GPT-6 Luna 101: OpenAI's Cheapest GPT-6 Tier Aiming for GPT-5.6 Sol Quality at Haiku Prices

GPT-6 Luna is OpenAI's lower-cost GPT-6 model, launched on September 22, 2026, alongside GPT-6 Sol. OpenAI describes both models as faster and more affordable models built on advances behind GPT-6 Astra, with Luna aimed at focused, high-volume work. It first appeared in pre-launch community chatter, but the model is now officially available through the API and is rolling out across OpenAI's products. Developers track it because its pricing is dramatically below the GPT-5.6 Luna rates while its capabilities target practical coding, computer-use, and agentic workloads.

Key Takeaways

• GPT-6 Luna launched on September 22, 2026, as part of the GPT-6 family alongside GPT-6 Sol and GPT-6 Astra.
• OpenAI positions Luna as a faster, more affordable model for focused, high-volume work, while Sol is aimed at more complex professional and agentic workflows.
• GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens through the API.
• OpenAI reports that Luna improves on GPT-5.6 Luna by 5.4 percentage points on AutomationBench at 58% lower cost per task.
• Luna is available in the API and is rolling out in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users. Free and Go users can try it in the desktop app.
• Independent evaluations show mixed results rather than a universal capability jump: Luna improves on some tests and regresses on others compared with GPT-5.6 Luna.

What Is GPT-6 Luna?

GPT-6 Luna is the lower-cost, high-volume tier of OpenAI's GPT-6 lineup. OpenAI introduced it on September 22, 2026, alongside GPT-6 Sol, after introducing GPT-6 Astra earlier in the month. The recurring pre-launch theory that Astra would serve the hardest tasks while Luna handled cheaper, repetitive work was broadly reflected in the final product positioning.

OpenAI says Sol and Luna were trained with methods similar to GPT-6 Astra, bringing advances in professional work, factuality, coding, computer use, and alignment to faster, more affordable models. The company also attributes the lower prices to more efficient caching and inference. Our earlier first look at the GPT-6 family covers the broader lineup context.

GPT-6 Luna is now a shipped model, not merely a community name. The launch material positions it for focused, high-volume tasks where token economics matter, while Sol is intended for more demanding work at a still-reduced cost.

GPT-6 Luna at a Glance

Specification	Current information
Developer	OpenAI
Model family	GPT-6
Type	Lower-cost general-purpose model for focused, high-volume work
Modality	Not fully specified in OpenAI's launch announcement
Context window	1,050,000 tokens listed by a third-party provider; not independently confirmed in the supplied launch material
Maximum output	Up to 128,000 tokens listed by a third-party provider; not independently confirmed in the supplied launch material
API model identifier	gpt-6-luna
Input pricing	$0.10 per million tokens
Output pricing	$0.50 per million tokens
ChatGPT availability	ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users; Luna is also available to Free and Go users in the desktop app
API availability	Available
Positioning	Faster, lower-cost GPT-6 model for focused, high-volume tasks
License	Proprietary; no public weights
Model weights	Not publicly released
Release date	September 22, 2026
Reported platform availability	Arena availability was reported after launch; GitHub Copilot availability was also reported separately

The table separates confirmed launch information from specifications that still come from a single provider listing or from third-party platform reports. The release date, API pricing, and initial OpenAI product access are confirmed; the exact context window, output ceiling, and complete platform matrix remain less firmly established.

How GPT-6 Luna Works / What Makes It Different

The defining trait of GPT-6 Luna is Luna Pricing — the low per-token cost that made GPT-5.6 Luna attractive for high-volume work. The GPT-6 version keeps that cost floor while bringing the new generation's training and infrastructure improvements to a cheaper model.

Luna costs $0.10 per million input tokens and $0.50 per million output tokens. GPT-5.6 Luna was priced at $0.20 per million input tokens and $1.20 per million output tokens. OpenAI describes the GPT-6 reductions as 50% lower than GPT-5.6 promotional pricing; calculated directly from the listed Luna rates, the output reduction is 58.3%.

