GLM-5.1 - Long-Horizon Agentic Coding
GLM-5.1 is Z.ai's open-source flagship model for agentic software engineering. Built for sustained long-horizon work — the kind of build that involves hundreds of iterations, complex refactors, and multi-file coordination across a real codebase. MIT licensed, with weights on HuggingFace.
Why Choose GLM-5.1?
Perfect for:
- Full-stack web apps requiring deep multi-file coordination
- Repository-level refactors with many interconnected changes
- Builds where the agent needs to stay sharp across many steps
- Cost-sensitive projects that need more than GLM-4.6 can offer
Benchmark Performance
| Benchmark | Score | Context |
|---|---|---|
| SWE-bench Pro | 58.4% | Beats GPT-5.4 (57.7%) and Claude Opus 4.6 (57.3%) |
| Terminal-Bench 2.0 | 69.0 | Claude Code harness |
| NL2Repo | 42.7 | Repository generation |
| CyberGym | 68.7 | Significant jump from GLM-5 |
What You Get
- SOTA Coding: 58.4% SWE-bench Pro — ahead of GPT-5.4 and Claude Opus 4.6 on this benchmark
- Terminal-Bench Leader: 69.0 on Terminal-Bench 2.0 (Claude Code harness)
- 200K Context: Holds large codebases in a single session
- Long-Horizon Stability: Tested at 600+ iterations and 6,000+ tool calls without degradation
- Open Source: MIT license, weights on HuggingFace and ModelScope
Cost
Official Rates: $1.40 per 1M input tokens / $4.40 per 1M output tokens
Typical costs: ~$0.10 for a landing page, ~$0.30 for a small app, ~$0.70 for a complex build.
Building Web Apps with GLM-5.1 on Softgen
GLM-5.1 is the pick when a build involves a lot of connected changes. Its long-horizon stability — tested at thousands of tool calls without degrading — translates to coherent multi-file refactors inside Softgen. The 200K context lets the agent reason across many files at once. Deploy when it looks right.
Strong choice when you want coding benchmark performance close to Claude Opus tier without the price.
When to Use a Different Model
- Maximum coding reasoning and vision (try Claude Opus 4.7)
- Multilingual EN/ZH builds on a tighter budget (try GLM-4.6)
- Visual-first front-end from screenshots (try Kimi K2.5)
- Established Anthropic workflows (try Claude Sonnet 4.5)
The Bottom Line
GLM-5.1 is a strong open-source option for agentic coding on Softgen. It edges past GPT-5.4 on SWE-bench Pro and leads Terminal-Bench 2.0 (Claude Code harness), with 200K context and MIT licensing. The long-horizon stability is the real differentiator — it holds up across complex sessions where other models start making mistakes.
Best for: Multi-file web apps, repository-level refactors, terminal-heavy agentic sessions, and teams that want open-source weights without sacrificing coding quality.
Want to learn more? Read the official GLM-5.1 announcement from Z.ai for technical benchmarks and capabilities.
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