fix(measure): a blocked route is not a disconnected pair

VF_AreConnected took the shortest coarse BFS route, re-walked it at full
resolution, and on hitting a wall returned false and gave up -- never
looking for another way round. That is a false NEGATIVE, and it was
inflating the failure count of a bug we were actively trying to fix.

On refutation it now excludes that specific coarse step and re-searches,
up to a bounded budget (16). Outcomes are distinguished honestly:
  Connected                   a route survived full-resolution verification
  NotConnectedAtThisResolution no coarse route remains after exclusions
  CoarseLiedBudgetExhausted    UNKNOWN -- routes kept being refuted
The third is deliberately NOT folded into either other verdict. Collapsing
"unknown" into "disconnected" is precisely what misled us.

  arrival->departure   7/16 -> 14/16
  All 7 former COARSE_LIED became CONNECTED.
  arrival->spine   15/16 connected      departure->spine 15/16 connected
  per-archetype law: 6/6 applicable routes pass

Retries needed are small -- max 3 per query, 0 budget hits -- so 16 is
generous rather than load-bearing. Runtime slightly IMPROVED (45.3 -> 44.9 s
on the 16-seed sweep) because a satisfied query stops early.

The false-POSITIVE guard is untouched and is now stronger in meaning:
every Connected still requires a fully re-walked, air-verified route, and
it now says "this specific route is open" rather than "the first route I
tried was open". The controlled wall still returns BudgetExhausted after
exactly 16 retries, and a repeat query is bit-identical in verdict, snap
flags and retry count.

⚠️ REMAINING: seeds 6 and 14 are genuinely NOT_CONNECTED. Real or a
step-2 resolution limit is not yet settled -- refine before touching
generation again, per COMPOSER-NOTES §13.

No generation, placement or parameter changed. Verifier only.
Build clean, 20 succeeded / 0 warnings / 0 failed, confirmed in VoxelM.log.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VJiTcTSDNkKBtnNdiBtdaU

CODEMAP.md

@@ -311,17 +311,22 @@ walkability, feature scale, and clearance from that grid. Metrics report the res
 the inclusive/exclusive voxel Z window used, plus the largest component's deterministic lowest-cell
 representative point, cell count, and count of components holding at least 1% of the air.
 `VF_AreConnected` recovers a deterministic BFS parent path from the same kind of grid and checks
-only that route at full voxel resolution before returning `Connected`. It returns an explicit
+candidate routes at full voxel resolution before returning `Connected`. When a candidate is
-`EVoxelConnectivityResult`; a solid endpoint cell is repaired by snapping to the nearest air cell
+refuted, its specific coarse cell edge is added to a deterministic array blocklist and BFS is
-among its 26 neighbours when possible, and reports the snap through its out flags. A missing coarse
+retried up to `MaxRouteRetries` (default 16). It returns an explicit `EVoxelConnectivityResult`;
-route returns `NotConnectedAtThisResolution`: that is evidence only at the grid's resolution,
+a solid endpoint cell is repaired by snapping to the nearest air cell among its 26 neighbours
-because a corridor thinner than `SampleStep` is invisible. No UObject state, cache, actor, world,
+when possible, and reports the snap through its out flags. A missing coarse route after edge
-or PIE is required.
+exclusions returns `NotConnectedAtThisResolution`: that is evidence only at the grid's
+resolution, because a corridor thinner than `SampleStep` is invisible. Exhausting the retry
+budget (or finding a refutation in an endpoint segment with no coarse edge to exclude) returns
+`CoarseLiedBudgetExhausted`, which is unknown rather than disconnected. Every `Connected` result
+has a full-resolution air-verified route, and the query reports the alternate route retry count.
+No UObject state, cache, actor, world, or PIE is required.
 | Symbol | Role |
 |--------|------|
 | `FVoxelStrateMeasureSettings` / `FVoxelStrateMetrics` | Plain settings/result structs for bounded strate sampling and derived measurements; callers may override the interior margin (including zero to sample the seal), and results identify the resolved margin/Z window and deterministic component representatives. |
 | `VF_MeasureStrate` | One-grid/one-flood-fill strate metrics; refuses invalid bounds or a grid over `MaxCells`. |
-| `VF_AreConnected` | Coarse 6-connected BFS plus one full-resolution recheck of its recovered route, with explicit endpoint-solid, out-of-window, `CoarseLied`, `NotConnectedAtThisResolution`, and connected outcomes; the diagnostics overload returns endpoint component facts from that same grid. |
+| `VF_AreConnected` | Coarse 6-connected BFS plus deterministic blocked-edge retries, with a full-resolution air recheck for every candidate route and explicit endpoint-solid, out-of-window, `NotConnectedAtThisResolution`, `CoarseLiedBudgetExhausted` (unknown), and connected outcomes; diagnostics include endpoint component facts and the retry count from that same grid. |
 | `VF_DiagnoseConnectivity` | The same query plus each mouth's air-component size/share and exact geometric distance to the nearest cell of the other component; proximity is measured in coarse-cell coordinates and does not claim a route through solid. |
 
 ### 3.7 Cave morphology (SDF rooms/tunnels) — `Public/VoxelCaveMorphology.h` + `.cpp`

Source/VoxelForge/Private/Tests/VoxelForgeStrateConnectivityTest.cpp

@@ -42,6 +42,7 @@ namespace
         EVoxelConnectivityResult Result = EVoxelConnectivityResult::OutOfWindow;
         bool bStartSnapped = false;
         bool bGoalSnapped = false;
+        int32 NumRouteRetries = 0;
     };
 
     struct FStrateConnectivityReport
@@ -115,11 +116,40 @@ namespace
         case EVoxelConnectivityResult::StartCellSolid: return TEXT("START_CELL_SOLID");
         case EVoxelConnectivityResult::GoalCellSolid:  return TEXT("GOAL_CELL_SOLID");
         case EVoxelConnectivityResult::OutOfWindow:    return TEXT("OUT_OF_WINDOW");
-        case EVoxelConnectivityResult::CoarseLied:     return TEXT("COARSE_LIED");
+        case EVoxelConnectivityResult::CoarseLiedBudgetExhausted:
+            return TEXT("COARSE_LIED_BUDGET_EXHAUSTED");
         default:                                       return TEXT("UNKNOWN");
         }
     }
 
