Claude Mythos 5.1 vs o3-pro

Pricing verdict: Claude Mythos 5.1 vs o3-pro: Claude Mythos 5.1 is cheaper for input-heavy usage ($10.00/M vs $20.00/M input tokens), while Claude Mythos 5.1 is better for long-context tasks (1,000,000 tokens).

Direct answer: choose Claude Mythos 5.1 for lower token spend and choose Claude Mythos 5.1 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

o3-pro

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Claude Mythos 5.1 pricing page o3-pro 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

o3-pro

Per Request:$0.06

Daily:$6.00

Monthly:$180.00

Yearly:$2,190.00

Cost Differences

+$0.025

Per Request

+$2.50

Daily

+$75.00

Monthly

+$912.50

Yearly

o3-pro costs more than Claude Mythos 5.1

Quick Recommendation

Winner for direct API pricing: Claude Mythos 5.1. At the default workload, Claude Mythos 5.1 saves about $75.00/month ($912.50/year) versus o3-pro.

Claude Mythos 5.1 full pricing breakdown o3-pro 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	o3-pro
Provider	Anthropic	OpenAI
Input Price	$10.00/1M tokens	$20.00/1M tokens
Output Price	$50.00/1M tokens	$80.00/1M tokens
Context Window	1,000,000 tokens	1,000,000 tokens
Max Output	128,000 tokens	131,072 tokens
Category	flagship	reasoning
Capabilities	textvisionreasoningcode	textreasoningcode
Release Date	9/1/2026	6/10/2025

Claude Mythos 5.1 vs o3-pro: Which Should You Choose?

Choosing between Claude Mythos 5.1 and o3-pro depends on your priorities: cost efficiency, context length, or raw capability. Claude Mythos 5.1 is the more affordable option at $10.00/1M input tokens — 50% cheaper than o3-pro.

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 o3-pro is reasoning. This means they're optimized for different workloads. Claude Mythos 5.1 is built for complex tasks that require deeper reasoning, while o3-pro offers better value for routine operations.

Output costs matter too. Claude Mythos 5.1 charges $50.00/1M output tokens vs $80.00 for o3-pro. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. Claude Mythos 5.1 has the edge here at $50.00/1M output tokens.

Multimodal capabilities: Claude Mythos 5.1 supports vision (image inputs) while o3-pro is text-only. If your application needs image understanding, this narrows your choice.

Best Use Cases

Choose Claude Mythos 5.1 when:

• Budget is a primary concern
• You need more capabilities (vision)
• You're already using Anthropic's API ecosystem

Choose o3-pro when:

• You need longer outputs (up to 131,072 tokens)
• You're already using OpenAI's API ecosystem

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

• Trade-offs are minor in this matchup.

o3-pro

• Input pricing: $20.00/M tokens
• Output pricing: $80.00/M tokens
• Context window: 1,000,000 tokens
• Max output: 131,072 tokens

Watch out for

• Higher input cost than Claude Mythos 5.1
• Higher output cost than Claude Mythos 5.1

Try Different Scenarios

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

Claude Mythos 5.1 (Anthropic)

Cost Calculator

Provider

Model

Input Tokens

Output Tokens

Requests/Day

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o3-pro (OpenAI)

Cost Calculator

Provider

Model

Input Tokens

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 o3-pro?▼

Claude Mythos 5.1 is cheaper for input tokens at $10.00 per million tokens vs $20.00 for o3-pro — that's 50% savings on input costs.

What is the context window difference between Claude Mythos 5.1 and o3-pro?▼

Claude Mythos 5.1 supports 1,000,000 tokens while o3-pro supports 1,000,000 tokens — a difference of 0 tokens in favor of Claude Mythos 5.1.

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

Both models support text, code, reasoning. For ai agent / agentic workflows, Claude Mythos 5.1 is the lower-cost option, while Claude Mythos 5.1 offers a larger context window (1,000,000 vs 1,000,000 tokens). Choose Claude Mythos 5.1 for budget sensitivity or Claude Mythos 5.1 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 o3-pro costs about $180.00/month. Overall, Claude Mythos 5.1 has lower combined input + output rates ($10.00 in, $50.00 out) vs o3-pro.

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.