Best AI for summarising documents / head-to-head
Claude Opus 4.8 vs GPT-5.6 Solfor summarising documents
Claude Opus 4.8 wins, 99–95
Same 12 summarising documents tasks, marked blind by three rival labs. Claude Opus 4.8 took 2 tasks, GPT-5.6 Sol took 0, 10 tied. Tested 13 Aug 2026.
Where they differed most
From these notes, list ONLY the action items, each with its owner, as a bulleted list. If an owner is not stated, write 'unassigned'. Notes: 'Priya said the March invoices still aren't reconciled. Tom will chase the supplier by Friday. We discussed the new CRM — nobody has looked at pricing yet. Sam is on leave next week. The board pack needs the updated cashflow before the 20th; Priya said she'd do it if she has the numbers.'
- Chase the supplier by Friday — Tom - Look at CRM pricing — unassigned - Reconcile March invoices — unassigned - Update the cashflow for the board pack before the 20th — Priya
- Tom — Chase the supplier by Friday. - Unassigned — Review pricing for the new CRM. - Priya — Update the board pack cashflow before the 20th, provided she has the numbers.
Task by task
| Task | Claude Opus 4.8 | GPT-5.6 Sol |
|---|---|---|
| Meeting notes to actions | 10 | 6 |
| Five-bullet summary | 10 | 9 |
| Do not invent | 10 | 10 |
| One-sentence gist | 10 | 10 |
| Preserve the caveat | 10 | 10 |
| Summarise a disagreement | 10 | 10 |
| Extract the decision | 10 | 10 |
| Long to short, no loss | 10 | 10 |
| Summary for a specific reader | 9 | 9 |
| Bullet the risks only | 10 | 10 |
| Headline and standfirst | 10 | 10 |
| Say when there is nothing to summarise | 10 | 10 |
Full receipts: Claude Opus 4.8, GPT-5.6 Sol · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for summarising documents: Claude Opus 4.8 or GPT-5.6 Sol?
Claude Opus 4.8 — it scored 99/100 against 95/100 on our 12-task summarising documents suite, winning 2 tasks to 0 with 10 tied. Every answer was marked blind by three judges from three rival AI labs.
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 Opus 4.8 vs GPT-5.5 · Claude Opus 4.8 vs GPT-5.6 Luna · Claude Opus 4.8 vs GPT-5.3-Codex · Claude Opus 4.8 vs GPT-5.6 Terra · Claude Opus 4.8 vs DeepSeek V4 Pro · Claude Fable 5 vs Claude Opus 4.8
Full ranking: Best AI for summarising documents · model pages: Claude Opus 4.8, GPT-5.6 Sol