Time and Sync

Time and Sync

Robots do not run on one global timestep. Cameras, state estimators, planners, policies, controllers, and operators all update on different schedules.

Retriever makes this explicit with two graph-level choices:

• Clock: when a Flow wakes up.
• Sync policy: how each incoming event buffer is sampled before step(...) runs.

Each Flow has its own schedule. Each edge declares how upstream history becomes one aligned input.

The intuition

# before this Flow steps:
image = Latest(camera_events)
state = Latest(robot_state_events)
goal = Latest(goal_events)
obs = SkillObs(image=image, state=state, goal=goal)
chunk = vla_flow.step(obs)

The important part is not the exact adapter name. The important part is that sampling is part of the graph instead of being hidden in callback timing.