Stabilize bounded regex consumer-break test

TESTING_GUIDE.md

@@ -746,7 +746,7 @@ Candidate-ordered parallel-index recovery tests must prove that the fatal result
   Python graph fixtures cover streamed decorator arguments, annotations, runtime type checks, typing factories, dataclass/framework integrations, and dynamic imports. `BoundedRegexTests.EnumerateMatches_InstanceRegex_StartsAtRequestedOffset` fixes the no-prefix-rescan contract used by decorator arguments, while `EnumerateMatches_InstanceRightToLeftRegex_PreservesDefaultStartAndOrder` preserves instance-regex default direction.
   Direct instance-enumerator coverage in `BoundedRegexTests` also fixes lazy invalid-`startAt` validation, zero-length progress, `\G` continuation, explicit right-to-left start positions, one terminal timeout diagnostic after a successful prefix, early disposal without suffix work, unsupported `Reset`, and intentional LINQ compatibility.
   PHP, Ruby, R, and Perl graph fixtures cover streamed attributes/docblocks/types, DSL command targets, namespace/member/resource references, and arrow calls. Keep nested token/type enumeration cap-aware. `ReferenceExtractorTests.Extract_PhpDocblockMethod_ReturnPrecedesParametersAtReferenceLimit` fixes PHP docblock preamble ordering and container state: an `@method` return type consumes the remaining reference slot before its parameter types while retaining the enclosing-class container snapshot.
-  Secondary-language graph fixtures cover streamed Fortran, Visual Basic, F#, Pascal, Objective-C, Haskell, Elixir, Smalltalk, Lua, Dart, Razor, JSON, JavaScript, GitHub Actions, and C++ compound-requirement matches. `BoundedRegexTests.EnumerateMatches_StaticPatternCustomTimeout_ReturnsEmpty` and `EnumerateMatches_StaticPatternCustomTimeout_StopsAfterConsumerBreak` preserve explicit-timeout failure and early-disposal behavior.
+  Secondary-language graph fixtures cover streamed Fortran, Visual Basic, F#, Pascal, Objective-C, Haskell, Elixir, Smalltalk, Lua, Dart, Razor, JSON, JavaScript, GitHub Actions, and C++ compound-requirement matches. `BoundedRegexTests.EnumerateMatches_StaticPatternCustomTimeout_ReturnsEmpty` preserves explicit-timeout failure, while `EnumerateMatches_StaticPatternCustomTimeout_StopsAfterConsumerBreak` uses a scheduler-tolerant custom timeout and proves early disposal returns the prefix without recording a timeout.
   `PerformanceTests.ReferenceExtraction_BoundedDenseFSharpPipeline_StopsAtCapacity` fixes the bounded-list contract across line-phase handoffs and action-based call emitters: a 4,000-stage F# pipeline capped at one reference must not enumerate the unused stages. `PerformanceTests.ReferenceMatchEnumeration_BoundedListDoesNotRequestMatchAfterCapacity` and `ReferenceMatchEnumeration_ConcreteRegexDoesNotRequestSuffixAfterCapacity` prove that generic and concrete wrappers do not call the underlying enumerator's next `MoveNext()` after the cap is filled. `ReferenceMatchEnumeration_BelowCapacity_DoesNotAllocateWrapperEnumerators` keeps 10,000 ordinary generic below-cap scans free of wrapper-enumerator heap allocations. The blocking `net8.0` tests `BoundedRegexEnumeration_DirectNoMatchScansDoNotAllocateEnumerators` and `ReferenceMatchEnumeration_PrefilledCapacityDoesNotAllocateOrLookAhead` each run 10,000 concrete scans with a budget below 1,024 allocated bytes, covering both direct no-match enumeration and the already-full cap path.
   `PerformanceTests.ReferenceExtraction_PrologCallFreeRules_AvoidsPerLineLists` keeps 8,000 call-free Prolog rules from allocating empty goal lists or copying populated directive lists; its `net8.0` allocation budget is blocking.
   `PerformanceTests.Utf8LineStarts_DenseInput_AllocatesOnlyFinalOffsetArray` fixes 100,000 UTF-8 line offsets to the single exact-capacity result array used by both JSON symbol and reference extraction; its `net8.0` allocation budget is blocking.
@@ -1839,7 +1839,7 @@ dotnet test --filter "FullyQualifiedName~GitHelperTests"
   Python graph fixture は decorator argument、annotation、runtime type check、typing factory、dataclass / framework integration、dynamic import の逐次走査を検証します。`BoundedRegexTests.EnumerateMatches_InstanceRegex_StartsAtRequestedOffset` は decorator argument が prefix を再走査しない契約を固定し、`EnumerateMatches_InstanceRightToLeftRegex_PreservesDefaultStartAndOrder` は instance regex の既定方向を維持します。
   `BoundedRegexTests` の direct instance-enumerator coverage はさらに、invalid `startAt` の遅延検証、zero-length の進行、`\G` continuation、right-to-left の明示開始位置、prefix 成功後に1回だけ記録して終了する timeout、suffix work を行わない早期 Dispose、未対応の `Reset`、意図的な LINQ 互換性を固定します。
   PHP、Ruby、R、Perl の graph fixture は attribute / docblock / type、DSL command target、namespace / member / resource reference、arrow call の逐次走査を検証します。nested token / type enumeration も cap-aware のままにしてください。`ReferenceExtractorTests.Extract_PhpDocblockMethod_ReturnPrecedesParametersAtReferenceLimit` は PHP docblock preamble の順序と container state を固定し、`@method` の return type が parameter type より先に残り1枠を消費しつつ、enclosing class の container snapshot を保持することを検証します。
-  secondary-language graph fixture は Fortran、Visual Basic、F#、Pascal、Objective-C、Haskell、Elixir、Smalltalk、Lua、Dart、Razor、JSON、JavaScript、GitHub Actions、C++ compound requirement の逐次走査を検証します。`BoundedRegexTests.EnumerateMatches_StaticPatternCustomTimeout_ReturnsEmpty` と `EnumerateMatches_StaticPatternCustomTimeout_StopsAfterConsumerBreak` は、明示 timeout の失敗時挙動と早期破棄を固定します。
+  secondary-language graph fixture は Fortran、Visual Basic、F#、Pascal、Objective-C、Haskell、Elixir、Smalltalk、Lua、Dart、Razor、JSON、JavaScript、GitHub Actions、C++ compound requirement の逐次走査を検証します。`BoundedRegexTests.EnumerateMatches_StaticPatternCustomTimeout_ReturnsEmpty` は明示 timeout の失敗時挙動を固定し、`EnumerateMatches_StaticPatternCustomTimeout_StopsAfterConsumerBreak` は scheduler の揺れに耐える custom timeout を使い、timeout を記録せずに prefix を返して早期破棄することを検証します。
   `PerformanceTests.ReferenceExtraction_BoundedDenseFSharpPipeline_StopsAtCapacity` は、行 phase の引き継ぎと action-based call emitter をまたぐ bounded-list 契約を固定します。上限1の4,000段 F# pipeline は未使用の段を列挙してはなりません。`PerformanceTests.ReferenceMatchEnumeration_BoundedListDoesNotRequestMatchAfterCapacity` と `ReferenceMatchEnumeration_ConcreteRegexDoesNotRequestSuffixAfterCapacity` は、generic / concrete wrapper が上限到達後に下位 enumerator の次の `MoveNext()` を呼ばないことを固定します。`ReferenceMatchEnumeration_BelowCapacity_DoesNotAllocateWrapperEnumerators` は通常の generic 上限未到達 scan 10,000回で wrapper enumerator の heap allocation がないことを固定します。blocking な `net8.0` test `BoundedRegexEnumeration_DirectNoMatchScansDoNotAllocateEnumerators` と `ReferenceMatchEnumeration_PrefilledCapacityDoesNotAllocateOrLookAhead` は、direct no-match と既に満杯の cap 経路をそれぞれ10,000回走査し、allocation を1,024 bytes未満に固定します。
   `PerformanceTests.ReferenceExtraction_PrologCallFreeRules_AvoidsPerLineLists` は8,000件の call-free Prolog rule で empty goal list と populated directive list の copy を防ぎます。`net8.0` の allocation budget は blocking です。
   `PerformanceTests.Utf8LineStarts_DenseInput_AllocatesOnlyFinalOffsetArray` は JSON symbol / reference extraction が共有する100,000件の UTF-8 line offset を exact-capacity の結果 array 1つに固定します。`net8.0` の allocation budget は blocking です。

