kasm-browser

KASM Browser via CDP

When invoked, drive a persistent KASM Chrome browser using Chrome DevTools Protocol. Use this when a flow needs login state, cookies that persist, captcha/2FA, or React-style synthetic events.

Inputs

• action -- one of: navigate, click, type, screenshot, close_tab, eval
• url -- target URL (for navigate)
• selector -- CSS selector (for click, type)
• text -- text to type (for type)
• tab_id -- existing tab to target (optional; otherwise pick or create)
• output_path -- for screenshot action, where to save the PNG

Output

• screenshot action: file path to PNG.
• Other actions: status + DOM snapshot or evaluated value.

Steps

1. Confirm CDP reachable: docker exec <container> curl -s http://localhost:9222/json/version.
2. List tabs: docker exec <container> curl -s http://localhost:9222/json.
3. Pick or create the target tab; capture its webSocketDebuggerUrl.
4. Open a WebSocket to that URL from inside the container.
5. Send the CDP commands for the action, applying the Human-Speed Rule between every meaningful step.
6. Capture results (DOM, screenshot, console output).
7. Close the WebSocket; tidy up any tabs your flow created.

The Human-Speed Rule (mandatory)

Slow IS fast.

• Minimum 1.5-3 seconds between meaningful actions.
• Typing: one key at a time, 80-150 ms between keystrokes with jitter. Do NOT blast a full string via input.value = "..." on sites that profile typing cadence.
• Wait for Page.loadEventFired before queuing a second navigation.
• Self-imposed rate limit: ~20 CDP calls per 10 seconds.

Bot-detection systems flag burst patterns even when intent is benign. Human-speed pacing is free immunity. Apply regardless of how impatient the user is.

Example: navigate + read title

const sock = new ws(tab.webSocketDebuggerUrl);
// ... open WS, set up send() helper ...
await send("Page.navigate", { url: "https://example.com" });
await new Promise(r => setTimeout(r, 3000));   // human-speed wait
const title = (await send("Runtime.evaluate", { expression: "document.title" })).result.result.value;