a place, between Fable’s medium (56 for $3.80) and its high.

Two other measures agree. On FrontierCode, Fable at high matches Opus at max (45.3% against 45.5%) for 48% less a task. On Vals AI’s index, which runs every model through one harness, Fable 5.2 scores higher than Opus 5.5 (71.3% against 70.1%) and costs 28% less a test ($17.94 against $24.77).

The top of the ladder is poor value. From high to max, Fable gains 3 index points for 2.9 times the money. Xhigh adds nothing over high on Artificial Analysis’s index, and on FrontierCode max scores below xhigh (45.7% against 49.1%) at 3.2 times the cost. Anthropic’s documentation says as much: start at high, move to xhigh only where a gain has been measured, and keep max for finding the model’s ceiling.

Anthropic’s advice is still to start most work on Opus 5.5 and move up to Fable for harder jobs. Below about $3 a task the numbers agree: Opus at medium, its default, scores 48 for $2.45 in about 7 minutes, and nothing Fable offers is that cheap. Above $3 the advice costs money. Fable is also rationed. On Pro and standard Team plans it is included for launch week only, for up to half of weekly limits. Our reading, which Anthropic hasn’t stated, is that capacity is part of why it steers volume to Opus; pack 017 asks whether its compute can keep up with its demand.

Across labs the same thing holds: token prices rank models badly. GPT-6.1 Sol at max scores 55 for $1.27 a task, a point under Fable at medium for a third of the cost. Gemini 4 Carbon at high scores 60 for $7.76 at its standard price, half Fable’s per token: 85% of what Fable at high costs a task, for two points less. And the cheapest tokens are not the cheapest tasks. DeepSeek’s V4.1 Flash 1017 at max scores 33 for $0.60 a task; GPT-6.1 Terra at medium scores 38 for $0.17.

What deflates and what doesn’t

Frontier cost deflation is three different prices, and they are moving in different directions.

• The sticker at the top moves in steps and is up on the year: $25 per million output tokens then, $40 now. Within a tier it has been falling 20% every five to ten months.
• A fixed result gets cheaper fast. A FrontierCode score of 45% cost $12.82 a task on September 22 (Opus 5.5 at max) and $6.72 on November 9 (Fable 5.2 at high): 48% less in 48 days. Fable 5.1’s best run, 32.4% for $8.68, is beaten by Fable 5.2 at low for $2.10: 76% less in 69 days. On Artificial Analysis’s index, the 50 points that cost $10.85 a task with Fable 5.1 at xhigh, its best setting, cost $0.59 with GPT-6.1 Sol at high: an 18th of the cost, from a model that arrived 28 days after Fable 5.1.
• The best available result has just got much dearer. The top score on the index cost $10.04 a task when Opus 5.5 took it in September and $7.76 when Gemini 4 Carbon took it in October. With Fable 5.2 at max it costs $26.54, 2.6 times what Opus 5.5’s cost, and the last 3 points account for $17.46 of it.

Put together, a lab keeps its revenue per task at the frontier by selling more tokens per task at a slowly falling price, while everything behind the frontier falls toward what it costs to serve. OpenRouter’s own figures show the second half: the blended price paid per million tokens for closed models fell from $1.21 in January to $0.52 in October, and for open-weight ones from $0.28 to $0.084. Anthropic describes its own pricing in cost per task: its S-1 says Opus 5.5 cut customers’ cost per task by about 40% against Opus 5. The list price fell 20%.

For deflation from here, that means three things. The top list price keeps falling in small steps. New rungs keep appearing above it; fast mode already doubles it. And most of the fall in the cost of a given result comes from the tier below catching up, not from the price list.

From frontier to affordable

Each of Anthropic’s last three flagships was matched at half its price within seven weeks, and at a tenth within five months. We take each model that launched at the top of Anthropic’s price list, the Opus models up to 4.8 and then the Fables, and find the first later model, from any lab, to match it on Epoch’s index at a fraction of its list price.

