Qwen2.5-7B-Instruct-borg-merge-v1

A training-free cross-family weight merge of Qwen2.5-7B-Instruct with 8 donors from 4 architecture families. Lifts GSM8K +3.3 pp, ARC-Challenge +3.2 pp, and IFEval +2.6 pp absolute over the unmerged anchor. No fine-tuning. No distillation. No router. Drop-in safetensors.

Task Anchor SOLO This model Δ
GSM8K (exact_match,strict-match) 0.8120 0.8446 +0.0326
ARC-Challenge (acc_norm,none) 0.5256 0.5572 +0.0316
IFEval (inst_level_strict_acc,none) 0.6547 0.6811 +0.0264
MMLU (acc,none) 0.7180 0.7094 -0.0086
TruthfulQA mc2 (acc,none) 0.6475 0.6285 -0.0190
HellaSwag (acc,none) 0.6895 0.6830 -0.0065
PIQA (acc,none) 0.8030 0.8014 -0.0016
HumanEval (pass@1,greedy) 0.6463 0.5854 -0.0610

Lifts on 3 of 8 standard benchmarks vs. the unmerged anchor -- on the tasks where the donor pool is competence-concentrated (instruction following + broad reasoning). Regresses on HumanEval, where the donor pool was code-light by design. The regression structure is itself a falsifiable prediction about the recipe.

Quick start

from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

model = AutoModelForCausalLM.from_pretrained(
    "Optitransfer/Qwen2.5-7B-Instruct-borg-merge-v1",
    torch_dtype=torch.float16,
    device_map="auto",
)
tokenizer = AutoTokenizer.from_pretrained("Optitransfer/Qwen2.5-7B-Instruct-borg-merge-v1")

prompt = "Q: What is 17 multiplied by 23? Show your work.\nA:"
ids = tokenizer(prompt, return_tensors="pt").to(model.device)
out = model.generate(**ids, max_new_tokens=128, do_sample=False)
print(tokenizer.decode(out[0], skip_special_tokens=True))

Compatible with vLLM, llama.cpp (after GGUF conversion), text-generation-inference, text-generation-webui, and any standard HuggingFace inference stack.

What's special about this merge

Cross-family weight merging across architecture families (Llama, Phi, NeoX, OPT) is conventionally considered impossible -- different attention head dimensions, different FFN expansion factors, different vocabularies. A naive linear interpolation between, say, a Qwen attention block and a Mistral attention block does not even type-check.

This model is the result of a training-free pipeline that solves this:

  1. Canonicalize each donor's tensors into a shared key namespace via per-architecture detectors (10 architecture families covered: BERT, RoBERTa, Llama/Qwen, Mistral, Pythia, OPT, Phi, T5, w2v-bert, and more).
  2. Procrustes-align each donor's basis to the anchor via per-tensor orthogonal rotation (smaller-side SVD).
  3. Compute donor deltas in canonical space; filter via per-role tolerance (asymmetric: τ_attn=0.05, τ_ffn=0.20); keep top-3 SVD components.
  4. Absorb the rotated, filtered, low-rank delta into the anchor with anchor blend β=0.60.
  5. Decanonicalize to the anchor's native key namespace; save as standard safetensors.

This is the asymmetric tolerance recipe: tight on attention to preserve circuits, loose on FFN to absorb knowledge.

Donor pool (8 donors, 4 architecture families)

Source Family License
Qwen/Qwen2.5-7B-Instruct (anchor) Qwen / Llama-arch Apache 2.0
mistralai/Mistral-7B-Instruct-v0.3 Mistral / Llama-arch Apache 2.0
microsoft/Phi-3-mini-4k-instruct Phi (new) MIT
microsoft/phi-2 Phi (old) MIT
HuggingFaceTB/SmolLM2-1.7B-Instruct Llama-arch (small) Apache 2.0
ibm-granite/granite-3.0-2b-instruct Llama-arch (Granite tweaks) Apache 2.0
EleutherAI/pythia-2.8b NeoX Apache 2.0
EleutherAI/pythia-1.4b NeoX Apache 2.0
facebook/opt-2.7b OPT OPT license

Verification

  • Cross-run reproducibility: an independent preflight evaluation two days prior to the headline run produces byte-identical scores to all 16 decimal places across every overlapping (variant, task) cell. The merge is fully deterministic.
  • Pre-flight gates: G1 round-trip across all 6 cross-family canonicalization tests reports r_max=0.0, n_bad=0 (lossless canonical key namespace). G3 multi-seed slice-bias on the anchor MMLU 200-sample slice returns 0.7480126320374605 to 16 decimal places across seeds 7, 42, 1337. G4 anchor MMLU full matches the published Qwen2.5-7B-Instruct leaderboard reference.
  • Behavioural inspection: 5 reasoning-heavy prompts (math word problem, French translation, long-multiplication, recursive Fibonacci, factual enumeration) produce coherent, instruction-following, mathematically-correct output with no gibberish, no tokenizer drift, no instruction-format collapse.
  • Eval framework: lm-eval-harness 0.4.4 with transformers 4.55.0, tokenizers 0.21.4, datasets >=2.20 <4.0, fp16, batch 2, single A100 80GB.