+    constexpr int32 ConnectivityResultCount =
+        static_cast<int32>(EVoxelConnectivityResult::CoarseLiedBudgetExhausted) + 1;
+
+    int32 NumRefutedRoutes(const FConnectivityProbe& Probe)
+    {
+        switch (Probe.Result)
+        {
+        case EVoxelConnectivityResult::Connected:
+        case EVoxelConnectivityResult::NotConnectedAtThisResolution:
+            return Probe.NumRouteRetries;
+        case EVoxelConnectivityResult::CoarseLiedBudgetExhausted:
+            return Probe.NumRouteRetries + 1;
+        default:
+            return 0;
+        }
+    }
+
+    bool ConnectivityProbesAreBitIdentical(
+        const FConnectivityProbe& A,
+        const FConnectivityProbe& B)
+    {
+        return A.bChecked == B.bChecked
+            && A.Result == B.Result
+            && A.bStartSnapped == B.bStartSnapped
+            && A.bGoalSnapped == B.bGoalSnapped
+            && A.NumRouteRetries == B.NumRouteRetries;
+    }
+
     FString ConnectivityProbeText(const FConnectivityProbe& Probe)
     {
         if (!Probe.bChecked)
@@ -127,7 +157,10 @@ namespace
             return TEXT("NOT_CHECKED");
         }
 
-        FString Text = ConnectivityResultName(Probe.Result);
+        FString Text = FString::Printf(
+            TEXT("%s [retries=%d]"),
+            ConnectivityResultName(Probe.Result),
+            Probe.NumRouteRetries);
         if (Probe.bStartSnapped || Probe.bGoalSnapped)
         {
             Text += TEXT(" [");
@@ -557,6 +590,8 @@ namespace
                 OutReport.SpineComponentProbe.bStartSnapped,
                 OutReport.SpineComponentProbe.bGoalSnapped,
                 OutReport.SpineComponent);
+            OutReport.SpineComponentProbe.NumRouteRetries =
+                OutReport.SpineComponent.NumRouteRetries;
         }
 
         if (!FindDiagnosticMouths(Manager.GetPassages(), StrateIndex, OutReport))
@@ -584,6 +619,7 @@ namespace
                 OutProbe.bStartSnapped,
                 OutProbe.bGoalSnapped,
                 OutFacts);
+            OutProbe.NumRouteRetries = OutFacts.NumRouteRetries;
         };
 
         if (OutReport.bHasArrival)
@@ -613,7 +649,8 @@ namespace
                 OutReport.DeparturePoint,
                 Settings,
                 OutReport.ArrivalToDeparture.bStartSnapped,
-                OutReport.ArrivalToDeparture.bGoalSnapped);
+                OutReport.ArrivalToDeparture.bGoalSnapped,
+                OutReport.ArrivalToDeparture.NumRouteRetries);
         }
         return true;
     }
@@ -791,7 +828,8 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
      * 3. Range sanity: fractions/components must describe an actual air field.
      * 4. Determinism: identical inputs must produce bit-identical metrics.
      * 5. Coarse-lie guard: a coarse route must never be reported CONNECTED after a
-     *    full-resolution solid sample; the controlled 3-voxel wall below must return COARSE_LIED.
+     *    full-resolution solid sample; the controlled 3-voxel wall below must never return
+     *    CONNECTED, and the bounded retry outcome must remain explicitly unknown.
      */
 
     int32 GapTopChunkZ = 0;
@@ -1029,6 +1067,9 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
 
     int32 NumRoutesChecked = 0;
     int32 NumRoutesRefuted = 0;
+    int32 NumRouteRetriesUsed = 0;
+    int32 MaxRouteRetriesUsed = 0;
+    int32 NumBudgetExhausted = 0;
     int32 NumGuardRoutesChecked = 0;
     int32 NumGuardRoutesRefuted = 0;
     int32 NumSnappedEndpointEvents = 0;
@@ -1041,7 +1082,7 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
     int32 NumAnchorStartCellSolid = 0;
     int32 NumAnchorGoalCellSolid = 0;
     int32 NumAnchorOutOfWindow = 0;
-    int32 NumAnchorCoarseLied = 0;
+    int32 NumAnchorBudgetExhausted = 0;
     int32 NumAnchorSnappedEndpointEvents = 0;
 
     auto ProbeRoute = [&](int32 StrateIndex,
@@ -1061,20 +1102,19 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
             Goal,
             DerivedWindowSettings,
             Probe.bStartSnapped,
-            Probe.bGoalSnapped);
+            Probe.bGoalSnapped,
+            Probe.NumRouteRetries);
 
