Darwin-4B-Opus is a reasoning-enhanced model created by merging google/gemma-4-E4B-it (Father) and arsovskidev/Gemma-4-E4B-Claude-4.6-Opus-Reasoning-Distilled (Mother) using the Darwin V6 engine.
Darwin V6 diagnoses both parent models at the tensor level before merging, assigning an independent optimal ratio to each tensor. This is fundamentally different from conventional merging tools that apply a single uniform ratio across all tensors.
As the smallest member of the Darwin Opus family, Darwin-4B-Opus delivers Claude Opus-level reasoning distillation in a highly efficient 4B parameter MoE architecture, making it ideal for edge deployment, rapid prototyping, and resource-constrained environments while maintaining strong benchmark performance (0.8292 ARC-Challenge).
Claude 4.6 Opus high-effort reasoning distillation, enhanced code/science/analysis
Model Diagnostic Scan (MDS)
Father (gemma-4-E4B-it) MDS Scan
Mother (Claude-Opus-Distill) MDS Scan
Left: Father (gemma-4-E4B-it) — balanced generalist with low activation across most probes. Right: Mother (Claude-Opus-Distill) — strong REASONING concentration in later layers, CODE activation in late layers. The Mother shows significantly more specialized layer patterns from Claude Opus distillation.
Benchmarks
Benchmark
Darwin-4B-Opus
Condition
ARC-Challenge
82.92%
loglikelihood, zero-shot
Note: Gemma 4 architecture (Gemma4ForConditionalGeneration) has limited compatibility with lm-eval's loglikelihood method due to its multimodal wrapper structure. Only generative evaluation produces valid results for Gemma 4 based models. Full extended evaluation with Majority Voting is planned.
Darwin V6 vs Conventional Merging
Capability
mergekit (DARE-TIES)
Darwin V6
Implementation
Library call (mergekit CLI)
Direct PyTorch tensor operations, no external dependency
Ratio selection
Uniform ratio across all tensors
Per-tensor ratio from MDS diagnostic (independent ratios per tensor)
ratio < 0.15 → Father 100%, ratio > 0.85 → Mother 100% (zero interpolation noise)
Post-merge validation
Benchmark score only
Layer-by-layer Health Check: child vs both parents, interference and function loss detection
Search method
Manual tuning
CMA-ES evolution with adaptive 14-dimensional genome
Reproducibility
Config file
genome_hash seed guarantees identical output for identical genome
GPU efficiency
Single merge per run
Phase 1 proxy (200 steps, seconds) → Phase 2 real merge (top-k only evaluated)
How Darwin V6 Works
Darwin V6 does not use mergekit or any external merge library. It re-implements DARE-TIES (Yadav et al., 2023) directly via PyTorch tensor operations with per-tensor diagnostic ratios.
Before merging, Darwin performs a Model Diagnostic Scan (MDS) on both parents. For every tensor, it measures Shannon entropy (information density), standard deviation (activation spread), and L2 norm (energy). Additionally, 5 diagnostic probes (REASONING, CODE, MATH, KNOWLEDGE, LANGUAGE) are passed through the model, measuring cosine distance when each layer is skipped to determine functional importance.
The mri_trust parameter itself is optimized by the CMA-ES evolutionary algorithm, allowing the system to automatically determine the optimal balance between diagnostic prescription and evolutionary search for each model pair.
Key observations from the genome: ffn_ratio=0.90 indicates the FFN layers strongly favor the Mother (Claude Opus Distill), carrying the bulk of the reasoning enhancement. block_5 (final layers)=0.84 shows the reasoning core layers also strongly favor Mother, consistent with the pattern seen across all Darwin Opus models where Claude's reasoning capability concentrates in the final layers. Meanwhile, attn_ratio=0.18 firmly preserves Father's attention structure, maintaining the original Gemma 4 multimodal and context capabilities. Notably, mri_trust=0.49 shows the system found near-equal value in both diagnostic analysis and evolutionary search, suggesting a well-balanced optimization.