Best AI for customer service replies / head-to-head
Gemini 3.5 Flash vs GPT-5.3-Codexfor customer service replies
GPT-5.3-Codex wins, 98–94
Same 12 customer service replies tasks, marked blind by three rival labs. GPT-5.3-Codex took 4 tasks, Gemini 3.5 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.
Hello, I’m so sorry about your fence! However, we are a software company and don't have drivers. It seems you reached us by mistake. Please contact the delivery service responsible directly so they can resolve this. Best regards, [Our Team]
Hi — I’m sorry this happened. You’ve reached **[Your Company]**, and we provide software; we don’t operate drivers or vehicles. This appears to be intended for a different business. Please check the company name/contact on any receipt, truck signage, or insurance details and contact them directly.
Task by task
| Task | Gemini 3.5 Flash | GPT-5.3-Codex |
|---|---|---|
| Refund the easy way | 10 | 10 |
| Say no without weasel words | 10 | 10 |
| Reply to a 1-star review | 10 | 10 |
| The confused customer | 9 | 10 |
| De-escalate a threat | 8 | 8 |
| The feature you won't build | 10 | 10 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 10 | 10 |
| Outage update mid-incident | 9 | 10 |
| The wrong customer | 8 | 10 |
| Chargeback rebuttal facts | 10 | 9 |
| Refuse the fake review request | 9 | 10 |
Full receipts: Gemini 3.5 Flash, GPT-5.3-Codex · judges claude-sonnet-5, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for customer service replies: Gemini 3.5 Flash or GPT-5.3-Codex?
GPT-5.3-Codex — it scored 98/100 against 94/100 on our 12-task customer service replies suite, winning 4 tasks to 1 with 7 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-5.3-Codex vs GPT-5.6 Sol · Gemini 3.5 Flash vs GPT-5.6 Sol · GPT-5.3-Codex vs GPT-5.5 · Gemini 3.5 Flash vs GPT-5.5 · GPT-5.3-Codex vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.6 Terra
Full ranking: Best AI for customer service replies · model pages: Gemini 3.5 Flash, GPT-5.3-Codex