GLM 5.1

Technical Specifications of GLM-5.1

What is GLM-5.1

GLM-5.1 is Z.ai’s frontier-class language model optimized for long-horizon autonomous tasks. Unlike traditional LLMs that excel at short, single-turn interactions, it is engineered for sustained execution loops—planning, coding, testing, benchmarking, debugging, and iterative optimization—over extended periods without human intervention.

Key Features of GLM-5.1

1. Long-Horizon Autonomous Work

8-Hour Sustained Execution: GLM-5.1 is Z.AI’s latest flagship model for long-horizon tasks, and the official docs say it can work continuously and autonomously on a single task for up to 8 hours. It is positioned to handle the full loop from planning and execution to iterative optimization and final delivery.

Closed-Loop Optimization: A core feature of GLM-5.1 is its ability to keep iterating through an “experiment → analyze → optimize” cycle, rather than stopping at one-shot output. Z.AI describes this as a major step toward autonomous engineering and long-horizon coding agents.

2. Strong Coding and Reasoning Ability

Broad Capability Balance: GLM-5.1 is broadly aligned with Claude Opus 4.6 in general capability and coding performance, and that it shows a balanced profile across reasoning, coding, agents, tool use, and browsing benchmarks.

Advanced Engineering Workflows: GLM-5.1 is designed for real-world development workflows, including complex engineering optimization, debugging, and production-grade delivery. Z.AI positions it as a foundation for autonomous agents and long-horizon coding agents.

3. Better Support for Complex Tasks

Larger Context and Output: The migration guide lists GLM-5.1’s maximum context length as 200K and maximum output as 128K, which makes it more suitable for large tasks and extended sessions.

Deep Thinking and Tool Streaming: GLM-5.1 supports deep thinking mode, and Z.AI also adds streaming output during tool calls with tool_stream=true, which helps expose tool-call parameters in real time.

4. Built for Agentic Engineering

From Code Generation to Autonomous Delivery: Z.AI’s positioning for GLM-5.1 is not just “generate code,” but “deliver engineering work.” The docs describe it as a new-generation flagship model for “Agentic Engineering,” emphasizing planning, execution, optimization, and delivery in one workflow.

Stronger Stability Over Long Tasks: The release notes say GLM-5.1 improves stability, consistency, and tool use over extended tasks, supported by multi-turn SFT, RL, and process-quality evaluation.

GLM-5.1 vs Other Models

GLM-5.1 stands out as one of the strongest open-source options and a direct competitor to closed frontier models in coding and agentic scenarios:

• vs. Claude Opus 4.6: ~94–100% of coding performance on SWE-Bench Pro (58.4 vs. 57.3); superior long-horizon autonomy and lower cost via open weights/aggregators.
• vs. GPT-5.4: Outperforms on SWE-Bench Pro (58.4 vs. 57.7); competitive or slightly behind in some pure reasoning tasks.
• vs. GLM-5 (predecessor): 28% coding uplift and dramatically better sustained execution.
• vs. Llama 3.1 / Qwen / DeepSeek: Stronger agentic and long-horizon results; open MIT license provides greater customization freedom than many alternatives.

Its primary advantages are open-source accessibility, cost efficiency at scale, and specialized optimization for real-world engineering agents.

Use Cases

GLM-5.1 excels wherever long-running, iterative intelligence is required:

• Autonomous Software Engineering: Full-stack feature development, code migration, large-scale refactoring, and end-to-end testing with minimal oversight.
• Performance Optimization: Kernel-level improvements, database tuning, and multi-iteration benchmarking (e.g., 6.9× vector query speedup).
• Agentic Workflows: Integration into coding agents (Claude Code, OpenClaw) for repository-scale tasks or complex system building.
• Enterprise Productivity: Long-document analysis, report generation, and structured office artifacts.
• Research & Prototyping: Rapid iteration on ambiguous problems requiring hundreds of self-correcting steps.

How to Access GLM-5.1 via CometAPI

CometAPI, a unified AI model aggregator, provides immediate, OpenAI-compatible access to GLM-5.1 (and GLM-5) alongside 500+ other models. Developers simply sign up at cometapi.com, obtain an API key, and route requests to the GLM-5.1 endpoint(glm-5.1) using standard OpenAI SDKs or Chat Completions. No infrastructure setup is required—CometAPI handles inference routing, load balancing, and failover.

Current CometAPI Pricing (approximate, as of mid-April 2026):

• Input: $0.8 per million tokens
• Output: $3.2 per million tokens

This is significantly lower than Z.ai’s direct rates (~$1.4 / $4.4) and a fraction of equivalent Western frontier models.