Claude Sonnet 5.5 vs GLM-5.3-Flash vs GPT-6.1 Sol
GLM-5.3-Flash comes out ahead, 79 to 72 and 71 on our weighted score, and it is the cheaper option too.
AnthropicClaude Sonnet 5.5
71/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
- Our pick
Z.ai (Zhipu)GLM-5.3-Flash
79/100- ECI151.9
- Price$0.15 / $0.50
- Context1M
OpenAIGPT-6.1 Sol
72/100- ECI—
- Price$2.00 / $10.00
- Context1.05M
GLM-5.3-Flash is our pick
GLM-5.3-Flash is the better all-round choice, scoring 79/100 against GPT-6.1 Sol (72) and Claude Sonnet 5.5 (71). It leads on price and inputs & features. GPT-6.1 Sol wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025), because GPT-6.1 Sol has no Capabilities Index score yet.
- CapabilityGPT-6.1 SolShared benchmarks: GPT-6.1 Sol 96.4% · Claude Sonnet 5.5 94.8% · GLM-5.3-Flash 79.9%
- Lowest priceGLM-5.3-FlashGLM-5.3-Flash $0.237 · Claude Sonnet 5.5 $4.00 · GPT-6.1 Sol $4.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6.1 SolGPT-6.1 Sol 1,050,000 · Claude Sonnet 5.5 1,000,000 · GLM-5.3-Flash 1,000,000 tokens
- Widest inputsGLM-5.3-FlashClaude Sonnet 5.5: Text, Images, PDFs · GLM-5.3-Flash: Text, Images, PDFs, Video · GPT-6.1 Sol: Text, Images, PDFs
- Self-hostingGLM-5.3-FlashPublishes downloadable weights
| Measure | Weight | Claude Sonnet 5.5 | GLM-5.3-Flash | GPT-6.1 Sol |
|---|---|---|---|---|
| CapabilityShared benchmarks | 50% | 95 | 80 | 96 |
| Price | 25% | 21 | 79 | 21 |
| Inputs & features | 15% | 80 | 90 | 80 |
| Context window | 10% | 60 | 60 | 61 |
| Overall | 100% | 71/100 | 79/100 | 72/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Sonnet 5.5Anthropic | GLM-5.3-FlashZ.ai (Zhipu) | GPT-6.1 SolOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 165.2 (best) | 151.9 | — |
| ECI rank | #3 of 148 (best) | #42 of 148 | — |
| GPQA DiamondGraduate-level science questions | 95.6% (best) | 90.2% | 95.4% |
| FrontierMath Tiers 1–3Research-level mathematics | 88.8% | 55.8% | 93.7% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% (best) | 93.9% | 100% (best) |
| SimpleQA VerifiedShort factual questions | 46.5% | — | 73.9% (best) |
| Price per million tokens | |||
| Input | $2.00 | $0.15 (best) | $2.00 |
| Output | $10.00 | $0.50 (best) | $10.00 |
| Cached input | $0.20 | $0.03 (best) | $0.10 |
| Blended (3:1) | $4.00 | $0.237 (best) | $4.00 |
| Long-context rate | Same rate | Same rate | Over 272K: $4.00 / $15.00 |
| Price source | Official Anthropic API | Official Z.AI API | Official OpenAI API |
| Limits | |||
| Context window | 1,000,000 tokens | 1,000,000 tokens | 1,050,000 tokens (best) |
| Max output | 128,000 tokens | 131,072 tokens (best) | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | No | No |
| Video | No | Yes | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · high · max | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Open | Proprietary |
| API model ID | claude-sonnet-5-5 | glm-5.3-flash | gpt-6.1-sol |
| API providers | 23 | 65 (best) | 21 |
| Released | Sep 28, 2026 | Aug 26, 2026 | Sep 29, 2026 |
| Knowledge cutoff | Jun 2026 | — | Apr 30, 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Sonnet 5.5$40.00
- GLM-5.3-Flash$2.50
- GPT-6.1 Sol$40.00
Which should you choose?
Which is better: Claude Sonnet 5.5, GLM-5.3-Flash or GPT-6.1 Sol?
GLM-5.3-Flash is the better all-round choice, scoring 79/100 against GPT-6.1 Sol (72) and Claude Sonnet 5.5 (71). It leads on price and inputs & features. GPT-6.1 Sol wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025), because GPT-6.1 Sol has no Capabilities Index score yet.
Which is cheaper, Claude Sonnet 5.5, GLM-5.3-Flash or GPT-6.1 Sol?
GLM-5.3-Flash is cheaper at $0.15 input / $0.50 output per million tokens (official Z.AI API price). Claude Sonnet 5.5 costs $2.00 input / $10.00 output per million tokens (official Anthropic API price); GPT-6.1 Sol costs $2.00 input / $10.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $0.237 per million tokens for GLM-5.3-Flash versus $4.00 for Claude Sonnet 5.5 (17× as much) and $4.00 for GPT-6.1 Sol (17× as much).
Which scores higher on benchmarks?
Not every model here has a Capabilities Index score, so we compare the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025): GPT-6.1 Sol 96.4%, Claude Sonnet 5.5 94.8% and GLM-5.3-Flash 79.9%. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, GPT-6.1 Sol 95.4%, GLM-5.3-Flash 90.2%; FrontierMath Tiers 1–3 — GPT-6.1 Sol 93.7%, Claude Sonnet 5.5 88.8%, GLM-5.3-Flash 55.8%; OTIS Mock AIME 2024–2025 — Claude Sonnet 5.5 100%, GPT-6.1 Sol 100%, GLM-5.3-Flash 93.9%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 5.5, GLM-5.3-Flash and GPT-6.1 Sol yet, so there is no like-for-like coding score. On overall capability, GPT-6.1 Sol 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 has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Sonnet 5.5 and 1,000,000 for GLM-5.3-Flash. Maximum output per response: Claude Sonnet 5.5 up to 128,000, GLM-5.3-Flash up to 131,072, GPT-6.1 Sol up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Claude Sonnet 5.5 accepts text, images and PDFs; GLM-5.3-Flash accepts text, images, PDFs and video; GPT-6.1 Sol accepts text, images and PDFs. GLM-5.3-Flash handles the widest range of inputs.
Are any of these open source?
GLM-5.3-Flash publishes its weights and can be self-hosted; Claude Sonnet 5.5 and GPT-6.1 Sol is proprietary.
Which is newer?
GPT-6.1 Sol is the newest, released Sep 29, 2026. Claude Sonnet 5.5 came out Sep 28, 2026; GLM-5.3-Flash came out Aug 26, 2026. Knowledge cutoff: Claude Sonnet 5.5 Jun 2026, GPT-6.1 Sol Apr 30, 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 Oct 4, 2026.
