F1 is a 4.2B-parameter Vision-Language-Action model that reformulates robotic control as foresight-guided inverse dynamics. Rather than reactive state-to-action mappings, F1 predicts plausible future visual states and derives actions to achieve them, enabling robust planning in dynamic environments with 82.2% real-world task success rate.
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F1 is a 4.2B-parameter Vision-Language-Action model that reformulates robotic control as foresight-guided inverse dynamics. Rather than reactive state-to-action mappings, F1 predicts plausible future visual states and derives actions to achieve them, enabling robust planning in dynamic environments with 82.2% real-world task success rate.
Outcome: Build a Foresight-Guided Robot Control System
Implement a robot controller that explicitly predicts future visual goals before deciding actions. F1 transforms reactive visuomotor policies into planning-aware systems by decomposing the control problem into three modular experts: one understanding language and observations, one generating visual foresight, and one predicting inverse dynamics conditioned on predicted futures.
Problem Context
Traditional vision-language-action (VLA) models map raw observations directly to motor commands without explicit planning. This reactive paradigm struggles in dynamic environments where future states are uncertain and long-horizon tasks require coordination. F1 addresses this by making prediction of visual futures an explicit intermediate step, allowing the model to learn that actions should drive the environment toward anticipated goal states rather than blindly mimicking training trajectories.
Core Concept
F1 treats robotic control as a three-stage pipeline:
Understanding: Encode language instructions and visual observations into a shared semantic space using a pretrained vision-language model backbone.
Generation: Predict a goal-conditioned visual foresight—a plausible future frame that represents the intermediate or final state the robot should achieve.
Action: Compute motor commands as inverse dynamics, deriving actions that would transition from the current visual state toward the predicted future state.
This formulation decouples planning from execution: the generation expert learns "what good futures look like" while the action expert learns "how to reach those futures." The hierarchical attention scheme ensures information flows correctly without shortcuts.
Architecture Overview
F1 employs a Mixture-of-Transformer design with three specialized experts:
Understanding Expert: Inherits from a pretrained multimodal large language model (MLLM) backbone. Processes textual instructions and visual observations to produce semantic tokens that establish shared multimodal grounding.
Generation Expert: Synthesizes goal-conditioned visual foresight using next-scale prediction. Decomposes predicted frames into multi-resolution tokens via residual VQ-VAE encoding. Operates at four spatial scales to balance computational cost with planning accuracy.
Action Expert: Predicts action sequences conditioned on both current observations and predicted future visual states. Uses flow matching objectives for training, enabling continuous action space prediction.
Hierarchical UGA Attention: Enforces causal information flow where generation tokens attend to understanding tokens, and action tokens attend to both understanding and generation. Prevents shortcut correlations and ensures proper modular reasoning.
The full model contains 4.2B parameters with a Gemma transformer backbone. During inference, real-time operation is maintained through efficient tokenization and streaming prediction.
Implementation
Stage I: Alignment Phase
Align the generation expert with the pretrained understanding expert through supervised learning on image token prediction.
Explanation: The understanding expert starts with pretrained weights from a multimodal foundation model. In this stage, we keep those weights frozen and train the generation expert to produce image tokens that match ground-truth image encodings provided by the understanding expert. This initializes the generation expert's ability to produce valid visual continuations.
Train all three experts jointly on diverse robotic datasets using autoregressive generation and flow-matching action losses.
Explanation: With the generation expert initialized, we now train the entire system end-to-end. The understanding expert is unfrozen. We feed trajectory data (sequences of observations and actions) through the pipeline. The generation expert learns to predict realistic future frames contextually, and the action expert learns that its predicted actions should approximately match the inverse dynamics needed to reach the predicted future. Flow matching provides a continuous action space formulation that is more stable than discrete action prediction.
# Stage II: Joint Three-Expert Pretraining with Flow Matchingfrom diffusers.models import FlowMatchingScheduler
import torch.nn.functional as F
classStageIITrainer:
def__init__(self, understanding_expert, generation_expert, action_expert,
vq_vae_encoder, device, num_diffusion_steps=1000):
self.understanding_expert = understanding_expert.to(device)
self.generation_expert = generation_expert.to(device)
self.action_expert = action_expert.to(device)
self.vq_vae = vq_vae_encoder.to(device)
self.device = device
# All experts trainable nowself.params = list(understanding_expert.parameters()) + \
list(generation_expert.parameters()) + \
list(action_expert.parameters())
self.optimizer = AdamW(self.params, lr=2e-5, weight_decay=1e-4)
self.flow_scheduler = FlowMatchingScheduler(num_steps=num_diffusion_steps)
self.num_diffusion_steps = num_diffusion_steps
defencode_image_tokens(self, images):
"""Encode images to multi-scale VQ-VAE tokens"""# Residual VQ-VAE: encode at multiple scales
z = self.vq_vae.encode(images) # [B, num_tokens_fine]# Generate coarser scales through downsampling
coarse_scales = []
current_z = z
for scale inrange(3): # 4 scales total
coarse_scales.append(current_z)
# Downsample by factor of 2
current_z = current_z[:, ::2]
return [z] + coarse_scales
defcompute_flow_matching_loss(self, model_pred, target_action, t):
"""
Flow matching loss for continuous action prediction.
