MDL-4956 EST.2026 · IDX.779 Language model In production ⇄ Compare
GPT-5.6 OpenAI · USA · 2026
OpenAI's mid-2026 frontier family — the Sol, Luna and Terra line rolled out from late June.
GPT-5.6 is OpenAI's flagship line of mid-2026, shipped as the Sol, Luna and Terra variants tuned for different speed-capability trade-offs. It advances multimodal reasoning, long-context coherence and agentic tool use across ChatGPT and the API, continuing the staged-rollout strategy OpenAI adopted for its frontier releases.
#frontier #multimodal #Sol Luna Terra #reasoning
Official website ↗ ▸ SpecificationsClass & identity
Model class Frontier LLM family
Version / release Staged rollout, from late June 2026 Architecture
Architecture Transformer (Sol / Luna / Terra variants)
Parameters —
Context window 1,050,000 tokens · output: up to 128,000 tokens
Modalities Text, vision, audio
Knowledge cutoff / data — Performance (benchmarks)
MMLU —
GPQA Diamond —
SWE-bench —
MATH / AIME —
Chatbot Arena Elo —
Domain benchmark — Capabilities Text Vision Audio input Function calling Computer use Extended reasoning Long context (≥200k) Multilingual Agentic coding
Reasoning mode Configurable reasoning effort
Tool use / agentic Function calling, computer use, agentic
Multilinguality Multilingual
Key strengths Multimodal reasoning, long-context coherence, agentic tools Access & deployment
Availability Proprietary API (ChatGPT + API)
License Proprietary
Pricing Top tier (Sol) $4 / 1M input, $20 / 1M output, $0.40 cached input since 21 Aug 2026 (promotional through 21 Nov 2026); Terra $2 / $12; Luna $0.20 / $1.20; requests above 272,000 input tokens billed at 2x input and 1.5x output
Deployment API / cloud
Safety / alignment OpenAI safety systems Compiled to the wujec.ai Spec Standard v1 — “—” means not publicly disclosed.