btl-2-coder

BTL-2 Coder 7B

BTL-2 Coder 7B is a LoRA adapter for unsloth/Qwen2.5-Coder-7B-Instruct, trained for structured code-review findings.

Code and evaluation scripts are available at:

https://github.com/Badtheorylabs/btl-2-coder

Intended Use

This adapter is intended for local-first code review. It is trained to produce structured findings with:

• severity
• file path
• line number
• title
• evidence
• recommendation
• numeric confidence

The main supported issue classes are SQL injection, path traversal, authorization bypass, missing error handling, boundary/off-by-one logic, and related security/correctness findings.

The adapter is optimized for review output rather than broad chat behavior.

Training

• Base model: unsloth/Qwen2.5-Coder-7B-Instruct
• Method: LoRA SFT with Unsloth
• Data mix: 4,000 API-generated review traces + 1,000 template traces
• Train/eval split: 4,500 train examples + 500 eval examples
• Epochs: 2
• Max sequence length: 4096

Only redacted, opt-in traces should be used for future training.

Recommended Prompt Contract

Use strict schema prompting:

Return only a JSON array. No markdown and no wrapper object.
Each finding must include: severity, file, line, title, evidence, recommendation, confidence.
severity must be exactly one of: critical, high, medium, low.
Never put a category in severity.
confidence must be a number from 0 to 1, never a string label.
Every finding must include concrete evidence and a non-empty recommendation.

Example output:

[
  {
    "severity": "critical",
    "file": "src/users.ts",
    "line": 42,
    "title": "SQL injection through string-built query",
    "evidence": "The user id is concatenated directly into the SQL string.",
    "recommendation": "Use a parameterized query.",
    "confidence": 0.96
  }
]

Load The Adapter

from peft import PeftModel
from transformers import AutoModelForCausalLM, AutoTokenizer

base = "unsloth/Qwen2.5-Coder-7B-Instruct"
adapter = "badtheorylabs/btl-2-coder"

tokenizer = AutoTokenizer.from_pretrained(adapter)
model = AutoModelForCausalLM.from_pretrained(base, device_map="auto")
model = PeftModel.from_pretrained(model, adapter)

Evaluation

Measured on an NVIDIA H200 with 4-bit adapter inference.

Notes:

• Heldout precision/recall is marked n/a because the heldout set is broader and does not use one normalized ground-truth finding per example.
• The seeded benchmark is a controlled regression suite with known findings.
• Reported results use the recommended strict schema prompt.

Scope

• Primary task: structured security and correctness review.
• Output format: JSON findings with severity, location, evidence, recommendation, and confidence.
• Best runtime path: strict schema prompting, with optional constrained decoding.
• Evaluation focus: code-review findings, file hits, schema validity, and seeded precision/recall.
• Next track: patch proposals and terminal workflows.

Files

This repository contains a PEFT/LoRA adapter:

• adapter_model.safetensors
• adapter_config.json
• tokenizer.json
• tokenizer_config.json
• chat_template.jinja
• training_args.bin
• SHA256SUMS