Mercury 2.5 vs Muse Spark Open
Muse Spark Open leads Mercury 2.5 on coding, 47.4 to 1.6 on the Vibe Coding Index, and Mercury 2.5 costs 28.3x less per output token ($0.15 vs $4.25 per million). Updated October 22, 2026; 11 benchmarks have a result for both.
Mercury 2.5 or Muse Spark Open: which to pick
Pick Muse Spark Open for coding: it scores 47.4 on the Vibe Coding Index against 1.6 for Mercury 2.5.
Pick Mercury 2.5 for output tokens 28.3x cheaper ($0.15 vs $4.25 per million).
- Shared results
- 11
- Mercury 2.5 only
- 11
- Muse Spark Open only
- 17
- Like-for-like categories
- 4 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
Muse Spark Open
Muse Spark Open scores 47.4 against 1.6.
2 and 4 benchmarks behind the scores
Intelligence
AA Intelligence Index
No call
Only Mercury 2.5 has a AA Intelligence Index result, 12.3.
Directional only
Web design
Design Arena: websites
No call
Only Muse Spark Open has a Design Arena: websites result, 1310.
Directional only
General
Vals Index
No call
Only Muse Spark Open has a Vals Index result, 48.6%.
Directional only
Long documents
Listed context window
Muse Spark Open
Muse Spark Open takes 1.05M tokens against 260K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 2.5
Mercury 2.5 $0.0001, Muse Spark Open $0.0034 per turn.
List prices
At a glance
- Coding index
- Mercury 2.5 1.6 from 2 benchmarks, Muse Spark Open 47.4 from 4 benchmarks.
- Widest category
- Agentic work, 36.3 points apart on average over 4 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Mercury 2.5 3.7% against Muse Spark Open 76.2%, 72.5 points apart on a 0 to 100 scale.
- Output price
- Mercury 2.5 $0.15 against Muse Spark Open $4.25 per million output tokens, 28.3x apart.
- Context window
- Mercury 2.5 takes 260K tokens, Muse Spark Open 1.05M.
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 2.5 | Bars | Muse Spark Open | Ties |
|---|---|---|---|---|
| Coding | 0 | 5 | ||
| Agentic work | 0 | 4 | ||
| Reasoning | 0 | 1 | ||
| General | 0 | 1 | ||
| All shared boards | 0 | 11 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index05
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| LiveBench coding | Not measured | 73.6% | Only Muse Spark Open measured |
| LMArena WebDev | Not measured | 1528 | Only Muse Spark Open measured |
| Terminal-Bench 4 (Vals AI) | 0.0% | 6.6% | Muse Spark Open |
| Vibe Code Bench (Vals AI) | 3.7% | 76.2% | Muse Spark Open |
| Code migration (Vals AI) | 4.5% | 21.2% | Muse Spark Open |
| IOI (Vals AI) | 2.4% | Not measured | Only Mercury 2.5 measured |
| Terminal-Bench 2.1 (Vals AI) | 34.5% | Not measured | Only Mercury 2.5 measured |
| SkillsBench (Vals AI) | 18.1% | Not measured | Only Mercury 2.5 measured |
| CyberBench (Vals AI) | 45.5% | Not measured | Only Mercury 2.5 measured |
| SciCode | 38.5% | 58.4% | Muse Spark Open |
| ALE-Bench | 301.6 | 1590.1 | Muse Spark Open |
| LMArena WebDev: React | Not measured | 1529 | Only Muse Spark Open measured |
| LMArena WebDev: HTML | Not measured | 1495 | Only Muse Spark Open measured |
| Neither model has a result on the other 26 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| AA Intelligence Index | 12.3 | Not measured | Only Mercury 2.5 measured |
| Epoch Capabilities Index | Not measured | 155.1 | Only Muse Spark Open measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| LiveBench research | Not measured | 80.3% | Only Muse Spark Open measured |
| LiveBench browser | Not measured | 36.0% | Only Muse Spark Open measured |
| LiveBench long agentic | Not measured | 18.9% | Only Muse Spark Open measured |
| Finance Agent (Vals AI) | 18.9% | 61.3% | Muse Spark Open |
| Tax Agent Bench (Vals AI) | 2.5% | 26.3% | Muse Spark Open |
