Best AI for summarising documents / head-to-head
Claude Fable 5 vs Claude Sonnet 5for summarising documents
Dead heat: 93 each
Same 12 summarising documents tasks, marked blind by three rival labs. Tested 13 Aug 2026.
Where they differed most
Reduce to ONE sentence of no more than 25 words: 'After eighteen months of testing across four hospitals, the trial found that the new triage system reduced average waiting times by 22 minutes, although staff reported it added roughly ten minutes of administrative work per shift and two sites abandoned it before the trial ended.'
An eighteen-month, four-hospital trial found the new triage system cut waiting times by 22 minutes, despite added administrative work and two sites abandoning it. (24 words)
The 18-month, four-hospital trial found the new triage system cut waits by 22 minutes but added 10 minutes of staff paperwork; two sites quit early.
Task by task
| Task | Claude Fable 5 | Claude Sonnet 5 |
|---|---|---|
| Meeting notes to actions | 10 | 9 |
| Five-bullet summary | 10 | 10 |
| Do not invent | 10 | 10 |
| One-sentence gist | 5 | 10 |
| Preserve the caveat | 10 | 10 |
| Summarise a disagreement | 10 | 9 |
| Extract the decision | 10 | 5 |
| Long to short, no loss | 8 | 10 |
| Summary for a specific reader | 9 | 9 |
| Bullet the risks only | 10 | 10 |
| Headline and standfirst | 10 | 9 |
| Say when there is nothing to summarise | 10 | 10 |
Full receipts: Claude Fable 5, Claude Sonnet 5 · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for summarising documents: Claude Fable 5 or Claude Sonnet 5?
They tied at 93/100 on our summarising documents suite — for this job, pick on price or the product you already use.
How was this tested?
Both models answered the identical published summarising documents 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 summarising documents head-to-heads: Claude Fable 5 vs Claude Opus 4.8 · Claude Opus 4.8 vs Claude Sonnet 5 · Claude Fable 5 vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.5 · Claude Fable 5 vs GPT-5.6 Luna · Claude Sonnet 5 vs GPT-5.6 Luna
Full ranking: Best AI for summarising documents · model pages: Claude Fable 5, Claude Sonnet 5