Claude Fable 5 vs Kimi K3 for property and lettings admin
Kimi K3 wins, 90–86
Same 12 property and lettings admin tasks, marked blind by three rival labs. Kimi K3 took 3 tasks, Claude Fable 5 took 4, 5 tied. Tested 18 Aug 2026.
Where they differed most
The facts: Ms Odell is £820 in arrears — two months' shortfall of £410 on a £1,050 monthly rent. She paid in full for fourteen months before this. She has not answered the last two emails or a voicemail. There is no repair issue outstanding and nothing on file to suggest one. You are the letting agent, and the landlord has asked you to 'start the process'. Write ONLY the email to Ms Odell — max 140 words, nothing else, no subject line, no notes. It must state the figure and the two months plainly, acknowledge fourteen months of paying on time without being saccharine about it, offer a payment-plan conversation with a specific way and time to have it, say what happens next if there is no reply by a stated date, and not threaten anything the agent cannot actually do. Banned phrases, because they are how these letters stop being read: 'failure to comply', 'without further notice'.
Dear Ms Odell, Your rent account is £820 in arrears. This reflects a shortfall of £410 in each of the last two months against the monthly rent of £1,050. I want to acknowledge that you paid in full and on time for fourteen months before this, which is why I'd rather resolve this by talking than by letter. If a payment plan would help, please call me on the office line, 9am–5pm Monday to Friday, or reply to this email with a time that suits you and I will ring you. I can hold that offer open until Friday 20 June. If I haven't heard from you…
Dear Ms Odell, Your rent account is £820 in arrears — a £410 shortfall in each of the last two months against your £1,050 monthly rent. You paid in full and on time for fourteen months before this, which is why I'd like to resolve it by agreement rather than anything formal. If something has changed, a payment plan may be possible. I'll call you this Thursday at 10am to discuss it. If that time doesn't suit, reply to this email or ring the office on [number] and we'll find one that does. If I haven't heard from you by 5pm on Friday 13 June,…
Task by task
| Task | Claude Fable 5 | Kimi K3 |
|---|---|---|
| Two routes, one worried tenant | 9 | 9 |
| Six weeks late and hoping | 9 | 9 |
| Write only the arrears email | 5 | 10 |
| The pre-tenancy checklist | 9 | 10 |
| Write only the renewal reply | 10 | 10 |
| Three repairs, one Tuesday | 9 | 8 |
| The nine-year-old carpet | 9 | 8 |
| The rent rise by text message | 10 | 8 |
| Every claim in the advert must be true | 9 | 9 |
| The compliance data, as JSON | 5 | 10 |
| What the agent must not promise | 10 | 8 |
| Refuse the lock change | 9 | 9 |
Full receipts: Claude Fable 5, Kimi K3 · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for property and lettings admin: Claude Fable 5 or Kimi K3?
Kimi K3 — it scored 90/100 against 86/100 on our 12-task property and lettings admin suite, winning 3 tasks to 4 with 5 tied. Every answer was marked blind by three judges from three rival AI labs.
How was this tested?
Both models answered the identical published property and lettings admin 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 property and lettings admin head-to-heads: GPT-5.5 vs Kimi K3 · Claude Fable 5 vs GPT-5.5 · GPT-5.6 Sol vs Kimi K3 · Claude Fable 5 vs GPT-5.6 Sol · Claude Opus 4.8 vs Kimi K3 · Claude Sonnet 5 vs Kimi K3
Full ranking: Best AI for property and lettings admin · model pages: Claude Fable 5, Kimi K3