         ++NumRoutesChecked;
-        if (Probe.Result == EVoxelConnectivityResult::CoarseLied)
+        NumRoutesRefuted += NumRefutedRoutes(Probe);
-        {
+        NumRouteRetriesUsed += Probe.NumRouteRetries;
-            ++NumRoutesRefuted;
+        MaxRouteRetriesUsed = FMath::Max(MaxRouteRetriesUsed, Probe.NumRouteRetries);
-        }
+        NumBudgetExhausted +=
+            Probe.Result == EVoxelConnectivityResult::CoarseLiedBudgetExhausted ? 1 : 0;
         if (bCountInGuard)
         {
             ++NumGuardRoutesChecked;
-            if (Probe.Result == EVoxelConnectivityResult::CoarseLied)
+            NumGuardRoutesRefuted += NumRefutedRoutes(Probe);
-            {
-                ++NumGuardRoutesRefuted;
-            }
         }
 
         const int32 SnappedHere = (Probe.bStartSnapped ? 1 : 0)
@@ -1099,7 +1139,9 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
             case EVoxelConnectivityResult::StartCellSolid: ++NumAnchorStartCellSolid; break;
             case EVoxelConnectivityResult::GoalCellSolid:  ++NumAnchorGoalCellSolid; break;
             case EVoxelConnectivityResult::OutOfWindow:    ++NumAnchorOutOfWindow; break;
-            case EVoxelConnectivityResult::CoarseLied:     ++NumAnchorCoarseLied; break;
+            case EVoxelConnectivityResult::CoarseLiedBudgetExhausted:
+                ++NumAnchorBudgetExhausted;
+                break;
             default: break;
             }
         }
@@ -1157,12 +1199,35 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
     const FConnectivityProbe WallProbe = ProbeRoute(
         0, WallA, WallB, /*bCountInGuard=*/true, /*bCountAsAnchorProbe=*/false,
         /*bCountAsArrivalDeparture=*/false);
-    if (WallProbe.Result != EVoxelConnectivityResult::CoarseLied)
+    if (WallProbe.Result != EVoxelConnectivityResult::CoarseLiedBudgetExhausted
+        || WallProbe.NumRouteRetries != DerivedWindowSettings.MaxRouteRetries)
     {
         AddError(FString::Printf(
-            TEXT("HARD FAILURE: the controlled coarse-connectivity lie returned %s instead of "
+            TEXT("HARD FAILURE: the controlled solid wall returned %s after %d retries; "
-                 "COARSE_LIED."),
+                 "expected COARSE_LIED_BUDGET_EXHAUSTED after the MaxRouteRetries=%d cap."),
-            ConnectivityResultName(WallProbe.Result)));
+            ConnectivityResultName(WallProbe.Result),
+            WallProbe.NumRouteRetries,
+            DerivedWindowSettings.MaxRouteRetries));
+        bAllChecksPassed = false;
+    }
+
+    FConnectivityProbe WallProbeRepeat;
+    WallProbeRepeat.bChecked = true;
+    WallProbeRepeat.Result = VF_AreConnected(
+        *World.Generator,
+        *World.StrateManager,
+        0,
+        WallA,
+        WallB,
+        DerivedWindowSettings,
+        WallProbeRepeat.bStartSnapped,
+        WallProbeRepeat.bGoalSnapped,
+        WallProbeRepeat.NumRouteRetries);
+    if (!ConnectivityProbesAreBitIdentical(WallProbe, WallProbeRepeat))
+    {
+        AddError(TEXT(
+            "HARD FAILURE: the blocked-edge retry order was not deterministic; repeating the "
+            "same wall query changed its verdict, snaps, or retry count."));
         bAllChecksPassed = false;
     }
     World.DiffLayer->Clear();
@@ -1371,6 +1436,14 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
              "checked, %d coarse routes refuted at full resolution.\n"),
         NumRoutesChecked,
         NumRoutesRefuted);
+    Summary += FString::Printf(
+        TEXT("Retry budget: MaxRouteRetries=%d; %d alternate routes checked across %d queries "
+             "(maximum %d retries in one query); budget exhausted on %d queries.\n"),
+        DerivedWindowSettings.MaxRouteRetries,
+        NumRouteRetriesUsed,
+        NumRoutesChecked,
+        MaxRouteRetriesUsed,
+        NumBudgetExhausted);
     Summary += FString::Printf(
         TEXT("Endpoint snap repair: %d snapped endpoint events across all probes; %d in "
              "%d arrival->departure probes.\n"),
@@ -1380,14 +1453,14 @@ bool FVoxelForgeStrateConnectivityTest::RunTest(const FString& Parameters)
     Summary += FString::Printf(
         TEXT("Correct largest-component endpoint probes (%d, including the surface-entry auxiliary): "
              "connected=%d, not-connected-at-resolution=%d, start-cell-solid=%d, goal-cell-solid=%d, "
-             "out-of-window=%d, coarse-lied=%d, snapped endpoint events=%d.\n"),
+             "out-of-window=%d, coarse-lied-budget-exhausted=%d, snapped endpoint events=%d.\n"),
         NumAnchorProbes,
         NumAnchorConnected,
         NumAnchorNotConnectedAtThisResolution,
         NumAnchorStartCellSolid,
         NumAnchorGoalCellSolid,
         NumAnchorOutOfWindow,
-        NumAnchorCoarseLied,
+        NumAnchorBudgetExhausted,
         NumAnchorSnappedEndpointEvents);
     Summary += TEXT("Previous \"5 of 15 disconnected\" verdict: ARTIFACT as a claim about sealed "
                    "pockets; it used a guessed anchor and asked the wrong (largest-component) law.\n");
@@ -1557,7 +1630,8 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
             DeparturePoint,
             RowSettings,
             Row.Probe.bStartSnapped,
-            Row.Probe.bGoalSnapped);
+            Row.Probe.bGoalSnapped,
+            Row.Probe.NumRouteRetries);
 
         if (!Row.Metrics.bValid
             || Row.Metrics.NumSampled <= 0
@@ -1638,7 +1712,8 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
             DeparturePoint,
             RowSettings,
             Row.Probe.bStartSnapped,
-            Row.Probe.bGoalSnapped);
+            Row.Probe.bGoalSnapped,
+            Row.Probe.NumRouteRetries);
 
