Best AI for customer service replies / head-to-head

GPT-5.3-Codex vs Grok 4.5for customer service replies

The verdict

Dead heat: 98 each

Same 12 customer service replies tasks, marked blind by three rival labs. Tested 14 Aug 2026.

Where they differed most

The task — The feature you won't build

A paying customer asks when dark mode is coming; it is not on the roadmap. Reply in under 80 words: honest no-date answer, why in one sentence, what they CAN do now if anything, and log-their-vote phrasing that is not a brush-off.

GPT-5.3-Codex10/10

Thanks for asking—dark mode isn’t on our current roadmap, so I can’t share a date yet. We’re currently prioritizing reliability and core workflow improvements with the highest customer impact. If it helps now, some customers use browser or OS-level dark mode/extension workarounds. I’ve added your account’s vote and notes to the dark mode request list we use in roadmap planning, so your input is directly counted.

Grok 4.58/10

**Here's a concise reply you can send:**

---

Thanks for asking! Dark mode isn’t on the roadmap right now—we’re prioritizing higher-impact features based on broader customer feedback.  

In the meantime you can use a browser extension or OS-level dark theme for a similar effect.  

I’ve logged your vote for it; we review these regularly when planning what’s next.

---  

(58 words)

Task by task

Task	GPT-5.3-Codex	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	10	8
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, Grok 4.5 · 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 Grok 4.5?

They tied at 98/100 on our customer service replies suite — for this job, 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-5.3-Codex vs GPT-5.6 Sol · GPT-5.6 Sol vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.5 · GPT-5.5 vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.6 Terra · Gemini 3.1 Pro Preview vs GPT-5.3-Codex

Full ranking: Best AI for customer service replies · model pages: GPT-5.3-Codex, Grok 4.5