diff --git a/hermes_cli/web_server.py b/hermes_cli/web_server.py
index f2ea0bdb78c8..e6acc5542833 100644
--- a/hermes_cli/web_server.py
+++ b/hermes_cli/web_server.py
@@ -11439,6 +11439,15 @@ async def auth_mcp_server(name: str, request: Request, profile: Optional[str] =
             status_code=429,
             detail="Too many MCP OAuth flows are already in progress",
         )
+    if any(
+        flow.server_name == name
+        and flow.status in {"starting", "authorization_required"}
+        for flow in _mcp_oauth_flows.values()
+    ):
+        raise HTTPException(
+            status_code=409,
+            detail=f"MCP OAuth for '{name}' is already in progress",
+        )
     with _profile_scope(profile):
         servers = _get_mcp_servers()
     if name not in servers:
diff --git a/tests/hermes_cli/test_mcp_dashboard_oauth.py b/tests/hermes_cli/test_mcp_dashboard_oauth.py
index 142b4ba54ac1..fdf4be82f15f 100644
--- a/tests/hermes_cli/test_mcp_dashboard_oauth.py
+++ b/tests/hermes_cli/test_mcp_dashboard_oauth.py
@@ -159,6 +159,29 @@ def test_hosted_auth_start_bounds_pending_flow_registry():
     assert response.status_code == 429
 
 
+def test_hosted_auth_rejects_overlapping_flow_for_same_server():
+    from hermes_cli import web_server
+    from tools.mcp_dashboard_oauth import DashboardOAuthFlow
+
+    client = _client()
+    client.post(
+        "/api/mcp/servers",
+        json={"name": "reports", "url": "https://mcp.example/mcp", "auth": "oauth"},
+    )
+    existing = DashboardOAuthFlow(
+        flow_id="existing-reports",
+        server_name="reports",
+        profile="other-profile",
+        redirect_uri="https://agent.example/callback/existing",
+    )
+    web_server._mcp_oauth_flows[existing.flow_id] = existing
+
+    response = client.post("/api/mcp/servers/reports/auth")
+
+    assert response.status_code == 409
+    assert "already in progress" in response.text
+
+
 def test_flow_status_does_not_expose_authorization_code():
     from hermes_cli import web_server
     from tools.mcp_dashboard_oauth import DashboardOAuthFlow
diff --git a/tests/tools/test_mcp_dashboard_oauth.py b/tests/tools/test_mcp_dashboard_oauth.py
index 77e9630e340a..116612668604 100644
--- a/tests/tools/test_mcp_dashboard_oauth.py
+++ b/tests/tools/test_mcp_dashboard_oauth.py
@@ -72,6 +72,28 @@ def test_dashboard_flow_rejects_second_callback():
         flow.deliver_callback(code="second", state="state", error=None)
 
 
+def test_dashboard_flow_cannot_resurrect_after_terminal_error():
+    from tools.mcp_dashboard_oauth import DashboardOAuthFlow
+
+    flow = DashboardOAuthFlow(
+        flow_id="flow-terminal",
+        server_name="reports",
+        profile=None,
+        redirect_uri="https://agent.example/mcp/oauth/callback/flow-terminal",
+    )
+    flow.mark_error("start timed out")
+
+    with pytest.raises(RuntimeError, match="already ended"):
+        asyncio.run(
+            flow.publish_authorization_url(
+                "https://idp.example/authorize?state=too-late"
+            )
+        )
+
+    assert flow.status == "error"
+    assert flow.authorization_url is None
+
+
 def test_dashboard_context_overrides_redirect_and_handlers():
     from tools.mcp_dashboard_oauth import (
         DashboardOAuthFlow,
diff --git a/tools/mcp_dashboard_oauth.py b/tools/mcp_dashboard_oauth.py
index 112049e4b4c2..da2fda39bc7a 100644
--- a/tools/mcp_dashboard_oauth.py
+++ b/tools/mcp_dashboard_oauth.py
@@ -36,6 +36,8 @@ class DashboardOAuthFlow:
     _callback_ready: threading.Event = field(default_factory=threading.Event, init=False, repr=False)
 
     async def publish_authorization_url(self, url: str) -> None:
+        if self.status in {"approved", "error"}:
+            raise RuntimeError("OAuth flow already ended")
         state = parse_qs(urlparse(url).query).get("state", [None])[0]
         if not state:
             raise ValueError("OAuth authorization URL did not include state")