diff --git a/agent/monitoring/gateway_health_export.py b/agent/monitoring/gateway_health_export.py
index 9295072da98..04fff71a381 100644
--- a/agent/monitoring/gateway_health_export.py
+++ b/agent/monitoring/gateway_health_export.py
@@ -72,6 +72,20 @@ def _safe_resource_attributes(raw: Any) -> Dict[str, str]:
     return attrs
 
 
+def _runtime_resource_attributes(
+    config: Dict[str, Any], *, telemetry_scope: str
+) -> Dict[str, str]:
+    """Build the safe OTLP resource shared by metrics and diagnostic logs."""
+    gh = _gateway_health_config(config)
+    attrs = _safe_resource_attributes(gh.get("resource_attributes"))
+    from agent.monitoring.gateway_health import _safe_instance_id
+
+    attrs["service.name"] = "hermes-gateway"
+    attrs["service.instance.id"] = _safe_instance_id(_install_id(config))
+    attrs["telemetry.scope"] = telemetry_scope
+    return attrs
+
+
 def _diagnostic_log_attributes(event: Dict[str, Any]) -> Dict[str, Any]:
     attrs: Dict[str, Any] = {}
     for key in _DIAGNOSTIC_ATTRIBUTE_KEYS:
@@ -299,9 +313,9 @@ def _start_metric_provider(config: Dict[str, Any], sdk: Dict[str, Any]) -> Any:
     exporter = sdk["OTLPMetricExporter"](endpoint=endpoint, headers=headers or None)
     interval_ms = max(5, int(gh.get("export_interval_seconds", 60))) * 1000
     reader = sdk["PeriodicExportingMetricReader"](exporter, export_interval_millis=interval_ms)
-    resource_attrs = _safe_resource_attributes(gh.get("resource_attributes"))
-    resource_attrs["service.name"] = "hermes-gateway"
-    resource_attrs["telemetry.scope"] = "gateway_health"
+    resource_attrs = _runtime_resource_attributes(
+        config, telemetry_scope="gateway_health"
+    )
     provider = sdk["MeterProvider"](
         metric_readers=[reader],
         resource=sdk["Resource"].create(resource_attrs),
@@ -354,12 +368,11 @@ class GatewayDiagnosticLogStreamer:
 
     def __init__(self, config: Dict[str, Any], sdk: Dict[str, Any]):
         otlp = _otlp_config(config)
-        gh = _gateway_health_config(config)
         headers = _resolve_headers(otlp.get("headers_env"))
         endpoint = _logs_endpoint(str(otlp.get("endpoint")))
-        resource_attrs = _safe_resource_attributes(gh.get("resource_attributes"))
-        resource_attrs["service.name"] = "hermes-gateway"
-        resource_attrs["telemetry.scope"] = "gateway_diagnostics"
+        resource_attrs = _runtime_resource_attributes(
+            config, telemetry_scope="gateway_diagnostics"
+        )
         self._provider = sdk["LoggerProvider"](resource=sdk["Resource"].create(resource_attrs))
         self._processor = sdk["BatchLogRecordProcessor"](
             sdk["OTLPLogExporter"](endpoint=endpoint, headers=headers or None)
diff --git a/agent/monitoring/otlp_exporter.py b/agent/monitoring/otlp_exporter.py
index 27c600dcf8b..c9268b4ee5a 100644
--- a/agent/monitoring/otlp_exporter.py
+++ b/agent/monitoring/otlp_exporter.py
@@ -115,12 +115,20 @@ def build_exporter(config: Dict[str, Any]):
     return sdk["OTLPSpanExporter"](endpoint=endpoint, headers=headers or None)
 
 
+def _resource_attributes(config: Dict[str, Any]) -> Dict[str, str]:
+    from agent.monitoring.gateway_health import _safe_instance_id
+    from agent.monitoring.policy import ensure_install_id
+
+    return {
+        "service.name": "hermes-gateway",
+        "service.instance.id": _safe_instance_id(ensure_install_id(config)),
+        "telemetry.scope": "gateway_monitoring",
+    }
+
+
 def _make_provider(config: Dict[str, Any]):
     sdk = _require_sdk()
-    resource = sdk["Resource"].create({
-        "service.name": "hermes-gateway",
-        "telemetry.scope": "gateway_monitoring",
-    })
+    resource = sdk["Resource"].create(_resource_attributes(config))
     provider = sdk["TracerProvider"](resource=resource)
     processor = sdk["BatchSpanProcessor"](build_exporter(config))
     provider.add_span_processor(processor)
diff --git a/tests/monitoring/test_gateway_health_export.py b/tests/monitoring/test_gateway_health_export.py
index 715de681bf8..363b86cdfc4 100644
--- a/tests/monitoring/test_gateway_health_export.py
+++ b/tests/monitoring/test_gateway_health_export.py
@@ -299,6 +299,28 @@ def test_instance_id_hash_is_stable_and_distinguishes_instances():
     assert "install-1" not in first
 
 
+def test_runtime_resource_attributes_include_stable_hashed_instance():
+    from agent.monitoring.gateway_health_export import _runtime_resource_attributes
+
+    config = {
+        "monitoring": {
+            "install_id": "private-install-id",
+            "gateway_health_export": {
+                "resource_attributes": {"deployment.environment.name": "staging"}
+            },
+        }
+    }
+
+    attrs = _runtime_resource_attributes(config, telemetry_scope="gateway_health")
+
+    assert attrs["service.name"] == "hermes-gateway"
+    assert attrs["service.instance.id"].startswith("sha256:")
+    assert len(attrs["service.instance.id"]) == len("sha256:") + 24
+    assert "private-install-id" not in str(attrs)
+    assert attrs["deployment.environment.name"] == "staging"
+    assert attrs["telemetry.scope"] == "gateway_health"
+
+
 def test_diagnostic_log_attributes_are_allowlisted_redacted_and_profile_free():
     from agent.monitoring.gateway_health_export import _diagnostic_log_attributes
 
diff --git a/tests/monitoring/test_otlp_exporter.py b/tests/monitoring/test_otlp_exporter.py
index 56edd566524..91ba7ede553 100644
--- a/tests/monitoring/test_otlp_exporter.py
+++ b/tests/monitoring/test_otlp_exporter.py
@@ -76,6 +76,18 @@ def test_is_enabled_requires_endpoint_and_flag():
     assert not OE.is_enabled({})
 
 
+def test_trace_resource_includes_stable_hashed_instance():
+    attrs = OE._resource_attributes(
+        {"monitoring": {"install_id": "private-install-id"}}
+    )
+
+    assert attrs["service.name"] == "hermes-gateway"
+    assert attrs["service.instance.id"].startswith("sha256:")
+    assert len(attrs["service.instance.id"]) == len("sha256:") + 24
+    assert "private-install-id" not in str(attrs)
+    assert attrs["telemetry.scope"] == "gateway_monitoring"
+
+
 def test_export_otlp_feature_specs_match_pyproject():
     from tools.lazy_deps import LAZY_DEPS
     import re