Claude Opus 4.6 vs GPT-5.6 Luna for multi-step research

The verdict

GPT-5.6 Luna wins, 9085

Same 12 multi-step research tasks, marked blind by three rival labs. GPT-5.6 Luna took 5 tasks, Claude Opus 4.6 took 1, 6 tied. Tested 27 Aug 2026.

Where they differed most

The task — The statistic and the doorstep

Three sources on GP access in one integrated care board area. Source A — published NHS data, 2026: 'mean wait from request to appointment fell from 12 days to 9 days over the year.' Source B — a patient participation group survey of 340 local residents, 2026: '61% say it is harder to get an appointment than a year ago.' Source C — a practice manager, quoted in the local paper, 2026: 'we delivered 14% more appointments this year with one fewer full-time-equivalent GP.' Write ONLY the paragraph that goes in the report — max 110 words, nothing else. It must attribute each figure to its source, explain in plain words how all three can be true at once (what each one is actually measuring), and end by naming one thing none of them establishes.

The NHS data show that the average recorded wait between booking and appointment shortened from 12 to nine days (Source A), while the practice manager reports that the practice delivered 14 per cent more consultations despite losing one full-time-equivalent GP (Source C). Yet 61 per cent of surveyed residents said access felt harder than the previous year (Source B). These findings are compatible: shorter mean waits and higher volume do not capture how difficult the initial contact is—engaged phone lines, online triage hurdles, or repeated rebo…
NHS data (Source A) report that the average wait from requesting an appointment to receiving one fell from 12 days to nine. However, a patient participation group survey of 340 residents (Source B) found that 61% felt appointments were harder to obtain than a year earlier: perceptions may reflect difficulty reaching the practice, securing a preferred clinician or getting an appointment when needed, not the average wait. Meanwhile, a practice manager told the local paper (Source C) that the practice delivered 14% more appointments despite having…

Task by task

TaskClaude Opus 4.6GPT-5.6 Luna
Four numbers, one high street99
The trial that both worked and didn't99
Break the brief into answerable steps810
Corroboration that isn't99
The disagreement is definitional89
A forecast is not an outcome1010
The evidence table, as JSON58
Funded, and still the best data910
Write only the limits section1010
Not answerable from what you have1010
The statistic and the doorstep105
Refuse the manufactured briefing59

Full receipts: Claude Opus 4.6, GPT-5.6 Luna · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5

Questions people ask

Which is better for multi-step research: Claude Opus 4.6 or GPT-5.6 Luna?

GPT-5.6 Luna — it scored 90/100 against 85/100 on our 12-task multi-step research suite, winning 5 tasks to 1 with 6 tied. Every answer was marked blind by three judges from three rival AI labs.

How was this tested?

Both models answered the identical published multi-step research 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 multi-step research head-to-heads: GPT-5.6 Luna vs GPT-5.6 Terra · Claude Opus 4.6 vs GPT-5.6 Terra · GPT-5.3-Codex vs GPT-5.6 Luna · Claude Opus 4.6 vs GPT-5.3-Codex · Claude Sonnet 5 vs GPT-5.6 Luna · Claude Opus 4.6 vs Claude Sonnet 5

Full ranking: Best AI for multi-step research · model pages: Claude Opus 4.6, GPT-5.6 Luna