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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Streamable HTTP transport fails when accessing MCP server on Cloud Run using sdk","articleBody":"### Initial Checks\n\n- [x] I confirm that I'm using the latest version of MCP Python SDK\n- [x] I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue\n\n### Description\n\n### Description\n\nWhen using the `python-sdk` with transport set to `streamable-http`, the connection to a remote MCP server deployed on **Google Cloud Run** does not establish. The API stays in a **pending** state, and no updates are received.\n\nHowever, the same MCP server works fine under the following conditions:\n\n* When accessed via **Google Cloud Proxy**\n* When transport is changed to **SSE**\n* When using the **JS SDK**, streamable-http transport works without issues\n\nThis suggests a compatibility or configuration issue specifically between `python-sdk`'s streamable-http transport and direct access to Cloud Run URLs.\n\n---\n\n### Reproduction Steps\n\n1. Deploy an MCP server to Cloud Run using this official guide:\n   [https://cloud.google.com/blog/topics/developers-practitioners/build-and-deploy-a-remote-mcp-server-to-google-cloud-run-in-under-10-minutes](https://cloud.google.com/blog/topics/developers-practitioners/build-and-deploy-a-remote-mcp-server-to-google-cloud-run-in-under-10-minutes)\n2. Use:\n   * Transport: `streamable-http`\n   * Endpoint: Public URL of Cloud Run MCP server\n3. Attempt to connect using \u003ccloud_run_url\u003e/mcp\n4. Observe: API status remains in `pending` and no data is received\n\n---\n\n### Observations\n\n* Switching transport to **SSE** resolves the issue.\n* Using a **Cloud Proxy** to access the MCP server also works with streamable-http.\n* **JS SDK** does not face this issue under the same deployment conditions.\n* The Cloud Run URL is publicly accessible and works with other tools.\n\n---\n\n### Environment\n\n* SDK: `python-sdk` (v1.9.4)\n* MCP Server: Deployed on Cloud Run\n* Python version: \\[3.12.11]\n* OS - Docker image: \\[linux/amd64]\n\n---\n\n### Expected Behavior\n\nThe SDK should establish a connection to the Cloud Run-hosted MCP server and transition the API status from pending to active.\n\n---\n\n### Additional Notes\n\nThis might point to either:\n\n* SDK's HTTP streaming implementation not being fully compatible with Cloud Run’s networking behavior\n* Some internal headers or keep-alive expectations that differ between SSE and streamable-http\n\nAny guidance, workaround, or fix would be appreciated.\n\n\n### Example Code\n\n```Python\nfrom mcp.server.fastmcp import FastMCP\n\n# Create server\nmcp = FastMCP(\"Echo Server\")\n\n\n@mcp.tool()\ndef echo(text: str) -\u003e str:\n    \"\"\"Echo the input text\"\"\"\n    return text\n\n\ndef main():\n    mcp.run(transport=\"streamable-http\", host=\"0.0.0.0\", port=8080)\n\n\nif __name__ == \"__main__\":\n    main()\n```\n\n### Python \u0026 MCP Python SDK\n\n```Text\nSDK Version: 1.9.4\nPython Version: 3.12.11\n```","author":{"url":"https://github.com/sidgangs99","@type":"Person","name":"sidgangs99"},"datePublished":"2025-06-28T15:29:19.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/1053/python-sdk/issues/1053"}