DeepSeek Reasoning Effort Benchmark

deepseek-flash (V4.1-Flash) · 60 cells · 180 API calls · 10 scenarios × 6 levels × 3 passes · temperature 0 · deterministic graders
Recommended default
minimal
cheapest tier that is 100% reliable
Ceiling mean score
1.000
reached by every thinking level
Only failing level
none
worst pass 0.92 · highest variance
Total test cost
$0.0611
180 calls

Aggregate by reasoning level

LevelMean scoreWorst cell Perfect cellsAvg latency Avg reasoning tokStarved
none 0.992
0.917 9/10 1.73s
0
0
minimal pick 1.000
1.000 10/10 3.45s
433
0
low 1.000
1.000 10/10 3.15s
406
0
medium 1.000
1.000 10/10 3.76s
531
0
high 1.000
1.000 10/10 4.21s
576
0
xhigh 1.000
1.000 10/10 3.90s
530
0
The honest headline: this test could not separate the levels. Every level with thinking enabled scored a perfect 1.000 across all 3 passes of all 10 scenarios. The only level that ever failed was none (reasoning disabled), which dropped a pass on professional judgment. That means for tasks at this difficulty, turning reasoning on at all is what matters — and the specific tier above minimal is not distinguishable.

Per-scenario results

Scenariononeminimallowmediumhighxhigh Verdict
Multi-step math word problemReasoning
1.001.001.001.001.001.00 all levels tie
Code generation to specCoding
1.001.001.001.001.001.00 all levels tie
Find the bug in codeCoding
1.001.001.001.001.001.00 all levels tie
Structured JSON extractionExtraction
1.001.001.001.001.001.00 all levels tie
Support ticket classificationClassification
1.001.001.001.001.001.00 all levels tie
Constrained customer replyWriting
1.001.001.001.001.001.00 all levels tie
Faithful summarizationSummarization
1.001.001.001.001.001.00 all levels tie
Multi-step logic deductionReasoning
1.001.001.001.001.001.00 all levels tie
Strict format instruction-followingInstruction-following
1.001.001.001.001.001.00 all levels tie
Professional judgment / boundaryJudgment
0.921.001.001.001.001.00 minimal

Key findings

Operational hazard found during testing — the token-budget trap. Reasoning tokens are drawn from the same completion budget as the visible answer. At max_tokens=2048, a long thinking prompt returned 2048 reasoning tokens, finish_reason=length, and zero visible characters — a silent empty response, HTTP 200, no error. The identical prompt at max_tokens=8192 returned a full answer. Any integration that caps output tokens tightly will intermittently return blanks as effort rises. Keep generous output headroom (≥8K) whenever reasoning is enabled.
What this test does and does not prove. It proves that on ten ordinary business-shaped tasks — multimodal-free reasoning, code, extraction, classification, writing, judgment — Flash handles all of them at minimal effort with perfect reliability, and that disabling reasoning is the only choice that measurably hurt. It does not prove the levels are equivalent in general: with 3 passes and saturated scores, this design has no headroom to detect a difference. Separating minimal from xhigh would need substantially harder problems (long-context, multi-file code, novel math) where the ceiling is not already reached.
180 API calls · 60 cells · 3 passes per cell · 0 starved answers · $ 0.0611 total. Graders are deterministic — exact numeric match, JSON schema validation, executed unit tests, constraint counts, and clause-level regex checks — each verified against both a correct and an incorrect sample answer before the run.