# BTL-3 (27B)

> Agent-oriented Qwen3.6-27B derivative that adds a rank-32 LoRA adapter for coding, structured tool use, and long multi-turn execution.

| Property | Value |
| --- | --- |
| Lab | Bad Theory Labs (Nigeria) |
| Released | 2026-07-20 |
| Decoder type | Dense hybrid |
| Family | Dense hybrid |
| Scale | 27B base + 934 MB LoRA adapter |
| Context window | 262,144 tokens |
| Attention | 3:1 Gated DeltaNet and Gated Attention |
| Layer mix | 16 gated attention + 48 DeltaNet |
| KV cache / token (bf16) | 64 KiB (Low) |
| License | Apache License 2.0 |

**Key detail:** Retains Qwen3.6-27B's 64-layer hybrid stack while adapting its attention, DeltaNet, and FFN projections through rank-32 LoRA.

## Architecture concepts

- [Hybrid Attention (Hybrid attention)](https://llm-atlas-7or.pages.dev/concepts/hybrid-attention.md): Mixes cheap linear-attention or state-space layers with a few full-attention layers.
- [Grouped-Query Attention (GQA)](https://llm-atlas-7or.pages.dev/concepts/gqa.md): Several query heads share one key/value head, shrinking the KV cache with little quality loss.
- [Gated Attention (Gated attention)](https://llm-atlas-7or.pages.dev/concepts/gated-attention.md): A learned sigmoid gate scales the attention output before it re-enters the residual stream.
- [QK-Norm (QK-Norm)](https://llm-atlas-7or.pages.dev/concepts/qk-norm.md): RMSNorm applied to queries and keys before attention to keep logits well-behaved.

## Links

- Architecture diagram: https://sebastianraschka.com/llm-architecture-gallery/images/architectures/btl-3-27b.webp
- adapter_config.json: https://huggingface.co/badtheorylabs/BTL-3/blob/main/adapter_config.json
- License: https://huggingface.co/badtheorylabs/BTL-3/blob/main/LICENSE
- Source card (source of truth): https://sebastianraschka.com/llm-architecture-gallery/#card-btl-3-27b
- Web page: https://llm-atlas-7or.pages.dev/models/btl-3-27b/
- JSON: https://llm-atlas-7or.pages.dev/api/models/btl-3-27b.json

_Data from Sebastian Raschka's LLM Architecture Gallery (https://sebastianraschka.com/llm-architecture-gallery/). Synced 2026-11-04._