Reapply "feat(seer): Attribute autofix referrer to MCP for MCP requests (#117521)" (#117735)

Relands #117521 ("feat(seer): Attribute autofix referrer to MCP for MCP
requests"), which was reverted in 3a75f61.

Attributes the autofix referrer to MCP for requests originating from the
official Sentry MCP server, and centralizes MCP request detection in a
shared `is_mcp_request` helper in `sentry.utils.http`.

Agent transcript:
https://claudescope.sentry.dev/share/YnvnJme51BPsRo02v1xZr1dl1u0_fTENx2hxgIcuo5A

Author: chromy

src/sentry/issues/action_log/base.py

@@ -18,6 +18,7 @@
 from sentry.users.models.user import User
 from sentry.users.services.user import RpcUser
 from sentry.utils import metrics
+from sentry.utils.http import is_mcp_request
 
 logger = logging.getLogger(__name__)
 
@@ -31,7 +32,6 @@
 # If you're adding a new caller to an instrumented function (e.g. GroupAssignee.objects.assign),
 # wrap it with action_context_scope() so the action gets proper source attribution.
 
-MCP_USER_AGENT_PREFIX = "sentry-mcp/"
 MCP_CLIENT_FAMILY_HEADER = "HTTP_X_SENTRY_MCP_CLIENT_FAMILY"
 SEER_REFERRER_HEADER = "HTTP_X_SEER_REFERRER"
 
@@ -77,7 +77,7 @@ def resolve_action_source(request: Request) -> str:
     """
     user_agent = request.META.get("HTTP_USER_AGENT", "")
 
-    if user_agent.startswith(MCP_USER_AGENT_PREFIX):
+    if is_mcp_request(request):
         family = request.META.get(MCP_CLIENT_FAMILY_HEADER, "").strip().lower()
         if family in KNOWN_MCP_CLIENT_FAMILIES:
             return f"{ActionSource.MCP}:{family}"

src/sentry/issues/endpoints/group_details.py

@@ -48,7 +48,6 @@
     resolve_action_actor,
     resolve_action_source,
 )
-from sentry.issues.action_log.base import MCP_USER_AGENT_PREFIX
 from sentry.issues.action_log.types import ViewAction
 from sentry.issues.constants import (
     ISSUE_VIEW_CACHE_KEY_TTL,
@@ -76,6 +75,7 @@
 from sentry.types.ratelimit import RateLimit, RateLimitCategory
 from sentry.users.services.user.service import user_service
 from sentry.utils import metrics
+from sentry.utils.http import is_mcp_request
 
 logger = logging.getLogger(__name__)
 
@@ -506,8 +506,7 @@ def send_issue_view_attribution(request: Request, response: Response, group: Any
     if not isinstance(group, Group):
         return
 
-    user_agent = request.META.get("HTTP_USER_AGENT", "")
-    if isinstance(user_agent, str) and user_agent.startswith(MCP_USER_AGENT_PREFIX):
+    if is_mcp_request(request):
         client_family = request.headers.get("x-sentry-mcp-client-family") or "unknown"
         analytics.record(
             IssueViewedEvent(

src/sentry/seer/endpoints/group_ai_autofix.py

@@ -70,6 +70,7 @@
 from sentry.seer.models import SeerPermissionError
 from sentry.types.ratelimit import RateLimit, RateLimitCategory
 from sentry.users.services.user.service import user_service
+from sentry.utils.http import is_mcp_request
 
 logger = logging.getLogger(__name__)
 
@@ -80,8 +81,12 @@ def _is_unknown_run_id_error(error: SeerPermissionError) -> bool:
     return getattr(error, "message", None) == UNKNOWN_RUN_ID_FOR_GROUP
 
