GPT-5.4: what is it, and how does it compare to GPT-5.6 Luna?

What is GPT-5.4?

GPT-5.4 is a large language model developed by OpenAI, released on March 5, 2026 as a replacement for GPT-5.2. OpenAI presents it as its most effective model for professional work, with strengths in coding, tool and computer use, and a context window of up to 1 million tokens. On GDPval, a test that evaluates AI's ability to produce professional-grade work across 44 occupations, GPT-5.4 matches or exceeds industry professional level in 83% of comparisons, versus 71% for GPT-5.2.

OpenAI first launched it in two versions, Thinking and Pro, reserved for paid accounts, before adding faster and more affordable mini and nano versions designed for high-volume tasks.

Find out how to use ChatGPT and its models effectively:

How to Use ChatGPT? Simple Guide and Examples

Published: July 2, 2026 I Reading time: 7 minutes 10s

GPT-5.4 vs GPT-5.6 Luna: what the comparison shows

GPT-5.6 Luna is the fastest and most affordable model in the new GPT-5.6 family (alongside Terra and Sol), released in July 2026, so four months after GPT-5.4. A quantified comparison between the two models, carried out by the independent tool LMSpeed, produces several findings:

• Price: Luna is significantly cheaper to use; around €0.20 per million input tokens versus €2.50 for GPT-5.4, a price cut by more than 10x.
• Categories where GPT-5.4 stays ahead: code, reasoning, general knowledge, and multimodal (image/text) understanding.
• Categories where GPT-5.6 Luna takes the lead: agentic tasks (autonomous tool use) and math, where the gap is clear.
• Weighted overall score: on LMSpeed's methodology (which weighs benchmark categories at 80% and price, speed, and availability at 20%), GPT-5.4 comes out on top with 65.3 points against 34.7 for Luna; mainly because it wins in more benchmark categories, despite a higher price.

In short: GPT-5.6 Luna isn't simply "GPT-5.4 but better." It's a model built for speed and cost, even if that means giving up ground on code and pure reasoning against GPT-5.4, which remains very solid on those uses several months after its release.

How to try GPT-5.4 for free on Ai-chatpro

On Ai-chatpro, GPT 5.4 Nano is among the free models available with no subscription. As with all free models on the platform, you get three messages every 24 hours to try the tool with no commitment.

To go further, GPT 4o, GPT 5.5, GPT 5.6 Terra, and GPT 5.6 Sol are available with the PRO subscription, letting you compare several generations of GPT models from a single interface, without juggling multiple OpenAI accounts.

Which GPT model should you choose?

• Quick question or occasional use: GPT 5.4 Nano (free) is more than enough.
• Versatile daily use: GPT 4o remains a good compromise.
• Writing, analysis, or more demanding tasks: GPT 5.5 or GPT 5.6 Terra offer more precision.
• Complex reasoning or advanced professional tasks: GPT 5.6 Sol, the most advanced model available on Ai-chatpro.

Check out our guides on what ChatGPT is and how to use it:

ChatGPT: Which One to Choose for Your Use Case?

Published: September 3, 2026 I Reading time: 3 minutes 40s

What to Remember

• GPT-5.4 is an OpenAI model from March 2026, built for professional work, code, and tool use.
• Against GPT-5.6 Luna (July 2026), GPT-5.4 keeps the edge in code, reasoning, knowledge, and multimodal tasks; Luna dominates on agents, math, and price.
• On Ai-chatpro, GPT 5.4 Nano is free, with three messages offered every 24 hours; the other GPT models are available with PRO.
• With Luna not yet offered on the platform, GPT 5.6 Terra remains the best speed/price alternative among the GPT models on Ai-chatpro.