Caching is another part of the economics. Artificial Analysis reports that cache reads receive a 90% discount and cache writes carry a 25% premium. OpenAI says caching and inference are more efficient, while the detailed cache pricing and behavior come from third-party analysis rather than the launch announcement alone.

The most concrete launch-era capability result is on AutomationBench. OpenAI reports that GPT-6 Luna at high effort improves on GPT-5.6 Luna by 5.4 percentage points while reducing cost per task by 58%. Other comparisons are less uniform. Artificial Analysis describes the Intelligence Index and Coding Agent Index results as broadly level with GPT-5.6 overall, with improvements on some evaluations and regressions on others. Its reported Coding Agent Index score for Luna is 41, down from 43 for GPT-5.6 Luna, while other tests show gains.

That mixed picture matters. Luna's strongest confirmed advantage is cost efficiency, not a universal benchmark lead. The launch makes it practical to run more attempts, longer workflows, and larger volumes of routine tasks, even when the model does not win every capability comparison.

What You Can Do With GPT-6 Luna

Because GPT-6 Luna is now available, its use cases can be described from the launch positioning and the early evaluation data rather than from projections alone.

• High-volume implementation. Codex users described running Luna as an implementer under a stronger planner, citing large token savings. One r/codex thread is titled "We need GPT6 Luna" and asks for Luna to become "a reliable implementer." That pre-launch discussion helps explain the demand for the model's low operating cost.
• Parallel and QA roles. In the same thread, a user assigns Luna medium/high to feature, security, and accessibility QA roles while a stronger model orchestrates.
• Computer-use tasks. OpenAI lists computer use among the areas where GPT-6 Sol and Luna bring advances from Astra's training approach. Early posts also compared Luna favorably on computer-use cost, although the broader independent evaluation picture remains mixed.
• Focused, repetitive workloads. Luna's pricing is suited to summarisation, extraction, routine coding assistance, and other workloads that run frequently or at scale. The launch positioning emphasizes this cost-efficiency curve rather than maximum frontier performance.
• Lower-cost ChatGPT and Codex work. Plus, Pro, Business, Enterprise, and Edu users can access Luna through ChatGPT Work and Codex as rollout reaches their accounts. Free and Go users can try Luna in the desktop app.

For the hardest work, OpenAI still positions GPT-6 Astra as its best model across the board. You can compare that flagship with the lower-cost tier through GPT-6 Astra.

How GPT-6 Luna Compares

The confirmed GPT-6 launch lineup is Astra, Sol, and Luna. Astra remains the flagship, Sol occupies the more capable middle position for complex professional and agentic work, and Luna is the lower-cost option for focused, high-volume tasks.

Model	Current position	Status
GPT-6 Astra	Flagship, highest-cost model	Launched earlier in September 2026
GPT-6 Sol	More capable lower-cost tier for complex work	Launched September 22, 2026
GPT-6 Luna	Lowest-cost tier for focused, high-volume work	Launched September 22, 2026
GPT-6 Terra	Not included in the announced Sol-and-Luna launch	No GPT-6 Terra launch is established in the reporting so far

The distinction between Sol and Luna is therefore primarily one of task profile and cost. Sol is positioned for complex coding and agentic workflows, while Luna is designed to make repeated, lower-cost work practical. Our GPT-6 Sol breakdown covers the tier directly above Luna in more detail.

Availability: How to Access GPT-6 Luna

GPT-6 Luna is available through the OpenAI API under the model identifier gpt-6-luna, at $0.10 per million input tokens and $0.50 per million output tokens.

OpenAI's launch announcement says GPT-6 Luna is rolling out in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users. Free and Go users can try Luna in the desktop app. The supplied rollout descriptions do not list the standard ChatGPT Chat interface as an access route, so access there should not be assumed.

