GPT-5.4 Mini vs Mercury 2
GPT-5.4 Mini leads Mercury 2 on the Artificial Analysis Intelligence Index, 24.1 to 10.8, and Mercury 2 costs 6.0x less per output token ($0.75 vs $4.50 per million). Updated October 22, 2026; 34 benchmarks have a result for both.
GPT-5.4 Mini or Mercury 2: which to pick
Only GPT-5.4 Mini has a coding score, 35.8 on the Vibe Coding Index; Mercury 2 has none, so the two cannot be ranked on coding.
Pick Mercury 2 for output tokens 6.0x cheaper ($0.75 vs $4.50 per million).
- Shared results
- 34
- GPT-5.4 Mini only
- 55
- Mercury 2 only
- 8
- Like-for-like categories
- 6 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
Only GPT-5.4 Mini has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
GPT-5.4 Mini
GPT-5.4 Mini leads, 24.1 against 10.8.
Same board, both measured
Agentic work
AA Agentic Index
GPT-5.4 Mini
GPT-5.4 Mini leads, 17.9 against 1.6.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only GPT-5.4 Mini has a GPQA Diamond result, 83.1%.
Directional only
Math
AIME
No call
Only GPT-5.4 Mini has a AIME result, 95.6%.
Directional only
Knowledge
MMLU Pro
No call
Only GPT-5.4 Mini has a MMLU Pro result, 84.5%.
Directional only
Web design
Design Arena: websites
No call
Only Mercury 2 has a Design Arena: websites result, 1036.
Directional only
Long documents
Listed context window
GPT-5.4 Mini
GPT-5.4 Mini takes 400K tokens against 128K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 2
GPT-5.4 Mini $0.0030, Mercury 2 $0.0006 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only GPT-5.4 Mini has the number, $0.70.
Directional only
At a glance
- Coding index
- GPT-5.4 Mini 35.8 from 5 benchmarks, Mercury 2 not benchmarked.
- Widest category
- Coding, 21.5 points apart on average over 10 shared benchmarks.
- Widest single gap
- LMArena WebDev: React: GPT-5.4 Mini 1386 against Mercury 2 1160, 37.8 points apart on a 0 to 100 scale.
- Output price
- GPT-5.4 Mini $4.50 against Mercury 2 $0.75 per million output tokens, 6.0x apart.
- Context window
- GPT-5.4 Mini takes 400K tokens, Mercury 2 128K.
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 | GPT-5.4 Mini | Bars | Mercury 2 | Ties |
|---|---|---|---|---|
| Coding | 10 | 0 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 2 | 0 | ||
| Reasoning | 5 | 0 | ||
| Knowledge | 3 | 0 | ||
| General | 13 | 0 | ||
| All shared boards | 34 | 0 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index100
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| LMArena WebDev | 1397 | 1171 | GPT-5.4 Mini |
| AA Coding Index | 56.1 | 31.1 | GPT-5.4 Mini |
| LiveCodeBench (Vals AI) | 81.5% | Not measured | Only GPT-5.4 Mini measured |
| SWE-bench Verified (Vals AI) | 73.0% | Not measured | Only GPT-5.4 Mini measured |
| Terminal-Bench 4 (Vals AI) | 2.5% | Not measured | Only GPT-5.4 Mini measured |
| Vibe Code Bench (Vals AI) | 48.0% | Not measured | Only GPT-5.4 Mini measured |
| Code migration (Vals AI) | 12.9% | Not measured | Only GPT-5.4 Mini measured |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only GPT-5.4 Mini measured |
| Terminal-Bench 2.1 (Vals AI) | 54.7% | Not measured | Only GPT-5.4 Mini measured |
| SciCode | 52.1% | 37.7% | GPT-5.4 Mini |
| Terminal-Bench Hard (Artificial Analysis run) | 52.3% | 26.5% | GPT-5.4 Mini |
| FrontierCode | 27.0% | Not measured | Only GPT-5.4 Mini measured |
| WeirdML | 60.3% | 43.2% | GPT-5.4 Mini |
| ALE-Bench | 1188.6 | 785.6 | GPT-5.4 Mini |
| LMArena Text: coding | 1438 | 1390 | GPT-5.4 Mini |
| LMArena Text: software and IT | 1436 | 1385 | GPT-5.4 Mini |
| LMArena WebDev: React | 1386 | 1160 | GPT-5.4 Mini |
| LMArena WebDev: HTML | 1419 | 1199 | GPT-5.4 Mini |
| Neither model has a result on the other 21 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| AA Intelligence Index | 24.1 | 10.8 | GPT-5.4 Mini |