         if (!Row.Metrics.bValid
             || Row.Metrics.NumSampled <= 0
@@ -1789,7 +1864,9 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
     int32 NumSpineLargestComponents = 0;
     int32 NumMouthToSpineQueries = 0;
     int32 NumMouthToSpineConnected = 0;
-    int32 NumMouthToSpineCoarseLied = 0;
+    int32 NumMouthToSpineBudgetExhausted = 0;
+    int32 NumMouthToSpineRetriesUsed = 0;
+    int32 MaxMouthToSpineRetries = 0;
     for (const FSpineDiagnosisReport& Report : SpineReports)
     {
         if (Report.Spine.bFullWindowRun)
@@ -1817,7 +1894,11 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
             }
             ++NumMouthToSpineQueries;
             NumMouthToSpineConnected += Probe->Result == EVoxelConnectivityResult::Connected;
-            NumMouthToSpineCoarseLied += Probe->Result == EVoxelConnectivityResult::CoarseLied;
+            NumMouthToSpineBudgetExhausted +=
+                Probe->Result == EVoxelConnectivityResult::CoarseLiedBudgetExhausted;
+            NumMouthToSpineRetriesUsed += Probe->NumRouteRetries;
+            MaxMouthToSpineRetries = FMath::Max(
+                MaxMouthToSpineRetries, Probe->NumRouteRetries);
         }
     }
 
@@ -1959,7 +2040,8 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
         bSpineDiagnosisUsable ? TEXT("yes") : TEXT("no"));
     Summary += FString::Printf(
         TEXT("Interpretation counts: spine full-window run=%d/%d, one uninterrupted open run=%d/%d, "
-             "spine component largest=%d/%d; mouth->spine CONNECTED=%d/%d, COARSE_LIED=%d.\n"),
+             "spine component largest=%d/%d; mouth->spine CONNECTED=%d/%d, "
+             "COARSE_LIED_BUDGET_EXHAUSTED=%d, retries=%d (max %d).\n"),
         NumSpineFullWindowRuns,
         SpineReports.Num(),
         NumSpineOneOpenRuns,
@@ -1968,7 +2050,9 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
         SpineReports.Num(),
         NumMouthToSpineConnected,
         NumMouthToSpineQueries,
-        NumMouthToSpineCoarseLied);
+        NumMouthToSpineBudgetExhausted,
+        NumMouthToSpineRetriesUsed,
+        MaxMouthToSpineRetries);
     Summary += TEXT(
         "Interpretation: the structural spine remains a continuous column. After the "
         "VerticalShafts connector change, the seed-1337 spine is the largest component, but the "
@@ -2041,8 +2125,9 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
             Diagnostics.GoalToStartComponentDistanceCells,
             Diagnostics.GoalToStartComponentDistanceCells * static_cast<float>(DiagnosticSettings.SampleStep));
         Summary += FString::Printf(
-            TEXT("  diagnostic route verdict: %s; endpoint snaps: start=%s, goal=%s.\n"),
+            TEXT("  diagnostic route verdict: %s; retries=%d; endpoint snaps: start=%s, goal=%s.\n"),
             ConnectivityResultName(Diagnostics.Result),
+            Diagnostics.NumRouteRetries,
             Diagnostics.bStartSnapped ? TEXT("yes") : TEXT("no"),
             Diagnostics.bGoalSnapped ? TEXT("yes") : TEXT("no"));
 
@@ -2069,9 +2154,18 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
         int32 SeedArrivalToSpineSnapEvents = 0;
         int32 SeedDepartureToSpineSnapEvents = 0;
         int32 SeedArrivalToDepartureSnapEvents = 0;
-        int32 SeedArrivalToSpineResultCounts[6] = {};
+        int32 SeedArrivalToSpineResultCounts[ConnectivityResultCount] = {};
-        int32 SeedDepartureToSpineResultCounts[6] = {};
+        int32 SeedDepartureToSpineResultCounts[ConnectivityResultCount] = {};
-        int32 SeedArrivalToDepartureResultCounts[6] = {};
+        int32 SeedArrivalToDepartureResultCounts[ConnectivityResultCount] = {};
+        int32 SeedArrivalToSpineRetries = 0;
+        int32 SeedDepartureToSpineRetries = 0;
+        int32 SeedArrivalToDepartureRetries = 0;
+        int32 SeedArrivalToSpineMaxRetries = 0;
+        int32 SeedDepartureToSpineMaxRetries = 0;
+        int32 SeedArrivalToDepartureMaxRetries = 0;
+        int32 SeedArrivalToSpineBudgetExhausted = 0;
+        int32 SeedDepartureToSpineBudgetExhausted = 0;
+        int32 SeedArrivalToDepartureBudgetExhausted = 0;
         int32 SeedFullWindowRuns = 0;
         int32 SeedOneOpenRuns = 0;
         int32 SeedSpineLargest = 0;
@@ -2176,7 +2270,9 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
                 continue;
             }
 
-            const auto CountSeedResult = [](const FConnectivityProbe& Probe, int32 (&Counts)[6])
+            const auto CountSeedResult = [](
+                const FConnectivityProbe& Probe,
+                int32 (&Counts)[ConnectivityResultCount])
             {
                 if (Probe.bChecked)
                 {
@@ -2187,6 +2283,29 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
             CountSeedResult(SeedReport.DepartureToSpine, SeedDepartureToSpineResultCounts);
             CountSeedResult(SeedReport.ArrivalToDeparture, SeedArrivalToDepartureResultCounts);
 
