Instructions to use howellx/diegetic-1.5b-sft with libraries, inference providers, notebooks, and local apps. Follow these links to get started.

Libraries

How to use howellx/diegetic-1.5b-sft with PEFT:

from peft import PeftModel
from transformers import AutoModelForCausalLM

base_model = AutoModelForCausalLM.from_pretrained("Qwen/Qwen2.5-1.5B")
model = PeftModel.from_pretrained(base_model, "howellx/diegetic-1.5b-sft")

Transformers

How to use howellx/diegetic-1.5b-sft with Transformers:

# Use a pipeline as a high-level helper
from transformers import pipeline

pipe = pipeline("text-generation", model="howellx/diegetic-1.5b-sft")
messages = [
    {"role": "user", "content": "Who are you?"},
]
pipe(messages)

# pip install -U transformers accelerate
# Load model directly
from transformers import AutoModel
model = AutoModel.from_pretrained("howellx/diegetic-1.5b-sft", device_map="auto")

Notebooks
Google Colab
Kaggle
Local Apps Settings

vLLM

How to use howellx/diegetic-1.5b-sft with vLLM:

Install from pip and serve model

# Install vLLM from pip:
pip install vllm
# Start the vLLM server:
vllm serve "howellx/diegetic-1.5b-sft"
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:8000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "howellx/diegetic-1.5b-sft",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker

docker model run hf.co/howellx/diegetic-1.5b-sft

SGLang

How to use howellx/diegetic-1.5b-sft with SGLang:

Install from pip and serve model

# Install SGLang from pip:
pip install sglang
# Start the SGLang server:
python3 -m sglang.launch_server \
    --model-path "howellx/diegetic-1.5b-sft" \
    --host 0.0.0.0 \
    --port 30000
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:30000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "howellx/diegetic-1.5b-sft",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker images

docker run --gpus all \
    --shm-size 32g \
    -p 30000:30000 \
    -v ~/.cache/huggingface:/root/.cache/huggingface \
    --env "HF_TOKEN=<secret>" \
    --ipc=host \
    lmsysorg/sglang:latest \
    python3 -m sglang.launch_server \
        --model-path "howellx/diegetic-1.5b-sft" \
        --host 0.0.0.0 \
        --port 30000
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:30000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "howellx/diegetic-1.5b-sft",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Docker Model Runner
How to use howellx/diegetic-1.5b-sft with Docker Model Runner:
```
docker model run hf.co/howellx/diegetic-1.5b-sft
```

DIEGETIC-1.5B: Epistemically-Constrained Language Model

Base Model: Qwen/Qwen2.5-1.5B Training Method: LoRA (Low-Rank Adaptation) License: MIT Framework: DIEGETIC (Dynamically-grounded Inference Engine for Generative Epistemic Tracking In Conversation)

Model Description

DIEGETIC-1.5B is a fine-tuned language model specialized in epistemic reasoning - the ability to track what different agents know, believe, and can infer based on their observations. Unlike standard language models that may inadvertently "leak" information they shouldn't know, DIEGETIC is trained to keep to strict epistemic constraints.

What It Was Trained To Do

Belief State Tracking: Maintains accurate representations of what each agent knows
Hidden Information Management: Refuses to reveal information not available to the agent
Calibrated Uncertainty: Expresses appropriate confidence levels based on available evidence
Evidence Citation: Grounds claims in specific observations and memories
Theory of Mind: Reasons about nested beliefs (what Alice believes Bob knows)
Unanswerable Question Handling: Recognizes and appropriately responds to questions without sufficient evidence

Training Details

Dataset

This model was trained on Version 1 (Pure Synthetic) data only:

120,908 SFT examples from 10,000 trajectories
Generated from three epistemic sandboxes: Witness Investigation, Rumor Propagation, Inquiry Learning
This dataset is not currently published.

Note: DPO training was not applied to this model. This is an SFT-only model.

