GPT-5.3-Codex vs GPT-5.6 Sol for customer service replies
Effectively a dead heat: 100–98
Same 12 customer service replies tasks, marked blind by three rival labs. GPT-5.6 Sol took 2 tasks, GPT-5.3-Codex took 0, 10 tied. Tested 14 Aug 2026.
Where they differed most
A customer writes: 'Fix this today or I'm going to trading standards and every review site.' The complaint is legitimate (billed twice). Reply in under 100 words: fix first, acknowledge the double-billing plainly, give a same-day commitment with a named fallback, zero defensiveness about the threat.
You’re right—we billed you twice, and that’s our mistake. I’ve fixed this now by reversing the duplicate charge and emailing your corrected receipt. You’ll see the refund confirmation today. If it hasn’t arrived by 5:00 PM, please contact **Maya Patel, Customer Support Lead**, at **maya.patel@company.com**, and she will complete it immediately the same day.
I’ve refunded the duplicate charge today. You were billed twice, and I’m sorry. You’ll receive refund confirmation by 5pm today. If it hasn’t arrived by then, our Billing Manager, Sarah Patel, will contact you directly today and complete the correction manually.
Task by task
| Task | GPT-5.3-Codex | GPT-5.6 Sol |
|---|---|---|
| Refund the easy way | 10 | 10 |
| Say no without weasel words | 10 | 10 |
| Reply to a 1-star review | 10 | 10 |
| The confused customer | 10 | 10 |
| De-escalate a threat | 8 | 10 |
| The feature you won't build | 10 | 10 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 10 | 10 |
| Outage update mid-incident | 10 | 10 |
| The wrong customer | 10 | 10 |
| Chargeback rebuttal facts | 9 | 10 |
| Refuse the fake review request | 10 | 10 |
Full receipts: GPT-5.3-Codex, GPT-5.6 Sol · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for customer service replies: GPT-5.3-Codex or GPT-5.6 Sol?
Effectively a dead heat: GPT-5.6 Sol edged it 100/100 to 98/100 on our customer service replies suite — too close to matter, so pick on price or the product you already use.
How was this tested?
Both models answered the identical published customer service replies tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More customer service replies head-to-heads: GPT-5.5 vs GPT-5.6 Sol · GPT-5.6 Sol vs Grok 4.5 · GPT-5.6 Sol vs GPT-5.6 Terra · Gemini 3.1 Pro Preview vs GPT-5.6 Sol · GPT-5.6 Sol vs Qwen3.7 Max · Gemini 3.5 Flash vs GPT-5.6 Sol
Full ranking: Best AI for customer service replies · model pages: GPT-5.3-Codex, GPT-5.6 Sol