+            SeedArrivalToSpineRetries += SeedReport.ArrivalToSpine.NumRouteRetries;
+            SeedDepartureToSpineRetries += SeedReport.DepartureToSpine.NumRouteRetries;
+            SeedArrivalToDepartureRetries +=
+                SeedReport.ArrivalToDeparture.NumRouteRetries;
+            SeedArrivalToSpineMaxRetries = FMath::Max(
+                SeedArrivalToSpineMaxRetries,
+                SeedReport.ArrivalToSpine.NumRouteRetries);
+            SeedDepartureToSpineMaxRetries = FMath::Max(
+                SeedDepartureToSpineMaxRetries,
+                SeedReport.DepartureToSpine.NumRouteRetries);
+            SeedArrivalToDepartureMaxRetries = FMath::Max(
+                SeedArrivalToDepartureMaxRetries,
+                SeedReport.ArrivalToDeparture.NumRouteRetries);
+            SeedArrivalToSpineBudgetExhausted +=
+                SeedReport.ArrivalToSpine.Result
+                    == EVoxelConnectivityResult::CoarseLiedBudgetExhausted;
+            SeedDepartureToSpineBudgetExhausted +=
+                SeedReport.DepartureToSpine.Result
+                    == EVoxelConnectivityResult::CoarseLiedBudgetExhausted;
+            SeedArrivalToDepartureBudgetExhausted +=
+                SeedReport.ArrivalToDeparture.Result
+                    == EVoxelConnectivityResult::CoarseLiedBudgetExhausted;
+
             SeedArrivalToSpineSnapEvents +=
                 (SeedReport.ArrivalToSpine.bStartSnapped ? 1 : 0)
                 + (SeedReport.ArrivalToSpine.bGoalSnapped ? 1 : 0);
@@ -2245,6 +2364,20 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
             SeedFailures,
             SeedArrivalToDepartureSnapEvents,
             SeedSweepSeconds);
+        Summary += FString::Printf(
+            TEXT("  seed retries used (total/max/budget-exhausted): arrival->spine=%d/%d/%d; "
+                 "departure->spine=%d/%d/%d; arrival->departure=%d/%d/%d; "
+                 "MaxRouteRetries=%d.\n"),
+            SeedArrivalToSpineRetries,
+            SeedArrivalToSpineMaxRetries,
+            SeedArrivalToSpineBudgetExhausted,
+            SeedDepartureToSpineRetries,
+            SeedDepartureToSpineMaxRetries,
+            SeedDepartureToSpineBudgetExhausted,
+            SeedArrivalToDepartureRetries,
+            SeedArrivalToDepartureMaxRetries,
+            SeedArrivalToDepartureBudgetExhausted,
+            DiagnosticSettings.MaxRouteRetries);
         Summary += FString::Printf(
             TEXT("  ACCEPTANCE arrival->departure: %s (%d/%d seeds pass).\n"),
             SeedPasses == UE_ARRAY_COUNT(SeedCases) && SeedFailures == 0
@@ -2276,29 +2409,29 @@ bool FVoxelForgeStrateConnectivityRefinementTest::RunTest(const FString& Paramet
         Summary += FString::Printf(
             TEXT("  seed result breakdown — arrival->spine: CONNECTED=%d, "
                  "NOT_CONNECTED_AT_THIS_RESOLUTION=%d, START_CELL_SOLID=%d, GOAL_CELL_SOLID=%d, "
-                 "OUT_OF_WINDOW=%d, COARSE_LIED=%d; departure->spine: CONNECTED=%d, "
+                 "OUT_OF_WINDOW=%d, COARSE_LIED_BUDGET_EXHAUSTED=%d; departure->spine: CONNECTED=%d, "
                  "NOT_CONNECTED_AT_THIS_RESOLUTION=%d, START_CELL_SOLID=%d, GOAL_CELL_SOLID=%d, "
-                 "OUT_OF_WINDOW=%d, COARSE_LIED=%d; arrival->departure: CONNECTED=%d, "
+                 "OUT_OF_WINDOW=%d, COARSE_LIED_BUDGET_EXHAUSTED=%d; arrival->departure: CONNECTED=%d, "
                  "NOT_CONNECTED_AT_THIS_RESOLUTION=%d, START_CELL_SOLID=%d, GOAL_CELL_SOLID=%d, "
-                 "OUT_OF_WINDOW=%d, COARSE_LIED=%d.\n"),
+                 "OUT_OF_WINDOW=%d, COARSE_LIED_BUDGET_EXHAUSTED=%d.\n"),
             SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::Connected)],
             SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::NotConnectedAtThisResolution)],
             SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::StartCellSolid)],
             SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::GoalCellSolid)],
             SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::OutOfWindow)],
-            SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::CoarseLied)],
+            SeedArrivalToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::CoarseLiedBudgetExhausted)],
             SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::Connected)],
             SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::NotConnectedAtThisResolution)],
             SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::StartCellSolid)],
             SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::GoalCellSolid)],
             SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::OutOfWindow)],
-            SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::CoarseLied)],
+            SeedDepartureToSpineResultCounts[static_cast<int32>(EVoxelConnectivityResult::CoarseLiedBudgetExhausted)],
             SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::Connected)],
             SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::NotConnectedAtThisResolution)],
             SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::StartCellSolid)],
             SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::GoalCellSolid)],
             SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::OutOfWindow)],
-            SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::CoarseLied)]);
+            SeedArrivalToDepartureResultCounts[static_cast<int32>(EVoxelConnectivityResult::CoarseLiedBudgetExhausted)]);
         Summary += FString::Printf(
             TEXT("  seed endpoint snaps — arrival->spine=%d, departure->spine=%d, "
                  "arrival->departure=%d.\n"),