| Legal Research Bench (Vals AI) | 4.3% | 38.5% | Muse Spark Open |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 25.0% | Only Muse Spark Open measured |
| Excel Modeling Benchmark (Vals AI) | 8.8% | 53.7% | Muse Spark Open |
| Terminal-Bench-Science (Vals AI) | 0.0% | Not measured | Only Mercury 2.5 measured |
| APEX-Agents | Not measured | 33.4% | Only Muse Spark Open measured |
| Neither model has a result on the other 31 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| LiveBench reasoning | Not measured | 73.7% | Only Muse Spark Open measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 89.0% | Only Muse Spark Open measured |
| Humanity's Last Exam (Artificial Analysis run) | 11.8% | 43.9% | Muse Spark Open |
| Neither model has a result on the other 19 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| ProofBench | 3.0% | Not measured | Only Mercury 2.5 measured |
| Neither model has a result on the other 12 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| LegalBench (Vals AI) | 83.1% | Not measured | Only Mercury 2.5 measured |
| MedCode (Vals AI) | 31.3% | Not measured | Only Mercury 2.5 measured |
| Neither model has a result on the other 16 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index3 boards, none shared
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| Design Arena: websites | Not measured | 1310 | Only Muse Spark Open measured |
| Design Arena: game dev | Not measured | 1282 | Only Muse Spark Open measured |
| LiveBench design | Not measured | 60.3% | Only Muse Spark Open measured |
| Neither model has a result on the other 6 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Mercury 2.5 | Muse Spark Open | Leader |
|---|---|---|---|
| Vals Index | Not measured | 48.6% | Only Muse Spark Open measured |
| LiveBench data analysis | Not measured | 60.2% | Only Muse Spark Open measured |
| Public Benefits Bench (Vals AI) | 45.3% | Not measured | Only Mercury 2.5 measured |
| MedScribe (Vals AI) | 55.1% | Not measured | Only Mercury 2.5 measured |
| Long context reasoning (AA-LCR) | 71.7% | 78.3% | Muse Spark Open |
| Neither model has a result on the other 41 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Mercury 2.5 | Muse Spark Open | 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 2.5 costs less
Repository review
50K input + 3K output tokens
Mercury 2.5 costs less
Agent loop
200K input + 10K output tokens
Mercury 2.5 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 2.5 | Meta Muse Spark Open |
|---|---|---|
| Maker | Inception | Meta |
| Weights | No public weights listed | Open weights |
| Released | September 8, 2026 | October 15, 2026 |
| Context window | 260K | 1.05M |
| Input $/Mtok | $0.04 | $1.25 |
| Output $/Mtok | $0.15 | $4.25 |
| Coding index | 1.6 | 47.4 |
| Independent measurements behind it | 2 | 4 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Mercury 2.5 better than Muse Spark Open for coding?
Pick Muse Spark Open for coding: it scores 47.4 on the Vibe Coding Index against 1.6 for Mercury 2.5. Pick Mercury 2.5 for output tokens 28.3x cheaper ($0.15 vs $4.25 per million).
Which is cheaper, Mercury 2.5 or Muse Spark Open?
Mercury 2.5 costs $0.04 per million input tokens and $0.15 per million output tokens; Muse Spark Open costs $1.25 and $4.25. Cost per solved task is known for neither of them.
Which has the bigger context window, Mercury 2.5 or Muse Spark Open?
Muse Spark Open, with 1.05M tokens against 260K.
How many benchmarks is the Mercury 2.5 vs Muse Spark Open comparison based on?
11 benchmarks have a result for both models as of October 22, 2026. Mercury 2.5's coding index rests on 2 independent benchmarks and Muse Spark Open's on 4. Where only one model has a result, the page says so instead of naming a winner.