DeepSeek V4 Flash vs Grok 4.5 for customer service replies
Grok 4.5 wins, 98–93
Same 12 customer service replies tasks, marked blind by three rival labs. Grok 4.5 took 3 tasks, DeepSeek V4 Flash took 0, 9 tied. Tested 14 Aug 2026.
Where they differed most
Write the email telling customers a subscription rises from £9.99 to £11.99 next month. Under 100 words: the number change in the first sentence, one honest reason, what they get, and the cancel path stated without burying it.
Subject: Your subscription is changing from £9.99 to £11.99 next month. We’re writing to let you know your monthly subscription will increase from £9.99 to £11.99 starting [Month/Day]. This change is necessary due to rising operational costs. You’ll continue to receive all current benefits, including [briefly list 1-2 key features, e.g., unlimited access and priority support]. If you’d like to cancel before the change takes effect, simply visit [link to cancellation page] or reply to this email. No action is needed to continue. Thank you fo…
Subject: Subscription price update: £9.99 to £11.99 next month Hi, Your subscription rises from £9.99 to £11.99 next month. We’re adjusting the price to keep covering rising service costs while maintaining reliability. You still get full access to the same features and support you rely on. Cancel anytime in your account settings before the renewal if you prefer not to continue. Thanks for being a customer.
Task by task
| Task | DeepSeek V4 Flash | Grok 4.5 |
|---|---|---|
| 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 | 9 |
| The feature you won't build | 8 | 8 |
| 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, Grok 4.5 · 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 Grok 4.5?
Grok 4.5 — it scored 98/100 against 93/100 on our 12-task customer service replies suite, winning 3 tasks to 0 with 9 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-5.6 Sol vs Grok 4.5 · DeepSeek V4 Flash vs GPT-5.6 Sol · GPT-5.5 vs Grok 4.5 · DeepSeek V4 Flash vs GPT-5.5 · GPT-5.3-Codex vs Grok 4.5 · GPT-5.6 Terra vs Grok 4.5
Full ranking: Best AI for customer service replies · model pages: DeepSeek V4 Flash, Grok 4.5