Agentic Browser Fleet

Driving the browser fleet

Two commands, and the split matters:

• agentic-browser-fleet owns browsers -- start one, list them, hand one to the human, give it back. Run from the repo root via uv run.
• playwright-cli drives them -- look at the page, click, type, scroll.

uv run agentic-browser-fleet new
  -> started browser browser-1
     drive it:  playwright-cli -s=browser-1 attach --cdp=http://127.0.0.1:8083/browser-1/<token>
     then:      playwright-cli -s=browser-1 <command>

Run that attach line once. After that it is plain playwright-cli -s=browser-1 <command>.

playwright-cli --help is the command reference. It ships with the pinned version, so it is always correct -- this skill deliberately does not restate it. What this skill covers is everything --help cannot know: who owns the browser, what the human can do to it underneath you, and the handful of ways this goes wrong in practice.

No API key needed. Everything here is deterministic and keyless.

First: there are no browsers until you make one

The fleet starts empty. new prints a name (numbered browser-<N>, shown as "Browser N" in the workspace UI) and the attach line. Browsers are addressed by name everywhere.

• new mints the first free browser-<N>; new my-browser chooses the name (lowercase letters and digits joined by single dashes). A duplicate name is rejected -- note a crashed browser still holds its name until you close it.
• new returns as soon as the browser is registered; Chromium is still launching. If the attach line says it is still starting, wait a few seconds and run ls.
• The fleet is capped (2 by default). new past the cap returns 2/2 browsers open -- close one first.
• Browsers cannot be renamed. If the user asks, say so: the only option is close + new, which is a different browser with a fresh profile.

The loop

1. playwright-cli -s=<name> snapshot (or find "text") -- see what is on the page.
2. Decide what you want.
3. Act: click <ref>, fill <ref> "text", press Enter, hover <ref>, mousewheel 0 800...
4. Look again. Repeat.

Refs (e12) come from the latest snapshot. Re-snapshot after anything that changes the page -- refs survive DOM mutation, so a stale ref can silently resolve to a different element rather than erroring.

Fleet commands

uv run agentic-browser-fleet ls                      # the whole fleet: names, owners, tabs
uv run agentic-browser-fleet ls --include-tabs       # every tab of every browser
uv run agentic-browser-fleet new [name]              # start one; prints its name + attach line
uv run agentic-browser-fleet close <name>            # close it, retire the name, DELETE its profile
uv run agentic-browser-fleet acquire <name>          # reserve it (reprints the attach line)
uv run agentic-browser-fleet acquire <name> --reclaim   # take back from a human -- only if they said so
uv run agentic-browser-fleet release <name>          # hand it back (alias: unlock)
uv run agentic-browser-fleet handoff <name> "reason" # give it to the human (alias: request-human)

ls shows who controls each browser (you, agent <name>, human (took control), or free), its tab count, and its active URL -- so you can pick one.

close ends a whole browser and deletes its profile (cookies, logins) with it. For a single tab use playwright-cli tab-close.

Ownership rules

Every browser has exactly one controller. The human always wins, instantly -- the moment they take control, your very next command is refused mid-session.

• You auto-acquire and hold a sticky lease. No manual acquire needed for normal driving; your first command takes it.
• The lease goes idle after ~60s with no commands. Holding the connection open is not enough -- only actual commands count. If you step away and come back, just carry on; if it expired, re-acquire.
• Release when a browser leaves your active work (release <name>), so control returns to the human immediately rather than after the idle timeout: task finished, the user told you to stop, or you moved to a different browser.
• The human takes over. Your next command fails. Stop, tell the user the human took the wheel, and end your turn. Do not retry or --reclaim on your own. You are queued to resume first and will be messaged; on resume, take a fresh snapshot -- the page changed, and the view may have been resized while they held it, so every ref is stale.
• Agents never preempt each other. A browser another agent holds is theirs. Use a different one (or new); acquire only if you specifically need that browser and will queue for it.
• Never --reclaim a browser a human is holding on your own initiative. End your turn and ask. A bare "keep going" from the user counts as confirmation.

When something fails, run ls -- do not read the error

playwright-cli exits 1 for every failure and cannot tell you why. A revoked lease, a crashed browser and a stale ref all look identical; a refused command may report Execution context was destroyed or simply time out after 30s. None of that is diagnostic.

uv run agentic-browser-fleet ls

That is the only thing that distinguishes "the human took control" from "the browser crashed" from "your ref went stale". The fleet's own commands do return meaningful exit codes -- which is why acquire is worth running before a long stretch of driving.

Crashes and closed browsers

• A browser can crash (Chromium killed, e.g. out of memory), and from your side it looks like your connection simply dying: a generic disconnect, not a crash. Run ls, which says crashed. Then run new and use the attach line it prints.
• Do not re-attach the old name. Its Chromium is gone for good, the name stays reserved until someone closes it, and your playwright-cli session for that name is dead too -- a session whose socket drops never rebinds, and every command then hangs with empty output. new gives you a different name, so its session is clean.
• Same if a browser is closed while you are attached: the connection dies, ls says it is gone, start over with new.
• Browsers persist across a workspace restart -- tabs, order, and cookies/logins all come back, so a site you logged into earlier is probably still logged in. Right after a restart the fleet may still be restoring; ls works, driving may need a few seconds.

Long lists: "not found" is not the same as "not there"

The most expensive mistake on this tool. On a virtualized list only the visible rows exist in the DOM, so find and snapshot genuinely cannot see the rest. An agent that searches, gets No matches found, and reports "there are only 25 items" is wrong, and confidently so.