model_pred: predicted action from action expert
target_action: ground truth action from trajectory
t: timestep in [0, 1] for flow matching
"""# Interpolate between random noise and target action
noise = torch.randn_like(target_action)
flow_target = target_action - noise
# Compute L2 loss
loss = F.mse_loss(model_pred, flow_target)
return loss
deftrain_batch(self, trajectories, batch_size=32):
"""
trajectories: dict with keys 'observations', 'actions', 'language'
observations: [B, T, C, H, W]
actions: [B, T, action_dim]
language: [B, seq_len]
"""
observations = trajectories['observations'].to(self.device)
actions = trajectories['actions'].to(self.device)
language = trajectories['language'].to(self.device)
# Encode current and future observations
current_obs = observations[:, 0]
future_obs = observations[:, 1]
# Stage I: Understanding
semantic_repr = self.understanding_expert(
observations=current_obs,
language=language
)
# Stage II: Generation - predict future visual tokens
predicted_future_tokens = self.generation_expert(
semantic_repr=semantic_repr,
current_tokens=self.encode_image_tokens(current_obs)
)
# Get ground truth future tokenswith torch.no_grad():
target_future_tokens = self.encode_image_tokens(future_obs)
# Generation loss: cross-entropy across all scales
gen_loss = 0for scale_idx inrange(len(predicted_future_tokens)):
gen_loss += F.cross_entropy(
predicted_future_tokens[scale_idx].view(-1, self.vq_vae.vocab_size),
target_future_tokens[scale_idx].view(-1)
)
# Stage III: Action - inverse dynamics with flow matching# Sample random timestep for flow matching
t = torch.rand(observations.shape[0], device=self.device)
predicted_actions = self.action_expert(
current_tokens=self.encode_image_tokens(current_obs),
future_tokens=predicted_future_tokens,
semantic_repr=semantic_repr,
t=t
)
# Flow matching loss
action_loss = self.compute_flow_matching_loss(predicted_actions, actions[:, 0], t)
# Combined loss
total_loss = gen_loss + action_loss
self.optimizer.zero_grad()
total_loss.backward()
torch.nn.utils.clip_grad_norm_(self.params, 1.0)
self.optimizer.step()
return {
'total_loss': total_loss.item(),
'generation_loss': gen_loss.item(),
'action_loss': action_loss.item()
}
Stage III: Task-Specific Post-Training and Embodiment Adaptation
Fine-tune on target-domain trajectories to adapt the model to specific robot embodiments and refine task-specific manipulation skills.
Explanation: The pretrained model is now specialized to particular robots and tasks. We use significantly smaller learning rates and smaller batch sizes. The focus shifts from learning general visuomotor knowledge to adapting the model's action predictions to the specific kinematics, action spaces, and failure modes of a particular embodiment.
# Stage III: Task-Specific Fine-Tuning with Early StoppingclassStageIIITrainer:
def__init__(self, pretrained_model, device, validation_split=0.1):
self.model = pretrained_model.to(device)
self.device = device
self.validation_split = validation_split
# Lower learning rate for fine-tuningself.optimizer = AdamW(self.model.parameters(), lr=5e-6, weight_decay=1e-5)
self.scheduler = torch.optim.lr_scheduler.CosineAnnealingLR(
self.optimizer, T_max=100, eta_min=1e-7
)
self.best_val_loss = float('inf')
self.patience = 15self.patience_counter = 0deffine_tune_epoch(self, train_dataloader, val_dataloader):
"""
Fine-tune on task-specific data with early stopping.
