GPT-5.1 Codex mini vs Mercury 2
Too close to call on our weighted score (GPT-5.1 Codex mini 54, Mercury 2 52). The right pick depends on what you value most.
OpenAIGPT-5.1 Codex mini
54/100- ECI—
- Price$0.25 / $2.00
- Context400K
InceptionMercury 2
52/100- ECI—
- Price$0.25 / $0.75
- Context128K
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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-5.1 Codex mini 54/100, Mercury 2 52/100), so choose by what matters most for your work: Mercury 2 on price and GPT-5.1 Codex mini for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceMercury 2Mercury 2 $0.375 · GPT-5.1 Codex mini $0.688 per 1M tokens (3:1 blend)
- Longest contextGPT-5.1 Codex miniGPT-5.1 Codex mini 400,000 · Mercury 2 128,000 tokens
- Widest inputsGPT-5.1 Codex miniGPT-5.1 Codex mini: Text, Images · Mercury 2: Text
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | GPT-5.1 Codex mini | Mercury 2 |
|---|---|---|---|
| Price | 50% | 55 | 67 |
| Inputs & features | 30% | 60 | 45 |
| Context window | 20% | 44 | 24 |
| Overall | 100% | 54/100 | 52/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.1 Codex miniOpenAI | Mercury 2Inception |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | — | — |
| ECI rank | — | — |
| Price per million tokens | ||
| Input | $0.25 | $0.25 |
| Output | $2.00 | $0.75 (best) |
| Cached input | — | $0.025 |
| Blended (3:1) | $0.688 | $0.375 (best) |
| Long-context rate | Same rate | Same rate |
| Price source | Median of 16 providers | Official Inception API |
| Limits | ||
| Context window | 400,000 tokens (best) | 128,000 tokens |
| Max output | 128,000 tokens (best) | 50,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | No |
| PDFs | No | No |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yes | Yeslow · medium · high |
| Tool calling | Yes | Yes |
| Structured output | No | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | — | mercury-2 |
| API providers | 16 (best) | 7 |
| Released | Nov 13, 2025 | Feb 24, 2026 |
| Knowledge cutoff | Sep 30, 2024 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-5.1 Codex mini$6.50
- Mercury 2$4.00
Which should you choose?
Which is better: GPT-5.1 Codex mini or Mercury 2?
It is close. Our weighted score puts them within 2 points (GPT-5.1 Codex mini 54/100, Mercury 2 52/100), so choose by what matters most for your work: Mercury 2 on price and GPT-5.1 Codex mini for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, GPT-5.1 Codex mini or Mercury 2?
Mercury 2 is cheaper at $0.25 input / $0.75 output per million tokens (official Inception API price). GPT-5.1 Codex mini costs $0.25 input / $2.00 output per million tokens (median across 16 API providers). At a typical mix of three input tokens to one output token, that is $0.375 per million tokens for Mercury 2 versus $0.688 for GPT-5.1 Codex mini (1.8× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. GPT-5.1 Codex mini has not been scored yet and Mercury 2 has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.1 Codex mini and Mercury 2 yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.
Which has the bigger context window?
GPT-5.1 Codex mini has the largest context window at 400,000 tokens, against 128,000 for Mercury 2. Maximum output per response: GPT-5.1 Codex mini up to 128,000, Mercury 2 up to 50,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.1 Codex mini accepts text and images; Mercury 2 accepts text. GPT-5.1 Codex mini handles the widest range of inputs.
Are any of these open source?
No. GPT-5.1 Codex mini and Mercury 2 are proprietary and only available through APIs and apps.
Which is newer?
Mercury 2 is the newest, released Feb 24, 2026. GPT-5.1 Codex mini came out Nov 13, 2025. Knowledge cutoff: GPT-5.1 Codex mini Sep 30, 2024.
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 Nov 2, 2026.
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