CDP Client

src/cdp/client.ts exports CDPClient, the only thing in the extension that talks to chrome.debugger. One instance exists per attached tab.

const client = new CDPClient(tabId);
await client.attach();
await client.navigate('https://example.com');
await client.detach();

Every method returns the same shape, so callers never have to guess whether something worked:

interface CDPResult<T = unknown> {
    success: boolean;
    data?: T;
    error?: string;
}

Methods

Method	CDP used	Notes
`attach()`	`chrome.debugger.attach` (v1.3) then `DOM.enable`, `Page.enable`, `Runtime.enable`, `Log.enable`	`Log.enable` is what makes `Log.entryAdded` fire for the Console Logs tool
`detach()`	`chrome.debugger.detach`	Safe to call when not attached
`send(method, params)`	`chrome.debugger.sendCommand`	Returns an error result if not attached
`navigate(url)`	`Page.navigate`	The caller validates and normalises the URL. Fails if the response carries an `errorText` (e.g. `net::ERR_NAME_NOT_RESOLVED`), then waits for `document.readyState === 'complete'` (10 s cap) before returning
`captureScreenshot(format)`	`Page.captureScreenshot`	PNG, `captureBeyondViewport: false`
`click(x, y)`	`Input.dispatchMouseEvent` ×2	Raw press/release at viewport coordinates
`clickElement(selector)`	mixed	Bounding-box click, then `element.click()`, then focus + `Enter`
`type(text)`	`Input.insertText`	Single insert, so no double-typing
`typeInElement(selector, text)`	mixed	Click to focus, clear, verify empty, insert, then verify the text landed
`scroll(dx, dy)`	`Input.dispatchMouseEvent` (`mouseWheel`)	Returns the command's real result
`evaluate(expression)`	`Runtime.evaluate`	`returnByValue: true`, `awaitPromise: true`; surfaces `exceptionDetails.exception.description` as the error, falling back to `exceptionDetails.text`
`isAttached()`	—	Local flag

Design notes

Failures are values, not exceptions. Nothing here throws past the caller, and nothing returns success: true for a command that did not run. The background worker forwards the error text straight to the panel.
clickElement degrades in the open. If all three strategies fail it returns All click methods failed for: <selector> rather than reporting a click that never happened.
typeInElement verifies the clear, and then the write. After clearing it re-reads .value and forces it empty if content survived, so text is not appended to whatever was there. After inserting, it re-reads the element again and fails with an explanatory error if the text is not there — Input.insertText returns success at the protocol level even when the focused node accepts no text, so without this check the panel would report a write that never happened.
navigate does not trust Page.navigate. The command resolves successfully for a failed load and reports the reason in errorText, so that field is checked and turned into a failure. It then waits for the document to reach readyState === 'complete'.
evaluate surfaces the useful message. For a thrown error exceptionDetails.text is the literal string "Uncaught"; the real message and stack live on exceptionDetails.exception.description, which is what the panel is given.
Only four domains are enabled, matching the shipped tools exactly.

What it does not do

CDPClient has no methods for downloading, recording, network interception, cookie access or any form of persistent monitoring. It sends commands, one at a time, in response to a click in the panel.