Which is cheaper, Claude Opus 4.8 and GPT-6 Luna?

GPT-6 Luna has the lowest input price. Per 1M input tokens: Claude Opus 4.8 from $5.00 and GPT-6 Luna from $0.10.

Which has the larger context window, Claude Opus 4.8 and GPT-6 Luna?

Claude Opus 4.8 has the largest context window: Claude Opus 4.8 1,000,000 tokens and GPT-6 Luna 400,000 tokens.

Which is smarter, Claude Opus 4.8 and GPT-6 Luna?

Claude Opus 4.8 scores highest on the Artificial Analysis Intelligence Index: Claude Opus 4.8 41.8 and GPT-6 Luna 38.1.

Can I switch between Claude Opus 4.8 and GPT-6 Luna 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-opus-4.8, openai/gpt-6-luna).

Claude Opus 4.8 vs GPT-6 Luna

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

Claude Opus 4.8 Anthropicanthropic/claude-opus-4.8

GPT-6 Luna OpenAIopenai/gpt-6-luna

Creator

Anthropic

OpenAI

Released

May 27, 2026

Sep 22, 2026

Context window

400K

Max output

128K

Input / 1MLowest provider price

$5.00

$0.10

Output / 1MLowest provider price

$25.00

$0.50

Providers

IntelligenceArtificial Analysis index

41.8

38.1

CodingArtificial Analysis index

74.3

—

LatencyMedian time to first token

19s

—

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 Opus 4.8 vs GPT-6 Luna: summary

Claude Opus 4.8 and GPT-6 Luna are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Claude Opus 4.8, from Anthropic, has a 1,000,000-token context window, costs from $5.00/1M input and $25.00/1M output tokens across 3 providers and scores 41.8 on the Artificial Analysis Intelligence Index.

GPT-6 Luna, from OpenAI, has a 400,000-token context window, costs $0.10/1M input and $0.50/1M output tokens and scores 38.1 on the Artificial Analysis Intelligence Index.

GPT-6 Luna is the cheapest on input, 50× cheaper than the next model, Claude Opus 4.8 has the largest context window and Claude Opus 4.8 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-opus-4.8", messages=[...]) # or client.chat.completions.create(model="openai/gpt-6-luna", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis