OpenAI

GPT-5.6 Terra

Released Jul 9, 2026 · knowledge cutoff unpublished

Status: Unknown
Location: United States
Modality: Multimodal
Context window: 1M
Max output: 128K
Speed: —
Price ($/MTok in / out): $2 / $12
Cost per task (medium effort): $0.12
Open weights: No

Benchmarks1 of 8 reported

Terminal-Bench 2.1

87.4%

MMLU-Pro

—

GPQA Diamond

—

SWE-bench Verified

—

AIME (latest)

—

Humanity's Last Exam

—

LMArena Elo

—

ARC-AGI-2

—

Strengths & weaknesses

Strengths

Behaves like the flagship on ordinary work — the gap only opens on the hardest long-horizon agentic tasks
Long-context recall holds up close to Sol's, where the budget Luna tier falls away sharply
Full feature set rather than a cut-down one: image input, tool calling, extended reasoning, prompt caching and structured outputs

Weaknesses

OpenAI published no per-tier academic benchmarks, so where it really sits against rivals is hard to pin down
Trails Sol most on exactly the long-horizon agentic work that justifies reaching for a frontier model

Middle tier of the three-model GPT-5.6 family. OpenAI published only agentic suites per tier — Terminal-Bench 2.1 87.4%, Coding Agent Index 77.4, Agents' Last Exam 50.4, MRCR long-context recall 89.6% — and none of the site's tracked academic benchmarks, so those stay null. Artificial Analysis Intelligence Index 55 (vs Sol 59, Luna 51) at 140.4 output tokens/sec. Pricing is OpenAI's list rate, cut from $2.50/$15.00 to $2.00/$12.00 on 2026-07-30 (Luna was cut 80% in the same move). Context window per Artificial Analysis and OpenRouter; max output is tracker-reported, not from OpenAI's docs. Knowledge cutoff not published per tier.

For developers

API model strings

Not researched

Licence

Proprietary — weights not released

Retirement

No retirement announced

Lineage

No recorded predecessor