Start a new FakeSim episode. All three arguments are optional: omit them all to use the server's default scene (usually task 0 of the suite with initial layout 0), which is the most common use. To switch tasks, use list_tasks first: without arguments it lists the suites, with suite it gives the task_index and instruction of every task in that suite; then pass the chosen suite / task_index. init_state_index picks another object layout of the same task. If the server was started with --lock-task (task_locked is true in get_session_info), passing any of these arguments returns a task_locked error. If an episode is already running, returns already_running; call stop_episode first. Returns run (short run ID), task (suite, task_index, name, instruction, init_state_index), images (agentview and robot0_eye_in_hand: two separate PNGs), state (eef_pos_m is the end-effector XYZ position in meters; eef_rpy_rad.roll_x, pitch_y and yaw_z are the orientation about the robot base X/Y/Z axes in radians; gripper.command is the open/close target and gripper.opening_m the gripper opening in meters), step (simulation steps used) and steps_left (simulation steps left in this episode).

Read the current RGB images from two cameras and the end-effector/gripper state, without advancing the simulation or using the step budget. Returns images (agentview and robot0_eye_in_hand: two separate PNGs), state (eef_pos_m is the end-effector XYZ position in meters, eef_rpy_rad the orientation about the base XYZ axes in radians, gripper holds the target command and opening_m in meters), step (simulation steps used), steps_left (simulation steps left) and status (running).

Move the end effector by delta_xyz meters in the FakeSim world frame (z up, table surface at z=0.80 m), optionally rotating by delta_rpy about the robot base X/Y/Z axes (radians). The server approaches the target step by step with P control and returns only when a definite stop condition triggers, not after a fixed number of steps. action.stop_reason says why the call stopped, one of four:

• reached: Within the target tolerance (8 mm in position, 0.02 rad in orientation); the motion is complete.

• stalled: Barely moved for 3 consecutive steps (less than 1 mm in total) without reaching the target, which usually means something is blocking it: the table, an object, or a joint limit. Repeating the same command has no effect; change direction, or lift or back off first. This is the main signal of contact.

• step_cap: Hit the per-call internal step limit while the end effector was still moving toward the target. Call again with the remaining displacement in the same direction to continue.

• budget: The episode's total step budget ran out during the motion; only stop_episode can be called afterwards. Motion is a best-effort approach and may fall short of the requested delta: judge progress by action.achieved_delta_xyz (actual displacement of this call, meters) and action.remaining_distance_m (meters still missing to the requested target), and do not assume the request was achieved. Returns images (two separate PNGs), state (eef_pos_m is the end-effector XYZ position in meters, eef_rpy_rad the RPY orientation in radians, gripper holds command/opening_m), action (the requested delta_xyz/delta_rpy, executed_steps, stop_reason, achieved_delta_xyz, remaining_distance_m), step (simulation steps used after the call), steps_left (simulation steps left) and status (running). When the budget is already 0, returns a step_limit error instead of silently doing nothing.

Open or close the gripper. The server keeps sending the command and watches the opening width, and returns only when a definite stop condition triggers, not after a fixed number of steps. action.stop_reason says why the call stopped, one of four:

• settled: After at least 10 internal steps of the same command, the opening varied by less than 0.5 mm over the last 2 steps. This only means the opening is momentarily stable, possibly because something blocks it; it does not guarantee a fully open gripper, a firm grasp or a released object. Check state.gripper.opening_m and the images.

• step_cap: Hit the per-call internal step limit before the opening was confirmed stable; the gripper may still be starting or moving. Repeat the same command to continue.

• budget: The episode's total step budget ran out during the action; only stop_episode can be called afterwards.

• no_op: The request matches the current gripper target and no gripper call is pending; nothing was executed and no budget was used. It does not mean an object was released. Returns images (two separate PNGs), state (eef_pos_m is the end-effector XYZ position in meters, eef_rpy_rad the RPY orientation in radians, gripper.command the gripper target and gripper.opening_m the opening in meters), action (the requested gripper target, executed_steps, stop_reason, opening_m before and after), step (simulation steps used after the call), steps_left (simulation steps left) and status (running). When the budget is already 0, returns a step_limit error and the gripper target stays unchanged.

End the current simulation and save its frames, event log and summary. Returns run (short run ID), status (stopped) and artifacts (events: path of events.jsonl, frames: PNG frame directory, summary: path of summary.json).

Read the state of the current run: task context, instruction, step count and robot state. Renders no images and uses no step budget; callable at any time, including before the first reset_task. This only says where you are now. To see which tasks are available, use list_tasks. Returns run (short run ID), status (idle/running/stopped), step (simulation steps used), max_steps (the episode limit), steps_left (simulation steps left), task (suite, task_index, name, instruction, init_state_index), task_locked (true means the server fixed this run's scene, and reset_task accepts no scene arguments), and state (eef_pos_m is the XYZ position in meters, eef_rpy_rad the RPY orientation in radians, gripper holds command/opening_m). While status is idle there is no task or state; instead it returns default_scene (the scene a reset_task without arguments starts).

List the tasks FakeSim offers. Independent of the current run: callable at any time, renders no images, uses no step budget and does not change a running episode. Without arguments: returns suites, the name and task count of every suite, plus the total task count. Start here, pick a suite, then look inside it. With suite: returns task_index, instruction and n_init_states (the number of initial layouts of the same task) for every task in that suite. Pass the chosen suite and task_index to reset_task to start.