Question 1

Who Should Switch to Sonnet 4.6 Right Now?

Accepted Answer

I'm going to be direct about this, because "it depends" is a useless answer. Switch immediately if you're paying for Opus as your default model for coding, writing, or general-purpose tasks. The quality gap is 1.2 SWE-bench points. That's not worth 5x the price for everyday work. Switch and test if you're using Opus 4.5 or older Sonnet versions. Both are clearly outperformed by Sonnet 4.6 on modern benchmarks, and you're either overpaying (Opus 4.5) or underperforming (older Sonnet). Keep Opus if your work is specifically in the hardest reasoning tier: FrontierMath problems, complex multi-agent coordination where reasoning depth matters, or tasks routinely needing 128K+ token outputs. Opus genuinely earns its price in these cases. Consider GPT-5.2 if your primary use case is math, science, or research-heavy reasoning. GPT-5.2's $1.75/$14 pricing is genuinely attractive, and it leads on those specific benchmarks. Multi-model is the smart play in February 2026. Check our model comparison for the full breakdown.

Question 2

How does Sonnet 4.6 compare to GPT-5.2 and GPT-5.3 Codex for coding tasks?

Accepted Answer

Sonnet 4.6 scores 79.6% on SWE-bench Verified. GPT-5.2 scores 80.0%. GPT-5.3 Codex scores roughly 80% on SWE-bench but leads on Terminal-Bench at 77.3%. In blind user preference tests, Sonnet 4.6 was preferred over GPT-5.2 specifically for coding tasks. On pricing: Sonnet is $3/$15 per MTok vs GPT-5.2's $1.75/$14 and Codex's $6/$30. GPT-5.2 is cheaper on input tokens but Sonnet wins on coding quality per dollar for most developer workflows. See our full model comparison.

Question 3

Is GPT-4o still relevant in February 2026?

Accepted Answer

No. OpenAI retired GPT-4o from ChatGPT on February 13, 2026. API access still works but the model is no longer recommended for any new use case. GPT-4o's successors are GPT-5.2 ($1.75/$14 per MTok, general purpose) and GPT-5.3 Codex ($6/$30 per MTok, code-specialized research preview). If you're still building on GPT-4o, migrate to GPT-5.2 or consider Claude Sonnet 4.6 ($3/$15 per MTok), which scores higher on SWE-bench coding benchmarks.

Question 4

How do I migrate from budget_tokens to Adaptive Thinking?

Accepted Answer

Replace thinking: {type: "enabled", budget_tokens: N} with thinking: {type: "adaptive"}. Add effort: "medium" for Sonnet 4.6 or "high"/"max" for Opus 4.6 if you need more reasoning depth. The interleaved-thinking-2025-05-14 beta header is no longer needed either. Note: budget_tokens still works on older models (Sonnet 4.5 and below) but is deprecated on all 4.6 models.

Question 5

What is the Sonnet 4.6 context window limit?

Accepted Answer

Standard is 200K tokens (input context). A 1M token context window is available in beta. Output is capped at 64K tokens. If your task regularly needs 128K+ token outputs (for example: generating an entire codebase in one pass), that's a genuine reason to use Opus 4.6 instead. For most coding and writing tasks, 64K output is more than enough.

Question 6

Should I use Sonnet 4.6 or Opus 4.6 for Claude Code?

Accepted Answer

Sonnet 4.6 is the default model in Claude Code 2.1, and for most workflows it's the right choice. Claude Code's Agent Teams, Skills, and Hooks all work with Sonnet. The main reasons to switch to Opus within Claude Code: you're hitting the 64K output limit on large generation tasks, or you're working on genuinely hard architecture problems where reasoning depth matters. Start with Sonnet. Switch to Opus only when you feel the ceiling. See our Claude Code 2.1 review for the full setup guide.