Add custom fetch support to StreamableHTTP MCP transport #319
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This enhancement significantly improves the flexibility of the StreamableHTTPClientTransport class by enabling the injection of a custom fetch implementation. This change empowers users to exert fine-grained control over network requests, facilitating advanced use cases such as custom authentication flows, specialized request handling, and improved adaptability of the transport layer. Key improvements: - Added optional 'fetch' parameter to MCPServerStreamableHttpOptions interface - Updated NodeMCPServerStreamableHttp implementation to pass custom fetch to underlying transport - Enables custom authentication flows for corporate environments - Supports request/response logging and debugging capabilities - Allows retry logic implementation for unreliable connections - Facilitates testing with mock fetch implementations - Enables custom header injection and request modification The implementation is fully backward compatible - existing code continues to work unchanged as the fetch parameter is optional and defaults to the standard fetch implementation. Changes include: - packages/agents-core/src/mcp.ts: Added fetch parameter to interface with proper documentation - packages/agents-core/src/shims/mcp-server/node.ts: Updated transport initialization - docs/src/content/docs/guides/mcp.mdx: Updated English documentation - docs/src/content/docs/ja/guides/mcp.mdx: Updated Japanese documentation - examples/mcp/streamable-http-custom-fetch-example.ts: Added comprehensive usage example This change aligns with the MCP SDK's existing support for custom fetch implementations and provides a clean, type-safe API for advanced network request customization.
🦋 Changeset detectedLatest commit: ac9599f The changes in this PR will be included in the next version bump. This PR includes changesets to release 5 packages
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seratch
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Aug 11, 2025
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Thanks for sending a PR, and this could be indeed a good enhancement. Can you check the two things:
- Can you run
pnpm -F agents-core update @modelcontextprotocol/sdk@latestto upgrade MCP SDK to the latest? Older versions do not have this option - Check the CI failures and resolve them
This update ensures compatibility with the latest MCP SDK features including the fetch parameter support for StreamableHTTPClientTransport.
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This enhancement improves the flexibility of the StreamableHTTPClientTransport class by enabling the injection of a custom fetch implementation. This change empowers users to exert fine-grained control over network requests, facilitating advanced use cases such as custom authentication flows, specialized request handling, and improved adaptability of the transport layer.
Key improvements:
Changes include:
This change aligns with the MCP SDK's existing support for custom fetch implementations and provides a clean, type-safe API for advanced network request customization.