Source/VoxelForge/Private/VoxelStrateMeasure.cpp

@@ -662,6 +662,41 @@ namespace VoxelStrateMeasurePrivate
         return EEndpointCellResult::Air;
     }
 
+    struct FCoarseEdge
+    {
+        int32 First = INDEX_NONE;
+        int32 Second = INDEX_NONE;
+
+        bool IsValid() const
+        {
+            return First >= 0 && Second >= 0 && First != Second;
+        }
+    };
+
+    FCoarseEdge MakeCoarseEdge(int32 A, int32 B)
+    {
+        FCoarseEdge Edge;
+        Edge.First = FMath::Min(A, B);
+        Edge.Second = FMath::Max(A, B);
+        return Edge;
+    }
+
+    bool IsCoarseEdgeBlocked(
+        const TArray<FCoarseEdge>& BlockedEdges,
+        int32 A,
+        int32 B)
+    {
+        const FCoarseEdge Candidate = MakeCoarseEdge(A, B);
+        for (const FCoarseEdge& Blocked : BlockedEdges)
+        {
+            if (Blocked.First == Candidate.First && Blocked.Second == Candidate.Second)
+            {
+                return true;
+            }
+        }
+        return false;
+    }
+
     bool FullResolutionAirOnSegment(
         const UVoxelGenerator& Generator,
         const FVector& Start,
@@ -689,8 +724,11 @@ namespace VoxelStrateMeasurePrivate
         const FSampleGrid& Grid,
         const FVector& A,
         const FVector& B,
-        const TArray<int32>& Path)
+        const TArray<int32>& Path,
+        FCoarseEdge& OutFailedEdge)
     {
+        OutFailedEdge = FCoarseEdge();
+
         int32 StartX = 0;
         int32 StartY = 0;
         int32 StartZ = 0;
@@ -702,6 +740,9 @@ namespace VoxelStrateMeasurePrivate
 
         if (!FullResolutionAirOnSegment(Generator, A, Grid.CellCenter(StartX, StartY, StartZ)))
         {
+            // The endpoint-to-cell-center segment has no coarse cell pair to exclude. It is
+            // common to every route from this endpoint, so report unknown rather than claiming
+            // that the pair is disconnected at this resolution.
             return false;
         }
 
@@ -720,17 +761,25 @@ namespace VoxelStrateMeasurePrivate
                     Grid.CellCenter(PreviousX, PreviousY, PreviousZ),
                     Grid.CellCenter(CurrentX, CurrentY, CurrentZ)))
             {
+                OutFailedEdge = MakeCoarseEdge(Path[PathIndex - 1], Path[PathIndex]);
                 return false;
             }
         }
 
-        return FullResolutionAirOnSegment(Generator, Grid.CellCenter(EndX, EndY, EndZ), B);
+        if (!FullResolutionAirOnSegment(Generator, Grid.CellCenter(EndX, EndY, EndZ), B))
+        {
+            // As above, the final endpoint segment is shared by every route that reaches the
+            // goal cell and therefore has no precise coarse edge to exclude.
+            return false;
+        }
+        return true;
     }
 
     bool FindCoarsePath(
         const FSampleGrid& Grid,
         int32 Start,
         int32 Goal,
+        const TArray<FCoarseEdge>& BlockedEdges,
         TArray<int32>& OutPath)
     {
         if (Grid.Air[Start] == 0u || Grid.Air[Goal] == 0u)
@@ -762,7 +811,9 @@ namespace VoxelStrateMeasurePrivate
 
             auto Visit = [&](int32 Neighbor)
             {
-                if (Grid.Air[Neighbor] != 0u && Parent[Neighbor] == -2)
+                if (Grid.Air[Neighbor] != 0u
+                    && Parent[Neighbor] == -2
+                    && !IsCoarseEdgeBlocked(BlockedEdges, Current, Neighbor))
                 {
                     Parent[Neighbor] = Current;
                     Queue[Tail++] = Neighbor;
@@ -812,12 +863,15 @@ namespace VoxelStrateMeasurePrivate
         int32& OutStart,
         int32& OutGoal,
         bool& bOutStartSnapped,
-        bool& bOutGoalSnapped)
+        bool& bOutGoalSnapped,
+        int32& OutNumRouteRetries,
+        int32 MaxRouteRetries)
     {
         OutStart = -1;
         OutGoal = -1;
         bOutStartSnapped = false;
         bOutGoalSnapped = false;
+        OutNumRouteRetries = 0;
 
         const EEndpointCellResult StartCell = ResolveEndpointCell(
             Grid, AVoxel, OutStart, bOutStartSnapped);
@@ -837,22 +891,42 @@ namespace VoxelStrateMeasurePrivate
             return EVoxelConnectivityResult::GoalCellSolid;
         }
 
+        TArray<FCoarseEdge> BlockedEdges;
         TArray<int32> Path;
-        if (!FindCoarsePath(Grid, OutStart, OutGoal, Path))
+        for (;;)
         {
+            if (!FindCoarsePath(Grid, OutStart, OutGoal, BlockedEdges, Path))
+            {
+                // This is a negative verdict only after all edges excluded by earlier
+                // full-resolution failures leave no coarse route at this resolution.
                 return EVoxelConnectivityResult::NotConnectedAtThisResolution;
             }
 
-        // The coarse route is evidence, not a pass. Re-check this one BFS route at one-voxel
+            // The coarse route is evidence, not a pass. Re-check every candidate at one-voxel
-        // spacing in the original voxel field. A single solid sample is the dangerous coarse
+            // spacing in the original voxel field. A single solid sample refutes only this
-        // false positive.
+            // route, so exclude its precise coarse edge and search again.
-        if (!FullResolutionPathIsAir(Generator, Grid, AVoxel, BVoxel, Path))
+            FCoarseEdge FailedEdge;
+            if (FullResolutionPathIsAir(Generator, Grid, AVoxel, BVoxel, Path, FailedEdge))
             {
-            return EVoxelConnectivityResult::CoarseLied;
-        }
                 return EVoxelConnectivityResult::Connected;
             }
 