Comparison to recent work in the model-merging landscape

For a comprehensive map of model-merging methods, theory, and applications, see Yang et al.'s curated survey Awesome-Model-Merging-Methods-Theories-Applications (forthcoming ACM Computing Surveys 2026).

Closest direct relatives:

  • Transport and Merge (Cui et al., Feb 2026) -- cross-architecture merging via activation-space optimal transport. Different problem class: theirs produces a runtime-aligned composition; this model is a permanent merged checkpoint.
  • Unconstrained Model Merging for Enhanced LLM Reasoning (Zhang et al., Oct 2024) -- closest direct relative on substrate scale (7B-class) and donor count (9 reasoning-optimized LLMs). The result above extends this lineage with absolute benchmark deltas against a state-competitive instruction-tuned anchor.
  • Git Re-Basin (Ainsworth, Hayase & Srinivasa, ICLR 2023) -- same-architecture merging modulo permutation symmetries. The pipeline above is essentially the cross-architecture generalization (continuous Procrustes rotation rather than discrete permutation matching).
  • OT-Fusion (Singh & Jaggi, NeurIPS 2020) -- same-architecture optimal transport on weight rows. Spiritual ancestor of Cui et al.'s 2026 cross-architecture extension.
  • REPAIR (Jordan et al., 2022) -- re-normalization to address variance collapse after permutation interpolation. The pipeline above sidesteps this by using anchor-plus-delta absorption rather than midpoint interpolation.

Limitations

  • Code generation regresses by 6.10 pp on HumanEval. The donor pool was reasoning-heavy and instruction-tuned; it contained no code-specialist models (CodeLlama, StarCoder, Qwen2.5-Coder). Documented as falsifiable prediction: a code-heavy donor pool should restore HumanEval while preserving the GSM8K, ARC-Challenge, and IFEval gains. This is the explicit subject of the next research cycle.
  • Mild MMLU regression (-0.86 pp). The merge trades some broad knowledge for instruction-following + reasoning concentration. Within typical eval noise on TruthfulQA mc2 (-0.19), HellaSwag (-0.07), PIQA (-0.02).
  • Single substrate tested: results are on Qwen2.5-7B-Instruct. Generalization to other instruction-tuned 7B-class anchors (Llama-3.1-8B-Instruct, Mistral-7B-Instruct-v0.3 as anchor, etc.) is the next experiment.
  • HumanEval pass@1 measured via custom isolated-subprocess scorer, not via lm-eval (the pinned lm-eval-harness 0.4.4 does not ship the humaneval task). Greedy decoding, 164 problems, no temperature sweep. Identical methodology to bigcode-evaluation-harness with subprocess-isolated test execution.

Intended use

  • Research and evaluation of cross-family weight-merging techniques.
  • Drop-in replacement for Qwen/Qwen2.5-7B-Instruct in workflows where the trade-off (GSM8K / ARC-Challenge / IFEval lifts vs. mild HumanEval regression) is favorable.
  • Compatible with vLLM, llama.cpp (after GGUF conversion), TGI, text-generation-webui, and any standard HuggingFace inference stack.

Out of scope

  • Code generation as primary use case -- use Qwen/Qwen2.5-Coder-7B-Instruct instead, or wait for the next merge variant which targets a code-heavy donor pool.
  • Production deployment without your own evaluation on your specific task distribution.

Citation

If you use this model, please cite:

@misc{borg-merge-v1-2026,
  title  = {Conflict-Free Replicated Datatypes for Neural Network Model Merging},
  author = {Optitransfer},
  year   = {2026},
  url    = {https://huggingface.co/Optitransfer/Qwen2.5-7B-Instruct-borg-merge-v1}
}

Contact

  • rgillespie83@icloud.com
  • data@optitransfer.ch

For arXiv endorsement requests on the full technical paper covering cross-family weight merging (cs.LG / secondary cs.CL): same contacts, subject line "arXiv endorsement: cross-family weight merging".

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