feat(MCP): Set up Sentry error reporting

mcp/pyproject.toml

@@ -11,6 +11,7 @@ dependencies = [
     "opentelemetry-instrumentation-httpx>=0.46b0,<1.0.0", # Trace upstream API calls
     "prometheus-client>=0.21.0,<1.0.0",         # Export Prometheus metrics
     "pydantic-settings>=2.0.0,<3.0.0",          # Environment-driven configuration
+    "sentry-sdk>=2.63.0,<3.0.0",                # Capture errors and tracebacks
 ]
 
 [project.scripts]

mcp/src/flagsmith_mcp/config.py

@@ -9,6 +9,10 @@
 class Settings(BaseSettings):
     model_config = {"use_attribute_docstrings": True}
 
+    environment: Literal["local", "dev", "staging", "production"] = Field(
+        default="local",
+    )
+    """Deployment environment."""
     flagsmith_api_url: str = Field(
         default="https://api.flagsmith.com",
     )
@@ -47,6 +51,10 @@ class Settings(BaseSettings):
     )
     """Public base URL of this MCP server, advertised in OAuth protected-resource
     metadata. Override for HTTP deployments behind a proxy/public hostname."""
+    sentry_dsn: str | None = Field(
+        default=None,
+    )
+    """Sentry DSN for error reporting. Error capture is disabled when unset."""
 
     @model_validator(mode="after")
     def validate_stdio_token(self) -> "Settings":

mcp/src/flagsmith_mcp/server.py

@@ -18,7 +18,11 @@
 from flagsmith_mcp.metrics import PrometheusMiddleware
 from flagsmith_mcp.middleware import RootRouterMiddleware
 from flagsmith_mcp.oauth import FlagsmithResourceAuth
-from flagsmith_mcp.telemetry import propagate_span_attributes, setup_telemetry
+from flagsmith_mcp.telemetry import (
+    propagate_span_attributes,
+    setup_sentry,
+    setup_telemetry,
+)
 
 ROUTE_MAPS = [
     RouteMap(tags={"mcp"}, mcp_type=MCPType.TOOL),
@@ -92,6 +96,7 @@ async def health(request: Request) -> PlainTextResponse:
 def run() -> None:
     settings = config.Settings()
     setup_telemetry(settings)
+    setup_sentry(settings)
     server = create_server(settings)
     if settings.metrics_port is not None:
         start_http_server(settings.metrics_port)

mcp/src/flagsmith_mcp/telemetry.py

@@ -1,4 +1,5 @@
 import httpx
+import sentry_sdk
 from common.core.logging import setup_logging
 from common.core.otel import (
     add_otel_trace_context,
@@ -70,3 +71,13 @@ def setup_telemetry(settings: config.Settings) -> None:
         application_loggers=APPLICATION_LOGGERS,
         otel_processors=otel_processors,
     )
+
+
+def setup_sentry(settings: config.Settings) -> None:
+    """Initialise Sentry for error capture when a DSN is configured."""
+    if not settings.sentry_dsn:
+        return
+    sentry_sdk.init(
+        dsn=settings.sentry_dsn,
+        environment=settings.environment,
+    )

mcp/tests/unit/test_telemetry.py

@@ -117,6 +117,40 @@ def test_client_info_span_processor__outside_request_context__service_identity_o
     )
 
 
+def test_setup_sentry__no_dsn__init_not_called(mocker: MockerFixture) -> None:
+    # Given
+    mocker.patch.dict(os.environ, {}, clear=True)
+    sentry_sdk_mock = mocker.patch.object(telemetry, "sentry_sdk", autospec=True)
+    empty_settings = config.Settings()
+
+    # When
+    telemetry.setup_sentry(empty_settings)
+
+    # Then
+    sentry_sdk_mock.init.assert_not_called()
+
+
+def test_setup_sentry__dsn_set__initialises_error_capture(
+    mocker: MockerFixture,
+) -> None:
+    # Given
+    mocker.patch.dict(os.environ, {}, clear=True)
+    sentry_sdk_mock = mocker.patch.object(telemetry, "sentry_sdk", autospec=True)
+    settings = config.Settings(
+        sentry_dsn="https://public@sentry.example/1",
+        environment="staging",
+    )
+
+    # When
+    telemetry.setup_sentry(settings)
+
+    # Then
+    sentry_sdk_mock.init.assert_called_once_with(
+        dsn="https://public@sentry.example/1",
+        environment="staging",
+    )
+
+
 async def test_propagate_span_attributes__no_recording_span__headers_untouched() -> (
     None
 ):