diff --git a/tests/issues/test_2001_progress_related_request_id.py b/tests/issues/test_2001_progress_related_request_id.py
new file mode 100644
index 0000000000..b12269c836
--- /dev/null
+++ b/tests/issues/test_2001_progress_related_request_id.py
@@ -0,0 +1,103 @@
+# Regression test for issue #2001 - progress notifications via SSE in stateless HTTP
+# Root cause: send_progress_notification() called without related_request_id.
+# Fix: pass related_request_id=self.request_id - see mcpserver/context.py
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from mcp.server.context import ServerRequestContext
+from mcp.server.experimental.request_context import Experimental
+from mcp.server.mcpserver import Context
+
+pytestmark = pytest.mark.anyio
+
+
+async def test_report_progress_passes_related_request_id() -> None:
+    """report_progress must forward request_id as related_request_id."""
+    mock_session = AsyncMock()
+    mock_session.send_progress_notification = AsyncMock()
+
+    request_context = ServerRequestContext(
+        request_id="req-2001",
+        session=mock_session,
+        meta={"progress_token": "tok-progress"},
+        lifespan_context=None,
+        experimental=Experimental(),
+    )
+
+    ctx = Context(request_context=request_context, mcp_server=MagicMock())
+
+    await ctx.report_progress(25, 100, message="quarter done")
+    await ctx.report_progress(50, 100)
+    await ctx.report_progress(100, 100, message="complete")
+
+    assert mock_session.send_progress_notification.call_count == 3
+
+    mock_session.send_progress_notification.assert_any_call(
+        progress_token="tok-progress",
+        progress=25.0,
+        total=100.0,
+        message="quarter done",
+        related_request_id="req-2001",
+    )
+    mock_session.send_progress_notification.assert_any_call(
+        progress_token="tok-progress",
+        progress=50.0,
+        total=100.0,
+        message=None,
+        related_request_id="req-2001",
+    )
+    mock_session.send_progress_notification.assert_any_call(
+        progress_token="tok-progress",
+        progress=100.0,
+        total=100.0,
+        message="complete",
+        related_request_id="req-2001",
+    )
+
+
+async def test_report_progress_no_token_skips_notification() -> None:
+    """report_progress is a no-op when no progress_token is present."""
+    mock_session = AsyncMock()
+    mock_session.send_progress_notification = AsyncMock()
+
+    request_context = ServerRequestContext(
+        request_id="req-no-token",
+        session=mock_session,
+        meta={},
+        lifespan_context=None,
+        experimental=Experimental(),
+    )
+
+    ctx = Context(request_context=request_context, mcp_server=MagicMock())
+
+    await ctx.report_progress(50, 100)
+
+    mock_session.send_progress_notification.assert_not_called()
+
+
+async def test_report_progress_integer_token() -> None:
+    """report_progress works when progress_token is an integer (e.g. 0)."""
+    mock_session = AsyncMock()
+    mock_session.send_progress_notification = AsyncMock()
+
+    request_context = ServerRequestContext(
+        request_id="req-int-token",
+        session=mock_session,
+        meta={"progress_token": 0},
+        lifespan_context=None,
+        experimental=Experimental(),
+    )
+
+    ctx = Context(request_context=request_context, mcp_server=MagicMock())
+
+    await ctx.report_progress(1, 10)
+
+    mock_session.send_progress_notification.assert_awaited_once_with(
+        progress_token=0,
+        progress=1.0,
+        total=10.0,
+        message=None,
+        related_request_id="req-int-token",
+    )