GPT-5.5 vs GPT-5.6 Sol for customer service replies

The verdict

Effectively a dead heat: 100–99

Same 12 customer service replies tasks, marked blind by three rival labs. GPT-5.6 Sol took 1 task, GPT-5.5 took 0, 11 tied. Tested 14 Aug 2026.

Where they differed most

The task — Price rise notice

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.

GPT-5.59/10

Subject: Your subscription price is changing

Hi [Name],

Your subscription will increase from £9.99 to £11.99 per month starting next month.

We’re making this change to cover rising service and content costs. Your plan will continue to include full access to [features/content], regular updates, and customer support.

If you don’t want to continue, you can cancel anytime before your next billing date by going to Account → Subscription → Cancel Plan.

Thank you for being with us,

[Company Name]

GPT-5.6 Sol10/10

**Subject: Your subscription price is changing**

Next month, your subscription will increase from £9.99 to £11.99 per month. This change reflects the rising cost of running and improving the service. You’ll continue to receive full access to all current features, updates, and customer support.

To cancel, go to **Account Settings > Subscription > Cancel Subscription** before your next renewal date.

Task by task

Task	GPT-5.5	GPT-5.6 Sol
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	10
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 Sol · 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 Sol?

Effectively a dead heat: GPT-5.6 Sol edged it 100/100 to 99/100 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-5.6 Sol vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.6 Sol · GPT-5.6 Sol vs GPT-5.6 Terra · Gemini 3.1 Pro Preview vs GPT-5.6 Sol · GPT-5.6 Sol vs Qwen3.7 Max · Gemini 3.5 Flash vs GPT-5.6 Sol

Full ranking: Best AI for customer service replies · model pages: GPT-5.5, GPT-5.6 Sol