Coding Agents

Introduction

A coding agent reads a repo, plans changes, edits files, runs tests and iterates. Devin, Cursor Agent, Copilot Workspace and Cline are the famous examples.

Beginner analogy: a junior engineer with a fast feedback loop — write, test, fix, repeat.

Understanding the topic

Core concepts:

• Tools: read_file, edit_file, run_shell, run_tests, web_search.
• Plan-execute with reflection on test failures.
• Long context (whole repo via embeddings).
• Diff-based edits beat full-file rewrites.
• Always run tests before declaring done.

Syntax reference

Visual workflow / architecture:

Issue → plan → edit_file → run_tests
                      ▲              │
                      └─── reflect ──┘

Real-world use

Devin, Cursor Agent, Cline, Copilot Workspace, OpenHands (open-source).

Best practices

• Make edits diff-based.
• Cap LOC per turn.
• Run tests every cycle.

Common mistakes

• Whole-file rewrites — too many bugs introduced.

Hands-on exercise

Interview preparation — practice these questions:

• Q1. Tools a coding agent needs.
• Q2. Why diff edits beat full-file rewrites?
• Q3. Scenario: your coding agent keeps deleting tests. How do you constrain it?