Model comparison
GPT-5.5 Pro vs Kimi K2.5 (Reasoning)
Head-to-head evidence from 2 shared benchmark results across 2 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.5 Pro #38 (Estimated); Kimi K2.5 (Reasoning) #57 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.5 Pro and Kimi K2.5 (Reasoning) share 2 comparable benchmark results. 2 of 8 categories are comparable. 5 results are unique to GPT-5.5 Pro; 25 to Kimi K2.5 (Reasoning).
Updated July 22, 2026- Shared results
- 2
- GPT-5.5 Pro only
- 5
- Kimi K2.5 (Reasoning) only
- 25
- Comparable categories
- 2 / 8
Pick GPT-5.5 Pro if you want the stronger benchmark profile. Kimi K2.5 (Reasoning) only becomes the better choice if knowledge is the priority or you want the cheaper token bill.
Confidence note. This is a partial-evidence comparison with 2 shared benchmark results across 2 evidence categories; 2 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
GPT-5.5 Pro is clearly ahead on the BenchAlign aggregate, 63.69 to 59.35. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5 Pro's sharpest advantage is in agentic, where it averages 90.1 against 55. The single biggest benchmark swing on the page is BrowseComp, 90.1% to 60.6%. Kimi K2.5 (Reasoning) does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $0.60 input / $3.00 output per 1M tokens for Kimi K2.5 (Reasoning). That is roughly 60.0x on output cost alone. GPT-5.5 Pro gives you the larger context window at 1M, compared with 128K for Kimi K2.5 (Reasoning).
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.5 Pro | Δ | Kimi K2.5 (Reasoning) |
|---|---|---|---|
| Agentic | GPT-5.5 Pro90.1 | Margin← 35.1 | Kimi K2.5 (Reasoning)55.0 |
| Knowledge | GPT-5.5 Pro57.2 | Margin→ 30.0 | Kimi K2.5 (Reasoning)87.2 |
| Coding | GPT-5.5 ProNot measured | MarginNo overlap | Kimi K2.5 (Reasoning)76.8 |
| Math | GPT-5.5 Pro48.1 | MarginNo overlap | Kimi K2.5 (Reasoning)Not measured |
| Multimodal | GPT-5.5 ProNot measured | MarginNo overlap | Kimi K2.5 (Reasoning)78.5 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
BrowseComp
AgenticA 90.1%B 60.6%Winner: GPT-5.5 ProΔ 29.5BrowseComp: GPT-5.5 Pro scored 90.1%; Kimi K2.5 (Reasoning) scored 60.6%. GPT-5.5 Pro wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.5 Pro | Kimi K2.5 (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.5 Pro$30 input / $180 output | Kimi K2.5 (Reasoning)$0.6 input / $3 output | Kimi K2.5 (Reasoning) has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.5 ProNot available | Kimi K2.5 (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.5 ProNot available | Kimi K2.5 (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.5 Pro1M | Kimi K2.5 (Reasoning)128K | GPT-5.5 Pro lists the larger context window. |
Benchmark Deep Dive
AgenticGPT-5.5 Pro wins8 benchmarks
| Benchmark | GPT-5.5 Pro | Kimi K2.5 (Reasoning) | Result |
|---|---|---|---|
| BrowseCompSource | 90.1% | 60.6% | GPT-5.5 Pro leads |
| Terminal-Bench 2.0Source | — | 50.8% | Not comparable |
| APEX-Agents-AASource | — | 11.5% | Not comparable |
| τ²-bench resultsSource | — | 95.9% | Not comparable |
| Gert LabsSource | — | 32.58% | Not comparable |
| AA Agentic IndexSource | — | 21.7% | Not comparable |
| GDPval-AASource | — | 25.4% | Not comparable |
| GDPval-AASource | — | 1009 | Not comparable |
Coding4 benchmarks
Reasoning2 benchmarks
KnowledgeKimi K2.5 (Reasoning) wins10 benchmarks
| Benchmark | GPT-5.5 Pro | Kimi K2.5 (Reasoning) | Result |
|---|---|---|---|
| HLESource | 57.2% | — | Not comparable |
| HLE w/o toolsSource | 43.1% | — | Not comparable |
| GPQASource | — | 87.6% | Not comparable |
| MMLU-ProSource | — | 87.1% | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 35.4% | Not comparable |
| AA-GPQA DiamondSource | — | 87.9% | Not comparable |
| AA-HLESource | — | 29.4% | Not comparable |
| AA-Omniscience IndexSource | — | -8.1% | Not comparable |
| AA-Omniscience AccuracySource | — | 34.3% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 64.6% | Not comparable |
Math4 benchmarks
Multimodal3 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.5 Pro | Kimi K2.5 (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 70.2% | Not comparable |
Frequently Asked Questions (3)
Which is better, GPT-5.5 Pro or Kimi K2.5 (Reasoning)?
GPT-5.5 Pro is ahead on BenchLM's BenchAlign leaderboard, 63.69 to 59.35. The biggest single separator in this matchup is BrowseComp, where the scores are 90.1% and 60.6%.
Which is better for knowledge tasks, GPT-5.5 Pro or Kimi K2.5 (Reasoning)?
Kimi K2.5 (Reasoning) has the edge for knowledge tasks in this comparison, averaging 87.2 versus 57.2. GPT-5.5 Pro stays close enough that the answer can still flip depending on your workload.
Which is better for agentic tasks, GPT-5.5 Pro or Kimi K2.5 (Reasoning)?
GPT-5.5 Pro has the edge for agentic tasks in this comparison, averaging 90.1 versus 55. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
Related Comparisons
Explore More
Choose a model with this week’s evidence
Join 2,000+ readers for ranking moves, pricing changes, and the claims that still need proof.
One email each week. Unsubscribe anytime.