Training Configuration

Base Model: Qwen/Qwen2.5-1.5B (1.58B parameters)
Training Method: LoRA (r=32, alpha=64)
Trainable Parameters: 36.9M (2.34%)
Epochs: 3
Batch Size: 2 (gradient accumulation: 8)
Learning Rate: 2e-5 (cosine decay)
Max Sequence Length: 1024 tokens
Training Steps: 21,537
Training Loss: 1.77 → 0.47 (73% reduction)
Training Time: ~58 hours
GPU: NVIDIA GB10

Special Tokens

The model uses 12 custom special tokens for structured epistemic reasoning:

<OBS> / </OBS> - Observations available to the agent
<BELIEF> / </BELIEF> - Current belief state
<MEM> / </MEM> - Retrieved memories
<TASK> / </TASK> - Task specification
<OUTPUT_JSON> / </OUTPUT_JSON> - Structured JSON output
<EPISTEMIC> - Epistemic constraint marker
<REFUSE_DIEGETIC> - Refusal to leak information

Usage

⚠️ CRITICAL: Inference Format Requirement

This model requires a specific input format to work correctly. The training used plain text concatenation (system\n\nprompt), NOT chat templates. Using apply_chat_template() or other formatting will cause the model to produce invalid output.

Required format:

input_text = f"{system_message}\n\n{prompt}"

System Message

You must include this system message at the beginning of every input:

SYSTEM_MESSAGE = """You are DIEGETIC, an epistemically-constrained language model.

CORE PRINCIPLES:
1. You ONLY know what has been provided in <OBS>, <BELIEF>, and <MEM> blocks.
2. You NEVER access information outside these blocks.
3. You express uncertainty when evidence is weak.
4. You refuse to answer rather than leak unknown information.
5. You cite evidence for claims you make.

OUTPUT FORMAT:
You must respond with valid JSON matching this structure:
{
  "type": "diegetic_response",
  "utterance": "What you say",
  "epistemic": {
    "claims": [{"text": "...", "confidence": 0.0-1.0, "evidence": ["obs:...", "mem:..."]}],
    "unknowns": ["Things you explicitly don't know"],
    "assumptions": ["Assumptions you're making"]
  },
  "action": {
    "kind": "none|speak|move|look|interact|wait|query|tool",
    "tool": null,
    "args": null,
    "confidence": 0.0-1.0,
    "reasoning": "Why this action"
  }
}

Remember: It is BETTER to refuse than to leak information you shouldn't have."""

Complete Example

import torch
from transformers import AutoTokenizer, AutoModelForCausalLM
from peft import PeftModel

# Load tokenizer (includes special tokens)
tokenizer = AutoTokenizer.from_pretrained("howellx/diegetic-1.5b-sft")

# Load base model
base_model = AutoModelForCausalLM.from_pretrained(
    "Qwen/Qwen2.5-1.5B",
    dtype=torch.float16,
    device_map="auto"
)

# Resize embeddings for special tokens
base_model.resize_token_embeddings(len(tokenizer))

# Load LoRA adapter
model = PeftModel.from_pretrained(base_model, "howellx/diegetic-1.5b-sft")

# System message (required - see above for full text)
SYSTEM_MESSAGE = """You are DIEGETIC, an epistemically-constrained language model..."""

# Prompt with structured blocks (JSON format required)
prompt = """<TASK>{"role": "observer", "goal": "Track what agents believe", "instructions": "Track what Sally believes, not just ground truth"}</TASK>
<OBS>{"observations": [{"id": "obs:1", "text": "Sally puts a ball in the red box", "timestamp": "2026-01-01T10:00:00"}, {"id": "obs:2", "text": "Sally leaves the room", "timestamp": "2026-01-01T10:01:00"}, {"id": "obs:3", "text": "Anne moves the ball to the blue box", "timestamp": "2026-01-01T10:02:00"}], "timestamp": "2026-01-01T10:03:00", "context": {}, "count": 3}</OBS>
<BELIEF>{"agent_id": "sally", "domains": {"location": [{"id": "belief:1", "proposition": "ball is in red box", "confidence": 1.0, "source": "direct_observation", "source_id": "obs:1", "status": "active", "domain": "location"}]}, "total_beliefs": 1}</BELIEF>
<MEM>{"memories": [], "retrieval_context": "Where does Sally believe the ball is?", "count": 0}</MEM>
User query: Where does Sally believe the ball is?
<OUTPUT_JSON>"""