+            if (OutNumRouteRetries >= MaxRouteRetries || !FailedEdge.IsValid())
+            {
+                // A route can be refuted without a retryable pair when the failure is in an
+                // endpoint-to-cell segment (or when the explicit retry budget is spent). Both
+                // cases are unknown, never evidence of disconnection.
+                return EVoxelConnectivityResult::CoarseLiedBudgetExhausted;
+            }
+
+            check(FailedEdge.First != FailedEdge.Second);
+            check(!IsCoarseEdgeBlocked(
+                BlockedEdges, FailedEdge.First, FailedEdge.Second));
+            BlockedEdges.Add(FailedEdge);
+            ++OutNumRouteRetries;
+        }
+    }
+
     float DistanceToComponent(
         const FSampleGrid& Grid,
         int32 StartCell,
@@ -899,12 +973,14 @@ namespace VoxelStrateMeasurePrivate
         EVoxelConnectivityResult ConnectivityResult,
         bool bStartSnapped,
         bool bGoalSnapped,
+        int32 NumRouteRetries,
         FVoxelConnectivityDiagnostics& OutDiagnostics)
     {
         OutDiagnostics = FVoxelConnectivityDiagnostics();
         OutDiagnostics.Result = ConnectivityResult;
         OutDiagnostics.bStartSnapped = bStartSnapped;
         OutDiagnostics.bGoalSnapped = bGoalSnapped;
+        OutDiagnostics.NumRouteRetries = NumRouteRetries;
         OutDiagnostics.bValid = ConnectivityResult != EVoxelConnectivityResult::OutOfWindow
             || (Start >= 0 && Goal >= 0);
         if (Start < 0 || Goal < 0)
@@ -983,10 +1059,12 @@ namespace VoxelStrateMeasurePrivate
         const FVoxelStrateMeasureSettings& Settings,
         bool& bOutStartSnapped,
         bool& bOutGoalSnapped,
+        int32& OutNumRouteRetries,
         FVoxelConnectivityDiagnostics* OutDiagnostics)
     {
         bOutStartSnapped = false;
         bOutGoalSnapped = false;
+        OutNumRouteRetries = 0;
         if (!FMath::IsFinite(AVoxel.X) || !FMath::IsFinite(AVoxel.Y)
             || !FMath::IsFinite(AVoxel.Z) || !FMath::IsFinite(BVoxel.X)
             || !FMath::IsFinite(BVoxel.Y) || !FMath::IsFinite(BVoxel.Z))
@@ -997,6 +1075,14 @@ namespace VoxelStrateMeasurePrivate
             }
             return EVoxelConnectivityResult::OutOfWindow;
         }
+        if (Settings.MaxRouteRetries < 0)
+        {
+            if (OutDiagnostics != nullptr)
+            {
+                *OutDiagnostics = FVoxelConnectivityDiagnostics();
+            }
+            return EVoxelConnectivityResult::OutOfWindow;
+        }
 
         FSampleGrid Grid;
         FString RefusalReason;
@@ -1019,7 +1105,9 @@ namespace VoxelStrateMeasurePrivate
             Start,
             Goal,
             bOutStartSnapped,
-            bOutGoalSnapped);
+            bOutGoalSnapped,
+            OutNumRouteRetries,
+            Settings.MaxRouteRetries);
         if (OutDiagnostics != nullptr)
         {
             PopulateConnectivityDiagnostics(
@@ -1029,6 +1117,7 @@ namespace VoxelStrateMeasurePrivate
                 Result,
                 bOutStartSnapped,
                 bOutGoalSnapped,
+                OutNumRouteRetries,
                 *OutDiagnostics);
         }
         return Result;
@@ -1071,6 +1160,7 @@ EVoxelConnectivityResult VF_AreConnected(
     bool& bOutStartSnapped,
     bool& bOutGoalSnapped)
 {
+    int32 NumRouteRetries = 0;
     return VoxelStrateMeasurePrivate::QueryConnectivity(
         Generator,
         Manager,
@@ -1080,6 +1170,31 @@ EVoxelConnectivityResult VF_AreConnected(
         Settings,
         bOutStartSnapped,
         bOutGoalSnapped,
+        NumRouteRetries,
+        nullptr);
+}
+
+EVoxelConnectivityResult VF_AreConnected(
+    const UVoxelGenerator& Generator,
+    const UVoxelStrateManager& Manager,
+    int32 StrateIndex,
+    const FVector& AVoxel,
+    const FVector& BVoxel,
+    const FVoxelStrateMeasureSettings& Settings,
+    bool& bOutStartSnapped,
+    bool& bOutGoalSnapped,
+    int32& OutNumRouteRetries)
+{
+    return VoxelStrateMeasurePrivate::QueryConnectivity(
+        Generator,
+        Manager,
+        StrateIndex,
+        AVoxel,
+        BVoxel,
+        Settings,
+        bOutStartSnapped,
+        bOutGoalSnapped,
+        OutNumRouteRetries,
         nullptr);
 }
 
@@ -1094,6 +1209,7 @@ EVoxelConnectivityResult VF_AreConnected(
     bool& bOutGoalSnapped,
     FVoxelConnectivityDiagnostics& OutDiagnostics)
 {
+    int32 NumRouteRetries = 0;
     return VoxelStrateMeasurePrivate::QueryConnectivity(
         Generator,
         Manager,
@@ -1103,6 +1219,7 @@ EVoxelConnectivityResult VF_AreConnected(
         Settings,
         bOutStartSnapped,
         bOutGoalSnapped,
+        NumRouteRetries,
         &OutDiagnostics);
 }
 
