Dropbear

Cloud robot policy inference — one function call.

Pre-alpha SDK. Model access and deployment readiness are separate from package installation.

Install

Add Dropbear to a Python 3.11–3.14 project:

uv add "dropbear==0.1.0a21"

Install the CLI as a standalone tool:

uv tool install "dropbear==0.1.0a21"
dropbear login

The base package contains cloud inference, transport, model contracts, and robot-neutral observation helpers. Install a hardware or simulator stack only when you need it:

uv add "dropbear[so101]==0.1.0a21"
uv add "dropbear[sim]==0.1.0a21"
uv add "dropbear[dreamzero]==0.1.0a21"

The dreamzero extra installs the pinned H.264 codec used automatically by DreamZero-YAM's three persistent camera streams. DreamZero-DROID and all other models keep their existing JPEG transport and do not require this extra.

The base SDK supports Python 3.11 through 3.14. The so101 extra currently supports Python 3.12 and 3.13 because its pinned LeRobot dependency requires Python 3.12 and does not yet provide a wheel-compatible Python 3.14 dependency stack.

The sim extra is currently Linux/WSL2 only because of upstream LIBERO/robosuite limitations.

Bimanual YAM beta: setup and tasks

This beta requires organization access to the MolmoAct2 YAM model. Installing the SDK does not grant model access; dropbear doctor yam checks readiness.

For MolmoAct2, follow the YAM hardware guide: a dedicated Linux Python 3.12 install, guided LAN setup or --cli fallback, passive doctor, and attended prediction/execute tasks. Settings and local controllers persist between tasks. The complete custom camera/controller example also ships in the wheel and runs offline with python -m dropbear.examples.yam_custom.

Cloud policy inference

import dropbear

with dropbear.connect(model="molmoact2-so101") as policy:
    result = policy.predict(
        observation,
        instruction="pick up the cube",
    )

print(len(result.actions), len(result.actions[0]))

predict() returns one action chunk and does not actuate a robot. Build observation with the model-specific helper and validate every action locally before adding a motion path.

dropbear.connect() is the canonical SDK entrypoint. connect_so101() is a deprecated compatibility path for the legacy physical SO-101 safety loop and will be removed after that behavior is folded into the generic policy surface. New cloud-policy work should use dropbear.connect(). There is no first-class public connect_libero() or connect_franka() entrypoint; use dropbear.connect(model="molmoact2-libero") or select another checkpoint with model=.

Startup waits default to 900 seconds. For an intentionally longer cold start, pass a finite positive budget such as startup_timeout=1800 to dropbear.connect() or await dropbear.aconnect().

Use a context manager so every cloud session closes deterministically:

import dropbear

with dropbear.connect(model="molmoact2-libero") as policy:
    result = policy.run(
        instruction="put the mug on the plate",
        observe=observe,
        act=act,
        max_actions=220,
        strategy=dropbear.RunStrategy.libero_default(),
    )

Fresh current-position holds

Generic policies whose runtime contract uses current-position holds can read a fresh target at the moment the action buffer underruns. Synchronous callers pass a synchronous callback:

def read_hold_action(context):
    return robot.read_joint_positions()

with dropbear.connect(model="molmoact2-so101") as policy:
    result = policy.run(
        instruction="pick up the cube",
        observe=observe,
        act=act,
        read_hold_action=read_hold_action,
        max_actions=220,
    )

The async API also accepts an awaitable callback:

async def read_hold_action(context):
    return await robot.read_joint_positions()

policy = await dropbear.aconnect(model="molmoact2-so101")
async with policy:
    result = await policy.run(
        instruction="pick up the cube",
        observe=observe,
        act=act,
        read_hold_action=read_hold_action,
        max_actions=220,
    )

read_hold_action receives the stalled RunContext and runs only for an actual underrun when hold_behavior is current_position. Selecting repeat_last_action disables it. The result must contain exactly the runtime contract's action dimension as finite real numeric scalars; invalid output raises ValueError before hooks or actuation. DreamZero-DROID and DreamZero-YAM own their managed hold paths and reject this callback explicitly.

