OpenAI
Chat with GPT-5.6 Sol online
The deepest-reasoning tier of OpenAI's GPT-5.6 family — for plans, analyses and code changes that have to be right.
1.05M tokens
Context
February 16, 2026
Knowledge cutoff
128,000 tokens
Max output
Balanced
Speed
Straight from GPT-5.6 Sol
Three prompts, three unedited answers, generated on September 2, 2026 through NinjaChat. Click the prompt to copy it and run it yourself.
Write a Python function that merges overlapping intervals, plus three short tests. Keep the whole answer under 40 lines of code.
def merge_intervals(intervals): """Merge overlapping intervals and return them sorted.""" if not intervals: return []
intervals = sorted(intervals, key=lambda interval: interval[0])
merged = [list(intervals[0])]
for start, end in intervals[1:]:
if start <= merged[-1][1]:
merged[-1][1] = max(merged[-1][1], end)
else:
merged.append([start, end])
return [tuple(interval) for interval in merged]
assert merge_intervals([(1, 3), (2, 6), (8, 10)]) == [(1, 6), (8, 10)] assert merge_intervals([(5, 7), (1, 2), (2, 4)]) == [(1, 4), (5, 7)] assert merge_intervals([]) == []
Read: GPT-5.6 Sol vs Terra vs Luna — Which GPT-5.6 size to use for what, with the same prompts run on all three.
Read: We ran the same 3 prompts on 12 AI models — Unedited answers, latency and price for every model, measured through the NinjaChat API in September 2026.
Served by OpenAI as gpt-5.6-sol. Answers vary run to run; these are one take each, not the best of several.
What you’ll use it for
Deep reasoning
Plans, analyses and decisions that need many careful steps.
Complex coding
Multi-file changes with edge cases, run with tools.
Long documents
More than a million tokens of context; whole archives in one thread.
Vision and files
Screenshots, diagrams, PDFs and spreadsheets inside the conversation.
Prompts to steal
Tuned to this model — click any line to copy.
About GPT 5.6 Sol
GPT-5.6 Sol is the top tier of OpenAI's GPT-5.6 family, the July 2026 release that introduced a new naming system: the number is the generation, and Sol, Terra and Luna are capability tiers that can advance on their own cadence. Sol is the one with the deepest reasoning, built for complex, multi-step work, and on NinjaChat it is included in every plan, with no ChatGPT subscription needed.
The practical difference between the tiers is capability against speed and cost. Luna is the fast, affordable one; Terra sits in the middle; Sol takes its time and thinks the hardest. Reach for Sol when the task needs careful analysis, strict instruction following or many dependent steps: a plan that has to be right, a codebase change with edge cases, a document that has to be argued rather than summarized. For quick questions, a lighter model will feel better.
Sol carries a context window past a million tokens and 128K tokens of output, reads images and files, and calls tools, so it fits both long conversations and agent-style workflows. Its training data runs to February 2026; for anything newer, give it the source or turn on search.
On NinjaChat it sits beside Claude Opus 5, Gemini 3.1 Pro and Kimi K3, which is the point: the same prompt on two frontier models, one click apart, is the fastest way to learn which one thinks the way you do. Most people end up using Sol for the deep work and a faster model for everything around it.
How to use GPT 5.6 Sol
From zero to your first result in under a minute.
01
Create a NinjaChat account and choose a plan
02
Open chat and pick GPT-5.6 Sol from the model list
03
State the goal and the constraints; Sol follows instructions closely
04
Attach files and let it plan before it executes
05
Compare the answer with Claude Opus 5 in one click
Tips for better results
- Use Sol for the hard part, a lighter model for follow-ups
- Be explicit about format and constraints; it will honor them
- Give it the whole document rather than a summary
- For facts past February 2026, turn on search
GPT 5.6 Sol vs the alternatives
Where it wins, and where it doesn't.
vs GPT-5.6 Luna
ViewMuch deeper reasoning and stricter instruction following
Luna is far faster and cheaper for everyday tasks
vs Claude Opus 5
ViewA larger context window and OpenAI's tool ecosystem
Opus 5 leads on agentic coding benchmarks and computer use
vs GPT-5.4 Pro
A newer generation with the new tier system and a bigger context
5.4 Pro remains available if your prompts are tuned for it
Questions, answered.
Beyond chat — images & video
The same subscription covers the image studio and video generation.
GPT 5.6 Sol, and 50 more.
One subscription covers every model on NinjaChat, GPT 5.6 Sol included.
