Which is cheaper, Claude Fable 5.1 and GPT-5.5?

GPT-5.5 has the lowest input price. Per 1M input tokens: Claude Fable 5.1 from $10.00 and GPT-5.5 from $5.50.

Which has the larger context window, Claude Fable 5.1 and GPT-5.5?

GPT-5.5 has the largest context window: Claude Fable 5.1 1,000,000 tokens and GPT-5.5 1,050,000 tokens.

Which is better for coding, Claude Fable 5.1 and GPT-5.5?

Claude Fable 5.1 scores highest on the Artificial Analysis Coding Index: Claude Fable 5.1 79.1 and GPT-5.5 74.9.

Can I switch between Claude Fable 5.1 and GPT-5.5 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, openai/gpt-5.5).

Claude Fable 5.1 vs GPT-5.5

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

Claude Fable 5.1 Anthropicanthropic/claude-fable-5.1

GPT-5.5 OpenAIopenai/gpt-5.5

Creator

Anthropic

OpenAI

Released

Sep 1, 2026

Apr 24, 2026

Context window

1.05M

Max output

128K

Input / 1MLowest provider price

$10.00

$5.50

Output / 1MLowest provider price

$50.00

$33.00

Providers

IntelligenceArtificial Analysis index

51.2

38.4

CodingArtificial Analysis index

79.1

74.9

LatencyMedian time to first token

—

6.1s

ThroughputMedian tokens per second

—

<1 t/s

Accepts

Text, Image, Files

Files, Image, Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Fable 5.1 vs GPT-5.5: summary

Claude Fable 5.1 and GPT-5.5 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 51.2 on the Artificial Analysis Intelligence Index.

GPT-5.5, from OpenAI, has a 1,050,000-token context window, costs from $5.50/1M input and $33.00/1M output tokens across 2 providers and scores 38.4 on the Artificial Analysis Intelligence Index.

GPT-5.5 is the cheapest on input, 1.8× cheaper than the next model, GPT-5.5 has the largest context window, Claude Fable 5.1 scores highest for intelligence and Claude Fable 5.1 leads on coding.

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="openai/gpt-5.5", messages=[...])

Full API docs

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More comparisons

Benchmark scores sourced from ArtificialAnalysis