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Fix KeyNotFoundException during retry when headers lack correlation ID #5617

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Fix KeyNotFoundException during retry when headers lack correlation ID #5617

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Copilot Dec 10, 2025
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Fix KeyNotFoundException when headers don't contain correlation ID
Copilot Dec 10, 2025
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17 changes: 12 additions & 5 deletions src/client/Microsoft.Identity.Client/Http/HttpManager.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -140,17 +140,24 @@ public async Task<HttpResponse> SendRequestAsync(

if (headers != null && headers.Count > 0)
{
var correlationId = headers[OAuth2Header.CorrelationId];
string correlationIdMsg = headers.ContainsKey(OAuth2Header.CorrelationId) ?
$" CorrelationId: {correlationId}" :
string.Empty;
string correlationIdMsg = string.Empty;
string correlationId = null;

if (headers.ContainsKey(OAuth2Header.CorrelationId))
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@gladjohn gladjohn Dec 11, 2025

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Two lookups. But, in an exception‑path it’s not a big perf concern. Ideally the code could be,

if (headers.TryGetValue(OAuth2Header.CorrelationId, out var correlationId))
{
    correlationIdMsg = $" CorrelationId: {correlationId}";
    ex.CorrelationId = correlationId;
}

{
correlationId = headers[OAuth2Header.CorrelationId];
correlationIdMsg = $" CorrelationId: {correlationId}";
}

var ex = new MsalServiceException(
MsalError.RequestTimeout,
msg + correlationIdMsg,
timeoutException);

ex.CorrelationId = correlationId;
if (correlationId != null)
{
ex.CorrelationId = correlationId;
}

throw ex;
}
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41 changes: 41 additions & 0 deletions tests/Microsoft.Identity.Test.Unit/CoreTests/HttpTests/HttpManagerTests.cs
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Expand Up @@ -581,6 +581,47 @@ public async Task TestCorrelationIdWithRetryOnTimeoutFailureAsync(bool addCorrel
}
}

// Regression test for https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/XXXX
// Verifies that timeout with headers but without correlation ID does not throw KeyNotFoundException
[TestMethod]
public async Task TestRetryOnTimeoutWithHeadersButNoCorrelationIdAsync()
{
using (var httpManager = new MockHttpManager())
{
// Simulate permanent errors (to trigger the maximum number of retries)
const int Num500Errors = 1 + TestDefaultRetryPolicy.DefaultStsMaxRetries; // initial request + maximum number of retries
for (int i = 0; i < Num500Errors; i++)
{
httpManager.AddRequestTimeoutResponseMessageMockHandler(HttpMethod.Post);
}

// Create headers without correlation ID - this was causing KeyNotFoundException
var headers = new Dictionary<string, string>
{
["some-other-header"] = "some-value"
};

var exc = await AssertException.TaskThrowsAsync<MsalServiceException>(() =>
httpManager.SendRequestAsync(
new Uri(TestConstants.AuthorityHomeTenant + "oauth2/token"),
headers: headers,
body: new FormUrlEncodedContent(new Dictionary<string, string>()),
method: HttpMethod.Post,
logger: Substitute.For<ILoggerAdapter>(),
doNotThrow: false,
mtlsCertificate: null,
validateServerCert: null,
cancellationToken: default,
retryPolicy: _stsRetryPolicy))
.ConfigureAwait(false);

// Should get timeout error without KeyNotFoundException
Assert.AreEqual(MsalError.RequestTimeout, exc.ErrorCode);
Assert.AreEqual("Request to the endpoint timed out.", exc.Message);
Assert.IsNull(exc.CorrelationId);
}
}

[TestMethod]
public async Task TestWithCorrelationId_RetryOnTimeoutFailureAsync()
{
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