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Align x-mcp-header implementation with SEP-2243 spec clarifications (#1619)

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Co-authored-by: Tarek Mahmoud Sayed <tarekms@ntdev.microsoft.com>
This commit is contained in:
Tarek Mahmoud Sayed 2026-06-05 15:45:08 -07:00 • committed by GitHub
commit ed19286a08
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1 changed files with 1035 additions and 116 deletions
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48
tests/ModelContextProtocol.Tests/Client/McpHeaderEncoderTests.cs
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@ -59,10 +59,9 @@ public class McpHeaderEncoderTests
[Theory]
[InlineData(42, "42")]
[InlineData(3.14, "3.14")]
[InlineData(0, "0")]
[InlineData(-1, "-1")]
public void EncodeValue_Number_ConvertsToString(object input, string expected)
public void EncodeValue_Integer_ConvertsToString(object input, string expected)
{
var result = McpHeaderEncoder.EncodeValue(input);
Assert.Equal(expected, result);
@ -106,10 +105,12 @@ public class McpHeaderEncoderTests
}
[Fact]
public void DecodeValue_CaseInsensitivePrefix_Decodes()
public void DecodeValue_CaseSensitivePrefix_ReturnsLiteralValue()
{
// Per SEP-2243: sentinel markers are case-sensitive and MUST appear exactly as shown (lowercase).
// An uppercase prefix should NOT be decoded as base64.
var result = McpHeaderEncoder.DecodeValue("=?BASE64?SGVsbG8=?=");
Assert.Equal("Hello", result);
Assert.Equal("=?BASE64?SGVsbG8=?=", result);
}
[Fact]
@ -119,6 +120,15 @@ public class McpHeaderEncoderTests
Assert.Null(result);
}
[Fact]
public void DecodeValue_ValidBase64ButInvalidUtf8_ReturnsNull()
{
// "//4=" is valid Base64 that decodes to the bytes 0xFF 0xFE, which are not valid UTF-8.
// A strict decoder must reject this rather than substituting U+FFFD replacement characters.
var result = McpHeaderEncoder.DecodeValue("=?base64?//4=?=");
Assert.Null(result);
}
[Fact]
public void DecodeValue_MissingPrefix_ReturnsLiteralValue()
{
@ -160,4 +170,34 @@ public class McpHeaderEncoderTests
var decoded = McpHeaderEncoder.DecodeValue(result);
Assert.Equal("col1\tcol2", decoded);
}
[Theory]
[InlineData("=?base64?literal?=")]
[InlineData("=?base64?SGVsbG8=?=")]
[InlineData("=?base64??=")]
public void EncodeValue_SentinelCollision_Base64Encodes(string input)
{
var result = McpHeaderEncoder.EncodeValue(input);
Assert.NotNull(result);
Assert.StartsWith("=?base64?", result);
Assert.EndsWith("?=", result);
// The encoded value must be different from the input to avoid ambiguity
Assert.NotEqual(input, result);
// Verify round-trip: decode must recover the original literal value
var decoded = McpHeaderEncoder.DecodeValue(result);
Assert.Equal(input, decoded);
}
[Theory]
[InlineData("=?BASE64?literal?=")] // Case-sensitive: uppercase prefix does not match sentinel
[InlineData("=?base64?start")] // Missing suffix: no sentinel match
[InlineData("end?=")] // Missing prefix: no sentinel match
[InlineData("plain-text")] // No sentinel pattern
public void EncodeValue_NonSentinelPattern_NotBase64Encoded(string input)
{
var result = McpHeaderEncoder.EncodeValue(input);
Assert.Equal(input, result);
}
}