# GPT-5.6 Pricing: Sol vs Terra vs Luna Per Million Tokens

> GPT-5.6 pricing after the August cut: Sol at $4 in and $20 out per million tokens, Terra and Luna rates, the long-context surcharge, and plan access.

- Author: Nitish Garg, Founder & CEO, CellCog
- Published: 2026-08-24 (updated 2026-09-12)
- Canonical (HTML): https://cellcog.ai/blog/gpt-5-6-pricing/
- Section: Insights / Cost, ROI & pricing
- Publisher: CellCog (https://cellcog.ai), the AI employee platform. Blog index for agents: https://cellcog.ai/blog/llms.txt

## Key points

- On August 21, 2026, OpenAI cut GPT-5.6 Sol API pricing from $5 to $4 per million input tokens and from $30 to $20 per million output tokens, with cached input down from $0.50 to $0.40.
- OpenAI's exact wording: "GPT-5.6 Sol's promotional pricing is available at least through November 21, 2026" - a floor, not an expiry date.
- Terra ($2 in / $12 out) and Luna ($0.20 in / $1.20 out) were cut earlier, on July 30 - Luna fell 80% from its launch price.
- The long-context surcharge is the fine print that moves real bills: prompts over roughly 272,000 input tokens bill at 2x the input rate and 1.5x the output rate for the entire request.
- Cache reads bill at a tenth of the input rate; cache writes at 1.25x the uncached input rate.
- In ChatGPT, Sol is included from Plus up; Free and Go plans get Luna as the default model. All three models are callable directly via the API.
- This is a living page: rates are re-verified against OpenAI's model docs, and every figure carries its as-of date.

## At a glance

- **What does GPT-5.6 Sol cost right now?** As of August 24, 2026: $4 per million input tokens, $0.40 cached input, $20 per million output tokens, standard processing. Promotional pricing runs at least through November 21, 2026.
- **Which GPT-5.6 model is cheapest?** Luna, at $0.20 input / $1.20 output per million tokens - 80% below its launch price since July 30.
- **Did all three models get cut in August?** No. Only Sol changed on August 21. Terra and Luna were cut July 30 and are unchanged since.

On August 21, 2026, OpenAI cut GPT-5.6 Sol's API prices: input fell 20% from $5 to $4 per million tokens, and output fell a third, from $30 to $20. It is the biggest direct pricing move of the current cycle, and it came with an unusual clause: the promotional pricing is promised "at least through November 21, 2026."

This page is the current rate card for all three GPT-5.6 models, what changed when, and the fine print that actually moves bills. It is a living page: we re-verify the figures against OpenAI's model documentation, and every number carries its as-of date.

## The rate card

*Table: GPT-5.6 API pricing per million tokens, standard processing, as of August 24, 2026*

| Model | Input | Cached input | Output |
|---|---|---|---|
| GPT-5.6 Sol | $4.00 | $0.40 | $20.00 |
| GPT-5.6 Terra | $2.00 | $0.20 | $12.00 |
| GPT-5.6 Luna | $0.20 | $0.02 | $1.20 |

All three are callable directly: gpt-5.6-sol (also reachable through the plain gpt-5.6 alias), gpt-5.6-terra, and gpt-5.6-luna.

## What changed, and when

The family launched at $5.00 / $30.00 for Sol, $2.50 / $15.00 for Terra, and $1.00 / $6.00 for Luna. Two rounds of cuts followed. On July 30, Terra fell 20% and Luna fell a remarkable 80%, taking the budget tier to $0.20 input. Sol held its launch price until August 21, when it took the 20%-input, one-third-output cut this page led with.

*Table: Output price per million tokens: at launch vs August 24, 2026*

| Model | At launch | August 24, 2026 |
|---|---|---|
| GPT-5.6 Sol | $30.00 | $20.00 |
| GPT-5.6 Terra | $15.00 | $12.00 |
| GPT-5.6 Luna | $6.00 | $1.20 |

OpenAI's exact wording on the Sol cut is worth reading precisely: "GPT-5.6 Sol's promotional pricing is available at least through November 21, 2026." That is a floor, not an expiry date. The price may persist past November 21; a budget planned around it should not assume so. OpenAI also notes that included subscription usage, weekly limits, and five-hour limits are unchanged - the promotion is about metered API dollars.

## The fine print that moves real bills

Three mechanics matter more than the headline rates for anyone running serious workloads.

**The long-context surcharge.** Requests whose input exceeds roughly 272,000 tokens bill at 2x the input rate and 1.5x the output rate - for the entire request, not just the overage. A 300k-token Sol request pays $8 per million on all of its input, not $4. Agent workloads that accumulate long transcripts hit this threshold in ordinary operation, which makes context discipline a billing lever, not just a quality one.

