GPT-5.6 Terra vs GPT-5.6 Sol: workhorse or Sol within OpenAI's 2026 lineup?
By TechCompare · Updated · How we check
Default to Terra for production workloads. Pay for Sol only on tasks where Terra's reasoning demonstrably stalls. Sol's input price is 2x Terra's, and that only earns its keep on hardest-tier reasoning.
OpenAI: GPT-5.6 Terra
OpenAI's own price
- Input
- $2
- Output
- $12
- Cached
- $0.20
per 1M tokens
Price checked 2026-11-12
OpenAI: GPT-5.6 Sol
OpenAI's own price
- Input
- $4
- Output
- $20
- Cached
- $0.40
per 1M tokens
Price checked 2026-11-12
Cost Comparison
Based on 100,000 input tokens (50% cached), 5,000 output tokens, and 100 requests.Prices come live from OpenRouter at each maker's own price where it's listed. Temporary deals are left out.
OpenAI's GPT-5.6 family comes in three tiers: Luna (ultra-cheap), Terra (workhorse), and Sol (deep reasoning). Terra and Sol share the same lineage and tooling ecosystem, so the choice is mostly about where in the price-capability curve a workload sits.
Two members of OpenAI's 2026 lineup. Compare token rates and which one your workload needs.
Side-by-side specs
| Spec | GPT-5.6 Terra | GPT-5.6 Sol |
|---|---|---|
| Input Cost (per M) | $2.00 (better on this spec) | $4.00 |
| Output Cost (per M) | $12.00 (better on this spec) | $20.00 |
| Cached Input (per M)Cached input is text the provider has already processed. It costs less than fresh input. | $0.20 (better on this spec) | $0.40 |
| Batch input / output (per M) | $1.00 / $6.00 | $2.00 / $10.00 |
| Context Window | 1.05M | 1.05M |
How they differ
GPT-5.6 Terra is priced at $2.00 per million input tokens and $12.00 per million output tokens at OpenAI's list price, with a 90% caching discount ($0.20 per million). GPT-5.6 Sol is priced at $4.00 per million input tokens and $20.00 per million output tokens, also with a 90% caching discount ($0.40 per million).
Both share the 1.05M context window and a 50% batch discount. For a 100K input + 10K output request, Terra costs $0.32 vs Sol's $0.60, so Sol costs more per call. The decision is whether the workload's reasoning demand actually needs Sol's frontier depth, or whether Terra's workhorse tier covers it.
Verdict
Sol earns back its premium only when its frontier reasoning undoes a Terra retry. Terra runs $2.00/M input and $12.00/M output against Sol's $4.00 and $20.00, so Sol costs 2x as much on input and 1.7x as much on output. The gap holds on cached input at $0.20/M versus $0.40/M. Batch takes the same share off both, and context ties at 1.05M. A representative 100K input + 10K output call costs $0.32 on Terra against $0.60 on Sol, or $320,000 against $600,000 over a million calls.
Which should you pick?
Choose GPT-5.6 Terra
High-volume production: chat assistants, RAG, content generation, classification. Terra's list price of $2/$12 makes it the workhorse for everyday OpenAI-stack workloads.
Choose GPT-5.6 Sol
Frontier reasoning where Terra's quality falls short: hard math, deep multi-step planning, complex code synthesis. Caching narrows the dollar gap on cache-heavy agentic loops: a fully cached 100K-token prompt with 5K output costs $0.14 on Sol against $0.08 on Terra.