Model comparison
GPT-5.3-Codex vs Upstage Solar Pro 4
OpenAI against Upstage, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
OpenAI
GPT-5.3-Codex
Frontier
Upstage
Upstage Solar Pro 4
Frontier
| Specification | GPT-5.3-Codex | Upstage Solar Pro 4 |
|---|---|---|
| Provider | OpenAI | Upstage |
| Tier | Frontier | Frontier |
| Context window | 400K | Winner: 524K |
| Max output | 128K | Not verifiedUnverified |
| Input / 1M tokens | $1.75 | Winner: $0.30 |
| Output / 1M tokens | $14 | Winner: $1.20 |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | Not disclosedUnverified |
| Reasoning levels | none, low, medium, high, xhigh, max | low, medium, high |
| Modalities | text, image | text |
| API model id | gpt-5.3-codex | solar-pro-4 |
| Released | February 5, 2026 | August 10, 2026 |
| Artificial Analysis Intelligence Index [high] (2026-08-14) | 52 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index (2026-08-14) | Not verifiedUnverified | 50 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
Pricing tiers: GPT-5.3-Codex: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Purpose-built for the Codex agent. · Upstage Solar Pro 4: List $0.30/$1.20 per MTok; live promo rate is $0.03/$0.12 (90% off through 2026-09-10). Closed API. 524K context.
GPT-5.3-Codex
GPT-5.3-Codex is OpenAI's coding-specialised model powering the Codex agent at $1.75/$14.
Best for
- Autonomous coding
- Repo-scale refactors
- Test generation
Watch out
Tuned for coding, not general chat; use GPT-5.6 for broad reasoning.
Upstage Solar Pro 4
Solar Pro 4 is Upstage's closed flagship with a 524K context at a low launch price.
Best for
- Long-context
- Cost-sensitive API
- Korean + English
Watch out
Closed API; promo pricing may end.
When the cheaper one wins
Upstage Solar Pro 4 is cheaper on output at $1.20 per million tokens against $14 for GPT-5.3-Codex — about 12×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 3/5 core specs verified on both sides — Not published for at least one side: max output, parameter count.
- 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- GPT-5.3-Codex: OpenAI — Introducing GPT-5.3-Codex (accessed 2026-08-29)
- GPT-5.3-Codex: OpenAI API pricing (gpt-5.3-codex $1.75/$14) (accessed 2026-08-29)
- Upstage Solar Pro 4: Upstage — Solar Pro 4 (accessed 2026-08-29)
- Upstage Solar Pro 4: Upstage (accessed 2026-08-29)
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- Claude Mythos 5.1 vs GPT-5.3-Codex
- Claude Mythos 5.1 vs Upstage Solar Pro 4
Diving deeper on one model? GPT-5.3-Codex · Upstage Solar Pro 4
Common questions
GPT-5.3-Codex vs Upstage Solar Pro 4
Answered from the verified figures on this page rather than general guidance.
Is GPT-5.3-Codex or Upstage Solar Pro 4 cheaper for input?
Upstage Solar Pro 4 is cheaper at $0.30 per million input tokens, against $1.75 for GPT-5.3-Codex — roughly 5.8× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.3-Codex has tiered pricing: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Purpose-built for the Codex agent. Upstage Solar Pro 4 has tiered pricing: List $0.30/$1.20 per MTok; live promo rate is $0.03/$0.12 (90% off through 2026-09-10). Closed API. 524K context.
Is GPT-5.3-Codex or Upstage Solar Pro 4 cheaper for output?
Upstage Solar Pro 4 is cheaper at $1.20 per million output tokens, against $14 for GPT-5.3-Codex — roughly 12× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.3-Codex has tiered pricing: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Purpose-built for the Codex agent. Upstage Solar Pro 4 has tiered pricing: List $0.30/$1.20 per MTok; live promo rate is $0.03/$0.12 (90% off through 2026-09-10). Closed API. 524K context.
Which has the larger context window, GPT-5.3-Codex or Upstage Solar Pro 4?
Upstage Solar Pro 4 accepts 524K tokens against 400K for GPT-5.3-Codex. This only matters if you routinely send very long documents or large codebases.
Do GPT-5.3-Codex and Upstage Solar Pro 4 support the same reasoning levels?
GPT-5.3-Codex exposes none, low, medium, high, xhigh, max, while Upstage Solar Pro 4 exposes low, medium, high.
Should I use GPT-5.3-Codex or Upstage Solar Pro 4?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. GPT-5.3-Codex suits autonomous coding; Upstage Solar Pro 4 suits long-context.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: Upstage Solar Pro 4 costs $0.30 per 1M tokens versus $1.75 for GPT-5.3-Codex — a 5.8x difference at the headline tier.
- Context: Upstage Solar Pro 4 takes 524K against 400K for GPT-5.3-Codex — only decisive if your prompts approach the smaller window.
- Measured capability: GPT-5.3-Codex leads Artificial Analysis Intelligence Index 52 to 50 (measured 2026-08-14).
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.