diff --git a/sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/_tracing.py b/sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/_tracing.py
index b1d677ba9f13..b248b7a5ba2a 100644
--- a/sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/_tracing.py
+++ b/sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/_tracing.py
@@ -49,7 +49,7 @@
 _ATTR_GEN_AI_SYSTEM = "gen_ai.system"
 _ATTR_GEN_AI_PROVIDER_NAME = "gen_ai.provider.name"
 _ATTR_GEN_AI_AGENT_ID = "gen_ai.agent.id"
-_ATTR_GEN_AI_AGENT_BLUEPRINT_ID = "gen_ai.agent.blueprint.id"
+_ATTR_GEN_AI_AGENT_BLUEPRINT_ID = "microsoft.a365.agent.blueprint.id"
 _ATTR_GEN_AI_AGENT_TENANT_ID = "microsoft.tenant.id"
 _ATTR_GEN_AI_AGENT_NAME = "gen_ai.agent.name"
 _ATTR_GEN_AI_AGENT_VERSION = "gen_ai.agent.version"
diff --git a/sdk/agentserver/azure-ai-agentserver-core/tests/test_tracing.py b/sdk/agentserver/azure-ai-agentserver-core/tests/test_tracing.py
index 5eefa9ac2a27..600b587afab6 100644
--- a/sdk/agentserver/azure-ai-agentserver-core/tests/test_tracing.py
+++ b/sdk/agentserver/azure-ai-agentserver-core/tests/test_tracing.py
@@ -221,6 +221,21 @@ def test_agent_attrs_survive_framework_overwrite(self) -> None:
         assert attrs["gen_ai.agent.name"] == "my-agent"
         assert attrs["gen_ai.agent.id"] == "my-agent:1.0"
 
+    def test_blueprint_id_uses_correct_attribute_key(self) -> None:
+        """agent_blueprint_id must be emitted under microsoft.a365.agent.blueprint.id."""
+        proc = _FoundryEnrichmentSpanProcessor(
+            agent_name="my-agent", agent_version="1.0",
+            agent_id="my-agent:1.0", agent_blueprint_id="bp-abc-123",
+        )
+        provider, collector = self._create_provider(proc)
+        tracer = provider.get_tracer("test")
+
+        with tracer.start_as_current_span("span"):
+            pass
+
+        attrs = dict(collector.spans[0].attributes)
+        assert attrs["microsoft.a365.agent.blueprint.id"] == "bp-abc-123"
+
     def test_none_fields_are_skipped(self) -> None:
         proc = _FoundryEnrichmentSpanProcessor(
             agent_name=None, agent_version=None,