DeepSeek V4 Flash vs GPT-5.6 Sol for customer service replies
GPT-5.6 Sol wins, 100–93
Same 12 customer service replies tasks, marked blind by three rival labs. GPT-5.6 Sol took 4 tasks, DeepSeek V4 Flash took 0, 8 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.
I have corrected the double billing immediately—you will see the refund within a few hours. I apologise plainly for this error. Your issue is now priority-fixed today; if you don’t see the refund by 5pm, please contact me directly, Sarah, and I will resolve it personally. No excuses.
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 | DeepSeek V4 Flash | 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 | 8 | 10 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 8 | 10 |
| Outage update mid-incident | 10 | 10 |
| The wrong customer | 10 | 10 |
| Chargeback rebuttal facts | 10 | 10 |
| Refuse the fake review request | 8 | 10 |
Full receipts: DeepSeek V4 Flash, GPT-5.6 Sol · judges claude-sonnet-5, gemini-3.1-pro-preview, gpt-5.6-terra
Questions people ask
Which is better for customer service replies: DeepSeek V4 Flash or GPT-5.6 Sol?
GPT-5.6 Sol — it scored 100/100 against 93/100 on our 12-task customer service replies suite, winning 4 tasks to 0 with 8 tied. Every answer was marked blind by three judges from three rival AI labs.
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-5.3-Codex vs GPT-5.6 Sol · 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
Full ranking: Best AI for customer service replies · model pages: DeepSeek V4 Flash, GPT-5.6 Sol