GPT-6.1 Sol vs Inkling Small vs Claude Opus 5.5
GPT-6.1 Sol comes out ahead, 72 to 69 and 68 on our weighted score, though Inkling Small is 5× cheaper per token.
- Our pick
OpenAIGPT-6.1 Sol
72/100- ECI167.8
- Price$2.00 / $10.00
- Context1.05M
Thinking MachinesInkling Small
68/100- ECI150.5
- Price$0.58 / $1.44
- Context1.05M
AnthropicClaude Opus 5.5
69/100- ECI168.4
- Price$4.00 / $20.00
- Context1M
GPT-6.1 Sol is our pick
GPT-6.1 Sol is the better all-round choice, scoring 72/100 against Claude Opus 5.5 (69) and Inkling Small (68). Inkling Small wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityClaude Opus 5.5Capabilities Index (ECI): Claude Opus 5.5 168.4 · GPT-6.1 Sol 167.8 · Inkling Small 150.5
- Lowest priceInkling SmallInkling Small $0.795 · GPT-6.1 Sol $4.00 · Claude Opus 5.5 $8.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6.1 Sol and Inkling SmallGPT-6.1 Sol 1,050,000 · Inkling Small 1,048,576 · Claude Opus 5.5 1,000,000 tokens
- Widest inputsSame inputsGPT-6.1 Sol: Text, Images, PDFs · Inkling Small: Text, Images, Audio · Claude Opus 5.5: Text, Images, PDFs
- Self-hostingInkling SmallPublishes downloadable weights (Apache-2.0)
| Measure | Weight | GPT-6.1 Sol | Inkling Small | Claude Opus 5.5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 99 | 77 | 99 |
| Price | 25% | 20 | 52 | 7 |
| Inputs & features | 15% | 80 | 70 | 80 |
| Context window | 10% | 61 | 61 | 60 |
| Overall | 100% | 72/100 | 68/100 | 69/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-6.1 SolOpenAI | Inkling SmallThinking Machines | Claude Opus 5.5Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 167.8 | 150.5 | 168.4 (best) |
| ECI rank | #4 of 165 | #58 of 165 | #2 of 165 (best) |
| GPQA DiamondGraduate-level science questions | 95.4% (best) | 88.5% | 90.6% |
| FrontierMath Tiers 1–3Research-level mathematics | 93.7% (best) | 46.3% | 91.2% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% (best) | 90.0% | 100% (best) |
| SimpleQA VerifiedShort factual questions | 73.9% (best) | 19.1% | 72.2% |
| Price per million tokens | |||
| Input | $2.00 | $0.58 (best) | $4.00 |
| Output | $10.00 | $1.44 (best) | $20.00 |
| Cached input | $0.10 (best) | $0.116 | $0.20 |
| Blended (3:1) | $4.00 | $0.795 (best) | $8.00 |
| Long-context rate | Over 272K: $4.00 / $15.00 | Same rate | Same rate |
| Price source | Official OpenAI API | Official Thinking Machines API | Official Anthropic API |
| Limits | |||
| Context window | 1,050,000 tokens (best) | 1,048,576 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 1,048,576 tokens (best) | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | No | Yes |
| Audio | No | Yes | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | No | Yes |
| Availability | |||
| Weights | Proprietary | OpenApache-2.0 | Proprietary |
| API model ID | gpt-6.1-sol | thinkingmachines/Inkling-Small | claude-opus-5-5 |
| API providers | 33 | 12 | 36 (best) |
| Released | Sep 29, 2026 | Jul 30, 2026 | Sep 22, 2026 |
| Knowledge cutoff | Apr 30, 2026 | — | Jun 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-6.1 Sol$40.00
- Inkling Small$8.68
- Claude Opus 5.5$80.00
Which should you choose?
Which is better: GPT-6.1 Sol, Inkling Small or Claude Opus 5.5?
GPT-6.1 Sol is the better all-round choice, scoring 72/100 against Claude Opus 5.5 (69) and Inkling Small (68). Inkling Small wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-6.1 Sol, Inkling Small or Claude Opus 5.5?
Inkling Small is cheaper at $0.58 input / $1.44 output per million tokens (official Thinking Machines API price). GPT-6.1 Sol costs $2.00 input / $10.00 output per million tokens (official OpenAI API price); Claude Opus 5.5 costs $4.00 input / $20.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $0.795 per million tokens for Inkling Small versus $4.00 for GPT-6.1 Sol (5× as much) and $8.00 for Claude Opus 5.5 (10× as much).
Which scores higher on benchmarks?
Claude Opus 5.5 scores higher on the Capabilities Index (ECI): Claude Opus 5.5 168.4 (#2 of 165), GPT-6.1 Sol 167.8 (#4 of 165) and Inkling Small 150.5 (#58 of 165). The confidence ranges of the top two overlap (165.4–173.0 vs 164.3–172.5), so treat the gap as small. On individual benchmarks: GPQA Diamond — GPT-6.1 Sol 95.4%, Claude Opus 5.5 90.6%, Inkling Small 88.5%; FrontierMath Tiers 1–3 — GPT-6.1 Sol 93.7%, Claude Opus 5.5 91.2%, Inkling Small 46.3%; OTIS Mock AIME 2024–2025 — GPT-6.1 Sol 100%, Claude Opus 5.5 100%, Inkling Small 90.0%; SimpleQA Verified — GPT-6.1 Sol 73.9%, Claude Opus 5.5 72.2%, Inkling Small 19.1%.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-6.1 Sol, Inkling Small and Claude Opus 5.5 yet, so there is no like-for-like coding score. On overall capability, Claude Opus 5.5 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?
GPT-6.1 Sol and Inkling Small have the largest context windows (1,050,000 and 1,048,576 tokens), against 1,000,000 for Claude Opus 5.5. Maximum output per response: GPT-6.1 Sol up to 128,000, Inkling Small up to 1,048,576, Claude Opus 5.5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-6.1 Sol accepts text, images and PDFs; Inkling Small accepts text, images and audio; Claude Opus 5.5 accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
Inkling Small publishes its weights (Apache-2.0) and can be self-hosted; GPT-6.1 Sol and Claude Opus 5.5 is proprietary.
Which is newer?
GPT-6.1 Sol is the newest, released Sep 29, 2026. Claude Opus 5.5 came out Sep 22, 2026; Inkling Small came out Jul 30, 2026. Knowledge cutoff: GPT-6.1 Sol Apr 30, 2026, Claude Opus 5.5 Jun 2026.
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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