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Junior

Agent Browser Plugin

The Agent Browser plugin adds browser automation and visual QA skills backed by the agent-browser CLI.

Install

Section titled “Install”

Install the plugin package alongside @sentry/junior:

Terminal window
pnpm add @sentry/junior @sentry/junior-agent-browser

Runtime setup

Section titled “Runtime setup”

Add the package name to the plugin set exported from plugins.ts:

plugins.ts
import { defineJuniorPlugins } from "@sentry/junior";


export const plugins = defineJuniorPlugins(["@sentry/junior-agent-browser"]);

Config

Section titled “Config”

No plugin config is required.

Plugin-specific setup

Section titled “Plugin-specific setup”

This plugin adds two skills and installs a browser runtime into the sandbox snapshot:

  • /agent-browser for general browser interaction
  • /visual-web-qa for evidence-driven visual checks

Rebuild the sandbox snapshot after you enable the plugin so browser commands work in new sandboxes.

Use /agent-browser for general browser interaction:

/agent-browser Open https://example.com, capture a screenshot, and summarize what is on the page.

Use /visual-web-qa when a frontend or docs change needs scoped browser evidence:

/visual-web-qa Verify the updated docs navigation in light and dark themes, then share the evidence.

Verify

Section titled “Verify”
  1. Run /agent-browser with a simple open-and-snapshot request.
  2. Run /visual-web-qa against a reachable local or preview page.
  3. Confirm both turns can execute agent-browser commands successfully.
  4. Confirm visual QA reports the exact target, scoped result, and successfully shared screenshot or video evidence.

Failure modes

Section titled “Failure modes”
  • command not found: agent-browser: the plugin runtime did not load. Confirm the plugin is registered and rebuild the sandbox snapshot.
  • Browser launch fails during the turn: the snapshot browser runtime is missing or incomplete. Rebuild the sandbox snapshot after enabling the plugin.
  • Stale element references like @e*: the DOM changed after the snapshot was taken. Run a fresh snapshot -i after navigation or UI updates.
  • Page appears incomplete: the page had not finished loading before the next action. Wait explicitly with agent-browser wait --load networkidle before interacting.
  • Visual QA is blocked: no local server or preview URL is reachable. Start the repo-native development server or provide a preview URL, then retry.

Next step

Section titled “Next step”

Continue with Plugins to build provider-specific extensions or review Security Hardening for production controls.