Browser Use Version

0.12.2

Bug Description, Steps to Reproduce, Screenshots

Title

Agent.close() with keep_alive=True drops CDP WebSocket connections, triggering unnecessary reconnection cycle

Body

Context

We maintain a pool of pre-authenticated browsers using Browser(keep_alive=True). At startup, a lightweight agent logs each browser into our target application, then the browser sits idle in the pool until a real task arrives. This avoids repeating login for every task and lets us reuse authenticated sessions across sequential agent runs.

Bug Description

When Agent.close() completes with keep_alive=True, all CDP WebSocket connections are dropped. In 0.12.2, the built-in reconnection logic recovers (after ~1.7s), but this is unnecessary overhead — the connections shouldn't be dropped in the first place when the intent is to keep the browser alive.

Observed Behavior (0.12.2)

Immediately after warmup agent completes on a keep_alive=True browser:

WARNING  [BrowserSession] CDP WebSocket message handler exited unexpectedly (connection closed)
WARNING  [BrowserSession] CDP WebSocket message handler exited unexpectedly (connection closed)
WARNING  [BrowserSession] CDP WebSocket message handler exited unexpectedly (connection closed)
WARNING  [BrowserSession] WebSocket reconnection attempt 1/3...
INFO     [BrowserSession] [SessionManager] Cleared all owned data (targets, sessions, mappings)
WARNING  [BrowserSession] WebSocket reconnection attempt 1/3...
INFO     [BrowserSession] [SessionManager] Cleared all owned data (targets, sessions, mappings)
...
INFO     [BrowserSession] WebSocket reconnected after 1.7s (attempt 1)
INFO     [BrowserSession] WebSocket reconnected after 1.7s (attempt 1)

This happens for every Agent.close() on a keep_alive=True browser — multiple WebSocket handlers all disconnect and reconnect, clearing session manager data each time.

Expected Behavior

With keep_alive=True, Agent.close() should preserve the CDP WebSocket connections and session state. The browser should remain fully connected and ready for the next Agent.run() without any disconnection/reconnection cycle.

Impact

• ~1.7s recovery delay after every agent run before the browser is usable again
• Session manager data cleared on each reconnection ("Cleared all owned data (targets, sessions, mappings)")
• In pre-0.12.x (which lacked WebSocket reconnection), this same issue caused permanent CDP connection collapse — the browser became unusable after the first agent completed
• Multiple reconnection warnings per browser pollute logs in pooled setups

Reproduction

from browser_use import Agent, Browser

browser = Browser(keep_alive=True)

# First agent — e.g. a login warmup
agent1 = Agent(task="Navigate to example.com", browser=browser, llm=llm)
await agent1.run()
# Immediately after: CDP WebSocket handlers exit, reconnection cycle begins

# Browser recovers after ~1.7s, but all session data was cleared

Root Cause (from investigation)

In agent/service.py, Agent.close() with keep_alive=True tears down the event bus, which appears to cascade into closing CDP WebSocket connections. The 0.12.2 reconnection logic masks the issue but doesn't prevent the unnecessary disconnect.

Environment

• browser-use: 0.12.2
• Python: 3.13
• OS: Cloud Foundry (Linux) with Browserless container via CDP
• Setup: Pool of 3-5 Browser(keep_alive=True) instances, each warmed up by a login agent, then reused for sequential tasks

Failing Python Code

from browser_use import Agent, Browser

browser = Browser(keep_alive=True)

# First agent — e.g. a login warmup
agent1 = Agent(task="Navigate to example.com", browser=browser, llm=llm)
await agent1.run()
# Immediately after: CDP WebSocket handlers exit, reconnection cycle begins

# Browser recovers after ~1.7s, but all session data was cleared

LLM Model

No response

Operating System & Browser Versions

No response

Full DEBUG Log Output

The relevant section is:


WARNING  [BrowserSession] CDP WebSocket message handler exited unexpectedly (connection closed)
WARNING  [BrowserSession] CDP WebSocket message handler exited unexpectedly (connection closed)
WARNING  [BrowserSession] CDP WebSocket message handler exited unexpectedly (connection closed)
WARNING  [BrowserSession] WebSocket reconnection attempt 1/3...
INFO     [BrowserSession] [SessionManager] Cleared all owned data (targets, sessions, mappings)
WARNING  [BrowserSession] WebSocket reconnection attempt 1/3...
INFO     [BrowserSession] [SessionManager] Cleared all owned data (targets, sessions, mappings)
...
INFO     [BrowserSession] WebSocket reconnected after 1.7s (attempt 1)
INFO     [BrowserSession] WebSocket reconnected after 1.7s (attempt 1)