GLM-5.1 API 2026: 8-Hour Agentic Coding, 200K Context, and the CodeFast GLM Package
GLM-5.1 is one of 2026's most interesting Claude-alternative coding models with 200K context, 128K max output, tool calling, and long-running agentic coding positioning. While official Z.ai pricing lists $1.40/M input and $4.40/M output, the CodeFast GLM API package starts GLM experiments with a much lower entry cost: 600 TRY for 30 days with 750 daily uses.
Z.ai positions GLM-5.1 for complex reasoning, long context, and agentic work. The official docs highlight a 200K context window, 128K max output, thinking mode, streaming, function calling, structured output, context caching, and MCP support. That combination moves the model beyond a classic chatbot and closer to a developer agent that reads code, uses tools, plans, and iterates.
Z.ai's pricing page lists GLM-5.1 at $1.40 per 1M input tokens and $4.40 per 1M output tokens. That is aggressive for a capable model, but the real developer cost depends on the number of experiments, output length, retries, tool-call loops, and context size. In coding-agent work, the model does not simply answer once; it reads files, plans, retries, and can generate long outputs.
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