Half price has taken 21 to 145 days; for the last three, 42, 45 and 21. A tenth has taken 55 to 289 days, and less with almost every generation: 289 days for Opus 4.5, 216 for Opus 4.6, 174 for Opus 4.7, 132 for Opus 4.8, 139 for Fable 5 and 55 for Fable 5.1.

Opus 4.8 cost $5 / $25 on May 28. On October 7, 132 days later, Haiku 5.5 matched it on the index at $0.10 / $0.50, a fiftieth of the price. Fable 5.1 cost $10 / $50 on September 1; Opus 5.5 passed it at $4 / $20 three weeks later, GPT-6.1 Sol at $2 / $10 a week after that, and GPT-6.1 Terra at $1 / $5 on October 26.

The higher the sticker, the faster this goes: a tenth of Fable’s $50 is the price of a mid-tier model, and a tenth of Opus’s $25 was not. A match on the index is also not a match on everything, which the last sections come back to.

For Fable 5.2 the clock started on November 9. If it runs like the last three, a model at $4 / $20 or less matches it between the end of November and Christmas, and one at $0.80 / $4 by April. We’d bet on slower. Fable 5.2 opened 5.1 points clear of the next model on the index, the widest lead a new frontier model has had since o1 in December 2024.

A new best model every six or seven weeks

Anthropic released nine models that set a new high for it on Epoch’s index in the twelve months to November 9, against four in the twelve months before. The median gap between them fell from 81 days to 45. One of the nine, Opus 5, set its high by 0.2 of a point, which is inside the index’s noise. Counting every tier, Anthropic launched 13 models against 6.

The Fable line has moved twice, after 84 and 69 days; the Opus line moves every 42 to 73. Carried forward, that gives the table below: nine to twelve new best models in the next twelve months if the pace of the past year or half-year holds, four or five of them Fables, and about twice that in two years. These are extrapolations, not forecasts.

Is it accelerating? On the evidence so far, yes.

• The frontier gained 23.1 points on Epoch’s index in the twelve months to Fable 5.2, against 15.8 in the twelve months before and a trend of 16.6 since reasoning models arrived. Most of the difference is Fable 5.2 itself: the day before it shipped, the twelve-month gain was 18.0. Epoch says the model sits above the trend that earlier reasoning models followed. Its score is two days old, with an interval of 170 to 179.
• METR, after an eleven-week assessment, estimates Anthropic is improving capabilities on well-specified tasks at about twice its rate of March 2024 to October 2025 (1.9 times on the benchmark trend, 95% interval 1.5–2.8). Its rough guess is that about 80% of that is due to AI, and it found no convincing bottleneck for the next twelve months. Anthropic redacted the evidence METR found most informative, and METR says it would not be surprised by 1.3 times or 3.
• Anthropic’s amended S-1 says its internal estimates indicate it “may imminently meet” its own threshold for dramatically accelerated progress: roughly a doubling of the pace, driven by AI automating research. It also says no current model has crossed it. More than 90% of the changes merged into its core codebase are now written by Claude.

Three things pull the other way. Dario Amodei’s September essay called for the industry to slow the pace at which it improves models; “We called for pacing, not pausing,” Dianne Penn, Anthropic’s head of product management for research, told CNBC about this launch. Fable 5.2 was held in training to about Opus 5.5’s level on two skills that most directly speed up AI development, accelerator kernel optimization and LLM architecture improvement. And the S-1 discloses that Anthropic delayed pre-training a new frontier base model by more than a month to harden security. Point releases will keep coming; the next generation is later than it would have been.

What a year bought

Fable 5.2 scores 174.2 on Epoch’s index, 22.4 points above Opus 4.5, the best Anthropic model of a year ago. The 22 points before that took 17 months. Opus 4.5 arrived on November 24, 2025; on the exact anniversary Anthropic’s best was Sonnet 4.5, 26.6 points back.

