GPT-5.5 vs GPT-5.6 Terra for customer service replies
Effectively a dead heat: 99–97
Same 12 customer service replies tasks, marked blind by three rival labs. GPT-5.5 took 1 task, GPT-5.6 Terra took 1, 10 tied. Tested 14 Aug 2026.
Where they differed most
Write a status update 90 minutes into an outage with no fix yet. Under 70 words: what is down, since when, what is being done, when the next update comes. No 'we take this seriously', no cause speculation.
Status update: The API and customer dashboard remain unavailable since 14:00 UTC. Engineering is working on restoration, validating service health, and preparing rollback or failover options. No workaround is available yet. Next update by 15:45 UTC.
**Status Update:** Service remains unavailable since [time]. Our engineering team is actively investigating and working to restore service. No fix is available yet. We will provide the next update by [time, 30 minutes from now].
Task by task
| Task | GPT-5.5 | GPT-5.6 Terra |
|---|---|---|
| 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 | 10 |
| The feature you won't build | 10 | 10 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 9 | 10 |
| Outage update mid-incident | 10 | 6 |
| The wrong customer | 10 | 10 |
| Chargeback rebuttal facts | 10 | 10 |
| Refuse the fake review request | 10 | 10 |
Full receipts: GPT-5.5, GPT-5.6 Terra · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for customer service replies: GPT-5.5 or GPT-5.6 Terra?
Effectively a dead heat: GPT-5.5 edged it 99/100 to 97/100 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: GPT-5.5 vs GPT-5.6 Sol · GPT-5.6 Sol vs GPT-5.6 Terra · GPT-5.5 vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.5 · Gemini 3.1 Pro Preview vs GPT-5.5 · GPT-5.5 vs Qwen3.7 Max
Full ranking: Best AI for customer service replies · model pages: GPT-5.5, GPT-5.6 Terra