Never conclude a list is complete from a snapshot alone. If a list scrolls, the only way to know what is in it is to scroll to the end.

Check what kind of list you have before trusting any count:

playwright-cli -s=<name> eval "() => document.querySelectorAll('[role=row],li,tr,a').length"
playwright-cli -s=<name> mousewheel 0 800
playwright-cli -s=<name> eval "() => document.querySelectorAll('[role=row],li,tr,a').length"

• Count flat, content changed -> virtualized. Rows are recycled; find only ever sees the current window. Scroll to the end.
• Count grew -> infinite scroll. New rows are appended, usually after a network fetch, so give it a moment before searching again.
• Count already large, barely moved -> an ordinary long page. One scroll to the bottom does it.

To work a virtualized list: hover a row inside it (so the wheel lands on the right container), then repeat mousewheel 0 800 + find. Roughly 20 rows per 800px. You are at the bottom when the visible rows stop advancing between wheels -- not when find fails.

Scrolling the thing you meant

mousewheel scrolls at the last mouse position, which defaults to (0,0) -- the top-left corner. On a two-pane layout that is the sidebar, so you can scroll and see nothing move. hover <ref> inside the pane you mean first. If a scroll appears to do nothing, this is the first thing to check.

Snapshots are cheap, screenshots are not

Default to snapshot / find: text, cheap, and they give refs you can act on. snapshot prints the whole tree inline (5-15k tokens on a real page) -- prefer find "text" to locate something, eval to read one value, and snapshot --filename=/tmp/page.yml when you truly need the tree. The snapshot that comes back automatically after each command is a file link and costs nothing.

Take a screenshot only when the accessibility tree cannot answer the question:

• the content is a canvas, chart, map, video or PDF viewer -- there is no tree to read
• the question is visual: is this button disabled, is the row highlighted, did the layout break
• the snapshot is empty or nonsense but the page clearly rendered
• you are stuck: two attempts failed and the text does not tell you why

Do not screenshot to check a page loaded -- the per-command snapshot already gives URL and title.

Hitting a wall a human must clear (CAPTCHA / 2FA / login)

CAPTCHA, "verify you're human", an SMS/2FA code you don't have, or a login needing the user's own credentials: do not try to solve it yourself -- you will fail and may get the account flagged.

uv run agentic-browser-fleet handoff browser-1 "solve the CAPTCHA on the sign-in page"

handoff puts you at the front of the resume queue, hands control to the human (pinned, so it will not pass to another agent), and surfaces the pane. In the same turn: tell the user exactly what to do and on which page, then end your turn. You are woken first when they hand it back -- re-snapshot to confirm the challenge cleared, then carry on.

Live view vs. your output

The browser streams to a UI pane next to your chat, and it follows whatever tab you are acting on. new and your first command surface it automatically -- but only when the user is currently watching your chat. Do not manage panes yourself; if the user asks for a browser that is not showing, tell them to open it from the workspace + -> browser menu.

The pane is viewer only -- your real output is here in the CLI. Read and relay it; never tell the user to "check the tab" for results.

Multiple browsers, tabs, sub-agents

• Multiple browsers: new each one; they are independent and do not queue against each other. Drive several at once just by varying the name.
• Tabs: playwright-cli tab-list / tab-new / tab-select / tab-close, within one browser. The fleet's ls --include-tabs shows the same tabs in the same order.
• Drive the browser yourself, in this chat. A launch-task sub-agent runs in a separate, isolated container with no access to this workspace's fleet. If a sub-agent needs something from the web, have it tell you what it needs and you do the browsing.

Exit codes -- branch on these

These are the fleet's exit codes. playwright-cli has its own and they are not this granular (see "run ls" above).

Quick recipes

# Make a browser and start driving.
uv run agentic-browser-fleet new                       # prints the attach line -- run it once
playwright-cli -s=browser-1 goto https://example.com
playwright-cli -s=browser-1 find "More information"    # cheaper than a full snapshot
playwright-cli -s=browser-1 click e14

# Search and submit with the keyboard.
playwright-cli -s=browser-1 goto https://news.ycombinator.com
playwright-cli -s=browser-1 fill e3 "browser automation" --submit

# Read every row of a long list (see "Long lists" above for why this shape).
playwright-cli -s=browser-1 hover e12                  # put the wheel over the list
playwright-cli -s=browser-1 mousewheel 0 800
playwright-cli -s=browser-1 find "the thing you want"  # repeat until rows stop advancing

# Two browsers, independently (no queueing -- different names).
uv run agentic-browser-fleet new
uv run agentic-browser-fleet new

# Hit a CAPTCHA -- hand it over, then STOP.
uv run agentic-browser-fleet handoff browser-1 "solve the CAPTCHA on the sign-in page"

Don'ts

• Don't run playwright-cli close, attach (twice), detach, close-all, kill-all or delete-data. The fleet owns lifecycle. Ending a browser is agentic-browser-fleet close <name>, which also retires the name and deletes the profile.
• Don't re-attach a browser whose session died -- see "Crashes" above. It hangs rather than erroring, which is the one failure you cannot recover from.
• Don't interpret a playwright-cli failure. Run ls.
• Don't conclude a scrollable list is complete because find came up empty.
• Don't --reclaim a browser a human is holding without them explicitly saying so.
• Don't try to solve a CAPTCHA or 2FA challenge. Hand it off.