qwen3.5-35b-a3b

Qwen3.5-35B-A3B for hipfire

Pre-quantized Qwen3.5-35B-A3B (MoE, 35B total / 3B activated) for hipfire, a Rust-native LLM inference engine for AMD RDNA GPUs.

Quantized from Qwen/Qwen3.5-35B-A3B. Original A3B release of the Qwen3.5 line. Hybrid attention layout: 256 experts top-8, DeltaNet (linear) + Full Attention layers in a 3:1 ratio, head_dim=256 with partial_rotary_factor=0.25, shared expert, tied embeddings. Loaded by hipfire's arch_id=6 MoE forward path.

2026-05-07 Q8-router release

This is the first hipfire release of qwen3.5-35b-a3b.mq4 to land @fivetide's PR #180 — the MoE router (mlp.gate.weight and mlp.shared_expert_gate.weight) is now quantized at Q8F16 instead of MQ4, costing ~10 MB additional model size. The rationale and empirical evidence are documented at issue #171 and the investigation log at docs/investigations/2026-05-06-moe-quant-cliff-survey.

3.5-A3B was less affected by the broken-router cliff than its sibling 3.6-A3B (3.5 was clean at greedy + RP=1.05 even with 4-bit router; 3.6 was the canary that exposed the cliff on agentic prompts). 3.5-A3B is still re-quantized for parity and to keep both A3Bs on a uniform format.

Files

⭐ MQ4 is FWHT-rotated 4-bit with the routing tensors (mlp.gate.weight, mlp.shared_expert_gate.weight) pinned at Q8F16. Quality-gated against the Q8 reference on the hipfire coherence battery.

Usage

# Install hipfire (master, includes the router-Q8 fix)
curl -L https://raw.githubusercontent.com/Kaden-Schutt/hipfire/master/scripts/install.sh | bash

# Pull the model (defaults to MQ4)
hipfire pull qwen3.5:35b-a3b

hipfire run qwen3.5:35b-a3b "Write a Rust function that parses an ISO-8601 date."

To pull the MQ3 variant explicitly:

hf download schuttdev/hipfire-qwen3.5-35b-a3b qwen3.5-35b-a3b.mq3 \
    --local-dir ~/.hipfire/models

Configuration notes

• Greedy + RP=1.05 is the default sampler and is robust on this model across the reference 7-prompt × 5-sampler matrix (see issue #171 update). The HF-aligned temp=1.0 + top_k=20 + min_p=0.05 sampler is opt-in per request; greedy default delivers the cleanest output.
• thinking:auto — 3.5-A3B's thinking mode is healthy at MQ4.
• DFlash speculative decoding off by default for A3B — drafts reject most tokens (τ≈1.0–1.5 on non-math), so AR alone is faster unless a CASK sidecar is configured for the eviction-required long-context path.

Quantization format

• MQ4 (MagnumQuant-4) — FWHT-rotated 4-bit with asym3 KV cache default. Routing tensors at Q8F16. Matches Q8 output quality at ~Q4 bandwidth on hipfire's WMMA/dot2 fused kernel paths.
• MQ3 (MagnumQuant-3) — same FWHT-rotated approach at 3-bit for the bulk weights. Useful when MQ4 doesn't fit on the target host.

See docs/QUANTIZATION.md for details on the rotation invariance property and the quality gate.

License

Apache 2.0, following the upstream Qwen/Qwen3.5-35B-A3B license.