Overview Computer sessions have configurable lifetimes with automatic cleanup. Understanding the lifecycle helps you optimize costs and avoid unexpected terminations.
Timeouts Sessions have two independent timeout mechanisms:
Max Lifetime (timeout_seconds) The absolute maximum duration a session can exist.
# Session expires after 1 hour regardless of activity computer = client.create( kind = "browser" , timeout_seconds = 3600 # 1 hour max )
Default: Based on your plan tier (free: 1 hour, pro: 4 hours, enterprise: 24 hours)Inactivity Timeout (inactivity_timeout_seconds) How long a session can be idle before automatic termination.
# Terminate after 2 minutes of inactivity computer = client.create( kind = "browser" , inactivity_timeout_seconds = 120 , auto_kill = True # Enable auto-termination (default) )
Default: 120 seconds (2 minutes)auto_kill Controls whether the session automatically terminates on inactivity.
Value Behavior true (default)Session terminates after inactivity_timeout_seconds of no activity falseSession runs until timeout_seconds max lifetime, regardless of activity
Setting auto_kill=false means you’re billed for the full session duration even if idle. Always call terminate() when done.
Keepalive For long-running sessions with intermittent activity, use keepalive to prevent inactivity timeout.
from tzafon import Computer client = Computer() computer = client.create( kind = "browser" ) # Reset the inactivity timer computer.keep_alive()
When to use keepalive:
Processing data between actions (AI inference, API calls)
Waiting for external events before next action
Long pauses in interactive sessions
Every action automatically resets the inactivity timer. You only need explicit keepalive during periods with no actions.
Session Status Check the current status and remaining time for a session:
# Get session status status = client.computers.retrieve(computer.id) print ( f "Status: { status.status } " ) print ( f "Created: { status.created_at } " ) print ( f "Expires: { status.expires_at } " ) print ( f "Idle expires: { status.idle_expires_at } " ) print ( f "Last activity: { status.last_activity_at } " )
Status Fields Field Description statusCurrent state: ready, running, terminated created_atWhen the session was created expires_atWhen max lifetime expires idle_expires_atWhen inactivity timeout expires last_activity_atTimestamp of last action or keepalive max_lifetime_secondsConfigured max lifetime inactivity_timeout_secondsConfigured inactivity timeout auto_killWhether auto-termination is enabled
Plan Limits Your plan determines session limits:
Plan Max Concurrent Sessions Max Duration Free 2 1 hour Pro 10 4 hours Enterprise Unlimited 24 hours
Exceeding concurrent session limits returns HTTP 429 (Too Many Requests).
Billing Errors HTTP 402 - Payment Required If your account has insufficient credits or a payment issue:
import tzafon from tzafon import Computer try : client = Computer() computer = client.create( kind = "browser" ) except tzafon.APIStatusError as e: if e.status_code == 402 : print ( "Payment required - add credits at tzafon.ai/billing" ) raise
Common causes:
Account balance depleted
Payment method failed
Credit card expired
Resolution: Add credits or update payment method at tzafon.ai/billing .HTTP 429 - Rate Limited Too many requests or concurrent sessions:
import tzafon from tzafon import Computer import time try : client = Computer() computer = client.create( kind = "browser" ) except tzafon.RateLimitError: print ( "Rate limited - waiting before retry" ) time.sleep( 60 ) # Retry...
Common causes:
Exceeded concurrent session limit for your plan
Too many failed authentication attempts (10 failures in 10 minutes blocks IP)
Best Practices
Always terminate when done
Use context managers or explicit terminate() calls to stop billing immediately. # Good: Context manager handles cleanup with client.create( kind = "browser" ) as computer: # ...work... pass # Auto-terminates
Match timeouts to your workload. Short tasks should have short timeouts. # Quick scrape job computer = client.create( kind = "browser" , timeout_seconds = 300 , # 5 min max inactivity_timeout_seconds = 60 # 1 min idle )
Use keepalive for long processing
If processing takes longer than inactivity timeout, send keepalives. computer.screenshot() # Capture # Long AI processing... computer.keep_alive() # Don't timeout # More processing... computer.click(x, y) # Continue
Handle billing errors gracefully
Check for 402 errors and notify users to add credits. except tzafon.APIStatusError as e: if e.status_code == 402 : notify_admin( "Tzafon credits depleted" )
Lifecycle Diagram ┌─────────────────────────────────────────────────────────────┐ │ Session Lifecycle │ ├─────────────────────────────────────────────────────────────┤ │ │ │ create() ──► READY ──► RUNNING ──► TERMINATED │ │ │ ▲ │ │ │ │ │ │ ▼ │ │ │ ┌────────────────────┐ │ │ │ │ Action/Keepalive │──────┤ inactivity │ │ │ resets idle timer │ │ timeout │ │ └────────────────────┘ │ (if auto_kill) │ │ │ │ │ max lifetime ───────────────┘ │ │ terminate() ────────────────┘ │ │ │ └─────────────────────────────────────────────────────────────┘
Next Steps 
