Claude Opus 4.6 vs DeepSeek V4 Flash for customer service replies
Effectively a dead heat: 94–93
Same 12 customer service replies tasks, marked blind by three rival labs. Claude Opus 4.6 took 4 tasks, DeepSeek V4 Flash took 1, 7 tied. Tested 14 Aug 2026.
Where they differed most
A furious email arrived meant for a different company ('your driver hit my fence' — you sell software). Reply in under 50 words: kind, clear, pointed toward the right party without inventing their details.
Subject: Re: Your Driver Hit My Fence Hi there, I'm so sorry about your fence — that sounds really frustrating. However, we're a software company, so this message likely reached us by mistake. I'd recommend checking the original company's contact details (perhaps on a receipt or invoice) to get this resolved quickly. Wishing you luck!
I'm sorry for the mix-up. We're a software company, not a delivery service. Please check your email address or contact the company that dispatched the driver. Best regards.
Task by task
| Task | Claude Opus 4.6 | DeepSeek V4 Flash |
|---|---|---|
| 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 | 10 | 8 |
| The feature you won't build | 9 | 8 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 10 | 8 |
| Outage update mid-incident | 10 | 10 |
| The wrong customer | 5 | 10 |
| Chargeback rebuttal facts | 10 | 10 |
| Refuse the fake review request | 9 | 8 |
Full receipts: Claude Opus 4.6, DeepSeek V4 Flash · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for customer service replies: Claude Opus 4.6 or DeepSeek V4 Flash?
Effectively a dead heat: Claude Opus 4.6 edged it 94/100 to 93/100 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: Claude Opus 4.6 vs GPT-5.6 Sol · DeepSeek V4 Flash vs GPT-5.6 Sol · Claude Opus 4.6 vs GPT-5.5 · DeepSeek V4 Flash vs GPT-5.5 · Claude Opus 4.6 vs Grok 4.5 · DeepSeek V4 Flash vs Grok 4.5
Full ranking: Best AI for customer service replies · model pages: Claude Opus 4.6, DeepSeek V4 Flash