GLM + OpenCode: Free-Tier-Friendly Coding Agent

OpenCode is free and open source; GLM is one of the cheapest capable model families, with a flat coding plan from $18/month. Together they make a low-cost, fully terminal coding agent that reads your repo, edits files, and runs commands without OpenAI or Anthropic pricing.

This is the OpenCode + GLM setup: the provider block, model IDs, and the billing choice. For OpenCode’s general provider model, see OpenCode custom providers.

Step 1: Install OpenCode and get a Z.AI key#

npm install -g opencode-ai

Sign up at Z.AI for a key — pay-per-token or the GLM Coding Plan. On Windows, WSL gives the cleaner shell — see install OpenCode on Windows with WSL.

Step 2: Add the GLM provider#

OpenCode connects to OpenAI-compatible APIs through @ai-sdk/openai-compatible. Add Z.AI in opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "provider": {
    "zai": {
      "npm": "@ai-sdk/openai-compatible",
      "name": "Z.AI GLM",
      "options": {
        "baseURL": "https://api.z.ai/api/paas/v4",
        "apiKey": "{env:ZAI_API_KEY}"
      },
      "models": {
        "glm-5-turbo": { "name": "GLM-5 Turbo" },
        "glm-5": { "name": "GLM-5" }
      }
    }
  },
  "model": "zai/glm-5-turbo"
}

Export the key:

export ZAI_API_KEY="your-zai-key"

Step 3: Run it#

opencode

The default is zai/glm-5-turbo. Switch in the TUI or change the model key.

Pricing#

OpenCode is free; GLM bills via pay-per-token or the GLM Coding Plan (from $18/month, with rolling-window caps). Heavy daily users save with the plan. See GLM Coding Plan setup and GLM-4.6 vs GLM-5 vs GLM-5-Turbo.

Troubleshooting#

• Provider not found — the provider key (zai) must match the model prefix.
• Auth errors — ZAI_API_KEY not set in the launching shell.
• Format errors — you used /anthropic; switch to the OpenAI (paas/v4) URL.
• Access denied on glm-5 — plan tier doesn’t include it; use glm-5-turbo.

Wrapping up#

GLM with OpenCode is a cheap, open agent: add a Z.AI provider in opencode.json using @ai-sdk/openai-compatible on the OpenAI endpoint, list glm-5-turbo and glm-5, and set a default. Pay per token or use the GLM Coding Plan, and default to Turbo to stretch your usage.

For other GLM setups, see run GLM-5 with Claude Code and GLM + Cline in VS Code.