.NET: [BREAKING] Fix hosting bugs (#6388)

* Fix hosting bugs

* Address PR comments

dotnet/tests/Microsoft.Agents.AI.Foundry.Hosting.UnitTests/HostedFoundryMemoryProviderScopesTests.cs

@@ -43,7 +43,7 @@ public class HostedFoundryMemoryProviderScopesTests
     }
 
     [Fact]
-    public void PerUserAndChat_ComposesUserAndChatWithColon()
+    public void PerUserAndChat_ComposesUserAndChatWithEscapedSeparator()
     {
         // Arrange
         var session = CreateTaggedSession(TestUserId, TestChatId);
@@ -54,7 +54,51 @@ public class HostedFoundryMemoryProviderScopesTests
 
         // Assert
         Assert.NotNull(state);
-        Assert.Equal($"{TestUserId}:{TestChatId}", state.Scope.Scope);
+        Assert.Equal($"{TestUserId}::{TestChatId}", state.Scope.Scope);
+    }
+
+    [Fact]
+    public void PerUserAndChat_EscapesColonsInUserAndChat()
+    {
+        // Arrange
+        var session = CreateTaggedSession("alice:finance", "q2:final");
+        var initializer = HostedFoundryMemoryProviderScopes.PerUserAndChat();
+
+        // Act
+        var state = initializer(session);
+
+        // Assert - colons inside each part are escaped as \: , parts joined with ::
+        Assert.Equal(@"alice\:finance::q2\:final", state.Scope.Scope);
+    }
+
+    [Fact]
+    public void PerUserAndChat_EscapesBackslashesInUserAndChat()
+    {
+        // Arrange
+        var session = CreateTaggedSession(@"alice\corp", @"chat\1");
+        var initializer = HostedFoundryMemoryProviderScopes.PerUserAndChat();
+
+        // Act
+        var state = initializer(session);
+
+        // Assert - backslashes escaped first as \\ , parts joined with ::
+        Assert.Equal(@"alice\\corp::chat\\1", state.Scope.Scope);
+    }
+
+    [Fact]
+    public void PerUserAndChat_DistinctContextsDoNotCollide()
+    {
+        // Arrange - two distinct (UserId, ChatId) pairs that collide under raw-colon composition.
+        var sessionA = CreateTaggedSession("alice:finance", "q2");
+        var sessionB = CreateTaggedSession("alice", "finance:q2");
+        var initializer = HostedFoundryMemoryProviderScopes.PerUserAndChat();
+
+        // Act
+        var scopeA = initializer(sessionA).Scope.Scope;
+        var scopeB = initializer(sessionB).Scope.Scope;
+
+        // Assert
+        Assert.NotEqual(scopeA, scopeB);
     }
 
     [Fact]

dotnet/tests/Microsoft.Agents.AI.Hosting.UnitTests/ClaimsIdentitySessionIsolationKeyProviderTests.cs

@@ -16,6 +16,7 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
     private const string TestUserId = "test-user-id";
     private const string CustomClaimType = "custom-claim-type";
     private const string CustomClaimValue = "custom-claim-value";
+    private const string TestAuthenticationType = "TestAuth";
 
     private readonly Mock<IHttpContextAccessor> _httpContextAccessorMock;
 
@@ -101,7 +102,7 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
     public async Task GetSessionIsolationKeyAsyncExtractsDefaultClaimTypeAsync()
     {
         // Arrange
-        this.SetupHttpContextWithClaim(ClaimsIdentity.DefaultNameClaimType, TestUserId);
+        this.SetupHttpContextWithClaim(ClaimTypes.NameIdentifier, TestUserId);
         var provider = new ClaimsIdentitySessionIsolationKeyProvider(this._httpContextAccessorMock.Object);
 
         // Act
@@ -111,6 +112,25 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
         Assert.Equal(TestUserId, result);
     }
 
+    /// <summary>
+    /// Verify that the default claim type is the stable, unique NameIdentifier claim rather than the
+    /// non-unique display name claim. This guards against the session-isolation collision described in
+    /// the security report where two principals sharing the same name claim received the same key.
+    /// </summary>
+    [Fact]
+    public async Task GetSessionIsolationKeyAsyncIgnoresNameClaimByDefaultAsync()
+    {
+        // Arrange - only a display-name claim is present; the default provider must not use it.
+        this.SetupHttpContextWithClaim(ClaimsIdentity.DefaultNameClaimType, TestUserId);
+        var provider = new ClaimsIdentitySessionIsolationKeyProvider(this._httpContextAccessorMock.Object);
+
+        // Act
+        string? result = await provider.GetSessionIsolationKeyAsync();
+
+        // Assert
+        Assert.Null(result);
+    }
+
     /// <summary>
     /// Verify that GetSessionIsolationKeyAsync uses custom claim type when specified.
     /// </summary>
@@ -191,10 +211,10 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
         const string SecondValue = "second-value";
         var claims = new[]
         {
-            new Claim(ClaimsIdentity.DefaultNameClaimType, FirstValue),
-            new Claim(ClaimsIdentity.DefaultNameClaimType, SecondValue),
+            new Claim(ClaimTypes.NameIdentifier, FirstValue),
+            new Claim(ClaimTypes.NameIdentifier, SecondValue),
         };
-        var identity = new ClaimsIdentity(claims);
+        var identity = new ClaimsIdentity(claims, TestAuthenticationType);
         var principal = new ClaimsPrincipal(identity);
 
