Qwen / Qwen3.5-4B-heretic
Qwen3.5-4B-heretic
Decensored Qwen3.5-4B checkpoint for long-context chat, coding, and analysis. Supports optional thinking traces and sampling controls for output style.
Overview
Qwen3.5-4B Heretic is a decensored variant of Qwen3.5-4B. The Qwen team built the original Qwen3.5-4B model. A third party produced this Heretic checkpoint to reduce safety refusals. It can emit a visible thinking trace before the final answer.
What you can build
- Long-document Q&A and summarization with very large context windows
- Coding help for small scripts, refactors, and debugging explanations
- Step-by-step math and logic solutions when thinking is enabled
- Multilingual writing, rewriting, and translation across many languages
- Instruction-following chat for brainstorming, planning, and analysis
Inputs
- Thinking toggle that controls whether the model includes a visible reasoning block (default: True)
- A user prompt to answer (required)
- An optional system prompt that sets global behavior and style
- Optional user identifier for persisting chat history across runs
- Optional session identifier to separate multiple threads for the same user
- Sampling temperature from 0 to 5 to control randomness (default: 0.7)
- Top-p nucleus sampling from 0 to 1 (default: 0.95)
- Top-k sampling from 0 to 100, where 0 disables top-k filtering (default: 0)
- Repetition penalty from 0 to 5 to reduce repeated phrases (default: 1.0)
- Length penalty from 0 to 5 to bias toward shorter or longer outputs (default: 1.0)
- Maximum tokens to generate, where 0 delegates to the runtime default (default: 0)
- Minimum tokens to generate, where -1 disables the minimum constraint (default: 0)
- Backward-compatible max-new-tokens control (don’t set both this and max tokens)
- Backward-compatible min-new-tokens control (don’t set both this and min tokens)
- Stop sequences as a semicolon-separated list that halts generation on match
- Random seed for repeatable sampling (default: 123456)
- Quantization toggle to run reduced-precision weights when available
- Sampling mode toggle that switches between deterministic decoding and probabilistic sampling
Outputs
The model returns generated text.
When thinking is enabled, the output can include a <think>...</think> block before the final answer.
Recommended settings
- General chat with thinking on: thinking enabled, temperature 1.0, top-p 0.95, top-k 20, repetition penalty 1.0
- Precise coding with thinking on: thinking enabled, temperature 0.6, top-p 0.95, top-k 20, repetition penalty 1.0
- Fast direct answers: thinking disabled, temperature 0.7, top-p 0.8, top-k 20, repetition penalty 1.0
- If you see loops or repeated text: increase repetition penalty to 1.1–1.3, and add a stop sequence
Limitations
This is a modified checkpoint designed to reduce refusals. That change can increase the chance of unsafe, biased, or policy-violating outputs. The underlying model family supports a 262,144-token native context window. Some deployments can extend context up to about 1,010,000 tokens with RoPE scaling, but support varies. Very long contexts can require much more memory and may force a smaller usable context limit. If thinking is enabled, the reasoning trace consumes output tokens and can crowd out the final answer.
Safety & compliance
Don’t use this model to request or produce instructions for wrongdoing. Don’t use it for self-harm guidance, weapon construction, or targeted harassment. Treat outputs as untrusted text. Verify facts before acting on them. Add your own moderation and logging if you deploy it in a user-facing product. If you set user or session identifiers, avoid storing sensitive personal data in prompts.
API quick start
Run Qwen3.5-4B-heretic with a single API call.
{
"prompt": "Explain the Second Law of Thermodynamics …",
"user_id": "...",
"session_id": "...",
"enableThinking": "true"
}