Mercury 3 vs Step 3.7 Flash
Mercury 3 costs 3.3x less per output token than Step 3.7 Flash ($0.35 vs $1.15 per million). Updated October 21, 2026; 5 benchmarks have a result for both.
Mercury 3 or Step 3.7 Flash: which to pick
Neither model has a coding score yet, so the two cannot be ranked on coding.
Pick Mercury 3 for output tokens 3.3x cheaper ($0.35 vs $1.15 per million) and a larger context window (1M against 262K tokens).
- Shared results
- 5
- Mercury 3 only
- 0
- Step 3.7 Flash only
- 13
- Like-for-like categories
- 1 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Neither has a coding score yet.
One side not measured
Intelligence
AA Intelligence Index
No call
Only Step 3.7 Flash has a AA Intelligence Index result, 19.5.
Directional only
Web design
Design Arena: websites
Mercury 3
Mercury 3 leads, 1244 against 1196.
Same board, both measured
Long documents
Listed context window
Mercury 3
Mercury 3 takes 1M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 3
Mercury 3 $0.0003, Step 3.7 Flash $0.0008 per turn.
List prices
At a glance
- Coding index
- Mercury 3 not benchmarked, Step 3.7 Flash not benchmarked.
- Widest category
- Web design, 7.5 points apart on average over 5 shared benchmarks.
- Widest single gap
- Design Arena: UI components: Mercury 3 1270 against Step 3.7 Flash 1179, 11.4 points apart on a 0 to 100 scale.
- Output price
- Mercury 3 $0.35 against Step 3.7 Flash $1.15 per million output tokens, 3.3x apart.
- Context window
- Mercury 3 takes 1M tokens, Step 3.7 Flash 262K.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Mercury 3 | Bars | Step 3.7 Flash | Ties |
|---|---|---|---|---|
| Web design | 5 | 0 | ||
| All shared boards | 5 | 0 |
CodingDirectional onlySix of these boards feed the Vibe Coding Index4 boards, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| AA Coding Index | Not measured | 39.6 | Only Step 3.7 Flash measured |
| SciCode | Not measured | 43.9% | Only Step 3.7 Flash measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 35.6% | Only Step 3.7 Flash measured |
| ALE-Bench | Not measured | 694.1 | Only Step 3.7 Flash measured |
| Neither model has a result on the other 35 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | Not measured | 19.5 | Only Step 3.7 Flash measured |
| Neither model has a result on the other 1 board here | |||
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| τ²-Bench Telecom | Not measured | 98.5% | Only Step 3.7 Flash measured |
| Neither model has a result on the other 40 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| GPQA Diamond (Artificial Analysis run) | Not measured | 80.9% | Only Step 3.7 Flash measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 21.4% | Only Step 3.7 Flash measured |
| Neither model has a result on the other 20 boards here | |||
MathNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| Neither model has a result on 13 boards here | |||
KnowledgeNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| Neither model has a result on 18 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1244 | 1196 | Mercury 3 |
| Design Arena: UI components | 1270 | 1179 | Mercury 3 |
| Design Arena: game dev | 1227 | 1158 | Mercury 3 |
| Design Arena: data viz | 1207 | 1172 | Mercury 3 |
| Design Arena: 3D | Not measured | 1129 | Only Step 3.7 Flash measured |
| Design Arena: all code categories | 1240 | 1182 | Mercury 3 |
| Design Arena: SVG | Not measured | 1085 | Only Step 3.7 Flash measured |
| Design Arena: ASCII art | Not measured | 1152 | Only Step 3.7 Flash measured |
| Neither model has a result on the other 1 board here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| IFBench | Not measured | 67.3% | Only Step 3.7 Flash measured |
| Long context reasoning (AA-LCR) | Not measured | 73.7% | Only Step 3.7 Flash measured |
| Neither model has a result on the other 44 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Mercury 3 | Step 3.7 Flash | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Mercury 3 costs less
Repository review
50K input + 3K output tokens
Mercury 3 costs less
Agent loop
200K input + 10K output tokens
Mercury 3 costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Inception Mercury 3 | StepFun Step 3.7 Flash |
|---|---|---|
| Maker | Inception | StepFun |
| Weights | No public weights listed | Open weights |
| Released | October 16, 2026 | May 28, 2026 |
| Context window | 1M | 262K |
| Input $/Mtok | $0.10 | $0.20 |
| Output $/Mtok | $0.35 | $1.15 |
| Coding index | Not benchmarked | Not benchmarked |
| Independent measurements behind it | 0 | 0 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Mercury 3 better than Step 3.7 Flash for coding?
Neither model has a coding score yet, so the two cannot be ranked on coding. Pick Mercury 3 for output tokens 3.3x cheaper ($0.35 vs $1.15 per million) and a larger context window (1M against 262K tokens).
Which is cheaper, Mercury 3 or Step 3.7 Flash?
Mercury 3 costs $0.10 per million input tokens and $0.35 per million output tokens; Step 3.7 Flash costs $0.20 and $1.15. Cost per solved task is known for neither of them.
Which has the bigger context window, Mercury 3 or Step 3.7 Flash?
Mercury 3, with 1M tokens against 262K.
How many benchmarks is the Mercury 3 vs Step 3.7 Flash comparison based on?
5 benchmarks have a result for both models as of October 21, 2026. Mercury 3's coding index rests on 0 independent benchmarks and Step 3.7 Flash's on 0. Where only one model has a result, the page says so instead of naming a winner.