Head-to-head comparison
Nex-N2.5-Mini (Nex AGI) and GPT-5.5 (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.
Snapshot as of 9 September 2026
As of 9 September 2026, GPT-5.5 holds the stronger ModelCap Index position (#9 vs #22); Nex-N2.5-Mini is cheaper per output token (Free/1M vs $30.00/1M); GPT-5.5 offers the longer context window (1M vs 262K tokens); and Nex-N2.5-Mini ships open weights.
Evidence: global-corpus-prior over 182 held-out anchors (7%); launch card against 7 resolved peers on 8 rows (93%); optimism haircut 0 from cross-lab-probe; shrunk 1.4 toward the measured corpus · 7 public benchmark observations across 7 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.
Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.
Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.
GPT-5.5 ranks higher on the ModelCap Index as of 9 September 2026: #9 against #22. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.
Nex-N2.5-Mini is cheaper on output tokens: Free/1M against $30.00/1M. Input tokens are Free/1M for Nex-N2.5-Mini and $5.00/1M for GPT-5.5. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $0 for Nex-N2.5-Mini versus $25.00 for GPT-5.5. Nex-N2.5-Mini costs 100.0% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.
GPT-5.5 has the larger context window: 1M tokens against 262K.
The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.
Nex-N2.5-Mini: Open weights. GPT-5.5: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.
ModelCap currently lists 1 API provider for Nex-N2.5-Mini and 3 for GPT-5.5, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.
Every figure comes from the sealed ModelCap dataset published 9 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.