The one we'd pick if we could only keep one — most capable AI assistant for long-form work and complex reasoning we've tested in 2026.
- 200k-token context — drops in entire codebases or 100-page PDFs without truncation.
- Cleanest refusal logic — declines what it should, attempts what it can, rarely hedges.
- £20/mo for Pro, generous free tier, API metered per token — fair across all three.