Aider explained: AI coding in a repository with Git and tests

01 / Understand the product

aider at a glance

Interface

Terminal-based AI pair programming
Source reference ↗

Source workflow

Work with files in your project
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Git default

Documentation describes automatically committing generated edits
Source reference ↗

Undo route

The documented /undo command reverts the last AI change
Source reference ↗

Test integration

User-supplied test command with optional automatic execution
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Editor workflow

Watch-files mode responds to documented AI comment markers
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We reviewed Aider’s homepage and usage, Git, editor-watch and lint/test documentation. We did not install it, run paid inference or reproduce the publisher’s benchmarks.

02 / aider

What makes Aider relevant to an existing codebase?

An existing application contains decisions a generated greenfield example does not: routes, naming conventions, dependencies, security assumptions and tests. Aider’s documented workflow operates on repository files, so the useful evaluation is whether it can make a narrowly specified change while preserving those decisions. Starting a new demo is a different task from modifying a production codebase.

Choose a task that has an observable result and touches few files. For example, add an empty state to a search page while preserving its filtering behavior. Record the route, expected text, keyboard behavior and conditions under which the state appears. This gives the coding tool enough direction without asking it to redesign unrelated application structure.

03 / aider

A safe first Aider task: improve an empty state

Create a working branch or other recoverable copy and inspect the current diff. Provide the page component and any source needed to understand how search results are represented. Describe the requirement in terms of behavior: when a completed search has no results, show a clear message and a way to reset filters; loading and error states must remain distinct.

Ask for the smallest coherent implementation. After generation, read the diff before judging the preview. Look for changes to fetch logic, route paths, shared components and dependencies that were not necessary for the task. Then exercise a successful search, a zero-result search, loading and failure. A screenshot of the empty state alone cannot establish that the existing search still works.

Write down what you had to explain twice or repair manually. That feedback is more useful for choosing an agent workflow than an isolated success anecdote. A realistic pilot measures whether the tool helps you complete your own task with a review burden you can sustain.

1. 01

   Establish recovery

   Inspect existing work and choose a dedicated branch or copy.

2. 02

   Provide context

   Supply the relevant search component and result-state definitions.

3. 03

   Specify behavior

   Keep loading, errors and zero results separate.

4. 04

   Review the diff

   Check unrelated fetch, route and dependency changes.

5. 05

   Exercise all states

   Use normal, empty, loading and failed requests.

04 / aider

Automatic commits, dirty files and undo

The documentation describes automatically committing Aider edits and separately handling pre-existing uncommitted work. It also documents diff and undo commands and options to disable automatic or dirty-file commits. Understand this behavior before running it in a repository that already contains valuable uncommitted changes.

A local commit is not a remote publication. Review, pushing, opening a pull request and deployment are separate operations with their own credentials and consequences. A reassuring commit message does not establish that tests passed or that the change was published. Keep those distinctions in the handoff and in your project’s normal review process.

For a multi-step task, retain a clear sequence of changes. Review each coherent edit, then decide whether to continue, refine or undo. Avoid interleaving unrelated manual work in the same files while evaluating a generated patch unless your workflow clearly protects it. Recovery is easiest when the scope and baseline are explicit.

05 / aider

Configure linting and tests around real behavior

Aider documents a distinction between lint commands and test commands, including automatic test execution when configured. A command’s exit status matters: a tool needs a reliable failure signal before attempting a repair. A formatter that changes files is not necessarily a failing behavior test, so confirm what your chosen command actually reports.

Use a focused behavioral check for the task plus the project’s required gates. For the empty-state example, verify the state only appears after a completed zero-result search and that reset controls change the filters. An assertion that repeats the exact markup the model just wrote can pass while the feature remains broken.

Record runtime, network and environment failures separately from code failures. Missing credentials or a stopped service should not prompt the agent to invent a replacement integration just to make a test green. Include actual error output when requesting a repair, and preserve the original requirement through the retry.

06 / aider

Prompt context and editor-triggered changes

The documented watch-files workflow lets specially marked comments trigger coding or question behavior from an editor. This can be convenient when a request belongs next to the code, but a trigger does not remove the need for a clear task. Explain the invariant: what must remain true after the edit, not merely the line you want changed.

Context should be relevant, current and authorized to leave the machine through the configured model path. A large repository is not automatically a useful prompt. Keep secrets and unrelated customer records out of source shared with an inference service, and check the provider arrangement separately from the local terminal interface.

If the generated result is wrong, first ask whether the tool had the right source and acceptance criteria. A missing route file, stale branch or ambiguous requirement can produce plausible but unsuitable code. Fix the context gap before increasing the scope of the next request.

07 / aider

How to judge an Aider pilot fairly

Track completed tasks, review time, corrective edits and regressions caught by your checks. Do not compare only the number of lines generated or the speed of the first response. A tool that generates more code can increase the work needed to understand the application.

Try a second task with a different shape: a bug fix rather than visual polish. Use a reproducible failing case and ask for a minimal correction. If both tasks preserve the surrounding behavior, the tool may suit your workflow. That is a measured conclusion for your stack, not a universal ranking or a claim based on the publisher’s benchmarks.

Follow the evidence

Sources and editorial method

We reviewed Aider’s homepage and usage, Git, editor-watch and lint/test documentation. We did not install it, run paid inference or reproduce the publisher’s benchmarks.

• Aider official website ↗

  Terminal-based AI pair programming and documented feature links.

• Aider usage guide ↗

  Basic source-file and chat workflow.

• Aider Git integration ↗

  Automatic commits, dirty-file handling, diff/undo and disabling commit behavior.

• Aider linting and testing ↗

  Lint commands, test commands and automatic test configuration.

• Aider in your editor ↗

  Watch-files mode and AI comment triggers.

The evaluation examples and decision criteria are original Roseram analysis. Source statements are distinguished from tested results. Logos identify publishers and do not indicate sponsorship. Send a sourced correction.