Upstage Solar Pro 4 Jumps 28 Points on AA Intelligence Index — Terminal-Bench Up 4.8x, $0.30/$1.20 Per Million
Korean AI lab Upstage has released Solar Pro 4, its new proprietary flagship reasoning model. The model scores 42 on the Artificial Analysis Intelligence Index — a 28-point gain over Solar Pro 3’s 14, cleared in a single generation. At 42, Solar Pro 4 sits alongside Thinking Machines’ Inkling (xhigh, 42) and just behind Xiaomi MiMo-V2.5-Pro (43), placing it in the mid-tier frontier bracket rather than the sub-40 class where Korean models had previously plateaued.
Benchmark Numbers
The gains concentrate on agent execution, not general knowledge. Upstage’s own evaluation table:
| Category | Solar Open 2 | Solar Pro 4 | Change |
|---|---|---|---|
| Terminal-Bench v2.1 | 43.2 | 57.0 | +13.8 |
| GDPval-AA v2 | 31.4 | 38.8 | +7.4 |
| BrowseComp | 37.3 | 49.2 | +11.9 |
| SWE-Bench Verified (OpenHands) | 69.2 | 70.6 | +1.4 |
| MCP-Atlas | 58.2 | 61.4 | +3.2 |
| APEX-Agents | 16.6 | 18.7 | +2.1 |
| τ³-Banking | 18.1 | 23.0 | +4.9 |
| AA-LCR (long context) | 62.7 | 71.0 | +8.3 |
| GPQA Diamond | 85.6 | 89.0 | +3.4 |
Terminal task performance is up by a factor of 4.8 from Solar Pro 3. τ³-Banking multi-turn tool use is up 2.5x from the same baseline. The message from the benchmark mix is direct: Solar Pro 4 was built to complete longer agentic workflows, not to move individual-question leaderboards.
Where improvement is minimal is instructive. AIME 2026 fell 0.4 points. Korean and Japanese professional benchmarks (law, medicine, KMMLU-Pro) moved less than one point. Math reasoning headroom from Solar Pro 3 was already largely saturated; the engineering effort went elsewhere.
Pricing and Specs
- Input: $0.30 per million tokens
- Output: $1.20 per million tokens
- Cache hit: $0.06 per million tokens
- Context window: 512K tokens, up to 128K output
- Languages: English and Korean (stated), Japanese in scope
- Modes: reasoning-optimised for deep analysis, lighter for everyday tasks
Pricing is double Solar Pro 3’s $0.15/$0.60 rate. At $0.30 input and $1.20 output, Solar Pro 4 costs roughly the same per token as Gemini 3.5 Flash and less than a quarter of Gemini 3.1 Pro’s $2/$12 rate — significant positioning given that Solar Pro 4’s AA Index score of 42 closes to within a few points of where Gemini 3 Pro (index 44–46) sat a generation ago.
Third-Nation Context
South Korea now holds AA Intelligence Index rankings in the low-40s for two consecutive model generations, consolidating a position behind the US (with frontier models at 56–64+) and China (DeepSeek, Kimi K3, GLM-5.2 in the mid-to-upper tier). Upstage’s positioning emphasises agent work and Korean/Japanese professional domains — a differentiation strategy consistent with the customer base it has built in financial services, legal, and public sector applications in Northeast Asia.
Solar Pro 4 is available through Upstage Console. Benchmark scores are from Artificial Analysis and Upstage’s own evaluation environment; the AA public listing is described as forthcoming.