 
-def _parse_autofix_referrer(raw: str | None) -> AutofixReferrer:
+def _parse_autofix_referrer(raw: str | None, request: Request) -> AutofixReferrer:
     if raw is None:
+        # Fall back to the request origin: requests from the Sentry MCP server are
+        # attributed to MCP, everything else to the generic endpoint referrer.
+        if is_mcp_request(request):
+            return AutofixReferrer.MCP
         return AutofixReferrer.GROUP_AUTOFIX_ENDPOINT
     try:
         return AutofixReferrer(raw)
@@ -268,7 +273,7 @@ def post(
                 handoff_result: AutofixHandoffResponse = trigger_coding_agent_handoff(
                     group=group,
                     run_id=resolved_run_id,
-                    referrer=_parse_autofix_referrer(data.get("referrer")),
+                    referrer=_parse_autofix_referrer(data.get("referrer"), request),
                     integration_id=integration_id,
                     provider=provider,
                     user_id=request.user.id if request.user else None,
@@ -290,7 +295,7 @@ def post(
                 trigger_push_changes(
                     group,
                     resolved_run_id,
-                    referrer=_parse_autofix_referrer(data.get("referrer")),
+                    referrer=_parse_autofix_referrer(data.get("referrer"), request),
                     repo_name=repo_name,
                 )
             except SeerPermissionError:
@@ -341,7 +346,7 @@ def post(
             run_id = trigger_autofix_agent(
                 group=group,
                 step=AutofixStep(step),
-                referrer=_parse_autofix_referrer(data.get("referrer")),
+                referrer=_parse_autofix_referrer(data.get("referrer"), request),
                 stopping_point=AutofixStoppingPoint(stopping_point) if stopping_point else None,
                 run_id=resolved_run_id,
                 user_context=user_context,

src/sentry/utils/http.py

@@ -7,12 +7,17 @@
 from asgiref.sync import sync_to_async
 from django.conf import settings
 from django.http import HttpRequest
+from rest_framework.request import Request
 
 from sentry import options
 
 if TYPE_CHECKING:
     from sentry.models.project import Project
 
+# User-agent prefix set by the official Sentry MCP server (source of truth:
+# getsentry/sentry-mcp). Used to attribute requests originating from the MCP.
+MCP_USER_AGENT_PREFIX = "sentry-mcp/"
+
 
 class ParsedUriMatch(NamedTuple):
     scheme: str
@@ -212,6 +217,14 @@ def origin_from_request(request: HttpRequest) -> str | None:
     return rv
 
 
+def is_mcp_request(request: HttpRequest | Request) -> bool:
+    """
+    Whether the request originated from the official Sentry MCP server, identified
+    by its `sentry-mcp/` user-agent prefix.
+    """
+    return request.META.get("HTTP_USER_AGENT", "").startswith(MCP_USER_AGENT_PREFIX)
+
+
 def percent_encode(val: str) -> str:
     # see https://en.wikipedia.org/wiki/Percent-encoding
     return quote(val).replace("%7E", "~").replace("/", "%2F")

tests/sentry/seer/endpoints/test_group_ai_autofix.py

@@ -177,6 +177,43 @@ def test_post_continue_with_garbage_sentry_run_id_returns_400(self, mock_trigger
         assert response.status_code == 400, response.data
         mock_trigger_explorer.assert_not_called()
 
+    @patch("sentry.seer.endpoints.group_ai_autofix.trigger_autofix_agent")
+    def test_post_from_mcp_defaults_referrer_to_mcp(self, mock_trigger_explorer):
+        """A request from the Sentry MCP server defaults the referrer to api.mcp."""
+        group = self.create_group()
+        mock_trigger_explorer.return_value = 123
+
+        self.login_as(user=self.user)
+        response = self.client.post(
+            self._get_url(group.id),
+            data={"step": "root_cause"},
+            format="json",
+            headers={
+                "user-agent": "sentry-mcp/0.35.0 (https://mcp.sentry.dev)",
+                "X-Sentry-MCP-Client-Family": "cursor",
+            },
+        )
+
+        assert response.status_code == 202, response.data
+        assert mock_trigger_explorer.call_args.kwargs["referrer"] == AutofixReferrer.MCP
+
+    @patch("sentry.seer.endpoints.group_ai_autofix.trigger_autofix_agent")
+    def test_post_explicit_referrer_overrides_mcp_default(self, mock_trigger_explorer):
+        """An explicitly supplied referrer takes precedence over the MCP default."""
+        group = self.create_group()
+        mock_trigger_explorer.return_value = 123
+
+        self.login_as(user=self.user)
+        response = self.client.post(
+            self._get_url(group.id),
+            data={"step": "root_cause", "referrer": AutofixReferrer.WEB.value},
+            format="json",
+            headers={"user-agent": "sentry-mcp/0.35.0 (https://mcp.sentry.dev)"},
+        )
+
+        assert response.status_code == 202, response.data
+        assert mock_trigger_explorer.call_args.kwargs["referrer"] == AutofixReferrer.WEB
+
     @patch("sentry.seer.endpoints.group_ai_autofix.trigger_autofix_agent")
     def test_stopping_point(self, mock_trigger_explorer):
         """Stopping point forces the step to be root_cause"""