Claude Mythos 5.1 vs GPT-5.6 Luna

Pricing verdict: Claude Mythos 5.1 vs GPT-5.6 Luna: GPT-5.6 Luna is cheaper for input-heavy usage ($1.00/M vs $10.00/M input tokens), while GPT-5.6 Luna is better for long-context tasks (1,050,000 tokens).

Direct answer: choose GPT-5.6 Luna for lower token spend and choose GPT-5.6 Luna when your workload needs longer context.

Compare API pricing, input and output token costs, context windows, and monthly estimates on one page so you can pick the right model fast.

Anthropic

Claude Mythos 5.1

OpenAI

GPT-5.6 Luna

Try Anthropic →Try OpenAI →

Claude Mythos 5.1 pricing page GPT-5.6 Luna pricing page Anthropic provider overview OpenAI provider overview

Cost Comparison (1000 input + 500 output tokens, 100 requests/day)

Claude Mythos 5.1

Per Request:$0.035

Daily:$3.50

Monthly:$105.00

Yearly:$1,277.50

GPT-5.6 Luna

Per Request:$0.004000

Daily:$0.40

Monthly:$12.00

Yearly:$146.00

Cost Differences

$0.031

Per Request

$3.10

Daily

$93.00

Monthly

$1,131.50

Yearly

GPT-5.6 Luna costs less than Claude Mythos 5.1

Quick Recommendation

Winner for direct API pricing: GPT-5.6 Luna. At the default workload, GPT-5.6 Luna saves about $93.00/month ($1,131.50/year) versus Claude Mythos 5.1.

Claude Mythos 5.1 full pricing breakdown GPT-5.6 Luna full pricing breakdown Anthropic API pricing details OpenAI API pricing details Anthropic vs OpenAI API pricing GPT-6 Astra vs Codex Mini GPT-6 Astra vs o4-mini Deep Research

Feature Comparison

Feature	Claude Mythos 5.1	GPT-5.6 Luna
Provider	Anthropic	OpenAI
Input Price	$10.00/1M tokens	$1.00/1M tokens
Output Price	$50.00/1M tokens	$6.00/1M tokens
Context Window	1,000,000 tokens	1,050,000 tokens
Max Output	128,000 tokens	128,000 tokens
Category	flagship	efficient
Capabilities	textvisionreasoningcode	textvisioncodereasoning
Release Date	9/1/2026	6/26/2026

Claude Mythos 5.1 vs GPT-5.6 Luna: Which Should You Choose?

Choosing between Claude Mythos 5.1 and GPT-5.6 Luna depends on your priorities: cost efficiency, context length, or raw capability. GPT-5.6 Luna is the more affordable option at $1.00/1M input tokens — 90% cheaper than Claude Mythos 5.1. Meanwhile, GPT-5.6 Luna offers a significantly larger context window at 1,050,000 tokens vs 1,000,000 for Claude Mythos 5.1.

These models come from different providers — Anthropic and OpenAI — which means different API ecosystems, SDKs, rate limits, and terms of service. If you're already integrated with Anthropic, switching to OpenAIinvolves migration effort beyond just pricing. Factor in your existing infrastructure when deciding.

These models target different tiers: Claude Mythos 5.1 is a flagship model while GPT-5.6 Luna is efficient. This means they're optimized for different workloads. Claude Mythos 5.1 is built for complex tasks that require deeper reasoning, while GPT-5.6 Luna offers better value for routine operations.

Output costs matter too. Claude Mythos 5.1 charges $50.00/1M output tokens vs $6.00 for GPT-5.6 Luna. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. GPT-5.6 Luna has the edge here at $6.00/1M output tokens.

Multimodal capabilities: Both models support vision (image understanding), so you can send images alongside text prompts with either option.

Best Use Cases

Choose Claude Mythos 5.1 when:

• You're already using Anthropic's API ecosystem

Choose GPT-5.6 Luna when:

• Budget is a primary concern
• You need a larger context window (1,050,000 tokens)
• You're already using OpenAI's API ecosystem
• You're running high-volume, latency-sensitive workloads

Pros and Caveats at a Glance

Claude Mythos 5.1

• Input pricing: $10.00/M tokens
• Output pricing: $50.00/M tokens
• Context window: 1,000,000 tokens
• Max output: 128,000 tokens

Watch out for

• Higher input cost than GPT-5.6 Luna
• Higher output cost than GPT-5.6 Luna
• Smaller context window than GPT-5.6 Luna

GPT-5.6 Luna

• Input pricing: $1.00/M tokens
• Output pricing: $6.00/M tokens
• Context window: 1,050,000 tokens
• Max output: 128,000 tokens

Watch out for

• Trade-offs are minor in this matchup.

Try Different Scenarios

Use the calculator below to see how costs change with different usage patterns

Claude Mythos 5.1 (Anthropic)

Cost Calculator

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GPT-5.6 Luna (OpenAI)

Cost Calculator

Provider

Model

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Output Tokens

Requests/Day

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Start using Claude Mythos 5.1 today

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Frequently Asked Questions

Which is cheaper, Claude Mythos 5.1 or GPT-5.6 Luna?▼

GPT-5.6 Luna is cheaper for input tokens at $1.00 per million tokens vs $10.00 for Claude Mythos 5.1 — that's 90% savings on input costs.

What is the context window difference between Claude Mythos 5.1 and GPT-5.6 Luna?▼

Claude Mythos 5.1 supports 1,000,000 tokens while GPT-5.6 Luna supports 1,050,000 tokens — a difference of 50,000 tokens in favor of GPT-5.6 Luna.

Which model is better for AI Agent / Agentic Workflows?▼

Both models support text, code, reasoning. For ai agent / agentic workflows, GPT-5.6 Luna is the lower-cost option, while GPT-5.6 Luna offers a larger context window (1,050,000 vs 1,000,000 tokens). Choose GPT-5.6 Luna for budget sensitivity or GPT-5.6 Luna for longer context tasks.

Which model has better overall pricing for heavy usage?▼

At 100 requests/day with 1,000 input and 500 output tokens each, Claude Mythos 5.1 costs about $105.00/month and GPT-5.6 Luna costs about $12.00/month. Overall, GPT-5.6 Luna has lower combined input + output rates ($1.00 in, $6.00 out) vs Claude Mythos 5.1.

Where can I compare Anthropic and OpenAI API pricing beyond this model matchup?▼

See the Anthropic vs OpenAI provider comparison page for lineup-level averages, then review each model page for exact per-token rates.