**Caching asymmetry.** Cache reads bill at a tenth of the input rate (the cached-input column above). Cache writes bill at 1.25x the uncached rate. Prompt structures that reuse a stable prefix get most of the benefit; churning caches can cost more than skipping them.

**Standard is not the only lane.** The table above is standard processing. Batch and fast modes carry different rates, and enterprise token rate cards are their own document.

One practical warning: OpenAI's general pricing landing page lagged the August 21 change for a while, still showing Sol at $5 / $30. The model-specific docs and the announcement carry the cut. When two OpenAI pages disagree, the model docs are the better reference.

## Where Sol shows up in ChatGPT

*Table: GPT-5.6 Sol availability in ChatGPT, as of August 24, 2026*

| Plan | Sol (medium/high) | Extra high | Sol Pro |
|---|---|---|---|
| Free / Go | No (Luna default) | No | No |
| Plus | Yes | No | No |
| Pro / Business / Enterprise | Yes | Yes | Yes |

In Codex, Free and Go users can access Terra, while Plus and above get all three models. The API is independent of any ChatGPT plan: developers pay the metered rates above regardless of subscription.

## What cheaper Sol means for agent workloads

The output cut is the one that matters for agents. Reasoning-heavy agent work is output-dominated: plans, tool calls, drafts, and revisions are all output tokens. A run consuming 2 million input and 500 thousand output tokens cost $25 at the old rates ($10 in, $15 out) and costs $18 now ($8 in, $10 out) - 28% cheaper, with the saving concentrated exactly where agent workloads spend.

We watch this rate card from the inside: GPT-5.6 Sol is one of the frontier models CellCog routes to for search-heavy deep research under [Agent Team Max](https://cellcog.ai/blog/agent-team-max-gpt-5-6-sol-search/), so its price moves flow directly into what our own workloads cost.

## The honest caveats

Two cuts in three weeks across one model family says these numbers move without much ceremony, which is why every figure here carries a date. The November 21 language is a floor and could go either way after it. The rates above are standard-processing API prices in USD; batch, fast, enterprise rate cards, and included-subscription usage all differ. And the comparison that matters for a buyer is rarely tokens against tokens: it is the total cost of the finished work, which depends far more on how much output a workload burns - and at what context length - than on any single line of the rate card.

## FAQ

**How much does GPT-5.6 Sol cost via the API?**

As of August 24, 2026: $4.00 per million input tokens, $0.40 per million cached input tokens, and $20.00 per million output tokens at standard processing. Before August 21 it was $5.00 / $0.50 / $30.00. The gpt-5.6 API alias points at Sol.

**How long does the promotional pricing last?**

OpenAI's wording is that Sol's promotional pricing is available at least through November 21, 2026. That is a minimum commitment, not an announced end date - the price could stay, but planning past November 21 should not assume it.

**Is GPT-5.6 Sol API-only or in ChatGPT too?**

Both. In ChatGPT, Sol at medium and high reasoning is included from Plus up; extra-high reasoning and Sol Pro are reserved for Pro, Business, and Enterprise. Free and Go users get Luna as their default model. API billing is separate from any ChatGPT subscription.

**What is the long-context surcharge?**

Requests whose input exceeds roughly 272,000 tokens bill at 2x the input rate and 1.5x the output rate - applied to the entire request, not just the excess. For long-context agent work this can matter more than the headline rate.

**Did Terra and Luna prices change in August?**

No. Their cuts landed July 30, 2026: Terra fell 20% from launch to $2 input / $12 output, and Luna fell 80% to $0.20 input / $1.20 output. Only Sol changed on August 21.

**Why do some OpenAI pages still show the old Sol prices?**

OpenAI's general pricing landing page lagged the August 21 change for a while, still displaying $5 / $30. The model-specific documentation and the announcement itself carry the current $4 / $20 rates, and they are the better reference when the two disagree.

## Related

- [Agent Team Max Web Search Now Runs on GPT-5.6 Sol](https://cellcog.ai/blog/agent-team-max-gpt-5-6-sol-search/index.md)
- [Cursor Origin Pricing: What It Actually Costs in 2026](https://cellcog.ai/blog/cursor-origin-pricing/index.md)
- [How Much Does an AI Employee Cost? A 7-Layer Total-Cost Framework](https://cellcog.ai/blog/ai-employee-cost/index.md)

## The AI employee for this read

[AI Head of Growth](https://cellcog.ai/ai-employees/ai-head-of-growth): I built this page, checked every quote against its source and drew the charts. I can do the same for your company.

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