GPT-5.5 Instant vs Inkling vs Mistral Medium 3.5
Inkling comes out ahead, 59 to 55 and 51 on our weighted score, though Mistral Medium 3.5 is 42% cheaper per token.
OpenAIGPT-5.5 Instant
51/100- ECI142.5
- Price$5.00 / $30.00
- Context400K
- Our pick
Thinking MachinesInkling
59/100- ECI148.6
- Price$3.74 / $9.36
- Context1.05M
Mistral AIMistral Medium 3.5
55/100- ECI141.4
- Price$1.50 / $7.50
- Context262K
Inkling is our pick
Inkling is the better all-round choice, scoring 59/100 against Mistral Medium 3.5 (55) and GPT-5.5 Instant (51). It leads on capability and context window. GPT-5.5 Instant wins on inputs & features. Mistral Medium 3.5 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityInklingCapabilities Index (ECI): Inkling 148.6 · GPT-5.5 Instant 142.5 · Mistral Medium 3.5 141.4
- Lowest priceMistral Medium 3.5Mistral Medium 3.5 $3.00 · Inkling $5.14 · GPT-5.5 Instant $11.25 per 1M tokens (3:1 blend)
- Longest contextInklingInkling 1,048,576 · GPT-5.5 Instant 400,000 · Mistral Medium 3.5 262,144 tokens
- Widest inputsGPT-5.5 Instant and InklingGPT-5.5 Instant: Text, Images, PDFs · Inkling: Text, Images, Audio · Mistral Medium 3.5: Text, Images
- Self-hostingInkling and Mistral Medium 3.5Publishes downloadable weights (Apache-2.0)
| Measure | Weight | GPT-5.5 Instant | Inkling | Mistral Medium 3.5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 69 | 76 | 67 |
| Price | 25% | 0 | 16 | 27 |
| Inputs & features | 15% | 80 | 70 | 70 |
| Context window | 10% | 44 | 61 | 37 |
| Overall | 100% | 51/100 | 59/100 | 55/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.5 InstantOpenAI | InklingThinking Machines | Mistral Medium 3.5Mistral AI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 142.5 | 148.6 (best) | 141.4 |
| ECI rank | #89 of 148 | #57 of 148 (best) | #95 of 148 |
| GPQA DiamondGraduate-level science questions | 82.5% | 88.3% (best) | — |
| FrontierMath Tiers 1–3Research-level mathematics | 26.3% | 33.3% (best) | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 68.1% | 88.9% (best) | — |
| SimpleQA VerifiedShort factual questions | — | 40.3% | — |
| Price per million tokens | |||
| Input | $5.00 | $3.74 | $1.50 (best) |
| Output | $30.00 | $9.36 | $7.50 (best) |
| Cached input | — | $0.748 | $0.15 (best) |
| Blended (3:1) | $11.25 | $5.14 | $3.00 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Median of 3 providers | Official Thinking Machines API | Official Mistral API |
| Limits | |||
| Context window | 400,000 tokens | 1,048,576 tokens (best) | 262,144 tokens |
| Max output | 128,000 tokens | 1,048,576 tokens (best) | 262,144 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | No | No |
| Audio | No | Yes | No |
| Video | No | No | No |
| Reasoning | Yes | Yeslow · medium · high · xhigh · max | Yeshigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | No | Yes |
| Availability | |||
| Weights | Proprietary | OpenApache-2.0 | Open |
| API model ID | — | thinkingmachines/Inkling:peft:262144 | mistral-medium-2604 |
| API providers | 3 | 23 (best) | 12 |
| Released | May 5, 2026 | Jul 15, 2026 | Apr 29, 2026 |
| Knowledge cutoff | Dec 1, 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-5.5 Instant$110.00
- Inkling$56.12
- Mistral Medium 3.5$30.00
Which should you choose?
Which is better: GPT-5.5 Instant, Inkling or Mistral Medium 3.5?
Inkling is the better all-round choice, scoring 59/100 against Mistral Medium 3.5 (55) and GPT-5.5 Instant (51). It leads on capability and context window. GPT-5.5 Instant wins on inputs & features. Mistral Medium 3.5 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.5 Instant, Inkling or Mistral Medium 3.5?
Mistral Medium 3.5 is cheaper at $1.50 input / $7.50 output per million tokens (official Mistral API price). Inkling costs $3.74 input / $9.36 output per million tokens (official Thinking Machines API price); GPT-5.5 Instant costs $5.00 input / $30.00 output per million tokens (median across 3 API providers). At a typical mix of three input tokens to one output token, that is $3.00 per million tokens for Mistral Medium 3.5 versus $5.14 for Inkling (1.7× as much) and $11.25 for GPT-5.5 Instant (3.8× as much).
Which scores higher on benchmarks?
Inkling scores higher on the Capabilities Index (ECI): Inkling 148.6 (#57 of 148), GPT-5.5 Instant 142.5 (#89 of 148) and Mistral Medium 3.5 141.4 (#95 of 148). Their confidence ranges do not overlap (145.7–150.6 vs 140.0–145.3), so the gap is a real one.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.5 Instant, Inkling and Mistral Medium 3.5 yet, so there is no like-for-like coding score. On overall capability, Inkling leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Inkling has the largest context window at 1,048,576 tokens, against 400,000 for GPT-5.5 Instant and 262,144 for Mistral Medium 3.5. Maximum output per response: GPT-5.5 Instant up to 128,000, Inkling up to 1,048,576, Mistral Medium 3.5 up to 262,144 tokens.
Which can read images, PDFs, audio or video?
GPT-5.5 Instant accepts text, images and PDFs; Inkling accepts text, images and audio; Mistral Medium 3.5 accepts text and images. GPT-5.5 Instant handles the widest range of inputs.
Are any of these open source?
Inkling and Mistral Medium 3.5 publishes its weights (Apache-2.0) and can be self-hosted; GPT-5.5 Instant is proprietary.
Which is newer?
Inkling is the newest, released Jul 15, 2026. GPT-5.5 Instant came out May 5, 2026; Mistral Medium 3.5 came out Apr 29, 2026. Knowledge cutoff: GPT-5.5 Instant Dec 1, 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.