| Epoch Capabilities Index | 148.7 | Not measured | Only GPT-5.4 Mini measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| AA Agentic Index | 17.9 | 1.6 | GPT-5.4 Mini |
| Finance Agent (Vals AI) | 45.4% | Not measured | Only GPT-5.4 Mini measured |
| Tax Agent Bench (Vals AI) | 8.8% | Not measured | Only GPT-5.4 Mini measured |
| Legal Research Bench (Vals AI) | 12.5% | Not measured | Only GPT-5.4 Mini measured |
| Excel Modeling Benchmark (Vals AI) | 45.4% | Not measured | Only GPT-5.4 Mini measured |
| τ²-Bench Telecom | 83.3% | 70.8% | GPT-5.4 Mini |
| DeepResearch Bench | 36.3% | Not measured | Only GPT-5.4 Mini measured |
| Neither model has a result on the other 34 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| GPQA Diamond | 83.1% | Not measured | Only GPT-5.4 Mini measured |
| MMMU Pro (Vals AI) | 79.3% | Not measured | Only GPT-5.4 Mini measured |
| GPQA Diamond (Artificial Analysis run) | 87.5% | 77.0% | GPT-5.4 Mini |
| Humanity's Last Exam (Artificial Analysis run) | 28.1% | 17.1% | GPT-5.4 Mini |
| GPQA Diamond (Epoch AI run) | 86.9% | Not measured | Only GPT-5.4 Mini measured |
| ARC-AGI | 63.7% | Not measured | Only GPT-5.4 Mini measured |
| ARC-AGI-2 | 18.9% | Not measured | Only GPT-5.4 Mini measured |
| Chess puzzles | 23.0% | Not measured | Only GPT-5.4 Mini measured |
| Mystery game puzzles | 11.0% | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: hard prompts | 1424 | 1362 | GPT-5.4 Mini |
| LMArena Text: expert | 1435 | 1358 | GPT-5.4 Mini |
| LMArena Text: hard prompts in English | 1420 | 1374 | GPT-5.4 Mini |
| LMArena Vision: diagrams | 1266 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Vision: homework | 1285 | Not measured | Only GPT-5.4 Mini measured |
| Kagi LLM Benchmark | 37.9% | Not measured | Only GPT-5.4 Mini measured |
| Neither model has a result on the other 7 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index7 boards, none shared
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| AIME | 95.6% | Not measured | Only GPT-5.4 Mini measured |
| OTIS Mock AIME | 88.9% | Not measured | Only GPT-5.4 Mini measured |
| FrontierMath, tiers 1 to 3 | 51.2% | Not measured | Only GPT-5.4 Mini measured |
| FrontierMath, tier 4 | 9.8% | Not measured | Only GPT-5.4 Mini measured |
| ProofBench | 21.0% | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: math | 1418 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: mathematical work | 1429 | Not measured | Only GPT-5.4 Mini measured |
| Neither model has a result on the other 6 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| MMLU Pro | 84.5% | Not measured | Only GPT-5.4 Mini measured |
| CaseLaw (Vals AI) | 51.7% | Not measured | Only GPT-5.4 Mini measured |
| CorpFin (Vals AI) | 60.9% | Not measured | Only GPT-5.4 Mini measured |
| TaxEval (Vals AI) | 71.2% | Not measured | Only GPT-5.4 Mini measured |
| MortgageTax (Vals AI) | 63.5% | Not measured | Only GPT-5.4 Mini measured |
| SimpleQA Verified | 29.4% | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: science | 1417 | 1343 | GPT-5.4 Mini |
| LMArena Text: medicine and healthcare | 1395 | 1363 | GPT-5.4 Mini |
| LMArena Text: legal and government | 1414 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: business and finance | 1418 | 1349 | GPT-5.4 Mini |
| Neither model has a result on the other 8 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| Design Arena: websites | Not measured | 1036 | Only Mercury 2 measured |
| Design Arena: UI components | Not measured | 996 | Only Mercury 2 measured |
| Design Arena: game dev | Not measured | 984 | Only Mercury 2 measured |
| Design Arena: data viz | Not measured | 1009 | Only Mercury 2 measured |
| Design Arena: 3D | Not measured | 982 | Only Mercury 2 measured |
| Design Arena: all code categories | Not measured | 1021 | Only Mercury 2 measured |
| Design Arena: SVG | Not measured | 998 | Only Mercury 2 measured |
