Head-to-head comparison

Claude Fable 5.1 vs Claude Opus 5

Claude Fable 5.1 (Anthropic) and Claude Opus 5 (Anthropic) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 3 September 2026

As of 3 September 2026, Claude Fable 5.1 holds the stronger ModelCap Index position (#2 vs #3); and Claude Opus 5 is 2× cheaper per output token ($25.00/1M vs $50.00/1M).

Which should you choose?

Choose Claude Fable 5.1 if…

you want the stronger overall ModelCap Index position — #2 against #3 (84.1 vs 83.6 points).
AA Intelligence Index is your yardstick — 65.7 against 63.1.
AA Terminal-Bench 2.1 is your yardstick — 91.4% against 89.1%.
AA Humanity's Last Exam is your yardstick — 59.1% against 54.9%.
you want the more recently listed model — Claude Fable 5.1 was listed 1 September 2026, Claude Opus 5 24 July 2026.

Choose Claude Opus 5 if…

API cost matters — $25.00/1M output tokens against $50.00/1M, about 2× cheaper.
your workload is prompt-heavy — input tokens cost $5.00/1M against $10.00/1M.
you want provider choice — 5 listed API providers against 4.
ARC-AGI-2 is your yardstick — 90.4% against 90.0%.

Claude Fable 5.1 vs Claude Opus 5: specs, pricing and context

Specification comparison of Claude Fable 5.1 and Claude Opus 5
Field	Claude Fable 5.1Anthropic	Claude Opus 5Anthropic
ModelCap Index position	#2	#3
Index score	84.1	83.6
Evidence	Measured	Measured
Input price / 1M tokens	$10.00	$5.00
Output price / 1M tokens	$50.00	$25.00
Context window	1M tokens	1M tokens
Max output tokens	128K	128K
API providers listed	4	5
Weight access	API only	API only
Input modalities	Text, Image, File	Text, Image, File
First listed	1 September 2026	24 July 2026
Publisher	Anthropic	Anthropic

Evidence: 2 public benchmark observations across 2 boards · 6 public benchmark observations across 6 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Fable 5.1 vs Claude Opus 5

Public benchmark boards where Claude Fable 5.1 or Claude Opus 5 has a published result
Board	Claude Fable 5.1	Claude Opus 5	Leads
Arena codingArena (LMArena)	—	15331526–1541High	Only one result
LMArena AgentLMArena	—	13.8%12.0%–15.6%High	Only one result
ARC-AGI-2ARC Prize Foundation	90.0%Max	90.4%Max	Claude Opus 5
ARC-AGI-3ARC Prize Foundation	—	30.2%High	Only one result
AA Intelligence IndexArtificial Analysis	65.7intelligence-index	63.1intelligence-index	Claude Fable 5.1
AA Terminal-Bench 2.1Artificial Analysis	91.4%terminal-bench-2.1	89.1%terminal-bench-2.1	Claude Fable 5.1
AA Humanity's Last ExamArtificial Analysis	59.1%humanitys-last-exam	54.9%humanitys-last-exam	Claude Fable 5.1
Terminal-Bench 4.0Terminal-Bench (Laude Institute)	—	51.8%48.4%–55.2%Claude Code · Max	Only one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Fable 5.1 vs Claude Opus 5: common questions

Is Claude Fable 5.1 better than Claude Opus 5?

Claude Fable 5.1 ranks higher on the ModelCap Index as of 3 September 2026: #2 against #3. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.

Is Claude Fable 5.1 cheaper than Claude Opus 5?

Claude Opus 5 is cheaper on output tokens: $25.00/1M against $50.00/1M. Input tokens are $10.00/1M for Claude Fable 5.1 and $5.00/1M for Claude Opus 5. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, Claude Fable 5.1 or Claude Opus 5?

Both publish a 1M-token context window.

Which is better for coding, Claude Fable 5.1 or Claude Opus 5?

AA Terminal-Bench 2.1: Claude Fable 5.1 91.4%, Claude Opus 5 89.1% — Claude Fable 5.1 leads.

Are Claude Fable 5.1 and Claude Opus 5 open-weight models?

Claude Fable 5.1: API only. Claude Opus 5: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Fable 5.1 and Claude Opus 5?

ModelCap currently lists 4 API providers for Claude Fable 5.1 and 5 for Claude Opus 5, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Fable 5.1 vs Claude Opus 5 comparison?

Every figure comes from the sealed ModelCap dataset published 3 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.