Breaking

OpenAI Ships GPT-5.6 as Developer Claims a Self-Run 3D City Build

July 9, 2026 at 16:12 EDT

Foundation Models
AI Agents
Software Dev & Coding

OpenAI began general availability of its GPT-5.6 model family, including the flagship "Sol," on July 9, 2026. The same day, a developer claimed that GPT-5.6-Sol ran fully autonomously for nearly a week and built a voxel-based 3D Manhattan in a single run, drawing attention.

July 9, 2026 · OpenAI

GPT-5.6 Goes GA — and "Sol" Reportedly Built a 3D Manhattan in One Run

OpenAI released its GPT-5.6 family — flagship Sol, balanced Terra, low-cost Luna. A developer claims Sol ran autonomously for nearly a week to "one-shot" a voxel city — but disclosed no prompt, logs, or cost.

~1 wk

claimed autonomous run to build the voxel Manhattan

models: Sol · Terra · Luna, via ChatGPT, Codex & API

92.2%

Sol on BrowseComp benchmark

Official Benchmarks · Sol vs Fable 5

Coding Agent Index — proportional heights

77.2

Fable 5

80.0

Sol +2.8

< ½ the output tokens < ½ the time ~⅓ the cost

Pricing per 1M tokens (input / output)

Sol · flagship

$5.00 / $30.00

Terra · balanced

$2.50 / $15.00

Luna · lowest cost

$1.00 / $6.00

Developers impressed

Voxel build praised for "insane precision"
Partners cite "focus for days," 25% fewer steps
35–48% fewer tool calls in agent workflows

Skeptics push back

No prompt, repo, logs, or cost disclosed
"A supplied demo, not an audited benchmark"
Reproducibility & reliability questioned

The open question going forward:

Sol's headline is autonomous execution over long horizons and cost efficiency — but until the demo's details are verified, its real-world reliability stays unproven.

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