         var httpContext = new DefaultHttpContext
@@ -219,7 +239,7 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
     public async Task GetSessionIsolationKeyAsyncHandlesEmptyClaimValueAsync()
     {
         // Arrange
-        this.SetupHttpContextWithClaim(ClaimsIdentity.DefaultNameClaimType, string.Empty);
+        this.SetupHttpContextWithClaim(ClaimTypes.NameIdentifier, string.Empty);
         var provider = new ClaimsIdentitySessionIsolationKeyProvider(this._httpContextAccessorMock.Object);
 
         // Act
@@ -229,6 +249,66 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
         Assert.Equal(string.Empty, result);
     }
 
+    /// <summary>
+    /// Regression test for the session-isolation collision security report: two distinct authenticated
+    /// principals that share the same display-name claim but have different stable identifiers and tenants
+    /// must produce distinct isolation keys under the default options.
+    /// </summary>
+    [Fact]
+    public async Task GetSessionIsolationKeyAsyncDistinctForPrincipalsSharingNameClaimAsync()
+    {
+        // Arrange - both principals share the same name claim but differ by NameIdentifier and tenant.
+        const string CommonName = "John Doe";
+
+        var principalA = CreatePrincipal(
+            new Claim(ClaimsIdentity.DefaultNameClaimType, CommonName),
+            new Claim(ClaimTypes.NameIdentifier, "oid-user-a"),
+            new Claim("http://schemas.microsoft.com/identity/claims/tenantid", "tenant-a"));
+
+        var principalB = CreatePrincipal(
+            new Claim(ClaimsIdentity.DefaultNameClaimType, CommonName),
+            new Claim(ClaimTypes.NameIdentifier, "oid-user-b"),
+            new Claim("http://schemas.microsoft.com/identity/claims/tenantid", "tenant-b"));
+
+        var provider = new ClaimsIdentitySessionIsolationKeyProvider(this._httpContextAccessorMock.Object);
+
+        // Act
+        this._httpContextAccessorMock.Setup(x => x.HttpContext).Returns(new DefaultHttpContext { User = principalA });
+        string? principalAKey = await provider.GetSessionIsolationKeyAsync();
+
+        this._httpContextAccessorMock.Setup(x => x.HttpContext).Returns(new DefaultHttpContext { User = principalB });
+        string? principalBKey = await provider.GetSessionIsolationKeyAsync();
+
+        // Assert
+        Assert.Equal("oid-user-a", principalAKey);
+        Assert.Equal("oid-user-b", principalBKey);
+        Assert.NotEqual(principalAKey, principalBKey);
+    }
+
+    /// <summary>
+    /// Verify that GetSessionIsolationKeyAsync returns null when the request's user is not authenticated,
+    /// even if a claim of the configured type is present. The provider must not derive an isolation key
+    /// from claims on an unauthenticated identity.
+    /// </summary>
+    [Fact]
+    public async Task GetSessionIsolationKeyAsyncReturnsNullWhenUserNotAuthenticatedAsync()
+    {
+        // Arrange - identity has the claim but no authentication type, so IsAuthenticated is false.
+        var claims = new[] { new Claim(ClaimTypes.NameIdentifier, TestUserId) };
+        var unauthenticatedIdentity = new ClaimsIdentity(claims);
+        var principal = new ClaimsPrincipal(unauthenticatedIdentity);
+        var httpContext = new DefaultHttpContext { User = principal };
+        this._httpContextAccessorMock.Setup(x => x.HttpContext).Returns(httpContext);
+        var provider = new ClaimsIdentitySessionIsolationKeyProvider(this._httpContextAccessorMock.Object);
+
+        // Act
+        string? result = await provider.GetSessionIsolationKeyAsync();
+
+        // Assert
+        Assert.False(unauthenticatedIdentity.IsAuthenticated);
+        Assert.Null(result);
+    }
+
     #endregion
 
     #region Helper Methods
@@ -236,7 +316,7 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
     private void SetupHttpContextWithClaim(string claimType, string claimValue)
     {
         var claims = new[] { new Claim(claimType, claimValue) };
-        var identity = new ClaimsIdentity(claims);
+        var identity = new ClaimsIdentity(claims, TestAuthenticationType);
         var principal = new ClaimsPrincipal(identity);
 
         var httpContext = new DefaultHttpContext
@@ -247,5 +327,8 @@ public class ClaimsIdentitySessionIsolationKeyProviderTests
         this._httpContextAccessorMock.Setup(x => x.HttpContext).Returns(httpContext);
     }
 
+    private static ClaimsPrincipal CreatePrincipal(params Claim[] claims)
+        => new(new ClaimsIdentity(claims, TestAuthenticationType));
+
     #endregion
 }