GPT-5.6 Luna vs Grok Code Fast 1

Pricing verdict: GPT-5.6 Luna vs Grok Code Fast 1: Grok Code Fast 1 is cheaper for input-heavy usage ($0.20/M vs $1.00/M input tokens), while GPT-5.6 Luna is better for long-context tasks (1,050,000 tokens).

Direct answer: choose Grok Code Fast 1 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.

OpenAI

GPT-5.6 Luna

xAI

Grok Code Fast 1

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GPT-5.6 Luna pricing page Grok Code Fast 1 pricing page OpenAI provider overview xAI provider overview

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

GPT-5.6 Luna

Per Request:$0.004000

Daily:$0.40

Monthly:$12.00

Yearly:$146.00

Grok Code Fast 1

Per Request:$0.000950

Daily:$0.095

Monthly:$2.85

Yearly:$34.675

Cost Differences

$0.003050

Per Request

$0.305

Daily

$9.15

Monthly

$111.325

Yearly

Grok Code Fast 1 costs less than GPT-5.6 Luna

Quick Recommendation

Winner for direct API pricing: Grok Code Fast 1. At the default workload, Grok Code Fast 1 saves about $9.15/month ($111.325/year) versus GPT-5.6 Luna.

GPT-5.6 Luna full pricing breakdown Grok Code Fast 1 full pricing breakdown OpenAI API pricing details xAI API pricing details OpenAI vs xAI API pricing Codex Mini vs o4-mini Deep Research Codex Mini vs o3 Deep Research

Feature Comparison

Feature	GPT-5.6 Luna	Grok Code Fast 1
Provider	OpenAI	xAI
Input Price	$1.00/1M tokens	$0.20/1M tokens
Output Price	$6.00/1M tokens	$1.50/1M tokens
Context Window	1,050,000 tokens	256,000 tokens
Max Output	128,000 tokens	32,768 tokens
Category	efficient	standard
Capabilities	textvisioncodereasoning	textcodereasoning
Release Date	6/26/2026	2/1/2026

GPT-5.6 Luna vs Grok Code Fast 1: Which Should You Choose?

Choosing between GPT-5.6 Luna and Grok Code Fast 1 depends on your priorities: cost efficiency, context length, or raw capability. Grok Code Fast 1 is the more affordable option at $0.20/1M input tokens — 80% cheaper than GPT-5.6 Luna. Meanwhile, GPT-5.6 Luna offers a significantly larger context window at 1,050,000 tokens vs 256,000 for Grok Code Fast 1.

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

These models target different tiers: GPT-5.6 Luna is a efficient model while Grok Code Fast 1 is standard. This means they're optimized for different workloads. Grok Code Fast 1 targets more demanding workloads, while GPT-5.6 Luna provides a cost-effective option for everyday tasks.

Output costs matter too. GPT-5.6 Luna charges $6.00/1M output tokens vs $1.50 for Grok Code Fast 1. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. Grok Code Fast 1 has the edge here at $1.50/1M output tokens.

Multimodal capabilities: GPT-5.6 Luna supports vision (image inputs) while Grok Code Fast 1 is text-only. If your application needs image understanding, this narrows your choice.

Best Use Cases

Choose GPT-5.6 Luna when:

• You need a larger context window (1,050,000 tokens)
• You need more capabilities (vision)
• You need longer outputs (up to 128,000 tokens)
• You're already using OpenAI's API ecosystem
• You're running high-volume, latency-sensitive workloads

Choose Grok Code Fast 1 when:

• Budget is a primary concern
• You're already using xAI's API ecosystem

Pros and Caveats at a Glance

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

• Higher input cost than Grok Code Fast 1
• Higher output cost than Grok Code Fast 1

Grok Code Fast 1

• Input pricing: $0.20/M tokens
• Output pricing: $1.50/M tokens
• Context window: 256,000 tokens
• Max output: 32,768 tokens

Watch out for

• Smaller context window than GPT-5.6 Luna

Try Different Scenarios

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

GPT-5.6 Luna (OpenAI)

Cost Calculator

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Model

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Grok Code Fast 1 (xAI)

Cost Calculator

Provider

Model

Input Tokens

Output Tokens

Requests/Day

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Start using GPT-5.6 Luna today

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Frequently Asked Questions

Which is cheaper, GPT-5.6 Luna or Grok Code Fast 1?▼

Grok Code Fast 1 is cheaper for input tokens at $0.20 per million tokens vs $1.00 for GPT-5.6 Luna — that's 80% savings on input costs.

What is the context window difference between GPT-5.6 Luna and Grok Code Fast 1?▼

GPT-5.6 Luna supports 1,050,000 tokens while Grok Code Fast 1 supports 256,000 tokens — a difference of 794,000 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, Grok Code Fast 1 is the lower-cost option, while GPT-5.6 Luna offers a larger context window (1,050,000 vs 256,000 tokens). Choose Grok Code Fast 1 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, GPT-5.6 Luna costs about $12.00/month and Grok Code Fast 1 costs about $2.85/month. Overall, Grok Code Fast 1 has lower combined input + output rates ($0.20 in, $1.50 out) vs GPT-5.6 Luna.

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

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