AI coding agent

Definition
A model that acts inside your codebase, reading files, running commands and editing across a project, rather than only suggesting a line of code.

Why it matters

For a business owner who builds with AI, the agent changes the bottleneck. Typing code is no longer the slow part. Describing the work clearly, and checking the result, is. That makes a marketer or founder able to ship a landing page tweak, an internal tool or a data clean-up that once needed a developer's week.

The catch is that an agent is confident whether it is right or wrong. It needs the same management as a fast junior colleague.

How to apply it

  • Give it one bounded task with a clear definition of done, such as "the form saves the field and the existing tests still pass".
  • Put standing instructions in a rules file so each session starts with the same conventions.
  • Work on a separate branch under version control, so any change can be thrown away.
  • Read the final change before it goes live, ideally as a pull request.
  • Give it only the access the task needs. A test database is safer than the production one.

What it is

Early coding assistants worked like autocomplete: they predicted the next few lines while a person typed. An agent takes a goal such as "add a phone number field to the signup form and save it to the database" and works through the steps itself. It reads the relevant files, makes a plan, edits several files, runs the tests, reads the errors and tries again. Claude Code, Codex and the agent modes in editors such as Cursor are examples.

Common mistakes

  • Handing over a vague goal like "improve the site" and expecting a sensible result.
  • Merging changes without reading them because the tests passed.
  • Letting the agent hold live credentials or customer data it does not need.
Worked example

Suppose a marketing lead at a twelve-person firm wants a small change to its landing page: a fourth testimonial and a shorter form. Before coding agents, that meant a week in a developer's queue. The lead describes the task to a coding agent in Cursor: add the testimonial, remove two form fields and keep the existing tests passing. The agent reads the relevant files, edits them, runs the tests and reports what it changed. The change goes to a separate branch in GitHub, so a developer can read the final diff before it goes live. Say the agent gets it right first time in two of three runs. In the third, it changes a shared component, and the diff review catches it before any visitor sees it.

Tools in the example

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  1. Article

    Vibe coding

    Building software by directing an agent in plain language.

  2. Article

    Autonomous agent

    The wider category.

  3. Article

    Context window

    How much of the project an agent can keep in view at once.

Where it shows up

  • Writing copy that feels like conversation instead of marketing. How to sound like yourself.
    12 chapters