Quality knee
Where paying more on the frontier stops buying quality at a defensible rate. The rule is in data/knee.toml, not in a chart.
Definition source: docs/PRODUCT-SPEC.md. Left of the knee: commodity quality. Right: premium quality.
| From | To | $/pt | Δ Arena Elo |
|---|---|---|---|
| Llama 3.1 8B Instruct | gpt-oss-20b Check | 0.000 | +101.2 |
| gpt-oss-20b | Gemma 3 4B Check | 0.009 | +3.1 |
| Gemma 3 4B | gpt-oss-120b Check | 0.000 | +74.6 |
| gpt-oss-120b | DeepSeek V4 Flash 0423 Check | 0.001 | +66.7 |
| DeepSeek V4 Flash 0423 | Gemma 4 26B A4B Check | 0.008 | +1.8 |
| Gemma 4 26B A4B | MiMo-V2.6-Flash Check | 0.002 | +22.5 |
| MiMo-V2.6-Flash | DeepSeek V4.1 Flash Check | 0.001 | +6.1 |
| DeepSeek V4.1 Flash | GLM 5.3 Flash Check | 0.008 | +7.1 |
| GLM 5.3 Flash | MiMo-V2.6-Pro Check | 0.014 | +21.4 |
| MiMo-V2.6-Pro | Gemini 3.8 Flash Check | 0.410 | +6 |
| Gemini 3.8 Flash | Claude Opus 5.5 Check | 0.340 | +14.7 |
Read citation text and BibTeX
The first frontier step exceeding 10 times the running median cost per Arena Elo point is gpt-oss-20b to Gemma 3 4B: $0.008548/point against a $0.001090/point threshold. Standard-delivery Pareto frontier, LMArena human-preference Elo, balanced workload (75% input, 25% output), base context tier. This marginal-cost rule is not a task-success prediction. As of 2026-10-06. Lens: LMArena Elo (CC BY 4.0). https://undominated.ai/knee/ Method: https://undominated.ai/methodology/ Arena data: https://huggingface.co/datasets/lmarena-ai/leaderboard-dataset (CC BY 4.0). Derived calculations by Undominated.ai. Publication: sha256:ecef83f767cd4d2c21766f6a5b4dffa36c06351f23657542d473bc1a030c0932; calculation SHA-256: 5ae4d0bee9b70298dd437b05df87c32acb407040b50bf88240677f295f25955d; permitted inputs: https://undominated.ai/data/publications/manifests/ecef83f767cd4d2c21766f6a5b4dffa36c06351f23657542d473bc1a030c0932.json
@misc{undominated-knee-2026-10-06,
author = {{Undominated.ai}},
title = {knee evidence — Undominated.ai},
year = {2026},
url = {https://undominated.ai/knee/},
note = {as of 2026-10-06; LMArena Elo (CC BY 4.0)},
annote = {Publication: sha256:ecef83f767cd4d2c21766f6a5b4dffa36c06351f23657542d473bc1a030c0932; calculation SHA-256: 5ae4d0bee9b70298dd437b05df87c32acb407040b50bf88240677f295f25955d; permitted inputs: https://undominated.ai/data/publications/manifests/ecef83f767cd4d2c21766f6a5b4dffa36c06351f23657542d473bc1a030c0932.json}
}