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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Progress notifications not delivered via SSE in stateless HTTP mode","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## Summary\n\n`Context.report_progress()` notifications are not delivered to clients when using the streamable HTTP transport, while `Context.info()` and other logging methods work correctly.\n\n## Root Cause\n\nIn `src/mcp/server/fastmcp/server.py`, the `report_progress` method does not pass `related_request_id` to `send_progress_notification()`:\n\n```python\nasync def report_progress(self, progress: float, total: float | None = None, message: str | None = None) -\u003e None:\n    progress_token = self.request_context.meta.progressToken if self.request_context.meta else None\n\n    if progress_token is None:\n        return\n\n    await self.request_context.session.send_progress_notification(\n        progress_token=progress_token,\n        progress=progress,\n        total=total,\n        message=message,\n        # related_request_id is missing here\n    )\n```\n\nThe SSE transport uses `related_request_id` in the message metadata to route notifications to the correct client. Without it, progress notifications are silently dropped.\n\nIn contrast, `send_log_message` (used by `info()`, `warning()`, etc.) correctly passes `related_request_id`:\n\n## Fix\n\nAdd `related_request_id=self.request_id` to the `send_progress_notification()` call:\n```python\nawait self.request_context.session.send_progress_notification(\n    progress_token=progress_token,\n    progress=progress,\n    total=total,\n    message=message,\n    related_request_id=self.request_id,\n)\n```\n\n## Reproduction\n\n1. Create a FastMCP server with `stateless_http=True`\n2. In a tool, call both `await ctx.info(\"test\")` and `await ctx.report_progress(0.5, total=1.0, message=\"test\")`\n3. Observe that `info()` messages are delivered via SSE but `report_progress()` messages are not\n\n## Environment\n\n- MCP SDK version: 1.26.0\n- Python version: 3.11\n- Transport: Streamable HTTP (`stateless_http=True`)\n\n### Example Code\n\n```Python\n\n```\n\n### Python \u0026 MCP Python SDK\n\n```Text\n- MCP SDK version: 1.26.0\n- Python version: 3.11\n```","author":{"url":"https://github.com/hubbard-zlee","@type":"Person","name":"hubbard-zlee"},"datePublished":"2026-02-05T18:28:38.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/2001/python-sdk/issues/2001"}