The index is abstract, but Epoch’s model turns it into scores. On a benchmark where Opus 4.5 scored 20%, a model 22 points higher is expected to score between 60% and 97%, depending on how sharply that benchmark separates models. In odds that is 6 to 110 times.

On Epoch’s own tests the change is plainer. Research-level maths (FrontierMath, tiers 1 to 3) went from 34% to 95%. Its hardest tier went from 5% to 100%. Facts recalled without a search (SimpleQA Verified) went from 46% to 94%. The older, easier tests barely register it: GPQA Diamond went from 86% to 94%.

The measure closest to work is the Remote Labor Index: 240 real freelance projects worth $143,991, averaging 29 hours of human time, each scored on whether a reasonable client would accept the result. Opus 4.5 delivered 3.75% of the 230 that are scored. Fable 5.2 delivers 41.3%, 11 times as many, and nearly twice the next model, Opus 5.5 at 21.25%.

The best-known yardstick can no longer be read. METR put Opus 4.5’s time horizon, the length of task it completes half the time, at 4 hours 49 minutes. In May it put an early Claude Mythos Preview at 16 hours or more, with a warning that anything above 16 hours is unreliable on its task suite. It stopped updating the page in September.

Last year’s frontier against DeepSeek’s latest

DeepSeek’s latest model is clearly better than Anthropic’s best of a year ago, and about level with its best of last May. V4.1 Flash 1017, released on October 17 with open weights, scores 159.3 on Epoch’s index. That is 7.5 points above Opus 4.5, with intervals that don’t overlap, and within a point of Opus 4.8 (159.9) and Haiku 5.5 (160.3).

It costs $0.30 / $1.20 per million tokens at DeepSeek’s peak rate and half that off-peak, against the $5 / $25 Opus 4.5 launched at: about a twentieth of the price on output at peak and a fortieth off-peak, eleven months later. On Epoch’s own tests the September version already beat Opus 4.5 on research maths (67% against 34% on FrontierMath tiers 1 to 3), chess puzzles and mystery games, and roughly matched it on recall.

Against today’s frontier it has lost ground. A year ago DeepSeek’s best model trailed Anthropic’s best by 3.2 points on the index; today it trails by 14.9. DeepSeek gained 14.9 points in the year, a little under the frontier’s long-run pace. Anthropic gained 26.6.

The best open-weight model, Moonshot’s Kimi K3.1 Pro at 162.0, stands where the closed frontier stood on April 23, six months earlier, and where Anthropic stood in June. Epoch’s own published figure is shorter: four months on average since January. In points the gap was 7.1 the day before Fable 5.2 and is 12.2 now. Epoch counts Kimi K3.1 Pro as open-weight; when Artificial Analysis tested it in late October its weights were not yet out.

Where benchmark parity ends

Open-weight models match the frontier on tests that are public, short or saturated, and fall far behind on ones that are new, private or long.

Vals AI runs every model through the same harness. On its legal index DeepSeek’s V4.1 Flash 1017 scores 71.9% and Fable 5.2 69.2%, at $0.59 a test against $8.88. On legal research and finance the two are within three points, and on tax DeepSeek leads by twelve. On Terminal-Bench 4.0, hard multi-step work in a terminal, DeepSeek scores 31.8% and Fable 65.2%.

Epoch’s tests show the same split. On GPQA Diamond, DeepSeek’s September V4.1 Flash is four points behind Fable 5.2 (90% against 94%). On FrontierMath’s hardest tier it scores 27% against 100%; on spotting assembly mistakes in photographs, 34% against 90%; on recalling facts, 43% against 94%.

Artificial Analysis ran the experiment in October. When it rebuilt its index so that about 60% rests on private or held-out tests, the best open-weight model’s gap to the leader widened from 3 points to 12, and to 26 for the best model whose weights could be downloaded. Today DeepSeek’s latest scores 33 on it, about half of Fable 5.2’s 65.

