Run Ruff or ESLint after agent edits

AgentLint can run an existing linter after a supported file write or edit and return its findings to the agent. You keep the tool's configuration and suppression comments; AgentLint connects the result to the agent's working session.

This is a post-tool check. It does not prevent the initial write or roll it back. Confirm that the agent's post-tool hook is installed; pre-tool hooks also supply snapshots used for changed-line filtering. See hook coverage.

1. Confirm the linter runs in your project

For a Python project that already uses Ruff:

uv run ruff check src/app.py --output-format=concise

For a JavaScript project that already installs ESLint locally:

./node_modules/.bin/eslint src/app.js --format stylish

Use a command that works from the repository root and is available in the environment that starts your coding agent. AgentLint does not install these tools or provide their configuration.

2. Add a post-edit check

Merge the relevant command into agentlint.yml:

rules:
  cli-integration:
    timeout: 3
    severity: warning
    diff_only: true
    commands:
      - name: ruff
        glob: "**/*.py"
        command: "uv run ruff check {file.path} --output-format=concise"

cli-integration belongs to the default universal pack. No extra AgentLint package is required. The default tool filter is Write and Edit; the integration adapter maps supported native file tools to those names. Commands run from the project directory, and AgentLint shell-escapes placeholder values such as {file.path}.

Keep the total check time below the host's post-tool hook timeout. Claude Code's native setup and marketplace plugin configure a 10-second PostToolUse timeout; the 3-second per-command limit above leaves room for AgentLint to start, run other rules, and return feedback. Matching commands run sequentially, so budget their combined time, including any formatter. Set an explicit timeout for each added command or retain the rule-level timeout when replacing the Ruff entry below. For slower checks, increase the host hook timeout as well as the command timeout, or run the checks separately in CI. If the host terminates the hook first, the agent may receive no linter findings.

For ESLint, replace the command entry:

rules:
  cli-integration:
    commands:
      - name: eslint
        glob: "**/*.js"
        command: "./node_modules/.bin/eslint {file.path} --format stylish"
        diff_only: false

Use additional entries with suitable globs for .jsx, .ts, or .tsx files and ensure the linter supports them. ESLint's stylish output separates filenames and line numbers, so the example retains its complete output instead of relying on AgentLint's changed-line parser.

3. See feedback reach the agent

Ask your agent to make a small edit to a matching source file, then inspect the post-tool feedback. A nonzero linter exit produces a finding named cli-integration/ruff or cli-integration/eslint. The configured warning advises the agent to correct the issue; it does not undo the edit.

For Ruff's concise path:line:column output, diff_only: true filters located findings to changed lines when both pre- and post-edit contents are available. New files and edits without a pre-edit snapshot retain all findings. Unlocated failures remain visible.

If no check appears, verify the file glob, the installed post-tool hook, the linter command, and the agent's inherited PATH. An unresolvable placeholder skips the command. A timeout or startup error is logged rather than emitted as a linter finding; run the command directly when investigating.

Optional: format after each edit

For a deterministic formatter, add an entry with mode: auto-fix:

      - name: ruff-format
        glob: "**/*.py"
        command: "uv run ruff format {file.path}"
        mode: auto-fix

This command changes the file after the agent's write. Success is silent; a nonzero exit produces a finding. Review your diff as usual and keep CI checks for the final repository state.

Read the cli-integration reference for placeholders and per-command options, or add AgentLint to CI.