How do I build my own AI coding assistant?

Updated October 2026 · How we answer

Core building blocks

A basic assistant needs a model API, a loop that sends messages and reads replies, and a set of tools such as read file, write file, and run command. Each tool should have a clear name, a short description, and an input schema so the model knows how to use it.

Keep permissions tight. Let the tool read files in one project folder, and require approval before it runs shell commands or deletes anything. Tight limits make a bad model reply much less damaging.

• Model API access
• A message loop
• Tools with clear names and schemas
• Approval steps for risky actions

Testing your assistant

Test with small, safe tasks in a sandbox folder. Log every tool call so you can see what the model did and why. Logs make it much easier to find the step where things went wrong.

Add tests for your tools themselves, since bugs in a tool can cause bad edits even when the model behaves well. Test the tools first, then the full loop.

• Work in a sandbox folder
• Log every tool call
• Test each tool separately
• Add approval for file changes

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