"""
train_loss = 0
num_batches = 0self.model.train()
for batch in train_dataloader:
loss_dict = self.model.train_step(batch)
loss = loss_dict['total_loss']
self.optimizer.zero_grad()
loss.backward()
torch.nn.utils.clip_grad_norm_(self.model.parameters(), 0.5)
self.optimizer.step()
train_loss += loss.item()
num_batches += 1
train_loss /= num_batches
# Validation
val_loss = 0
val_batches = 0self.model.eval()
with torch.no_grad():
for batch in val_dataloader:
loss_dict = self.model.train_step(batch)
val_loss += loss_dict['total_loss'].item()
val_batches += 1
val_loss /= val_batches
self.scheduler.step()
# Early stoppingif val_loss < self.best_val_loss:
self.best_val_loss = val_loss
self.patience_counter = 0
torch.save(self.model.state_dict(), 'best_model.pt')
else:
self.patience_counter += 1ifself.patience_counter >= self.patience:
print(f"Early stopping at validation loss {self.best_val_loss:.4f}")
returnTrue# Stop trainingreturnFalse# Continue trainingdefprepare_task_dataset(self, raw_trajectories, task_id):
"""
Prepare dataset for a specific task embodiment.
raw_trajectories: list of trajectory dicts with obs, actions, language
"""
processed = []
for traj in raw_trajectories:
obs = traj['observations']
actions = traj['actions']
lang = traj['instruction']
# Normalize actions to [-1, 1] for this embodiment
action_mean = actions.mean(axis=0)
action_std = actions.std(axis=0) + 1e-8
normalized_actions = (actions - action_mean) / action_std
# Augment language with task context if available
augmented_lang = f"{lang} [Task ID: {task_id}]"
processed.append({
'observations': obs,
'actions': normalized_actions,
'language': augmented_lang,
'action_stats': {'mean': action_mean, 'std': action_std}
})
return processed
Inference: Closed-Loop Rollout with Foresight
Deploy the trained model for real-time control by repeatedly predicting future frames and deriving actions.
Explanation: At test time, we run the model in a closed-loop: at each timestep, the model predicts what the next visual state should look like, then predicts the action needed to reach that state. After executing the action, the new observation is fed back, and the cycle repeats. This allows the robot to continuously replan and adapt to deviations from the predicted trajectory.
# Inference: Closed-Loop Rollout with Adaptive ForesightclassF1InferenceController:
def__init__(self, model, robot_interface, device, max_steps=500):
self.model = model.eval().to(device)
self.robot = robot_interface
self.device = device
self.max_steps = max_steps
defrollout_episode(self, instruction, initial_obs, action_scale=1.0):
"""
Run a closed-loop episode guided by predicted visual foresight.
instruction: language goal (str)
initial_obs: starting observation [C, H, W]
action_scale: scale factor for action magnitude (safety mechanism)
Returns: trajectory dict with obs, actions, success flag
"""
trajectory = {
'observations': [initial_obs],
'actions': [],
'predicted_futures': [],
'language': instruction
}
current_obs = initial_obs.to(self.device).unsqueeze(0)
with torch.no_grad():
for step inrange(self.max_steps):
# Encode instruction
lang_tokens = self.model.tokenize_language(instruction)
# Stage 1: Understanding - establish semantic context
semantic_repr = self.model.understanding_expert(
observations=current_obs,
language=lang_tokens
)
# Stage 2: Generation - predict next visual frame
predicted_future_tokens = self.model.generation_expert(
semantic_repr=semantic_repr,
current_tokens=self.model.encode_tokens(current_obs)
)
# Decode tokens back to image space for monitoring
predicted_future_frame = self.model.vq_vae.decode(
predicted_future_tokens[0] # Use finest scale for control
)
trajectory['predicted_futures'].append(
predicted_future_frame.cpu().numpy()
)
# Stage 3: Action - compute inverse dynamics toward predicted future
action_pred = self.model.action_expert(
current_tokens=self.model.encode_tokens(current_obs),
future_tokens=predicted_future_tokens,
semantic_repr=semantic_repr,
t=torch.zeros(1, device=self.device) # Use deterministic flow at t=0
)
# Extract action and apply scaling for safety
action = action_pred[0].cpu().numpy()
action = action * action_scale
# Clip to valid range
action = np.clip(action, self.robot.action_min, self.robot.action_max)
trajectory['actions'].append(action)
# Execute action on robotself.robot.execute_action(action)
# Observe new state
new_obs = self.robot.get_observation()
trajectory['observations'].append(new_obs)
current_obs = new_obs.to(self.device).unsqueeze(0)
# Check for early termination signalsifself.should_terminate(current_obs, instruction):
trajectory['success'] = Truebreak
trajectory['num_steps'] = len(trajectory['actions'])
return trajectory
defshould_terminate(self, obs, instruction):
"""
Heuristic termination check: detect if task is complete.
Can be customized per task or learned from data.