changelog.d/unreleased/5113.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 5113
+affected:
+  - tests/CodeIndex.Tests/BoundedRegexTests.cs
+  - TESTING_GUIDE.md
+---
+
+## English
+
+- **Stabilized the bounded-regex consumer-break regression under parallel test load (#5113)** — the custom-timeout coverage now leaves scheduler headroom, verifies that the prefix match is returned, and confirms that early disposal records no suffix timeout.
+
+## 日本語
+
+- **並列テスト負荷時の bounded-regex consumer-break 回帰テストを安定化しました (#5113)** — custom timeout の検証に scheduler の余裕を持たせ、prefix match が返ることと、早期破棄で suffix timeout が記録されないことを確認します。

tests/CodeIndex.Tests/BoundedRegexTests.cs

@@ -99,17 +99,21 @@ public void EnumerateMatches_StaticPatternCustomTimeout_ReturnsEmpty()
     public void EnumerateMatches_StaticPatternCustomTimeout_StopsAfterConsumerBreak()
     {
         var input = "token " + new string('a', 10_000) + "!";
+        using var capture = BoundedRegex.CaptureTimeouts("csharp", "bounded_regex_test");
 
-        var match = BoundedRegex
+        var matches = BoundedRegex
             .EnumerateMatches(
                 input,
                 @"token|(?:a+)+$",
                 RegexOptions.CultureInvariant,
-                TimeSpan.FromMilliseconds(1))
+                // Keep this below the production default while leaving full-suite scheduler
+                // headroom; the one-millisecond budget used before #5113 could lose the prefix.
+                TimeSpan.FromSeconds(1))
             .Take(1)
-            .Single();
+            .ToArray();
 
-        Assert.Equal("token", match.Value);
+        Assert.Collection(matches, match => Assert.Equal("token", match.Value));
+        Assert.False(capture.HasTimeouts);
     }
 
     [Fact]