Even a matched score can be local. Kimi K3.1 Pro is level with the frontier on Terminal-Bench 4.0: 63.6% against 65.2% for Fable 5.2 on Vals AI’s runs. On Terminal-Bench-Science, a newer set of 70 research tasks, Artificial Analysis has it at 34% against 59% for Opus 5.5 and 63% for GPT-6 Astra. Epoch finds the same by domain: four months behind in general, six to seven on cyber, and about seven on a visual task in September, when most Chinese open-weight models still took no images (DeepSeek’s V4.1 Flash does).

Length is where small gaps become large ones. A job of a thousand steps finishes only if every step does: at 99.9% reliability a step it finishes 37% of the time, and at 99.99%, 90%. That is how a model can look level on short tests and be unusable on long ones. Anthropic’s example at launch: a thousand Fable 5.2 agents formalized Fermat’s Last Theorem in 30 hours, while Opus 5.5 in the same set-up had done 26% after 18 hours and barely moved after 30. Opus 5.5 is six points behind Fable 5.2 on Artificial Analysis’s index, and ahead of it on Vals AI’s legal index (72.4% against 69.2%).

Buyers already price this in. Open-weight models carry most of OpenRouter’s paid tokens and, by OpenRouter’s count, about a quarter of its paid spend, and the price gap between closed and open-weight tokens widened from 4.3 times to 6.2 between January and October.

One thing may lengthen the lag. Anthropic says the defences it added this autumn cut the reasoning data that distillers harvest from Claude by 90% to 99%, named Zhipu and Moonshot among those doing it, and says Fable 5.2 has its strongest protections yet. If copying is part of how open-weight models stay four to six months behind, the next few months will show it.

What else is in this launch

• Google answered in a day. At its standard price Gemini 4 Carbon costs $7.76 a task for 60 points on Artificial Analysis’s index; Fable at high costs $9.08 for 62. Until November 30 Carbon’s tokens are half price.
• The unrestricted version is not on general sale. Mythos 5.2 is the same model without Fable’s cybersecurity and biology safeguards, open to vetted organizations and, through Claude Security, to enterprise customers. On Fable those safeguards block about 55% less than Fable 5.1’s did.
• A drag on business use is being removed. Fable comes with 30 days of data retention for safety monitoring. Enterprise Frontier Safeguards, in private beta with Bridgewater, Salesforce and Stripe, runs the monitoring on data kept in the customer’s own infrastructure, which makes zero retention possible.
• It shipped below its own ceiling. Anthropic says it held two AI-research skills at about Opus 5.5’s level during training, so on those its best model is deliberately no better than the tier below. Agentic coding and general machine-learning research were not limited.
• It strays less. In Anthropic’s sandbox tests, Mythos 5.2 used credentials or files from outside its task in 3.1% of more than 1,800 scenarios, against 21% for Mythos 5.1 and 39% for Mythos 5. That matters for anyone leaving an agent to run for hours. The figures are Anthropic’s and haven’t been checked by anyone else.
• Fable as an advisor. Haiku, Sonnet or Opus can consult Fable on the hard steps of a task, which buys Fable’s tokens only where they matter. It is the price ladder used inside one job.
• The IPO. Anthropic set a range of $70–78 a share the day after this launch, which values it at up to $1.4T, with run-rate revenue of about $81B at the end of October, up from about $71B a month earlier.

What to watch

Weeks four and six on the tracker. 15% of OpenRouter spend by December 7, then 60% of that kept by December 21. The numbers update twice a day on the frontier launch tracker.

Opus 5.5’s share. If Fable’s middle settings are the better buy, some Opus spend should move up. On day one none did.

The first cheaper match. History says a model at half Fable 5.2’s price matches it by Christmas. A 5-point lead says later.

December 1, when Gemini 4 Carbon doubles to $4 / $20.

The next open-weight release, the first trained since Anthropic’s distillation defences took hold.

Epoch’s and METR’s next reports on acceleration, and the changes Anthropic is said to be considering to its Responsible Scaling Policy.