DeepSeek V4.1 Flash vs GPT 5.6 Luna
GPT 5.6 Luna faster in both pairings. DeepSeek V4.1 Flash has a slight quality edge in 1 of 2 pairings; none is a clear lead. 2 pairings; 24 merged changes in Stet-AI/stet. Compare the individual calls below to choose which setup to investigate.
What this comparison is
- 1 real repositoryStet-AI/stet, private; not public benchmark scores
- 24 merged changeseach run end to end by the coding agent from the repo as it was before the change
- Graded against the merged changeby the repo’s own tests and by judges comparing each patch with it
- Quality, cost and timea smaller sample than public benchmarks, but real agent work on a real codebase
Compare coding modelsLow vs high vs xhigh/max reasoning for coding agents
Recorded setup pairings
Each row is a separate recorded comparison. Scores are not pooled or averaged across effort settings. W/D/L means wins, draws and losses; undecided judgments remain undecided.
Stet score: A setup’s average chance of beating another setup on a task, from 0 to 100; 50 is even with the field.
| Setup pairing | Recorded quality call and record | Quality evidence | Cost per task | Agent time per task |
|---|---|---|---|---|
| DeepSeek V4.1 Flash max vs GPT 5.6 Luna maxDeepSeek V4.1 Flash max · max reasoningGPT 5.6 Luna max · max reasoning24/24 tasks observed by both setups. | No clear quality difference: DeepSeek V4.1 Flash max won 2, GPT 5.6 Luna max won 2, 19 tied, 1 undecided; DeepSeek V4.1 Flash max leads on cost: 1.8× cheaper; GPT 5.6 Luna max leads on agent time: 1.7× faster.Head to head, DeepSeek V4.1 Flash max won 2, tied 19 and lost 2 against GPT 5.6 Luna max, with 1 undecided. | No clear difference 2–2 head to head, 19 tiedDeepSeek V4.1 Flash max: 50.4 (95% range 46.7–54.8)GPT 5.6 Luna max: 49.7 (95% range 44.0–55.6) | DeepSeek V4.1 Flash max: $0.49 (from 23/24 tasks) GPT 5.6 Luna max: $0.90 | DeepSeek V4.1 Flash max: 49.3 min GPT 5.6 Luna max: 28.5 min |
| DeepSeek V4.1 Flash max vs GPT 5.6 Luna lowDeepSeek V4.1 Flash max · max reasoningGPT 5.6 Luna low · codex · low reasoning24/24 tasks observed by both setups. | DeepSeek V4.1 Flash max has a slight quality edge, 3–1 head to head with 19 tied and 1 undecided; GPT 5.6 Luna low leads on cost and agent time: 9.7× cheaper and 7.4× faster.Head to head, DeepSeek V4.1 Flash max won 3, tied 19 and lost 1 against GPT 5.6 Luna low, with 1 undecided. | Slight edge 3–1 head to head, 19 tiedDeepSeek V4.1 Flash max: 50.4 (95% range 46.7–54.8)GPT 5.6 Luna low: 44.6 (95% range 38.3–50.3) | DeepSeek V4.1 Flash max: $0.49 (from 23/24 tasks) GPT 5.6 Luna low: $0.05 | DeepSeek V4.1 Flash max: 49.3 min GPT 5.6 Luna low: 6.7 min |
Questions about these results
- Which is better for coding, DeepSeek V4.1 Flash or GPT 5.6 Luna?
- GPT 5.6 Luna faster in both pairings. DeepSeek V4.1 Flash has a slight quality edge in 1 of 2 pairings; none is a clear lead. 2 pairings; 24 merged changes in Stet-AI/stet. Compare the individual calls below to choose which setup to investigate.
- Where do these coding results come from?
- Both coding agents worked the same 24 merged changes from the private Stet-AI/stet repository, each in the real repo as it was before the change. The repo’s tests and judges graded every patch against the merged change; no public benchmark scores are used.
- Are reasoning settings combined into one model score?
- No. Each effort pairing keeps its own recorded quality call, head-to-head record, cost and agent time. Incompatible scores are never averaged.