GPT-6.1 and Claude Fable 5.1 are the two models most teams shortlist in late 2026. They are not close on price: Fable 5.1 costs about ten times more per token. They are closer on capability than that gap suggests.
Short verdict: Fable 5.1 wins the hardest coding, writing and long-horizon agent work. GPT-6.1 Sol wins on value, computer use and ecosystem breadth. Most teams should test both and route between them.
For all three vendors, see the AI model comparison for 2026.
Price
| GPT-6.1 Sol | GPT-6.1 Terra | Claude Fable 5.1 | |
|---|---|---|---|
| Input | $1 | $0.50 | $10 |
| Output | $5 | $2.50 | $50 |
| Marketplace | $2 / $10 | $1 / $5 | $10 / $50 |
| Cache reads | Tiered | Tiered | $0.25 |
| Batch | $1 / $5 | $0.50 / $2.50 | $5 / $25 |
Prices are per million tokens. GPT-6.1 prices are direct from OpenAI; marketplace listings are higher.
Fable 5.1 looks expensive until you price the cache. At $0.25 per million cached input tokens, an agent that resends a large system prompt and tool schema can cut its bill sharply. Anthropic puts the saving at around 25% for typical workloads and up to 45% for highly agentic ones.
Published benchmarks
| Benchmark | Claude Fable 5.1 | GPT-5.6 Sol | GPT-6.1 |
|---|---|---|---|
| Terminal-Bench 4.0 | 55.8% | 37.3% | Not published |
| Terminal-Bench-Science 0.1 | 52.6% | 22.4% | Not published |
| CursorBench 3.2.0 | 73.4% | 67.2% | Not published |
| AutomationBench | 31.4% | 19.6% | Not published |
| GDPval-AA v2 | 1853 | 1711 | Not published |
| Humanity’s Last Exam (tools) | 65.0% | — | Not published |
This is the honest state of the evidence. Anthropic published detailed numbers for Fable 5.1 against GPT-5.6 Sol, not GPT-6.1. OpenAI has not published GPT-6.1 scores on these benchmarks.
So the comparison rests on three things: Fable 5.1’s measured lead over the previous GPT generation, OpenAI’s positioning of GPT-6.1, and price. Anyone claiming a definitive head-to-head is filling the gap with opinion.
Where GPT-6.1 wins
Price. At $1 / $5 direct, Sol is one-tenth the input price and one-tenth the output price of Fable 5.1. Terra is cheaper again.
Computer use. Terra includes precise computer use at $0.50 / $2.50. For browser and desktop automation, that is the lowest-cost option among the three major vendors.
Ecosystem. OpenAI’s tooling, SDKs and integrations are broader, and more third-party products support it out of the box.
Batch economics. Sol batch at $1 / $5 makes large offline jobs affordable.
Where Fable 5.1 wins
Hardest coding. The measured lead on Terminal-Bench 4.0, CursorBench and Terminal-Bench-Science is large, especially on scientific and long-horizon terminal work.
Writing. Fable remains the strongest model for tone, structure and long-form editing. For documentation, proposals and customer-facing copy, the difference is visible.
Long agent runs. Fable 5.1 sustains coherence over multi-step work and finishes tasks in fewer turns, which offsets part of the token price.
Enterprise data controls. Anthropic’s Enterprise Frontier Safeguards keep data in customer-controlled cloud infrastructure while retaining misuse detection, with zero-retention access until EFS is fully rolled out.
Cache economics. If most of your input is repeated context, the $0.25 cache-read rate changes the maths more than the headline price suggests.
Cost per task
Take 10 million input tokens and 1 million output tokens a month:
| Model | Monthly cost |
|---|---|
| GPT-6.1 Terra | 10 × $0.50 + 1 × $2.50 = $7.50 |
| GPT-6.1 Sol | 10 × $1 + 1 × $5 = $15 |
| Claude Fable 5.1 | 10 × $10 + 1 × $50 = $100 |
Now add rework. If Fable finishes a task in 30% fewer turns and produces 20% fewer rejected patches, the effective gap narrows. If your work is routine, it does not narrow enough.
Verdict by use case
| Use case | Pick | Reason |
|---|---|---|
| Complex refactor | Claude Fable 5.1 | Measured lead on agentic coding |
| Product copy and documentation | Claude Fable 5.1 | Best writing quality |
| Long-running autonomous agent | Claude Fable 5.1 | Fewer turns, better coherence |
| Budget coding agent | GPT-6.1 Sol | One-tenth the price |
| Browser or desktop automation | GPT-6.1 Terra | Cheapest precise computer use |
| High-volume classification | GPT-6.1 Terra | Cost per token |
| Regulated enterprise deployment | Depends | Fable 5.1 has EFS; OpenAI has its own enterprise controls |
A practical answer: use both
Route by task. Send routine work to Terra, hard work to Sol, and the hardest coding, writing and agent runs to Fable 5.1. You get the quality where it matters and the price where it does not.
This only works if your model layer is swappable and you log which model handled which task. Build that first.
FAQ
Is GPT-6.1 better than Claude Fable 5.1?
Not on published coding benchmarks. Fable 5.1 leads, but GPT-6.1 is far cheaper. The right answer depends on how expensive a failed task is for you.
Is Fable 5.1 worth ten times the price?
Only when rework and failure are expensive. For routine work, no. For complex coding, long agents and polished writing, often yes.
Does GPT-6.1 have computer use?
Yes. GPT-6.1 Terra includes precise computer use, and it is the cheapest of the three vendors for that capability.
Which should a small business start with?
Start with GPT-6.1 Terra for cost, and test Fable 5.1 on the tasks where quality is visible to customers. Most small businesses do not need Fable for everything.
Next step
If you are deciding for a product, our AI app development cost guide covers the build side. For a short evaluation on your own tasks, contact 24Bit System.
Related reading: Best AI model for coding and AI model benchmarks explained.
