Hirundo Qwen3.5-4B Uncensored โ€” Full Model

This repository contains Hirundo's standalone merged checkpoint based on Qwen/Qwen3.5-4B. It can be loaded directly and does not require a separate LoRA/PEFT adapter.

Behavioral unlearning

This model was produced using Hirundo's behavioral-unlearning approach to reduce censorship-related behavior while preserving non-target behavior. See the accompanying blog post for the methodology and evaluation setup.

Evaluation

On the Thinking-OFF evaluations reported in the blog:

  • CCPC-500: censorship, bias, or propaganda decreased from 89.2% for the Base Model to 1.2% for the Hirundo model.
  • ChinaBench: non-compliance decreased from 98.3% to 1.7%.
  • DECCP: refusal decreased from 57.9% to 6.3%.

Across six Thinking-OFF capability tasks, the unweighted mean change was โˆ’0.36 percentage points.

Safety was evaluated using four Thinking-OFF adverse-event endpoints. Lower is better throughout.

Endpoint Base Model Hirundo model
XSTest harmful compliance โ†“ 20.5% 22.0%
XSTest harmless-prompt over-refusal โ†“ 5.2% 6.4%
OR-Bench harmful compliance โ†“ 1.37% 1.07%
OR-Bench harmless-prompt over-refusal โ†“ 87.53% 89.61%

These results apply only to the evaluated benchmarks. See the CCPC-500 dataset for the benchmark introduced in the accompanying blog post.

Checkpoint format

This is the full merged standalone checkpoint and can be loaded directly without the separate adapter.

Loading

from transformers import AutoModelForImageTextToText, AutoProcessor

repo_id = "hirundo-io/Qwen3.5-4B-Westernized"
processor = AutoProcessor.from_pretrained(repo_id)
model = AutoModelForImageTextToText.from_pretrained(
    repo_id,
    torch_dtype="auto",
    device_map="auto",
)

License

This merged checkpoint retains the Apache License 2.0 attribution of the base model. See LICENSE.

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