DreamZero-YAM quickstart

Install the dreamzero extra and sign in as shown above, then run the minimal DreamZero-YAM example:

python examples/dreamzero_yam.py

The example uses the canonical dropbear.connect("dreamzero-yam") managed loop and qualified defaults. Its callbacks are deliberately non-actuating: replace capture with synchronized top, left, and right RGB frames plus the current left-arm, left-gripper, right-arm, and right-gripper state. Camera timestamps must describe the real captures using the same clock as time.time_ns() and remain within 50 ms of one another.

After startup, the loop returns one 14-value absolute target at each native 30 Hz control tick in [left_j0..5, left_gripper, right_j0..5, right_gripper] order; it may initially hold the observed position while the first chunk is in flight. Keep the context manager so the cloud session closes, and validate joint, velocity, acceleration, workspace, collision, and gripper limits before replacing the example's print callback with physical actuation.

Keep compute warm between connections

Pass keep_warm as a number of seconds to reserve the same loaded compute after the connection closes:

with dropbear.connect(
    model="dreamzero-yam",
    idle_timeout=3600,
    keep_warm=900,
) as policy:
    result = policy.predict(observation, instruction="fold the towel")

keep_warm defaults to 60 seconds and accepts integer values from 0 to 3600; pass 0 to disable it. It is a duration, not a boolean. The reserved period remains billable because the GPU is held exclusively for that session. A later compatible connect() by the same user reclaims the exact AWS worker or exact Modal function call with a rotated session token, avoiding model or engine reload. The request must still match the model, resolved optimization profile, and region-routing constraints; otherwise normal placement is used.

idle_timeout is separate: it limits time without inference while a client is connected. If it ends a connection configured with keep_warm, the resource parks for the requested warm duration. Closing a connection drains accepted inference before parking, while queued work is discarded. An explicit dropbear sessions stop/session DELETE, access revocation, exhausted credit, or provider failure always ends the reservation. A legacy worker that does not support parking safely closes instead. Provider hard lifetimes can shorten a reservation near their own deadline; Dropbear never promises a keep-warm window beyond its conservative 24-hour Modal execution deadline. Independently, an attached Modal runtime exits after 3900 seconds without control-plane activity; it first drains any accepted inference, and current control traffic renews that local safety deadline.

DreamZero sampling

DreamZero uses one existing RunStrategy field; the server owns temporal admission and the SDK continues uploading observations while asynchronous inference is outstanding.

An omitted value means “use the qualified default for this model”; it does not disable sampling. YAM resolves omission to async_latest; DROID remains async_8. Explicit compatibility and reference selections remain available:

# YAM accepted default
strategy = dropbear.RunStrategy()

# Explicit compatibility mode
strategy = dropbear.RunStrategy(dreamzero_sampling="async_8")

# Synchronous reference/evaluation
strategy = dropbear.RunStrategy(dreamzero_sampling="upstream_eval")

In a managed upstream_eval run, the SDK waits for the eight-action boundary, captures and uploads one observation, waits for the chunk sourced from that exact observation, and then executes the next eight aligned actions at 15 Hz. The inference/network delay is an intentional pause in this reference mode; there is no continuous upload or action/inference overlap. Externally clocked step() callers may still provide every environment observation, but only ticks 0, 8, 16, ... are uploaded. The server—not the client—continues to construct T1 and exact eight-tick-history T4 windows.

async_latest does not create a client request queue. The SDK retains one latest unsent observation, while the YAM server admits at most one inference and collapses observations received while busy to the newest eligible control tick. Returned PolicyStepResult values expose source_control_tick and source_capture_to_execution_ms; hold actions without a source chunk report None for both.

The server returns absolute 24x14 YAM targets. For async_latest, the SDK keeps the existing two committed steps and motion-smooths only the remaining temporally aligned suffix: it blends adjacent absolute-target motion using 85% new and 15% old motion, then corrects toward the new absolute target over five steps. It never shifts or rebases a chunk. YAM grippers remain continuous absolute targets and are handled with the other 12 joints. async_8, upstream_eval, and DROID retain direct commit-prefix replacement. At each upstream boundary, the previous chunk's unexecuted suffix is discarded before the exact new chunk is installed, so upstream evaluation adds no smoothing, averaging, shifting, or rebasing confound.

