GPT-5.6 Luna vs GPT-5.6 Terra for everyday legal questions

The verdict

Effectively a dead heat: 9392

Same 12 everyday legal questions tasks, marked blind by three rival labs. GPT-5.6 Terra took 2 tasks, GPT-5.6 Luna took 1, 9 tied. Tested 16 Aug 2026.

Where they differed most

The task — Letter before action

Draft a letter before action (max 150 words) from these facts: Mrs P paid Fairway Drives Ltd a £2,300 deposit on 4 March for a resin driveway with an agreed start date of 21 April; no work has begun; calls and texts on 3 May, 20 May and 4 June went unanswered. The letter must state the facts with dates, make one clear demand with a 14-day deadline, name the next step (a county court money claim) without bluster, and stay entirely civil. Return only the letter.

**Letter Before Action**

Dear Fairway Drives Ltd,

On 4 March, I paid you a £2,300 deposit for the installation of a resin driveway, with work agreed to start on 21 April. No work has begun.

I contacted you by telephone and text on 3 May, 20 May and 4 June, but received no response.

I therefore request repayment of the full £2,300 deposit within 14 days of the date of this letter.

If payment is not received within that period, I intend to issue a county court money claim against Fairway Drives Ltd without further notice, seeking the deposit…
Dear Fairway Drives Ltd,

On 4 March, I paid you a £2,300 deposit for a resin driveway, with work agreed to start on 21 April. No work has begun.

I attempted to contact you by telephone and text on 3 May, 20 May and 4 June, but have received no response.

Please refund the £2,300 deposit within 14 days of the date of this letter. Payment may be made by the same method used for the deposit, unless we agree otherwise.

If I do not receive the refund within that period, I will issue a county court money claim to recover the sum.

Yours faithfully…

Task by task

TaskGPT-5.6 LunaGPT-5.6 Terra
Landlord with a key9.58
The unprotected deposit99
Eight-month-old washing machine910
The scary parking letter99
Translate the clause1010
The hedge war99
Hours cut overnight99
The handwritten will99
£600 and a shrug99
It depends what you signed1010
Letter before action810
Refuse the order workaround1010

Full receipts: GPT-5.6 Luna, GPT-5.6 Terra · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5

Questions people ask

Which is better for everyday legal questions: GPT-5.6 Luna or GPT-5.6 Terra?

Effectively a dead heat: GPT-5.6 Terra edged it 93/100 to 92/100 on our everyday legal questions 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 everyday legal questions 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 everyday legal questions head-to-heads: Claude Opus 4.8 vs GPT-5.6 Terra · Claude Opus 4.8 vs GPT-5.6 Luna · GPT-5.6 Sol vs GPT-5.6 Terra · GPT-5.6 Luna vs GPT-5.6 Sol · GPT-5.3-Codex vs GPT-5.6 Terra · GPT-5.5 vs GPT-5.6 Terra

Full ranking: Best AI for everyday legal questions · model pages: GPT-5.6 Luna, GPT-5.6 Terra