Limits and behaviors

This page collects platform behaviors that aren’t obvious from the API surface. Read it before debugging; most “why is it doing that?” moments are listed here.

Browser sessions

Behavior	Details	What to do
Google domains blocked	Navigation to google.com and its subdomains is blocked (URLs merely containing google.com, like redirect params, are fine)	Use a different search engine, e.g. Bing or DuckDuckGo
chrome:// URLs blocked	Internal browser pages can’t be navigated to	Use API endpoints for browser state (e.g. /tabs for tab info)
Max 5 tabs	Opening a sixth tab fails; the last remaining tab can’t be closed	Close tabs you’re done with; reuse a tab by navigating it
No right_click	Right-click is not supported in browser sessions and returns a not-supported error	Use keyboard shortcuts or in-page UI instead; or use a desktop session
Downloads disabled	The browser denies all file downloads	Fetch the file’s URL with a shell curl on a desktop session, or extract content via html()
HTML is cached ~2 s	html() responses are cached for 2 seconds per URL	Wait 2 s (or navigate) before re-reading if you need fresh DOM
Typing is per-keystroke	type() sends real keystrokes at ~100 characters/second	Budget ~1 s per 100 chars; don’t set tight timeout_ms on long text
Navigation waits for network idle	navigate() waits for network idle up to 5 s, then returns anyway	For slow SPAs, add a short wait() and screenshot to confirm rendering

Desktop sessions

Behavior	Details	What to do
Scrolling is quantized	Scroll deltas snap to ~50 px wheel clicks	Use deltas that are multiples of 50; verify position with a screenshot
Uploads land in /workspace/uploads	File uploads go there; max 512 MB per file, transferred in 8 MB chunks	Reference uploaded files by that path in shell commands and apps
No file-download action	There’s no action that returns a file from the machine	Return small files via shell stdout (base64 file.bin); capture images via screenshots
Firefox may ignore navigate	Desktop Firefox sometimes doesn’t react to the navigate action	Fall back to hotkey(["ctrl", "l"]), type the URL, press Enter
Shell cwd is /workspace	exec commands run in /workspace unless you pass cwd	Pass cwd explicitly or use absolute paths

Sessions

Behavior	Details	What to do
Idle reaping	Sessions terminate after inactivity_timeout_seconds with no activity. Any executed action (screenshots included) or a keepalive call resets the clock, but if you pause between calls longer than the idle window, the session is reaped	Set inactivity_timeout_seconds to 20+ minutes for interactive development; call keep_alive() during long pauses
Hard lifetime cap	max_lifetime_seconds always applies, regardless of activity	Set it to cover your longest expected run; save state with persistent=True if you need to resume
One action at a time	Actions on a session are serialized; concurrent requests queue and can hit the timeout	Await each action before sending the next; use batch for sequences

Actions

Behavior	Details	What to do
Coordinates are screenshot pixels	x/y are pixel positions in the screenshot’s coordinate space	Take a fresh screenshot before clicking; don’t hardcode coordinates
Per-action timeout	Each action accepts a timeout_ms	Raise it for slow operations (long typing, heavy pages)
Batch stops on first error	A batch executes in order, stops at the first failure, and returns the results so far	Check executed vs total in the response and resume from the failed action

Screenshots

Behavior	Details	What to do
Presigned URLs	Screenshot URLs are presigned and expire after ~7 days	Download images you want to keep when you receive them
JPEG format	Screenshots are JPEG-compressed	Fine for vision models and review; don’t expect pixel-exact fidelity

Concurrency

Behavior	Details	What to do
Concurrent computer limit	The number of simultaneously running computers is plan-dependent; exceeding it returns a 429 with “Concurrent limit reached”	Delete computers when done, retry with backoff, or upgrade your plan in the dashboard

If a session behaves unexpectedly and it isn’t listed here, watch it happen: every computer has a live view at https://lightcone.ai/c/{computer_id}. See Observability.

See also

• Computers: computer lifecycle and actions
• Observability: live view, screencast, and traces
• Shell commands: run terminal commands
• Troubleshooting: common issues and solutions