The model was also reported in Arena after launch, and a separate GitHub announcement reported GPT-6 Sol and Luna as available in GitHub Copilot. Those platform reports expand the access picture, but they are separate from OpenAI's own statement about the API, ChatGPT Work, Codex, and the desktop app. Exact timing can still vary by account, product, or platform.

What We Don't Know Yet

• Independent capability ranking. Artificial Analysis reports broadly level Intelligence Index and Coding Agent Index results compared with GPT-5.6 Luna, with improvements on some evaluations and regressions on others. Arena testing was also announced, but a settled independent ranking is not established in the reporting so far.
• Complete technical specifications. A third-party listing gives Luna a 1,050,000-token context window and up to 128,000 output tokens, but the supplied OpenAI announcement does not state those limits. Official throughput, latency, rate limits, and the complete model specification remain open.
• Full modality and tool documentation. A provider listing attributes vision, function calling, reasoning, and web search to Luna. The reporting so far does not independently verify the complete set of supported modalities and tools across OpenAI's direct API.
• Platform-by-platform rollout details. API, ChatGPT Work, Codex, the desktop app, Arena, and GitHub Copilot are all covered in the reporting so far, but exact account eligibility, rollout timing, and regional or product-specific limits are not fully documented.
• GPT-6 Terra's future. Terra was discussed before launch, but the confirmed launch material covers Astra, Sol, and Luna. Whether a GPT-6 Terra will appear later remains open.

Frequently Asked Questions

What is GPT-6 Luna?

GPT-6 Luna is OpenAI's lower-cost GPT-6 model, launched on September 22, 2026. OpenAI describes Luna and GPT-6 Sol as faster, more affordable models built on advances behind GPT-6 Astra, with Luna aimed at focused, high-volume work.

How much does GPT-6 Luna cost?

GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens through the API. Those rates compare with $0.20 and $1.20 for GPT-5.6 Luna. OpenAI describes the GPT-6 pricing change as 50% lower than GPT-5.6 promotional pricing; the arithmetic reduction on Luna output pricing is 58.3%.

When was GPT-6 Luna released?

OpenAI launched GPT-6 Luna on September 22, 2026.

Is GPT-6 Luna open source?

No public weights have been released for GPT-6 Luna. A third-party model listing identifies it as proprietary, and the supplied launch material does not describe an open-source release.

GPT-6 Luna vs GPT-6 Sol: what's the difference?

GPT-6 Sol is positioned for more complex professional, coding, and agentic work, while GPT-6 Luna is the lower-cost option for focused, high-volume tasks. Sol costs $2 per million input tokens and $10 per million output tokens; Luna costs $0.10 and $0.50.

Is GPT-6 Luna better than GPT-5.6 Luna?

OpenAI says GPT-6 Sol and Luna improve on their GPT-5.6 counterparts across areas including coding, computer use, factuality, and alignment. Independent Artificial Analysis results show mixed movement: Luna improves on some evaluations and regresses on others, so a universal capability advantage is not established.

Where can I use GPT-6 Luna?

GPT-6 Luna is available in the API and is rolling out in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users. Free and Go users can try Luna in the desktop app. The supplied rollout information does not list the basic ChatGPT Chat interface as an access route.

What to Watch Next

The next useful signals are independent evaluations under matched conditions, complete OpenAI documentation for context, output, rate limits, and tools, and clearer product-by-product rollout details. The main question is no longer whether GPT-6 Luna exists or when it will launch; it is how its low cost translates into real-world quality across coding, computer use, and long-running agent workflows.

The launch already establishes Luna's central thesis: a GPT-6 model priced for frequent, high-volume use. What remains unsettled is how consistently its measured capability holds up outside OpenAI's comparisons and whether its reported technical limits and platform support are uniform across every access route.

Try related models on Kie.ai: GPT-6 Sol and Luna, GPT-5.6 and Claude Haiku 5.5.