#119 decisive probe: ACDREAM_DUMP_ENTITY one-shot entity dump (H-A/H-B/H-C discriminator)

The broken-state log (user-session-capture2.log) shows meshMissing=0 /
entSeen==entDrawn WHILE broken stairs are on screen - the staircase is
DRAWN WRONG, not missing. This probe discriminates the three live
hypotheses in ONE launch (handoff 2026-06-11 s4):

- HYDRATE dump (GameWindow.BuildInteriorEntitiesForStreaming): per-part
  placement-frame translations + dropped-part accounting at the MOMENT
  MeshRefs are constructed. H-A (SetupMesh.Flatten identity fallback /
  silent gfx-null part drops under degraded dat reads) shows here as
  zero translations or built<43.
- DRAW dump (WbDrawDispatcher, first tuple per entity): live MeshRefs
  translation summary + per-part loaded flags + Tier-1 classification
  cache state (batch count + RestPose translation summary), re-emitted
  compactly on signature change. H-B (partial/stale cached batch set)
  shows as correct translations + odd batch count.
- WALK-REJECT lines (rate-limited): attributes 'entity never reaches
  the draw loop' to the specific gate (visibleCellIds/frustum).
- Correct everything -> H-C (draw-side compose), instrument next.

Targets: ACDREAM_DUMP_ENTITY=0x020003F2,0x020005D8 (the 43-part spiral
staircase Setup + the wall barrels; H-A predicts the user's 'barrel' IS
the collapsed staircase). Probe is inert when the env var is unset.
Parser in RenderingDiagnostics (diagnostic-owner pattern) + 5 unit tests.

Suites: App 242+1skip / Core 1427+2skip / UI 420 / Net 294.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/AcDream.Core.Tests/Rendering/RenderingDiagnosticsTests.cs

@@ -139,4 +139,48 @@ public sealed class RenderingDiagnosticsTests
         // Env var is absent in the test host, so the flag must default false (inert probe).
         Assert.False(AcDream.Core.Rendering.RenderingDiagnostics.ProbePortalChurnEnabled);
     }
+
+    // ── ACDREAM_DUMP_ENTITY parser (#119 decisive probe) ──────────────────
+
+    [Fact]
+    public void ParseDumpEntityIds_NullOrEmpty_ReturnsEmptySet()
+    {
+        Assert.Empty(RenderingDiagnostics.ParseDumpEntityIds(null));
+        Assert.Empty(RenderingDiagnostics.ParseDumpEntityIds(""));
+        Assert.Empty(RenderingDiagnostics.ParseDumpEntityIds("   "));
+    }
+
+    [Fact]
+    public void ParseDumpEntityIds_CommaSeparatedWithPrefixes_ParsesAll()
+    {
+        var set = RenderingDiagnostics.ParseDumpEntityIds("0x020003F2,0x020005D8");
+        Assert.Equal(2, set.Count);
+        Assert.Contains(0x020003F2u, set);
+        Assert.Contains(0x020005D8u, set);
+    }
+
+    [Fact]
+    public void ParseDumpEntityIds_NoPrefixMixedCaseAndWhitespace_Parses()
+    {
+        var set = RenderingDiagnostics.ParseDumpEntityIds(" 020003f2 , 0X020005D8 ");
+        Assert.Equal(2, set.Count);
+        Assert.Contains(0x020003F2u, set);
+        Assert.Contains(0x020005D8u, set);
+    }
+
+    [Fact]
+    public void ParseDumpEntityIds_MalformedSegment_IgnoredNotFatal()
+    {
+        // A typo'd segment must not take the launch down — parse what's valid.
+        var set = RenderingDiagnostics.ParseDumpEntityIds("0x020003F2,zzz,,0x");
+        Assert.Single(set);
+        Assert.Contains(0x020003F2u, set);
+    }
+
+    [Fact]
+    public void DumpEntitySourceIds_DefaultsEmpty_WhenEnvUnset()
+    {
+        // Env var is absent in the test host → probe inert.
+        Assert.Empty(RenderingDiagnostics.DumpEntitySourceIds);
+    }
 }