DreamZero keeps its smoothing choice internal to this qualified mode; explicit DreamZero smoothing weights or modes remain unsupported. A managed run() callback may return ActResult(accepted_action=...) so the next merge anchors to the target accepted by the actuator. Externally clocked step() callers without actuator feedback anchor to the requested target.

Action smoothing

policy.run() smooths overlapping chunks automatically from the model's action space without changing the selected control mode or its inference cadence:

strategy = dropbear.RunStrategy()  # action_smoothing="auto"

auto resolves to output for delta-action models such as LIBERO and to motion for absolute-joint models such as SO101. The raw-absolute YAM contract is also an absolute target space, although DreamZero owns the narrower mode selection described above. output averages old and new action values at each overlapping logical timestep, using 70% new by default. motion blends consecutive target increments, using 85% new motion by default, then corrects gradually toward the new absolute targets. Absolute-position models still receive absolute-position targets; motion changes only how overlapping client trajectories are combined.

For controlled comparisons, set action_smoothing="output" or action_smoothing="motion". motion requires an absolute_joint_position or raw_absolute_joint contract. Its default correction horizon is max(3, ceil(chunk_size / 5)) action steps, so a 30-action SO101 chunk resolves to six steps. This is a recurring 1/6 correction gain, not a finite 200 ms transition. Optional expert overrides are smoothing_new_weight and smoothing_correction_steps. Existing motion tuning does not adapt to latency.

MolmoAct2 YAM also offers two opt-in experimental modes: motion_handover ends a disagreement-dependent correction exactly, and motion_speed reduces damping for slower intra-chunk arm motion. Their grippers follow incoming targets independently of arm-speed adaptation. See the YAM async guide for equations, limits, CLI commands and saved Rerun recordings. auto is unchanged.

Returned actions remain aligned to their original logical timesteps. Expired prefix steps are skipped, and a chunk that is entirely stale is discarded; it is never shifted forward and replayed. With eager inference, a predicted action can therefore be superseded or expire without ever being dispatched. This is intentional: inference stays reactive while the action loop executes only the currently resolved timestep.

For physical arms that clamp a requested target, return the accepted target so the next smoothing pass starts from what the robot was actually asked to execute:

def act(action, context):
    accepted = robot.send_and_return_accepted_target(action)
    return dropbear.ActResult(accepted_action=accepted)

accepted_action must be finite and have the same dimension as the requested action. Existing callbacks returning None, bool, or ActResult(done=...) remain supported.

policy.run() returns one RunResult and prints the same run-scoped summary immediately. Its counters and stop condition are deliberately narrow:

• result.done means the act() callback requested a stop; it does not assert task success or completion.
• result.actions counts control callback steps, not confirmed physical robot execution.
• On Ctrl+C or failure, completed callbacks and attempted callbacks remain distinct. The partial result reaches RunHooks.on_summary and policy.last_run_result; the original exception is preserved. Startup holds and execution underruns are counted separately.
• result.policy_calls counts completed policy responses accepted by that run.
• result.timing.policy_response_ms measures SDK observation submission through action-chunk receipt. It excludes observation construction and physical actuation.
• result.timing.data_plane_rtt_ms is an authenticated application-path round trip measured with a clock probe. It includes transport framing and any load-balancer or relay hops; it is not a one-way network-latency estimate.
• Worker queue, preprocessing, inference, and postprocessing summaries are derived from per-response worker timestamps. Missing samples remain missing rather than being inferred from client-side residual time.

region="nearest" is the default and pins the lowest measured HTTPS-latency region, even when another region is already warm. region="available" reuses compatible warm compute in any measured candidate region before starting cold compute. Passing an AWS region is an exact constraint with no regional fallback. The latency check uses five serial samples per region and reports when partial or failed evidence required a deterministic fallback.

transport="auto" uses an assigned session tunnel, or tries QUIC with hosted relay fallback; transport="quic" requires QUIC, and transport="relay" uses the relay directly.

Advanced SO101 placement

The service's SO101 region="available" launch policy tries AWS Sydney, then Modal Australia, then Modal US-west. Existing clients already support this route and its assigned WebSocket tunnel with transport="auto".

