GLM-5.1 vs GPT-5.5 Instant
GLM-5.1 (2026) and GPT-5.5 Instant (2026) are frontier reasoning models from Zhipu AI and OpenAI. GLM-5.1 ships a 200k-token context window, while GPT-5.5 Instant ships a 400k-token context window. On pricing, GLM-5.1 costs $1.05/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GLM-5.1 is ~376% cheaper at $1.05/1M; pay for GPT-5.5 Instant only for coding workflow support.
Decision scorecard
Local evidence first| Signal | GLM-5.1 | GPT-5.5 Instant |
|---|---|---|
| Best for | reasoning-heavy apps, tool-calling agents, and provider-routed production | multimodal apps and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 200k | 400k |
| Cheapest output | $3.50/1M tokens | $30/1M tokens |
| Provider routes | 5 tracked | 1 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- GLM-5.1 has the lower cheapest tracked output price at $3.50/1M tokens.
- GLM-5.1 has broader tracked provider coverage for fallback and route flexibility.
- GLM-5.1 uniquely exposes Reasoning in local model data.
- Local decision data tags GLM-5.1 for Coding, RAG, and Agents.
- GPT-5.5 Instant has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 Instant uniquely exposes Vision and Multimodal in local model data.
- Local decision data tags GPT-5.5 Instant for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GLM-5.1
$1,715
Cheapest tracked route/tier: OpenRouter
GPT-5.5 Instant
$11,500
Cheapest tracked route/tier: OpenAI API
Estimated monthly gap: $9,785. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for GLM-5.1 and GPT-5.5 Instant; plan for SDK, billing, or endpoint changes.
- GPT-5.5 Instant is $26.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning before moving production traffic.
- GPT-5.5 Instant adds Vision and Multimodal in local capability data.
- No overlapping tracked provider route is sourced for GPT-5.5 Instant and GLM-5.1; plan for SDK, billing, or endpoint changes.
- GLM-5.1 is $26.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision and Multimodal before moving production traffic.
- GLM-5.1 adds Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-07 | 2026-05-05 |
| Context window | 200k | 400k |
| Parameters | 754B total, 40B active | — |
| Architecture | Mixture of Experts | Decoder Only |
| License | MITOSI-approved | Proprietary |
| Openness | Open source | Proprietary |
| Weights | Available | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: permitted | Commercial use: conditional |
| Knowledge cutoff | 2025-11 | 2025-08 |
Pricing and availability
| Pricing attribute | GLM-5.1 | GPT-5.5 Instant |
|---|---|---|
| Input price | $1.05/1M tokens | $5/1M tokens |
| Output price | $3.50/1M tokens | $30/1M tokens |
| Providers |
Capabilities
| Capability | GLM-5.1 | GPT-5.5 Instant |
|---|---|---|
| Vision | No | Yes |
| Multimodal | No | Yes |
| Reasoning | Yes | No |
| JSON / Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark scores are currently available for this pair.
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Last reviewed: 2026-06-30. Data sourced from public model cards and provider documentation.