GPT-5.1 Codex mini vs Step 3.5 Flash vs Mistral Large 3
Step 3.5 Flash comes out ahead, 62 to 59 and 50 on our weighted score, and it is the cheaper option too.
OpenAIGPT-5.1 Codex mini
59/100- ECI—
- Price$0.25 / $2.00
- Context400K
- Our pick
StepFunStep 3.5 Flash
62/100- ECI—
- Price$0.10 / $0.30
- Context256K
Mistral AIMistral Large 3
50/100- ECI—
- Price$0.50 / $1.50
- Context262K
Step 3.5 Flash is our pick
Step 3.5 Flash is the better all-round choice, scoring 62/100 against GPT-5.1 Codex mini (59) and Mistral Large 3 (50). It leads on price. GPT-5.1 Codex mini wins on inputs & features and context window. 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 priceStep 3.5 FlashStep 3.5 Flash $0.15 · GPT-5.1 Codex mini $0.688 · Mistral Large 3 $0.75 per 1M tokens (3:1 blend)
- Longest contextGPT-5.1 Codex miniGPT-5.1 Codex mini 400,000 · Mistral Large 3 262,144 · Step 3.5 Flash 256,000 tokens
- Widest inputsGPT-5.1 Codex mini and Mistral Large 3GPT-5.1 Codex mini: Text, Images · Step 3.5 Flash: Text · Mistral Large 3: Text, Images
- Self-hostingStep 3.5 Flash and Mistral Large 3Publishes downloadable weights
| Measure | Weight | GPT-5.1 Codex mini | Step 3.5 Flash | Mistral Large 3 |
|---|---|---|---|---|
| Price | 50% | 58 | 89 | 56 |
| Inputs & features | 30% | 70 | 35 | 50 |
| Context window | 20% | 44 | 36 | 37 |
| Overall | 100% | 59/100 | 62/100 | 50/100 |
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 | Step 3.5 FlashStepFun | Mistral Large 3Mistral AI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $0.25 | $0.10 (best) | $0.50 |
| Output | $2.00 | $0.30 (best) | $1.50 |
| Cached input | — | $0.02 (best) | $0.05 |
| Blended (3:1) | $0.688 | $0.15 (best) | $0.75 |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Median of 10 providers | Official StepFun (Global) API | Official Mistral API |
| Limits | |||
| Context window | 400,000 tokens (best) | 256,000 tokens | 262,144 tokens |
| Max output | 128,000 tokens | 256,000 tokens | 262,144 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | No | Yes |
| PDFs | No | No | No |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yes | Yeslow · high | No |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | No | No |
| Availability | |||
| Weights | Proprietary | Open | Open |
| API model ID | — | step-3.5-flash | mistral-large-2512 |
| API providers | 10 | 8 | 13 (best) |
| Released | Nov 13, 2025 | Jan 29, 2026 | Dec 2, 2025 |
| Knowledge cutoff | Sep 30, 2024 | Jan 2025 | Nov 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
- Step 3.5 Flash$1.60
- Mistral Large 3$8.00
Which should you choose?
Which is better: GPT-5.1 Codex mini, Step 3.5 Flash or Mistral Large 3?
Step 3.5 Flash is the better all-round choice, scoring 62/100 against GPT-5.1 Codex mini (59) and Mistral Large 3 (50). It leads on price. GPT-5.1 Codex mini wins on inputs & features and context window. 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, Step 3.5 Flash or Mistral Large 3?
Step 3.5 Flash is cheaper at $0.10 input / $0.30 output per million tokens (official StepFun (Global) API price). GPT-5.1 Codex mini costs $0.25 input / $2.00 output per million tokens (median across 10 API providers); Mistral Large 3 costs $0.50 input / $1.50 output per million tokens (official Mistral API price). At a typical mix of three input tokens to one output token, that is $0.15 per million tokens for Step 3.5 Flash versus $0.688 for GPT-5.1 Codex mini (4.6× as much) and $0.75 for Mistral Large 3 (5× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. GPT-5.1 Codex mini has not been scored yet, Step 3.5 Flash has not been scored yet and Mistral Large 3 has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.1 Codex mini, Step 3.5 Flash and Mistral Large 3 yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. All three 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 262,144 for Mistral Large 3 and 256,000 for Step 3.5 Flash. Maximum output per response: GPT-5.1 Codex mini up to 128,000, Step 3.5 Flash up to 256,000, Mistral Large 3 up to 262,144 tokens.
Which can read images, PDFs, audio or video?
GPT-5.1 Codex mini accepts text and images; Step 3.5 Flash accepts text; Mistral Large 3 accepts text and images. GPT-5.1 Codex mini handles the widest range of inputs.
Are any of these open source?
Step 3.5 Flash and Mistral Large 3 publishes its weights and can be self-hosted; GPT-5.1 Codex mini is proprietary.
Which is newer?
Step 3.5 Flash is the newest, released Jan 29, 2026. Mistral Large 3 came out Dec 2, 2025; GPT-5.1 Codex mini came out Nov 13, 2025. Knowledge cutoff: GPT-5.1 Codex mini Sep 30, 2024, Step 3.5 Flash Jan 2025, Mistral Large 3 Nov 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 Oct 4, 2026.
