# Building a Coding Agent From Scratch

DevFeed: [Building a Coding Agent From Scratch](<https://devfeed.tech/articles/building-a-coding-agent-from-scratch-18293.md>)

Original publisher: [Read original article](<https://www.decodingai.com/p/building-a-coding-agent-from-scratch-system-design>)

Author: Paul Iusztin

Published: 2026-07-22T11:04:24Z

Content type: tutorial

Language: en

Sources: [Decoding ML](<https://devfeed.tech/sources/decoding-ml.md>)

Topics: [Agent Harness](<https://devfeed.tech/topics/agent-harness.md>), [AI-assisted coding](<https://devfeed.tech/topics/ai-assisted-coding.md>), [coding](<https://devfeed.tech/topics/coding.md>), [LangChain](<https://devfeed.tech/topics/langchain.md>), [Claude Code](<https://devfeed.tech/topics/claude-code.md>), [codex](<https://devfeed.tech/topics/codex.md>)

Tags: [agent-harness](<https://devfeed.tech/tags/agent-harness.md>), [ai](<https://devfeed.tech/tags/ai.md>), [ai-agents](<https://devfeed.tech/tags/ai-agents.md>), [ai-evals](<https://devfeed.tech/tags/ai-evals.md>), [benchmarks](<https://devfeed.tech/tags/benchmarks.md>), [claude-code](<https://devfeed.tech/tags/claude-code.md>), [codex](<https://devfeed.tech/tags/codex.md>), [coding-agents](<https://devfeed.tech/tags/coding-agents.md>), [langchain](<https://devfeed.tech/tags/langchain.md>)

## AI overview

This tutorial explains how to build a coding-agent harness from scratch in Python. It covers the agent loop, shell execution, context engineering, subagents, remote parallel agents, and evaluation workflows, using the project Decode as the practical example.

## Source excerpt

Designing the harness around the model, from the agent loop to a remote swarm.