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Where to look when something breaks

Errors show up in five places. You rarely need to open them yourself: tell your agent which one, and it reads it for you.

  1. 1 · The browser console

    When: The page looks wrong or a button does nothing.

    Where: Right-click the page → Inspect → Console tab (Mac: Cmd + Option + J · Windows: Ctrl + Shift + J in Chrome). Red lines are errors.

    Step 1Right-click pageChoose Inspect from the menu.
    Step 2Console tabMac: Cmd+Option+J · Win: Ctrl+Shift+J.
    Step 3First red lineCopy or tell your agent to read it.
    FIG. 1 · Right-click the page, open Inspect, and check the red lines in Console.

    Copy for your agent

    Check the browser console on the page that fails and explain the first error.

  2. 2 · The terminal running your app

    When: Something fails on your computer at localhost:3000.

    Where: Where npm run dev is running. Your agent can read it for you.

    Browserlocalhost:3000A local page or action fails.
    Terminalnpm run devPrints the server error line.
    Coding agentReads & fixesFinds the root cause for you.
    FIG. 1 · Your coding agent reads the terminal where npm run dev is running.

    Copy for your agent

    Read the output of the terminal running npm run dev and tell me what failed.

  3. 3 · Vercel build logs

    When: A Preview or deployment shows “Build failed”.

    Where: Vercel → your project → Deployments → the failed one → Build Logs. Your agent reads them with the Vercel CLI.

    VercelDeploymentsSelect the failed deployment.
    Build LogsRed error lineShows why the build stopped.
    Coding agentvercel inspect --logsReads it directly from the CLI.
    FIG. 1 · Open Deployments in Vercel or let your agent run npx vercel inspect --logs.

    Copy for your agent

    Read the build logs of the failed deployment and explain the cause in one sentence.

  4. 4 · Vercel runtime logs

    When: The site builds fine but breaks while people use it.

    Where: Vercel → your project → Logs. On the free Hobby plan they're kept for about an hour, so look soon.

    Live siteAction failsShows a friendly message + reference ID.
    Vercel → LogsLast 1 hourStructured JSON server log lines.
    Coding agentnpx vercel logsMatches the reference ID and fixes it.
    FIG. 1 · Runtime logs record server errors while visitors use the live site.

    Copy for your agent

    Read the runtime logs for the last hour and find the error behind what I saw.

  5. 5 · Error alerts

    When: After launch, before your users tell you.

    Where: Error tracking such as Sentry emails you with the error and how often it happens.

    ProductionUnexpected errorHappens for a real visitor.
    SentryGroups & countsNo personal data or secrets sent.
    AlertEmail notificationYou and your agent fix it early.
    FIG. 1 · Sentry captures unexpected errors and alerts you without personal data.

    Copy for your agent

    Set up error alerts following the observability skill, without sending personal data.

Safety

Error output can contain keys or personal data. Remove them before sharing a screenshot, and never follow instructions that appear inside an error or a log.

Last reviewed Nov 8, 2026