"""# Placeholder: implement task-specific success detection# Examples: gripper closed, object at goal location, etc.returnFalse
Practical Guidance
Hyperparameters and Training Configuration
Component
Parameter
Recommended Value
Notes
Understanding Expert
Learning Rate (Stage II)
2e-5
Frozen in Stage I, unfrozen in Stage II and beyond
Generation Expert
Learning Rate (Stage I)
1e-4
Higher initial rate; lower to 2e-5 in Stage II
Action Expert
Learning Rate (Stage II)
2e-5
Initialized from scratch; same rate as other experts
Fine-tuning (Stage III)
Learning Rate
5e-6
Much lower for task-specific adaptation
Action Loss
Flow Matching Steps
1000
Number of diffusion timesteps for flow matching schedule
Gradient Clipping
Max Norm
1.0
Prevents training instability
Fine-tuning Gradient Clipping
Max Norm
0.5
Tighter clipping for stability in Stage III
VQ-VAE Tokenization
Vocabulary Size
8192
Typical for image reconstruction quality
Transformer Backbone
Model Size
4.2B parameters
Gemma-based architecture
Training Data (Stage II)
Trajectory Count
330,000+
Across 136 diverse manipulation tasks
Batch Size (Stage II)
32-64
Depends on GPU memory; 4 A100s tested
Batch Size (Stage III)
8-16
Smaller for fine-tuning stability
Foresight Prediction Scales
Number of Scales
4
Coarse-to-fine hierarchical prediction
When to Use F1
Use F1 when you need:
Planning in dynamic environments: Tasks where reactive policies fail because the future is uncertain and action effects compound over time.
Long-horizon sequential manipulation: Multi-step tasks like pick-place-insert where intermediate visual milestones guide decisions.
Transfer across embodiments: Shared understanding and generation experts enable rapid adaptation to new robot morphologies.
Interpretable planning: Predicted future frames provide explicit intermediate goals, making the model's reasoning inspectable.
Real-time closed-loop control: The three-expert architecture enables streaming prediction with minimal latency.
F1 achieved 82.2% average success on real-world manipulation and ranked first on all four LIBERO simulation benchmarks.
When NOT to Use F1
Do not use F1 when:
Task requires discrete symbolic reasoning: F1 is not designed for high-level planning or symbolic state machines. Use classical planners or hybrid frameworks if you need explicit symbolic reasoning.
Visual observations are unreliable or heavily occluded: The entire approach depends on accurate visual feedback. If sensors are noisy or environments heavily occluded, ensure robust perception preprocessing.
Computational resources are severely limited: 4.2B parameters and multi-scale VQ-VAE encoding require significant GPU memory (tested on 4x A100). Smaller models may be necessary for edge deployment.
Actions are purely non-visual: If the task requires actions driven by non-visual state (e.g., pure force feedback, proprioception-based balance), F1's vision-centric foresight may be insufficient.
Training data is scarce: Stage II pretraining on 330k+ trajectories is crucial. With <10k task-specific trajectories, overfitting is likely; consider data augmentation or smaller models.
Real-time safety is critical: Foresight prediction adds latency. If millisecond-level reaction is needed (e.g., collision avoidance), reactive models may be more appropriate.
Common Pitfalls
Skipping Stage I Alignment: Stage I initializes the generation expert to produce valid visual continuations. Training without this warm-start causes the generation expert to output incoherent or static frames, degrading downstream action prediction.
Insufficient VQ-VAE Pretraining: The residual VQ-VAE must be well-trained before Stage II. Poor tokenization introduces reconstruction error that propagates through the pipeline. Verify reconstruction quality on validation frames before starting joint pretraining.
Misaligned Multi-Scale Tokenization: The hierarchical prediction across four scales relies on consistent downsampling. Ensure coarse and fine tokens are aligned (e.g., coarse token at (H/4, W/4) corresponds to a 4x4 patch in the fine tokens).
Ignoring Action Space Normalization in Stage III: Each embodiment has different action ranges and dynamics. Failing to normalize actions per task leads to poor fine-tuning performance. Always compute and apply task-specific action statistics.
Overfitting on Small Task-Specific Datasets: Stage III uses a lower learning rate and early stopping, but if the task dataset is <5k trajectories, consider freezing the understanding expert and only fine-tuning the generation and action experts to reduce parameter count.
Not Monitoring Foresight Quality: Predicted frames that drift far from reality will mislead the action expert. During training and validation, visualize predicted futures and check for hallucinations or mode collapse.
Treating Flow Matching Loss as Standard MSE: Flow matching is not equivalent to predicting a fixed target frame. The loss formulation involves interpolation between noise and target over diffusion steps. Using plain L2 loss will not converge properly.