| Design Arena: ASCII art | Not measured | 988 | Only Mercury 2 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index130
| Benchmark | GPT-5.4 Mini | Mercury 2 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 50.8% | Not measured | Only GPT-5.4 Mini measured |
| Vals Multimodal Index | 54.2% | Not measured | Only GPT-5.4 Mini measured |
| IFBench | 73.3% | 69.8% | GPT-5.4 Mini |
| Long context reasoning (AA-LCR) | 77.0% | 43.7% | GPT-5.4 Mini |
| DTBench | 80.0% | Not measured | Only GPT-5.4 Mini measured |
| LMCA | 40.8% | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text | 1412 | 1354 | GPT-5.4 Mini |
| LMArena Text: instruction following | 1405 | 1328 | GPT-5.4 Mini |
| LMArena Text: creative writing | 1370 | 1286 | GPT-5.4 Mini |
| LMArena Vision | 1245 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: English | 1412 | 1378 | GPT-5.4 Mini |
| LMArena Text: non-English | 1405 | 1330 | GPT-5.4 Mini |
| LMArena Text: Chinese | 1446 | 1414 | GPT-5.4 Mini |
| LMArena Text: German | 1408 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: Japanese | 1375 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: Korean | 1370 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: French | 1441 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: Spanish | 1405 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: Russian | 1417 | 1304 | GPT-5.4 Mini |
| LMArena Text: Polish | 1415 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Text: multi-turn | 1429 | 1357 | GPT-5.4 Mini |
| LMArena Text: longer queries | 1408 | 1329 | GPT-5.4 Mini |
| LMArena Text: writing and language | 1393 | 1300 | GPT-5.4 Mini |
| LMArena Text: entertainment and media | 1373 | 1314 | GPT-5.4 Mini |
| LMArena Vision: English | 1244 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Vision: Chinese | 1286 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Vision: reading text | 1253 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Vision: humor | 1235 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Vision: recognizing things | 1218 | Not measured | Only GPT-5.4 Mini measured |
| LMArena Vision: creative writing | 1222 | Not measured | Only GPT-5.4 Mini measured |
| Neither model has a result on the other 16 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | GPT-5.4 Mini | Mercury 2 | 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 costs less
Repository review
50K input + 3K output tokens
Mercury 2 costs less
Agent loop
200K input + 10K output tokens
Mercury 2 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 | OpenAI GPT-5.4 Mini | Inception Mercury 2 |
|---|---|---|
| Maker | OpenAI | Inception |
| Weights | No public weights listed | No public weights listed |
| Released | March 17, 2026 | March 4, 2026 |
| Context window | 400K | 128K |
| Input $/Mtok | $0.75 | $0.25 |
| Output $/Mtok | $4.50 | $0.75 |
| Coding index | 35.8 | Not benchmarked |
| Independent measurements behind it | 5 | 1 |
| Cost per solved task | $0.70 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.4 Mini better than Mercury 2 for coding?
Only GPT-5.4 Mini has a coding score, 35.8 on the Vibe Coding Index; Mercury 2 has none, so the two cannot be ranked on coding. Pick Mercury 2 for output tokens 6.0x cheaper ($0.75 vs $4.50 per million).
Which is cheaper, GPT-5.4 Mini or Mercury 2?
GPT-5.4 Mini costs $0.75 per million input tokens and $4.50 per million output tokens; Mercury 2 costs $0.25 and $0.75. Cost per solved task is known for GPT-5.4 Mini only.
Which has the bigger context window, GPT-5.4 Mini or Mercury 2?
GPT-5.4 Mini, with 400K tokens against 128K.
How many benchmarks is the GPT-5.4 Mini vs Mercury 2 comparison based on?
34 benchmarks have a result for both models as of October 22, 2026. GPT-5.4 Mini's coding index rests on 5 independent benchmarks and Mercury 2's on 1. Where only one model has a result, the page says so instead of naming a winner.