[Python] How do I prevent two VWAgent workers from deadlocking when they face each other after...

I’m working on a multi-agent grid environment using the VWAgent framework. I have three agents:

• White: explores and broadcasts cleaning assignments
• Green & Orange: wait until assignments, then move to clean their tiles

White explores correctly, broadcasts once, and then both workers start moving. The problem begins after the assignments: Green and Orange end up facing each other on the same corridor and both freeze forever. Neither moves, neither backs off — complete deadlock.

Here is the relevant part of the worker decide() method:

def decide(self) -> Iterable[VWAction]:
# Broadcast EXACTLY ONCE to avoid spamming workers
if self.__sent_assignments and self.__broadcast_action:
action = self.__broadcast_action
self.__broadcast_action = None # Clear it so we don't send again
return [cast(VWAction, action)]

if self.__backoff > 0:
return [VWIdleAction()]

obs = self.get_latest_observation()
appearance = self.get_own_appearance()

collision_action = self.__handle_collision(obs)
if collision_action is not None:
return [collision_action]

pos = self.get_own_position()

if self.__heading_home:
if (pos.get_x(), pos.get_y()) == self.__home_target:
self.__heading_home = False
else:
return [self.__move_towards(target=self.__home_target)]

• White finishes mapping and broadcasts tasks (good).
• Green and Orange start moving (good).
• They meet in a corridor facing each other.
• __handle_collision() keeps returning “blocked” for both.
• Both agents idle forever → deadlock.

One worker should yield or back off so the other can pass.

Both freeze because their movement logic is symmetric and neither gives way.

Question


How can I modify my movement/collision logic so that two workers facing each other do not deadlock? Is there a common pattern for resolving head-on collisions in VWAgent / multi-agent grid systems?

I’m happy to share the __handle_collision method if needed.

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