fix(hwfit): distinguish Apple Silicon bandwidth variants (#2564)

* fix: resolve Apple Silicon bandwidth variants

* fix(hwfit): preserve string lookup path in _lookup_bandwidth

* fix(hwfit): guard Apple bandwidth lookup against false GPU matches

Add "apple" not in gn check to _lookup_apple_bandwidth() so that
non-Apple GPUs with "m3"/"m4"/"m5" in their names (e.g. NVIDIA
Quadro M4 000) don't incorrectly match Apple bandwidth tiers.

Addresses @o3LL review comment on PR #2564.

tests/test_hwfit_apple_bandwidth.py

@@ -0,0 +1,40 @@
+from services.hwfit.fit import _lookup_bandwidth
+
+
+def test_m3_max_bandwidth_uses_gpu_cores():
+    assert _lookup_bandwidth({"gpu_name": "Apple M3 Max", "gpu_cores": 30}) == 300
+    assert _lookup_bandwidth({"gpu_name": "Apple M3 Max", "gpu_cores": 40}) == 400
+
+
+def test_m4_max_bandwidth_uses_gpu_cores():
+    assert _lookup_bandwidth({"gpu_name": "Apple M4 Max", "gpu_cores": 32}) == 410
+    assert _lookup_bandwidth({"gpu_name": "Apple M4 Max", "gpu_cores": 40}) == 546
+
+
+def test_m5_max_bandwidth_uses_gpu_cores():
+    assert _lookup_bandwidth({"gpu_name": "Apple M5 Max", "gpu_cores": 32}) == 460
+    assert _lookup_bandwidth({"gpu_name": "Apple M5 Max", "gpu_cores": 40}) == 614
+
+
+def test_apple_max_bandwidth_falls_back_conservatively_without_gpu_cores():
+    assert _lookup_bandwidth({"gpu_name": "Apple M3 Max"}) == 300
+    assert _lookup_bandwidth({"gpu_name": "Apple M4 Max"}) == 410
+    assert _lookup_bandwidth({"gpu_name": "Apple M5 Max"}) == 460
+
+
+def test_fixed_apple_bandwidth_entries_include_updated_m5_values():
+    assert _lookup_bandwidth({"gpu_name": "Apple M5 Pro"}) == 307
+    assert _lookup_bandwidth({"gpu_name": "Apple M5"}) == 153
+
+
+def test_non_apple_gpu_does_not_match_apple_bandwidth():
+    """NVIDIA Quadro M4 000 should NOT match Apple bandwidth lookup."""
+    assert _lookup_bandwidth({"gpu_name": "NVIDIA Quadro M4 000"}) is None
+    assert _lookup_bandwidth({"gpu_name": "NVIDIA Quadro M3 000"}) is None
+    assert _lookup_bandwidth({"gpu_name": "NVIDIA Quadro M5 000"}) is None
+
+
+def test_non_apple_gpu_with_cores_does_not_match():
+    """NVIDIA GPU with core count should not match Apple bandwidth."""
+    assert _lookup_bandwidth({"gpu_name": "NVIDIA GeForce RTX 4090", "gpu_cores": 128}) is None
+    assert _lookup_bandwidth({"gpu_name": "AMD Radeon RX 9070 XT", "gpu_cores": 64}) is None

tests/test_hwfit_macos.py

@@ -4,6 +4,8 @@ Covers the Metal-specific behavior added for Apple Silicon and locks in the
 guarantee that non-macOS (Linux/Windows) detection is unchanged.
 """
 
+import json
+
 from services.hwfit import hardware
 from services.hwfit.fit import rank_models
 from services.hwfit.models import get_models
@@ -22,7 +24,7 @@ def _metal_system(ram_gb=16.0, vram_gb=10.7):
     }
 
