Claude Opus 5.5 vs. Fable 5.2: Differences and How to Choose
Claude Fable 5.2 launched on November 9, 2026. With Opus 5.5 already out since September, many people are wondering which one to use and how different the prices really are.
This article breaks down the differences between the two models by price, performance and what you can actually use, with Japanese yen estimates alongside the dollar prices. It also covers how a small business can split the work between them.
In short ・For everyday work, start with Opus 5.5. Switch to Fable 5.2 only for difficult, long-running tasks ・Fable 5.2's API price is exactly double Opus 5.5's (input per 1M tokens: $8 (≈¥1,264) vs. $4 (≈¥632)) ・Fable performs better on many benchmarks, but it tends to be poor value on simple tasks ・Fable 5.2 is 20% cheaper across the board than the previous Fable 5.1 |
* Yen figures use $1 = ¥158 (the early-November 2026 level)
Where the two models fit
Opus 5.5 launched on September 22, 2026 and is Anthropic's flagship model. It handles a wide range of knowledge work, including coding, computer use and document creation, and costs less than the previous-generation Opus 5.
Fable 5.2 launched on November 9 and belongs to the "Mythos"-class family above Opus. Anthropic itself advises starting most work on Opus 5.5 and using Fable for "the most ambitious, open-ended technical work."
The basic specs are shared: a 1M-token input limit (context window), a 128K-token output limit per response, and a knowledge cutoff of June 2026. The differences come down mainly to the following four points.
Price
Performance
Restrictions from safety features
How much you can use on each plan
Price differences (per 1M tokens)
Fable 5.2's API prices are exactly double Opus 5.5's. Only cache reads cost the same.
Item | Opus 5.5 | Fable 5.2 |
Input | $4 (≈¥632) | $8 (≈¥1,264) |
Output | $20 (≈¥3,160) | $40 (≈¥6,320) |
Cache read | $0.20 (≈¥32) | $0.20 (≈¥32) |
Cache write (5 min) | $5 (≈¥790) | $10 (≈¥1,580) |
Batch (input / output) | $2 (≈¥316) / $10 (≈¥1,580) | $4 (≈¥632) / $20 (≈¥3,160) |
Fast mode (input / output) | $8 (≈¥1,264) / $40 (≈¥6,320) | $16 (≈¥2,528) / $80 (≈¥12,640) |
Batch processing is half the standard price and can't be combined with fast mode (up to about 2.5x faster output). The full 1M-token window is billed at the standard rate, with no long-context surcharge.
Fable 5.2 is 20% cheaper on every line than the previous Fable 5.1 (input $10 (≈¥1,580), output $50 (≈¥7,900)). If you were using 5.1, the same usage now costs less.
What it costs in practice
Even at double the unit price, the total depends on how the work gets finished. Converted to yen, examples from Anthropic and other write-ups look like this.
Example | Opus 5.5 | Fable 5.2 |
One coding session (3M input tokens, 90% cached, 150K output tokens) | $4.74 (≈¥749) | $8.94 (≈¥1,413) |
Batch review of 10,000 documents | $600 (≈¥94,800) | $1,200 (≈¥189,600) |
Per coding task (FrontierCode, highest-performance setting) | $12.82 (≈¥2,026) | $6.72 (≈¥1,062) |
The third row is Anthropic's estimate: with Fable at the "high" setting, accuracy was nearly the same as Opus 5.5 at its maximum setting (45.3% vs. 45.5%), at about half the cost per task. On hard problems, a stronger model can finish in fewer steps and end up cheaper.
A caution In a small third-party test, giving simple operations tasks (3 DevOps tasks) to Fable produced about twice as much output as Fable 5.1 and cost 56% more. Accuracy was about the same, and Opus 5.5 was cheaper and faster. Keep in mind that using Fable for simple work tends to be poor value. |
Performance differences
In the comparison table Anthropic published, Fable 5.2 beats Opus 5.5 on most items. The gaps are largest on evaluations of long, multi-step work.
Benchmark | Opus 5.5 | Fable 5.2 |
FrontierSWE v2 (practical coding) | 62.3% | 69.9% |
FrontierCode 2.0 (hard coding problems) | 45.5% | 49.1% |
Terminal-Bench-Science (scientific terminal work) | 58.7% | 74.6% |
OSWorld 2.1 (computer use) | 87.2% | 89.3% |
Humanity's Last Exam (with tools) | 67.7% | 74.2% |
Remote Labor Index (handing over whole jobs) | 21.3% | 41.3% |
AA-Briefcase (human-rated Elo for document creation and similar) | 1800 | 1785 |
The figures are from Anthropic, and the reasoning-effort settings differ between evaluations. They are not independently reproduced. On the document-creation Elo evaluation, Opus 5.5 is slightly ahead.
Put simply, Fable has a big edge on "work it has to plan and carry out on its own over a long time," while the gap is small for "everyday writing and document work." On speed, Fable 5.2 is up to 30% faster than 5.1, but third-party measurements also show Opus 5.5 being faster and cheaper.
Things to know before using Fable 5.2
It can get stopped by safety features. High-risk requests related to cyberattacks or biology (vulnerability testing, exploit generation and the like) are blocked automatically. Blocks are down about 55% from 5.1, but security-testing work may still get stopped.
It's harder to switch models midway. Reasoning content can only be carried over between Fable 5.2 and Mythos 5.2. If you switch to Opus 5.5 or another model, the earlier reasoning isn't carried over. Changing the system prompt or tools in the middle of a conversation also causes an error.
30-day data retention. For safety monitoring, data must be retained for 30 days. If you use it for sensitive work, check this condition first.
Limits by plan. Fable isn't available on the free plan. Pro pays extra through usage credits, while Max ($100/month, ≈¥15,800) and Ultra ($200/month, ≈¥31,600) get up to half of the weekly limit. Opus 5.5 is available on the Pro, Max, Team and Enterprise plans.
As a launch promotion through November 16 (US Pacific time), Pro and standard Team seats can use up to 50% of the weekly limit on Fable and get one limit reset. This week is the best time to try it.
How a small business should split the work
Type of work | Recommended |
Drafting emails, meeting minutes and proposals; summaries; translation | Opus 5.5 |
Processing large volumes of documents at once (batch) | Opus 5.5 |
Simple operations work and routine data cleanup | Opus 5.5 |
Conversations where speed and responsiveness matter | Opus 5.5 |
Handing off large code changes or system development for long stretches | Fable 5.2 |
Research and analysis using multiple tools, where it has to work out the steps | Fable 5.2 |
Hard problems that Opus 5.5 failed at after two tries | Fable 5.2 |
In practice, a three-step approach works well.
Start with Opus 5.5.It costs half as much, and it's enough for most work.
Switch to Fable only when the results fall short.Switch at a natural break in the conversation, keeping in mind that its reasoning isn't carried over.
Using both is an option too.Anthropic also suggests pairing them, with Fable as the "director/advisor" and a cheaper model as the "executor."
Summary
Key points of this article ・Fable 5.2's unit price is double Opus 5.5's, but 20% lower than Fable 5.1 ・Fable performs better, with the biggest gaps on "long, autonomous work" ・For simple work, Opus 5.5 is often cheaper and faster ・Start with Opus 5.5 and use Fable 5.2 only for hard problems: the best balance of cost and results |
At Robin Planning, we also take consultations on choosing AI for your business and on adoption and automation. Feel free to contact us.
Sources (all explainer articles and news coverage)
Comments