GPT-5.6 Sol vs GPT-5.3 Codex
Too close to call on our weighted score (GPT-5.6 Sol 66, GPT-5.3 Codex 64). The right pick depends on what you value most.
OpenAIGPT-5.6 Sol
66/100- ECI161.8
- Price$4.00 / $20.00
- Context1.05M
- OpenAI
GPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
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Make it a three-way comparison.
Too close to call
It is close. Our weighted score puts them within 2 points (GPT-5.6 Sol 66/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: GPT-5.6 Sol for raw capability and GPT-5.3 Codex on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.6 SolCapabilities Index (ECI): GPT-5.6 Sol 161.8 · GPT-5.3 Codex 156.8
- Lowest priceGPT-5.3 CodexGPT-5.3 Codex $4.81 · GPT-5.6 Sol $8.00 per 1M tokens (3:1 blend)
- Longest contextGPT-5.6 SolGPT-5.6 Sol 1,050,000 · GPT-5.3 Codex 400,000 tokens
- Widest inputsSame inputsGPT-5.6 Sol: Text, Images, PDFs · GPT-5.3 Codex: Text, Images, PDFs
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | GPT-5.6 Sol | GPT-5.3 Codex |
|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 93 | 87 |
| Price | 25% | 7 | 18 |
| Inputs & features | 15% | 80 | 80 |
| Context window | 10% | 61 | 44 |
| Overall | 100% | 66/100 | 64/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.6 SolOpenAI | GPT-5.3 CodexOpenAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 161.8 (best) | 156.8 |
| ECI rank | #8 of 148 (best) | #18 of 148 |
| GPQA DiamondGraduate-level science questions | 93.5% | — |
| FrontierMath Tiers 1–3Research-level mathematics | 89.1% | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | — |
| SWE-bench VerifiedFixing real GitHub issues | — | 74.8% |
| SimpleQA VerifiedShort factual questions | 69.7% | — |
| Price per million tokens | ||
| Input | $4.00 | $1.75 (best) |
| Output | $20.00 | $14.00 (best) |
| Cached input | $0.40 | $0.175 (best) |
| Blended (3:1) | $8.00 | $4.81 (best) |
| Long-context rate | Over 272K: $8.00 / $30.00 | Same rate |
| Price source | Official OpenAI API | Official OpenAI API |
| Limits | ||
| Context window | 1,050,000 tokens (best) | 400,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | Yes | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | gpt-5.6-sol | gpt-5.3-codex |
| API providers | 40 (best) | 19 |
| Released | Jul 9, 2026 | Feb 5, 2026 |
| Knowledge cutoff | Feb 16, 2026 | Aug 31, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-5.6 Sol$80.00
- GPT-5.3 Codex$45.50
Which should you choose?
Which is better: GPT-5.6 Sol or GPT-5.3 Codex?
It is close. Our weighted score puts them within 2 points (GPT-5.6 Sol 66/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: GPT-5.6 Sol for raw capability and GPT-5.3 Codex on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.6 Sol or GPT-5.3 Codex?
GPT-5.3 Codex is cheaper at $1.75 input / $14.00 output per million tokens (official OpenAI API price). GPT-5.6 Sol costs $4.00 input / $20.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $4.81 per million tokens for GPT-5.3 Codex versus $8.00 for GPT-5.6 Sol (1.7× as much).
Which scores higher on benchmarks?
GPT-5.6 Sol scores higher on the Capabilities Index (ECI): GPT-5.6 Sol 161.8 (#8 of 148) and GPT-5.3 Codex 156.8 (#18 of 148). The confidence ranges of the top two overlap (159.3–165.3 vs 153.5–160.8), so treat the gap as small.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.6 Sol yet, so there is no like-for-like coding score. On overall capability, GPT-5.6 Sol leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.
Which has the bigger context window?
GPT-5.6 Sol has the largest context window at 1,050,000 tokens, against 400,000 for GPT-5.3 Codex. Maximum output per response: GPT-5.6 Sol up to 128,000, GPT-5.3 Codex up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.6 Sol accepts text, images and PDFs; GPT-5.3 Codex accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. GPT-5.6 Sol and GPT-5.3 Codex are proprietary and only available through APIs and apps.
Which is newer?
GPT-5.6 Sol is the newest, released Jul 9, 2026. GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: GPT-5.6 Sol Feb 16, 2026, GPT-5.3 Codex Aug 31, 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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