From d7b5a3fa20ba51ad78dda8b291216207933359f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ale=C5=A1=20Prokop?= <ales.prokop.dev@gmail.com>
Date: Fri, 17 Jul 2026 10:54:00 +0200
Subject: [PATCH] Complete graph submissions on critical exceptions

Route critical graph scheduler exceptions through the build manager's thread-exception path so submissions complete and the fatal error is surfaced instead of hanging.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 62a2178b-372e-479c-a717-ed6e7af95980
---
 .../ProjectCache/ProjectCacheTests.cs         | 35 +++++++++++++++++++
 .../BackEnd/BuildManager/BuildManager.cs      | 20 ++++++++---
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/src/Build.UnitTests/ProjectCache/ProjectCacheTests.cs b/src/Build.UnitTests/ProjectCache/ProjectCacheTests.cs
index 74e5a5bf932..047918b5c92 100644
--- a/src/Build.UnitTests/ProjectCache/ProjectCacheTests.cs
+++ b/src/Build.UnitTests/ProjectCache/ProjectCacheTests.cs
@@ -1342,6 +1342,41 @@ public void EngineShouldHandleExceptionsFromCachePluginViaGraphBuild(ErrorLocati
             }
         }
 
+        [Fact]
+        public async Task CriticalExceptionFromGraphBuildCompletesSubmission()
+        {
+            const string exceptionMessage = "Critical exception from graph build";
+
+            var project = _env.CreateFile(
+                "1.proj",
+                """
+                <Project>
+                  <Target Name="Build" />
+                </Project>
+                """);
+            var graph = new ProjectGraph(project.Path);
+            var cache = new DelegatingMockCache(
+                (_, _, _) => throw new InternalErrorException(exceptionMessage));
+            var buildParameters = new BuildParameters
+            {
+                ProjectCacheDescriptor = ProjectCacheDescriptor.FromInstance(cache),
+                ShutdownInProcNodeOnBuildFinish = true
+            };
+            var requestData = new GraphBuildRequestData(graph, ["Build"]);
+
+            Task<InternalErrorException> buildTask = Task.Run(
+                () =>
+                {
+                    using var buildManager = new BuildManager();
+                    return Should.Throw<InternalErrorException>(() => buildManager.Build(buildParameters, requestData));
+                });
+
+            Task completedTask = await Task.WhenAny(buildTask, Task.Delay(TimeSpan.FromSeconds(10)));
+
+            completedTask.ShouldBeSameAs(buildTask, "Graph builds should complete after a critical exception.");
+            (await buildTask).Message.ShouldContain(exceptionMessage);
+        }
+
         [Fact]
         public void EndBuildShouldGetCalledOnceWhenItThrowsExceptionsFromGraphBuilds()
         {
diff --git a/src/Build/BackEnd/BuildManager/BuildManager.cs b/src/Build/BackEnd/BuildManager/BuildManager.cs
index 4b69ec5a6e2..7753a5fafd2 100644
--- a/src/Build/BackEnd/BuildManager/BuildManager.cs
+++ b/src/Build/BackEnd/BuildManager/BuildManager.cs
@@ -1772,9 +1772,9 @@ private void ExecuteSubmission(GraphBuildSubmission submission)
                             {
                                 ExecuteGraphBuildScheduler(submission);
                             }
-                            catch (Exception ex) when (!ExceptionHandling.IsCriticalException(ex))
+                            catch (Exception ex)
                             {
-                                HandleSubmissionException(submission, ex);
+                                HandleGraphSubmissionException(submission, ex);
                             }
                         },
                         _executionCancellationTokenSource!.Token,
@@ -1783,13 +1783,25 @@ private void ExecuteSubmission(GraphBuildSubmission submission)
                 }
             }
             // The handling of submission exception needs to be done outside of the lock
-            catch (Exception ex) when (!ExceptionHandling.IsCriticalException(ex))
+            catch (Exception ex)
             {
-                HandleSubmissionException(submission, ex);
+                HandleGraphSubmissionException(submission, ex);
                 throw;
             }
         }
 
+        private void HandleGraphSubmissionException(GraphBuildSubmission submission, Exception ex)
+        {
+            if (ExceptionHandling.IsCriticalException(ex))
+            {
+                OnThreadException(ex);
+            }
+            else
+            {
+                HandleSubmissionException(submission, ex);
+            }
+        }
+
         /// <summary>
         /// Creates the traversal and metaproject instances necessary to represent the solution and populates new configurations with them.
         /// </summary>