GLM 5.1 vs GPT-5.5 Pro
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for GLM 5.1 and GPT-5.5 Pro.
GLM 5.1
GLM-5.1 delivers a major leap in coding capability, with particularly significant gains in handling long-horizon tasks. Unlike previous models built around minute-level interactions, GLM-5.1 can work independently and continuously on...
GPT-5.5 Pro
GPT-5.5 Pro is OpenAI’s high-capability model optimized for deep reasoning and accuracy on complex, high-stakes workloads. It features a 1M+ token context window (922K input, 128K output) with support for...
Technical Specifications
| Specification | GLM 5.1 | GPT-5.5 Pro |
|---|---|---|
| Provider | Zhipu AI | OpenAI |
| Context Window | 202,752 tokens | 1,050,000 tokens |
| Agent Suitability | N/A | 98/100 |
| Time to First Token (TTFT) | N/A | 450 ms |
| Deployment Model | managed api | managed api |
| Production Stability | stable | beta |
| API Available | Yes | Yes |
| Released Date | 2026-04-07 | 2026-04-24 |
API Pricing Comparison
Input Price per Million Tokens
GLM 5.1
$0.97
GPT-5.5 Pro
$30.00
Output Price per Million Tokens
GLM 5.1
$3.04
GPT-5.5 Pro
$180.00
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
GLM 5.1 Quirks & Gotchas
No developer gotchas reported.
GPT-5.5 Pro Quirks & Gotchas
- ▸Best-in-class instruction following for complex agentic chains
- ▸Premium pricing — use GPT-5 for cost-sensitive workloads