Which is cheaper, Claude Fable 5.1 and Nemotron 3 Ultra 550B A55B?

Nemotron 3 Ultra 550B A55B has the lowest input price. Per 1M input tokens: Claude Fable 5.1 from $10.00 and Nemotron 3 Ultra 550B A55B from $0.50.

Which has the larger context window, Claude Fable 5.1 and Nemotron 3 Ultra 550B A55B?

Claude Fable 5.1 has the largest context window: Claude Fable 5.1 1,000,000 tokens and Nemotron 3 Ultra 550B A55B 262,144 tokens.

Which is smarter, Claude Fable 5.1 and Nemotron 3 Ultra 550B A55B?

Claude Fable 5.1 scores highest on the Artificial Analysis Intelligence Index: Claude Fable 5.1 47.2 and Nemotron 3 Ultra 550B A55B 11.8.

Can I switch between Claude Fable 5.1 and Nemotron 3 Ultra 550B A55B without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (anthropic/claude-fable-5.1, nvidia/nemotron-3-ultra-550b-a55b).

Claude Fable 5.1 vs Nemotron 3 Ultra 550B A55B

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

Estimate monthly cost for these models

Claude Fable 5.1 Anthropicanthropic/claude-fable-5.1

Nemotron 3 Ultra 550B A55B NVIDIAnvidia/nemotron-3-ultra-550b-a55b

Creator

Anthropic

NVIDIA

Released

Sep 1, 2026

May 16, 2026

Context window

262K

Max output

128K

16K

Input / 1MLowest provider price

$10.00

$0.50

Output / 1MLowest provider price

$50.00

$2.20

Providers

IntelligenceArtificial Analysis index

47.2

11.8

Accepts

Text, Image, Files

Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Fable 5.1 vs Nemotron 3 Ultra 550B A55B: summary

Claude Fable 5.1 and Nemotron 3 Ultra 550B A55B are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Claude Fable 5.1, from Anthropic, has a 1,000,000-token context window, costs $10.00/1M input and $50.00/1M output tokens and scores 47.2 on the Artificial Analysis Intelligence Index.

Nemotron 3 Ultra 550B A55B, from NVIDIA, has a 262,144-token context window, costs $0.50/1M input and $2.20/1M output tokens and scores 11.8 on the Artificial Analysis Intelligence Index.

Nemotron 3 Ultra 550B A55B is the cheapest on input, 20× cheaper than the next model, Claude Fable 5.1 has the largest context window and Claude Fable 5.1 scores highest for intelligence.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="anthropic/claude-fable-5.1", messages=[...]) # or client.chat.completions.create(model="nvidia/nemotron-3-ultra-550b-a55b", messages=[...])

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Benchmark scores sourced from ArtificialAnalysis