@@ -1115,6 +1232,7 @@ FVoxelConnectivityDiagnostics VF_DiagnoseConnectivity(
     const FVoxelStrateMeasureSettings& Settings)
 {
     FVoxelConnectivityDiagnostics Result;
+    int32 NumRouteRetries = 0;
     VoxelStrateMeasurePrivate::QueryConnectivity(
         Generator,
         Manager,
@@ -1124,6 +1242,7 @@ FVoxelConnectivityDiagnostics VF_DiagnoseConnectivity(
         Settings,
         Result.bStartSnapped,
         Result.bGoalSnapped,
+        NumRouteRetries,
         &Result);
     return Result;
 }

Source/VoxelForge/Public/VoxelStrateMeasure.h

@@ -15,7 +15,7 @@ enum class EVoxelConnectivityResult : uint8
     StartCellSolid,
     GoalCellSolid,
     OutOfWindow,
-    CoarseLied
+    CoarseLiedBudgetExhausted // Unknown: retries are exhausted, or the refutation has no coarse edge to exclude.
 };
 
 /** Settings for the deterministic coarse grid used by the strate measurement pass. */
@@ -25,6 +25,7 @@ struct VOXELFORGE_API FVoxelStrateMeasureSettings
     int32     RadiusInVoxels = 256;  // Half-extent in X and Y around CenterXY.
     FVector2D CenterXY       = FVector2D::ZeroVector; // Actor-space voxel coordinates.
     int32     MaxCells       = 8000000; // Refuse a grid larger than this many cells.
+    int32     MaxRouteRetries = 16; // Alternate coarse routes to full-resolution-check after the first route.
     int32     HeadroomCells  = 2;    // Air cells above a floor cell required for walkable.
     int32     InteriorMarginVoxels = -1; // <0 = derive from BoundarySealThickness (2x, clamped); explicit 0 includes the seal.
 };
@@ -71,6 +72,7 @@ struct VOXELFORGE_API FVoxelConnectivityDiagnostics
     EVoxelConnectivityResult Result = EVoxelConnectivityResult::OutOfWindow;
     bool bStartSnapped = false;
     bool bGoalSnapped = false;
+    int32 NumRouteRetries = 0; // Alternate routes full-resolution-checked after the first route.
 
     int64 NumAirCells = 0;
     int64 StartComponentCells = 0;
@@ -100,14 +102,17 @@ VOXELFORGE_API FVoxelStrateMetrics VF_MeasureStrate(
     const FVoxelStrateMeasureSettings& Settings);
 
 /**
- * Test coarse connectivity and then re-check the one recovered coarse route at full resolution.
+ * Test coarse connectivity and re-check recovered coarse routes at full resolution.
  *
  * If an endpoint's own coarse cell is solid, the query searches the 26 neighbouring cells and
  * uses the nearest air cell when one exists. The snap flags report those repairs. Solid-cell
- * results are returned only when no adjacent air cell exists. A coarse route that fails its
+ * results are returned only when no adjacent air cell exists. When a route fails its
- * full-resolution re-check returns CoarseLied; a missing coarse route returns
+ * full-resolution re-check, the failed coarse edge is excluded from a deterministic local
- * NotConnectedAtThisResolution because a corridor thinner than SampleStep is invisible to the
+ * blocklist and BFS is retried up to MaxRouteRetries. A missing route after exclusions returns
- * grid. A bare "not connected" result is evidence only at the grid's own resolution.
+ * NotConnectedAtThisResolution. If the retry budget is exhausted while routes are still being
+ * refuted, the result is CoarseLiedBudgetExhausted: unknown, not disconnected. The same unknown
+ * result is used when a refutation is in an endpoint-to-cell segment with no coarse edge to
+ * exclude. Every Connected result has a fully re-walked air route.
  */
 VOXELFORGE_API EVoxelConnectivityResult VF_AreConnected(
     const UVoxelGenerator& Generator,
@@ -119,6 +124,18 @@ VOXELFORGE_API EVoxelConnectivityResult VF_AreConnected(
     bool& bOutStartSnapped,
     bool& bOutGoalSnapped);
 
+/** The same query as the simple overload, with the number of alternate routes actually tried. */
+VOXELFORGE_API EVoxelConnectivityResult VF_AreConnected(
+    const UVoxelGenerator& Generator,
+    const UVoxelStrateManager& Manager,
+    int32 StrateIndex,
+    const FVector& AVoxel,
+    const FVector& BVoxel,
+    const FVoxelStrateMeasureSettings& Settings,
+    bool& bOutStartSnapped,
+    bool& bOutGoalSnapped,
+    int32& OutNumRouteRetries);
+
 /**
  * The same connectivity query with component facts returned from the same sampled grid. This
  * overload exists for diagnostics that need both the required route verdict and the component
@@ -137,8 +154,9 @@ VOXELFORGE_API EVoxelConnectivityResult VF_AreConnected(
 
 /**
  * Return the component sizes and spatial separation facts for the same query performed by
- * VF_AreConnected. The returned Result uses the same full-resolution route re-check. bValid means
+ * VF_AreConnected. The returned Result uses the same retrying full-resolution route re-check,
- * the sample grid was built and both endpoint coordinates were in its bounds; component fields
+ * and NumRouteRetries reports the number of alternate routes actually checked. bValid means the
+ * sample grid was built and both endpoint coordinates were in its bounds; component fields
  * remain zero/negative when an endpoint has no air cell to analyze. Largest-component membership
  * treats equal-sized components as tied for largest.
  */