Guardian — Multi-View VLM for Robotic Planning & Execution Failure Detection (Thinking variant)

Guardian is a vision-language model fine-tuned for unified planning and execution verification in robotic manipulation. Given an instruction and one or more images of the robot scene, it predicts whether a proposed plan is correct (planning verification) or whether a subtask was successfully executed (execution verification), and emits an explicit chain-of-thought reasoning trace alongside the final answer.

This checkpoint (guardian-thinking) is the thinking variant: it is trained and inferred with <think> ... </think> reasoning before the final <answer> and <category> tokens. A lighter no-CoT counterpart (guardian-vanilla) is released separately.

Project page	Paper	Code	Data
di.ens.fr/willow/research/guardian	arXiv:2512.01946	GitHub	🤗 Guardian collection

Model summary

Architecture: InternVL3-8B (Qwen2.5-7B LLM + InternViT-300M-448px-V2.5), fine-tuned with LoRA (rank 16) on the LLM only; visual encoder and MLP connector kept frozen.
Capabilities:
- Planning verification — from an initial scene image and a proposed list of subtasks, decide whether the plan is correct.
- Execution verification — from before/after observations of a subtask (single-view or multi-view), decide whether the subtask succeeded.
- Thinking mode — every prediction is preceded by an explicit reasoning trace.
Output format:
- Thinking: <think> reasoning </think> <answer> True|False </answer> <category> ... </category>
Training data: FailCoT (RLBench-Fail + BridgeDataV2-Fail), ~30K planning + execution failures with reasoning traces. See the paper Scaling Cross-Environment Failure Reasoning Data for Vision-Language Robotic Manipulation (Pacaud et al., 2026).

Quick start

The simplest way to run Guardian is the lightweight wrapper shipped in the Guardian repo (examples/guardian.py):

python

from examples.guardian import Guardian

guardian = Guardian(
    model_path="<path>/guardian-thinking",
    thinking=True,
)

# Planning verification: 1 image of the initial scene
answer, category = guardian.verify_plan(
    img_paths_list=["/path/to/start_img.png"],
    task_instruction="stack the red cup on the blue cup",
    plan=str([
        "grasp red cup",
        "move grasped object on top of blue cup",
        "release",
    ]),
)

# Execution verification: 2, 6, or 8 images (before/after, possibly multi-view)
answer, category = guardian.verify_subtask(
    img_paths_list=[
        "/path/to/start_left.png",
        "/path/to/start_right.png",
        "/path/to/start_wrist.png",
        "/path/to/end_left.png",
        "/path/to/end_right.png",
        "/path/to/end_wrist.png",
    ],
    task_instruction="stack the red cup on the blue cup",
    subtask_instruction="grasp red cup",
)

For execution verification, the wrapper accepts:

2 images — single-view: [start, end]
6 images — three views: [start_left, start_right, start_wrist, end_left, end_right, end_wrist]
8 images — four views, similarly ordered.

See docs/RUN_DEMO.md in the Guardian repo for the full demo.

Downloading the checkpoint

bash

hf download paulpacaud/guardian-thinking \
    --local-dir ./data/failure_forge/models/guardian-thinking

The codebase expects the checkpoint to live under ./data/failure_forge/models/guardian-thinking/.

Evaluation

Guardian is evaluated on three real-robot OOD benchmarks bundled at paulpacaud/Guardian-FailCoT-OOD-datasets — UR5-Fail, RoboFail, RoboVQA — plus the in-distribution test splits of FailCoT (RLBench-Fail / BridgeDataV2-Fail).

Reproduce evaluation results following docs/Offline_VQA_Evaluation.md in the Guardian repo. Headline numbers from Table II of the paper:

Benchmark	Execution acc.	Planning acc.
RoboFail	0.86	0.70
UR5-Fail	0.77	0.89
RoboVQA	0.85	—

Intended use

Guardian is designed as a plug-and-play verification module for robotic manipulation pipelines (e.g. as the verifier in 3D-LOTUS++): at each planning step or subtask boundary, query Guardian; on a failure, trigger replanning or re-execution.

Citation

bibtex

@misc{pacaud2026guardian_failcot,
  title  = {Scaling Cross-Environment Failure Reasoning Data for Vision-Language Robotic Manipulation},
  author = {Paul Pacaud and Ricardo Garcia and Shizhe Chen and Cordelia Schmid},
  year   = {2026},
  eprint = {2512.01946},
  archivePrefix = {arXiv},
  primaryClass  = {cs.RO}
}

If you specifically build on the earlier Guardian workshop paper:

bibtex

@inproceedings{pacaud2025guardian,
  title     = {Guardian: Detecting Robotic Planning and Execution Errors with Vision-Language Models},
  author    = {Paul Pacaud and Ricardo Garcia Pinel and Shizhe Chen and Cordelia Schmid},
  booktitle = {Workshop on Making Sense of Data in Robotics: Composition, Curation, and Interpretability at Scale at CoRL 2025},
  year      = {2025},
  url       = {https://openreview.net/forum?id=wps46mtC9B}
}

License

Released under the Apache 2.0 license, inheriting the license of the InternVL3-8B base model.