web Plugin

web is a real web-capability plugin. Its constructor receives only a profile; the Plugin creates the selected browser provider internally. Search and document services are read from the Agent Plugin context.

Playwright/CDP

import {
  PlaywrightBrowserProvider,
  WebPlugin,
} from "@downcity/plugins/web";

const web = new WebPlugin({
  browser: "playwright",
  cdp_url: "http://127.0.0.1:9222",
});

PlaywrightBrowserProvider connects to an already-running Chrome/Chromium CDP endpoint. It does not download browsers or execute installation commands. Browserbase, Browserless, Kitesurf, and other CDP-compatible backends can implement the same BrowserProvider protocol.

The provider creates one owned page per session in the CDP browser's existing default context. It does not create isolated contexts or take ownership of pages that were already open. Closing a session only closes the page created for that session.

CDP connections enable Playwright's noDefaults mode. This supports endpoints that do not implement Browser Context management but can create pages in the default context. The browser's existing download, focus, and media emulation settings remain unchanged; the provider does not override acceptDownloads, focus emulation, colorScheme, reducedMotion, forcedColors, or contrast.

The endpoint must still expose a default context and support creating a new page. Connection, default-context resolution, page creation, and page initialization failures include a stable stage identifier and a sanitized endpoint without credentials, query parameters, or browser identifiers.

Actions

Provider composition

const web = new WebPlugin({ browser: "playwright", cdp_url: "http://127.0.0.1:9222" });

Semantic capabilities are injected through an adapter and are not tied to one model vendor:

import { SemanticBrowserProviderAdapter } from "@downcity/plugins/web";

const browser = new SemanticBrowserProviderAdapter({
  name: "stagehand",
  browser: playwright_browser,
  semantic_act: (input) => stagehand_service.act(input),
  semantic_extract: (input) => stagehand_service.extract(input),
});

Computer Use can use ComputerUseBrowserProviderAdapter. It captures an observation with a screenshot before handing the goal to an OpenAI, Anthropic, Gemini, or custom model loop. The model never receives Playwright objects.

Use search or HTTP reading first. Create a browser for dynamic rendering, logged-in state, or interaction. Stagehand can be added inside a provider for semantic actions, while Computer Use should remain a visual fallback for pages that cannot be handled reliably through the DOM.

Lifecycle and safety

• WebPlugin accepts a profile and creates the selected browser provider internally.
• The provider owns browser sessions and is disposed when the Agent or Plugin is disposed.
• browser_act exposes deterministic browser actions. Host approval is required for consequential actions such as submit, send, purchase, upload, or delete.
• Playwright Browser, Page, and Buffer objects never cross the Plugin action boundary; results are JSON-serializable.
• Skill installation, discovery, and SKILL.md loading remain responsibilities of SkillPlugin.

Related docs

• Built-in Plugin overview
• Plugin Actions
• Plugin System