 
-def _fake_sysctl(brand="Apple M2 Pro", memsize_gb=32, wired_mb=None):
+def _fake_sysctl(brand="Apple M2 Pro", memsize_gb=32, wired_mb=None, display_json=None, display_text=None):
     def run(cmd):
         joined = " ".join(cmd)
         if "machdep.cpu.brand_string" in joined:
@@ -31,6 +33,12 @@ def _fake_sysctl(brand="Apple M2 Pro", memsize_gb=32, wired_mb=None):
             return str(int(memsize_gb * 1024**3))
         if "iogpu.wired_limit_mb" in joined:
             return str(wired_mb) if wired_mb is not None else None
+        if "system_profiler SPDisplaysDataType -json" in joined:
+            if isinstance(display_json, (dict, list)):
+                return json.dumps(display_json)
+            return display_json
+        if "system_profiler SPDisplaysDataType" in joined:
+            return display_text
         return None
     return run
 
@@ -98,16 +106,47 @@ def test_apple_silicon_detected_as_metal(monkeypatch):
     monkeypatch.setattr(hardware, "_remote_host", None)
     monkeypatch.setattr(hardware.platform, "system", lambda: "Darwin")
     monkeypatch.setattr(hardware.platform, "machine", lambda: "arm64")
-    monkeypatch.setattr(hardware, "_run", _fake_sysctl(memsize_gb=32))
+    monkeypatch.setattr(hardware, "_run", _fake_sysctl(
+        memsize_gb=32,
+        display_json={"SPDisplaysDataType": [{"sppci_model": "Apple M2 Pro", "sppci_cores": "19"}]},
+    ))
 
     info = hardware._detect_apple_silicon()
     assert info is not None
     assert info["backend"] == "metal"
     assert info["gpu_name"] == "Apple M2 Pro"
     assert info["unified_memory"] is True
+    assert info["gpu_cores"] == 19
     assert info["gpu_vram_gb"] == 24.0  # 32GB * 0.75
 
 
+def test_apple_silicon_gpu_cores_fall_back_to_plain_text(monkeypatch):
+    monkeypatch.setattr(hardware, "_remote_host", None)
+    monkeypatch.setattr(hardware.platform, "system", lambda: "Darwin")
+    monkeypatch.setattr(hardware.platform, "machine", lambda: "arm64")
+    monkeypatch.setattr(hardware, "_run", _fake_sysctl(
+        brand="Apple M4 Max",
+        memsize_gb=64,
+        display_json="{not-json",
+        display_text="Graphics/Displays:\n\nApple M4 Max:\n  Total Number of Cores: 32\n",
+    ))
+
+    info = hardware._detect_apple_silicon()
+    assert info is not None
+    assert info["gpu_cores"] == 32
+
+
+def test_apple_silicon_gpu_cores_are_optional(monkeypatch):
+    monkeypatch.setattr(hardware, "_remote_host", None)
+    monkeypatch.setattr(hardware.platform, "system", lambda: "Darwin")
+    monkeypatch.setattr(hardware.platform, "machine", lambda: "arm64")
+    monkeypatch.setattr(hardware, "_run", _fake_sysctl(memsize_gb=32))
+
+    info = hardware._detect_apple_silicon()
+    assert info is not None
+    assert "gpu_cores" not in info
+
+
 def test_apple_silicon_skipped_on_linux(monkeypatch):
     """Guarantee Linux detection is untouched: the Metal probe bails immediately."""
     monkeypatch.setattr(hardware, "_remote_host", None)
@@ -132,7 +171,7 @@ def test_detect_system_propagates_unified_memory(monkeypatch):
     monkeypatch.setattr(hardware, "_detect_apple_silicon", lambda: {
         "gpu_name": "Apple M4", "gpu_vram_gb": 10.7, "gpu_count": 1,
         "gpus": [], "gpu_groups": [], "homogeneous": True,
-        "backend": "metal", "unified_memory": True,
+        "backend": "metal", "unified_memory": True, "gpu_cores": 10,
     })
     monkeypatch.setattr(hardware, "_get_ram_gb", lambda: 16.0)
     monkeypatch.setattr(hardware, "_get_available_ram_gb", lambda: 11.0)
@@ -142,3 +181,4 @@ def test_detect_system_propagates_unified_memory(monkeypatch):
     s = hardware.detect_system(fresh=True)
     assert s["backend"] == "metal"
     assert s.get("unified_memory") is True
+    assert s["gpu_cores"] == 10