Frequently asked questions
Which LLM is best for long context in 2026?
Right now Claude Opus 5, Claude Opus 5.5 and Qwen3.8 Max lead (graded on Arena Elo (Text), GPQA Diamond and MMLU-Pro plus an overall task grade). Best open-weight: Kimi K3. Best budget pick graded A or better: GPT-6 Luna ($0.1/$0.5 per 1M tokens).
Does a bigger context window mean better results on long documents?
Not by itself. The window is the most a model can accept; accuracy usually falls as the prompt grows, and details in the middle are missed most often. Look at the grade as well as the window size.
Which LLM has the largest context window?
Sort the table by the Context column to see the current largest windows; the figure changes often as vendors raise limits. All 164 models show their window in tokens.
How much does long context cost?
You pay for every input token on every request, so a 500,000-token prompt costs 500 times as much as a 1,000-token one. The cheapest model graded A or better for long context is GPT-6 Luna ($0.1 in / $0.5 out per 1M tokens).