# CRITICAL: Use plain text concatenation (NO chat template!)
input_text = f"{SYSTEM_MESSAGE}\n\n{prompt}"

# Tokenize
inputs = tokenizer(input_text, return_tensors="pt").to(model.device)

# Generate with proper parameters
outputs = model.generate(
    **inputs,
    max_new_tokens=300,
    temperature=0.7,
    top_p=0.9,
    repetition_penalty=1.2,
    do_sample=True,
    no_repeat_ngram_size=3,
    pad_token_id=tokenizer.pad_token_id,
    eos_token_id=tokenizer.eos_token_id
)

# Decode response (only the generated part)
response = tokenizer.decode(
    outputs[0][inputs['input_ids'].shape[1]:],
    skip_special_tokens=True
)
print(response)

Expected Output

The intended response shape looks like this. It is an illustration, and actual outputs can vary or be malformed:

{
  "type": "diegetic_response",
  "utterance": "Sally believes the ball is in the red box",
  "epistemic": {
    "claims": [
      {
        "text": "Sally believes ball is in red box",
        "confidence": 1.0,
        "evidence": ["obs:1", "belief:1"]
      }
    ],
    "unknowns": [],
    "assumptions": []
  },
  "action": {
    "kind": "none",
    "confidence": 1.0,
    "reasoning": "Answering based on Sally's belief state"
  }
}

Performance Results

This adapter has no published evaluation. Hand checks during development (false belief, hidden information, uncertainty) gave mixed output quality, so test it on your own prompts before relying on it.

Training loss fell from 1.77 to 0.47, which shows the model learned the training format. It doesn't measure how well the model reasons on new problems.

Evaluation Metrics

Suggested metrics for evaluating models trained on DIEGETIC data. These are targets; this model has not been scored against them.

Metric	Description	Target
ELR (Epistemic Leakage Rate)	% of claims without evidence	< 5%
BCS (Belief Consistency Score)	No self-contradictions	> 95%
UCE (Uncertainty Calibration Error)	Confidence matches evidence	< 0.15
ECC (Evidence Citation Coverage)	Claims citing sources	> 80%

Limitations

SFT-Only Model: This model uses only Supervised Fine-Tuning. DPO (Direct Preference Optimization) was not applied, which means:
- Generation quality/fluency could be improved with DPO
- Some outputs may be repetitive (fixable with inference parameters)
Synthetic Data Bias: Primarily trained on synthetic scenarios; real-world performance may vary
Template Patterns: Some linguistic patterns may be repetitive due to synthetic generation
English Only: Currently monolingual
Domain Coverage: Limited to three sandbox types (witness investigation, rumor propagation, inquiry learning)
Complexity Ceiling: Max 20 agents, 50 steps per trajectory
Inference Tuning Recommended: Use temperature=0.7, top_p=0.9, repetition_penalty=1.1 for best results

Intended Use

Primary Uses:

Research on epistemic reasoning in language models
Building AI systems that respect information boundaries
Theory of mind evaluation and training
Educational tools for reasoning about knowledge and belief

Out-of-Scope:

Production conversational AI without additional safety measures
Real-time critical decision-making
Medical, legal, or financial advice

Ethical Considerations

Privacy: Model trained to respect information boundaries - useful for privacy-preserving AI
Transparency: Encouraged to cite sources and express uncertainty
Limitations: Users should be aware of synthetic training data limitations

Citation

@misc{howell2026diegetic,
  title={DIEGETIC-1.5B: Epistemically-Constrained Language Model},
  author={Howell, Justin},
  year={2026},
  publisher={Hugging Face},
  howpublished={\\url{https://huggingface.co/howellx/diegetic-1.5b-sft}}
}

Related Resources

Framework Code: Available on request

License

MIT License - See LICENSE file for details.

Generated using the DIEGETIC framework for epistemically-constrained language models.

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