GLM-5.2 is the June 2026 flagship in Z.ai's (formerly Zhipu AI) GLM-5 series — an open-weight Mixture-of-Experts model built specifically for long-horizon coding agents rather than general chat. It pairs a usable 1M-token context with native tool calling, MCP support, and structured JSON output, and ships under an MIT open-source license you can self-host. On GPTProto, the GLM-5.2 API is metered pay-as-you-go access with no regional sign-up barriers and one balance shared across 200+ models.
| Spec | GLM-5.2 |
|---|---|
| Developer | Z.ai (formerly Zhipu AI) |
| Architecture | Mixture-of-Experts, ~753B total / ~40B active per token |
| Context window | 1,000,000 tokens (lossless) |
| Max output | 131,072 tokens (~128K) |
| Modality | Text in, text out |
| Reasoning | Selectable effort — High / Max |
| Tool use | Native function calling, MCP, structured JSON |
| License | MIT (open weights) |
| Released | June 13, 2026 |
| GPTProto price | $1.26 in / $3.96 out per 1M tokens (10% under Z.ai list) |
| API model string | glm-5.2 (provider slug z-ai, full 1M context) |
GLM-5.2 vs GLM-5 and GLM-5.1
All three GLM-5 releases are live on GPTProto, so moving up a version is just a model-string swap — same key, same balance. The jump to 5.2 is mostly about context size and long-task stability:
| GLM-5 | GLM-5.1 | GLM-5.2 | |
|---|---|---|---|
| Released | Feb 2026 | Apr 2026 | Jun 2026 |
| Context window | ~200K-class | ~200K-class | 1,000,000 (≈5x) |
| SWE-bench Pro* | — | 58.4 | 62.1 |
| Long-context attention | standard | standard | IndexShare (−2.9x compute) |
| Speculative decoding | — | — | MTP (+~20% accepted tokens) |
| GPTProto output / 1M | $2.88 | $3.96 | $3.96 |
The practical takeaway: GLM-5.2 lists at the same $3.96 output rate as GLM-5.1 on GPTProto but gives you roughly 5x the context and a measurable bump in long-horizon coding — so for repository-scale work there's little reason to stay on 5.1.
GLM-5.2 vs GPT-5.5
GPT-5.5 is also on GPTProto, so this is a real swap, not a marketing comparison. On Z.ai's reported long-horizon coding benchmarks, GLM-5.2 edges GPT-5.5 on most agentic tasks while costing far less per token:
| Benchmark (vendor-reported, Z.ai) | GLM-5.2 | GPT-5.5 |
|---|---|---|
| SWE-bench Pro | 62.1 | 58.6 |
| FrontierSWE (long-horizon) | 74.4% | 72.6% |
| MCP-Atlas (tool use) | 77.0 | 75.3 |
| Humanity's Last Exam (w/ tools) | 54.7 | 52.2 |
| Terminal-Bench 2.1 | 81.0 | 84.0 |
| GPTProto price / 1M (in / out) | $1.26 / $3.96 | $4 / $24 |
On GPTProto the GLM-5.2 API runs about 3x cheaper on input and 6x cheaper on output than GPT-5.5 ($1.26/$3.96 vs $4/$24 per 1M). GPT-5.5 still leads on raw terminal tasks, so it isn't a clean sweep — but for agentic, tool-driven, multi-step coding the benchmark edge favors GLM-5.2 at a fraction of the spend. On the independent Artificial Analysis Intelligence Index v4.1, GLM-5.2 scores 51, competitive at the open frontier though not ahead of every closed model on general tasks.
Switching from the official Z.ai API
If you're already calling GLM-5.2 on Z.ai's API, moving to GPTProto is a drop-in: keep your request body, change the base URL and key. You get the same glm-5.2 model with no separate Z.ai account, no regional sign-up friction, and one balance that also covers GPT-5.5, Claude, Gemini, and 200+ other models. The exact endpoint and model string are in the Quick Start below.
