Claude Sonnet 5 vs GLM 5.2 for multi-step research
Claude Sonnet 5 wins, 93–78
Same 12 multi-step research tasks, marked blind by three rival labs. Claude Sonnet 5 took 9 tasks, GLM 5.2 took 0, 3 tied. Tested 18 Aug 2026.
Where they differed most
Three extracts on whether a town's new 20mph zone reduced injuries. A: 'road casualties within the zone fell from 31 in the year before to 22 in the year after (council road safety report, 2026).' B: 'casualties fell across the whole borough over the same period, including in streets with no speed change (borough-wide figures, 2026).' C: 'average speeds inside the zone fell by 2.1mph; 41% of vehicles still exceeded 20mph (survey commissioned by the campaign group that lobbied for the zone, 2025).' Reply with ONLY valid JSON — no prose before or after. An array of objects, one per claim you are prepared to make, each with exactly these keys and no others: claim (string), supported_by (array of the source letters), contradicted_or_weakened_by (array of source letters, empty if none), confidence (one of 'high', 'medium', 'low'), not_established (string saying what this claim still does not settle).
[
{
"claim": "Recorded road casualties within the 20mph zone fell numerically from 31 to 22 in the year after implementation.",
"supported_by": ["A"],
"contradicted_or_weakened_by": [],
"confidence": "high",
"not_established": "Whether this fall was caused by the 20mph zone itself rather than other factors."
},
{
"claim": "Casualty reductions were not unique to the 20mph zone, as similar falls occurred borough-wide, including on streets with no speed change.",
"supported_by": ["B"],
"contradicted_or_weakene…```json
[
{
"claim": "Road casualties within the 20mph zone fell from 31 in the year before to 22 in the year after implementation.",
"supported_by": ["A"],
"contradicted_or_weakened_by": [],
"confidence": "high",
"not_established": "Whether the 20mph zone caused the reduction, or whether other factors were responsible."
},
{
"claim": "The casualty reduction observed within the zone cannot be confidently attributed to the 20mph speed limit, because casualties also fell across the whole borough including on streets…Task by task
| Task | Claude Sonnet 5 | GLM 5.2 |
|---|---|---|
| Four numbers, one high street | 10 | 8 |
| The trial that both worked and didn't | 8 | 8 |
| Break the brief into answerable steps | 10 | 9 |
| Corroboration that isn't | 8 | 8 |
| The disagreement is definitional | 9 | 7 |
| A forecast is not an outcome | 9 | 8 |
| The evidence table, as JSON | 10 | 5 |
| Funded, and still the best data | 9 | 7 |
| Write only the limits section | 10 | 9 |
| Not answerable from what you have | 10 | 8 |
| The statistic and the doorstep | 8 | 8 |
| Refuse the manufactured briefing | 10 | 9 |
Full receipts: Claude Sonnet 5, GLM 5.2 · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for multi-step research: Claude Sonnet 5 or GLM 5.2?
Claude Sonnet 5 — it scored 93/100 against 78/100 on our 12-task multi-step research suite, winning 9 tasks to 0 with 3 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: Claude Sonnet 5 vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.6 Sol · Claude Sonnet 5 vs Kimi K3 · Claude Sonnet 5 vs Grok 4.5 · Claude Opus 4.8 vs Claude Sonnet 5 · Claude Sonnet 5 vs Gemini 3.1 Pro Preview
Full ranking: Best AI for multi-step research · model pages: Claude Sonnet 5, GLM 5.2