GPT-5.6 Terra
OpenAI released 2026-07-09 proprietary
GPT-5.6 Sol is both better and cheaper.
It scores +4.3 higher and costs 11% less ($4.00/M against $4.50/M) on this workload — and it does everything this model does.
GLM 5.3 is cheaper still (52% less) but drops 1.1M → 1.0M context, no file, image input.
The same model via batch is 50% cheaper ($2.25/M) — same weights, different latency.
Our take
editorial — not a measurementThe sensible middle of the 5.6 family and the one most teams should actually reach for: $2/$12 short-context, $4/$18 long. It is half Sol's input price and, in the absence of published per-tier evals, the burden is on Sol to justify 2x. Same 1.05M window, same 128k output. The long-context multiplier is gentler than Sol's on input (2x vs 2x) but much gentler on output (1.5x vs 1.5x) in absolute dollars. If you are standardising on OpenAI, benchmark Terra first and only escalate to Sol where it measurably fails.
Strengths
- $2/$12 short-context — half Sol's input cost
- 1.05M context, 128k max output
- Cached input at $0.20 and a 50% batch discount
- Same modality support as Sol (text, image, file)
Weaknesses
- Long-context tier raises it to $4/$18 at an unpublished threshold
- No independent benchmark score captured for it
- Still ~4x the price of comparable open-weight models
Reach for it when
- Default OpenAI production model
- Cost-sensitive frontier work
- Workloads to A/B against Sol before paying 2x
Avoid it if
- Evals show Sol is materially better on your task
- You need the cheapest possible tokens
Sources: developers.openai.com
Every price dimension
| Input | $2.00/M |
|---|---|
| Output | $12.00/M |
| Cached input | $0.200/M |
| Cache write | $2.50/M |
| Web search | $0.01/call |
| Batch discount | 50% |
Past 272,000 tokens the price changes. Input goes to $4.00/M (2×) and output to $18.00/M. The headline rate does not apply to a long-context workload.
Independent scores
| Intelligence | 56.6 |
|---|---|
| Coding | 76.7 |
| Agentic | 50.2 |
| LMArena Elo | 1446xhigh |
Sources are listed separately rather than averaged. Across the 62 models both have scored they correlate at r = 0.806 — close agreement overall, but four models rank very differently between them, and a blended score would hide exactly those.
Capability
| Context window | 1.1M |
|---|---|
| Max output | 128K |
| Input modes | file, image, text |
| Tool use | yes |
| Reasoning | optional |
| Knowledge cutoff | 2026-02-16 |
| Open weights | no |
Provenance
| Price source | openrouter.ai |
|---|---|
| Fetched | 2026-08-24 |
| Quality data | verified |
| Cross-checked | vendor page |
GPT-5.6 Terra is a balanced model in OpenAI's GPT-5.6 series, positioned between the flagship Sol tier and the cost-efficient Luna tier. It is suited for everyday coding, reasoning, and agentic...