Starting with 0.1.0a16, connect() and aconnect() accept an optional hard provider="aws" or provider="modal" constraint for molmoact2-so101. Omit it for normal service-managed placement. For example:

with dropbear.connect(
    "molmoact2-so101",
    provider="modal",
    region="us-west-2",
    transport="auto",
    keep_warm=900,
) as policy:
    result = policy.predict(observation, instruction="Pick up the pen")

These are routing groups for Modal, not promises of physical AWS placement. Modal uses qualified H100 artifacts and requires transport="auto". provider="modal", region="nearest" is unsupported because AWS HTTPS probes do not measure Modal's locations. Exhaustion never relaxes an explicit provider or region constraint. Warm reuse respects the same constraints.

For molmoact2-bimanual-yam, the qualified US-West launch policy uses AWS Oregon L4, followed by Modal US-West L4 when AWS cannot start. Select region="available", transport="auto", rtc="off" to use this route. These YAM provider controls require SDK 0.1.0a17 or later:

with dropbear.connect(
    "molmoact2-bimanual-yam",
    region="available",
    transport="auto",
    rtc="off",
    keep_warm=60,
    startup_timeout=450,
) as policy:
    chunk = policy.predict(observation, instruction="Fold the cloth")

For diagnosis, add provider="aws" or provider="modal"; region="us-west-2" then limits selection to Oregon AWS or the Modal US-West routing group. YAM has no Australian or H100 fallback. Modal requires transport="auto" and uses an authenticated WSS tunnel. Explicit keep_warm=0 releases the reservation; 60 seconds is the default and 3,600 seconds the maximum. Fallback happens during startup; a running session is never migrated to another provider.

The advanced selector checks server support before creating compute. An older control plane produces an explicit error; the SDK never drops the selector. SDK 0.1.0a15 supports automatic fallback but does not have this optional argument.

MolmoAct2-DROID on Franka

MolmoAct2-DROID consumes an exterior RGB view and wrist RGB view. A second exterior view is optional; when omitted, Dropbear reuses the first exterior frame for the checkpoint's second exterior slot.

Robot state is seven Franka joint positions in radians followed by a gripper value in [0, 1].

import numpy as np
import dropbear

exterior_rgb = np.zeros((480, 640, 3), dtype=np.uint8)
wrist_rgb = np.zeros((480, 640, 3), dtype=np.uint8)

observation = dropbear.franka.observe(
    exterior_frame=exterior_rgb,
    wrist_frame=wrist_rgb,
    joint_positions=[0.0] * 7,
    gripper=0.5,  # 0=open, 1=closed
)

with dropbear.connect(model="molmoact2-droid") as policy:
    result = policy.predict(
        observation,
        instruction="pick up the green block",
    )

assert len(result.actions) == 15
assert all(len(action) == 8 for action in result.actions)

The checkpoint returns a 15-step chunk at 15 Hz. Each action is an absolute target [joint_0, ..., joint_6, gripper]; joints are radians and the gripper is in [0, 1].

predict() does not actuate hardware or provide a Franka safety controller. Validate joint, velocity, acceleration, workspace, collision, and gripper limits before sending any target to a robot.

Manual action loop

For a caller-owned control loop, pass the task instruction to policy.next_action(...). Dropbear owns inference, refill, action buffering, calibration, and RTC prefix context; the caller owns sensing, actuation, and loop cadence.

import time

dt = 1.0 / policy.action_hz
while running:
    tick = time.perf_counter()
    action = policy.next_action(
        observe(),
        instruction="put the mug on the plate",
    )
    robot.execute(action)
    time.sleep(max(0.0, dt - (time.perf_counter() - tick)))

CLI

Sign in once. Credentials are stored in ~/.dropbear/config.toml.

dropbear login
dropbear status

For headless setup, use bare --api-key to paste a key into a hidden prompt:

dropbear login --api-key

Run robot-neutral setup checks:

dropbear doctor

SO-101 and simulation checks are explicit:

dropbear doctor so101
dropbear doctor sim

Install shell completion with:

dropbear --install-completion

Useful session commands:

dropbear sessions list
dropbear sessions stop <session-id>
dropbear sessions stop --all

Documentation: https://docs.dropbear.dreamscalelabs.com