Release v1.3.0#1566
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jeffhandley merged 1 commit intomodelcontextprotocol:mainfrom May 8, 2026
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* Bump VersionPrefix from 1.2.0 to 1.3.0 in src/Directory.Build.props * Update docs/concepts/stateless/stateless.md to reference the new public ClientTransportClosedException type (was internal TransportClosedException) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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I would probably remove the breaking-change label and all language in the description about this being "breaking". I doubt anyone was relying on connection failures being surfaced as an InvalidOperationException rather than an IOException.
If we call label every minor update a breaking change, it becomes a less useful signal for updaters who might get fatigued.
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Release v1.3.0
v1.3.0 focuses on improved transport diagnostics and security-focused documentation. The new public
ClientTransportClosedExceptiongives stdio and HTTP clients structured access to transport closure details (exit codes, process IDs, stderr tails, HTTP status codes) without parsing exception messages. Two reliability fixes harden the stdio process pipeline (preventing host crashes from userStandardErrorLinescallbacks) and correct the stateless HTTP transport's capability advertisement. New conceptual documentation covers role/identity propagation in tool execution, allowed-hosts and CORS guidance for HTTP servers, and aligns the docs information architecture with the MCP specification structure.Release Notes
What's Changed
ClientTransportClosedExceptionpublic and unify transport exception handling Make ClientTransportClosedException public and unify transport exception handling #1467 by @stephentoub (co-authored by @halter73 @copilot)McpClient.CreateAsync(...)now surface asIOException(the newClientTransportClosedExceptionderives fromIOException) rather thanInvalidOperationException. Caller-triggeredOperationCanceledExceptionis also no longer wrapped, matching standard async cancellation semantics.Documentation Updates
Test Improvements
Repository Infrastructure Updates
Acknowledgements
listChangedcapabilities #1486 (resolved by Fix stateless HTTP transport advertising listChanged capability (#1486) #1509)Full Changelog: v1.2.0...release-1.3.0
API Compatibility Report
✅ All 3 packages pass API compatibility validation against baseline
v1.0.0(noCP*orPKV*warnings/errors duringdotnet pack).PackageValidationBaselineVersionremains at1.0.0(unchanged for MINOR release).API Diff Report
Generated with
Microsoft.DotNet.ApiDiff.Tool10.0.300-preview.26154.111 againstnet10.0. The other target frameworks (net9.0,net8.0,netstandard2.0) had no public surface changes.ModelContextProtocol.Core
namespace ModelContextProtocol.Client { + public sealed class ClientTransportClosedException + { + public ClientTransportClosedException(ModelContextProtocol.Client.ClientCompletionDetails details); + public ModelContextProtocol.Client.ClientCompletionDetails Details { get; } + } }ModelContextProtocol
No public API changes.
ModelContextProtocol.AspNetCore
No public API changes.