MCP Session Lifecycle State Transitionmedium

MCP Session Lifecycle State Transition

medium Agents in Production 15 min

NumPy allowed · plain Python earns 10 bonus points

Implement the real MCP session lifecycle state machine, governing valid connection state transitions between a client and server.

Task

Implement session_transition(current_state, event) with these valid transitions: ('uninitialized','initialize')->'initializing'; ('initializing','initialized')->'ready'; ('ready','shutdown')->'shutting_down'; ('shutting_down','exit')->'closed'; from ANY state, event 'error' transitions to 'closed'. Any other (state, event) pair is invalid -- return current_state unchanged.

Function Signature

session_transition(current_state: str, event: str) -> str

Examples

Example 1: normal init sequence step 1
Input: current_state = 'uninitialized'
event = 'initialize'
Output: 'initializing'

Example 2: normal init sequence step 2
Input: current_state = 'initializing'
event = 'initialized'
Output: 'ready'

Example 3: error from any state closes
Input: current_state = 'ready'
event = 'error'
Output: 'closed'

Constraints

current_state and event are strings

Python3Saved ✓

def session_transition(current_state, event):

# Your implementation here

pass

Case 1: normal init sequence step 1

Input: current_state = 'uninitialized'
event = 'initialize'

Expected: 'initializing'

Case 2: normal init sequence step 2

Input: current_state = 'initializing'
event = 'initialized'

Expected: 'ready'

Case 3: error from any state closes

Input: current_state = 'ready'
event = 'error'

Expected: 'closed'