diff --git a/src/harness_sdk/instrumentation/anthropic/__init__.py b/src/harness_sdk/instrumentation/anthropic/__init__.py
index 725ff55..8afcbd0 100644
--- a/src/harness_sdk/instrumentation/anthropic/__init__.py
+++ b/src/harness_sdk/instrumentation/anthropic/__init__.py
@@ -5,6 +5,7 @@
 Coverage:
   - Messages.create / AsyncMessages.create  (non-streaming and stream=True)
   - Messages.stream  / AsyncMessages.stream  (MessageStream API)
+  - AnthropicVertex / AsyncAnthropicVertex, including LangChain ChatAnthropicVertex
 
 The OTEL contrib ``AnthropicInstrumentor.instrument()`` only handles non-streaming
 ``Messages.create``; we call its inner ``messages_create(handler)`` wrapper directly
@@ -45,7 +46,32 @@
 logger = get_custom_logger(__name__)
 
 _ANTHROPIC_MESSAGES_MODULE = "anthropic.resources.messages"
-_ANTHROPIC = "anthropic"
+_PROVIDER_ANTHROPIC = "anthropic"
+_PROVIDER_VERTEX = "gcp.vertex_ai"
+
+
+def _resolve_provider(messages_instance: Any) -> str:
+    """Detect AnthropicVertex vs direct Anthropic API from Messages._client."""
+    client = getattr(messages_instance, "_client", None)
+    if client is None:
+        return _PROVIDER_ANTHROPIC
+    cls_name = type(client).__name__
+    if cls_name in ("AnthropicVertex", "AsyncAnthropicVertex"):
+        return _PROVIDER_VERTEX
+    return _PROVIDER_ANTHROPIC
+
+
+def _apply_vertex_client_attributes(attributes: dict[str, Any], messages_instance: Any) -> None:
+    """Best-effort gcp.project / gcp.location from AnthropicVertex client."""
+    client = getattr(messages_instance, "_client", None)
+    if client is None:
+        return
+    project = getattr(client, "project_id", None)
+    region = getattr(client, "region", None)
+    if project:
+        attributes["gcp.project"] = project
+    if region:
+        attributes["gcp.location"] = region
 
 
 def _get_handler() -> TelemetryHandler:
@@ -85,11 +111,14 @@ def _build_invocation(
     capture_content: bool,
 ) -> LLMInvocation:
     attributes = get_llm_request_attributes(params, instance)
+    provider = _resolve_provider(instance)
+    if provider == _PROVIDER_VERTEX:
+        _apply_vertex_client_attributes(attributes, instance)
     model_attr = attributes.get("gen_ai.request.model")
     request_model = model_attr if isinstance(model_attr, str) else params.model
     invocation = LLMInvocation(
         request_model=request_model,
-        provider=_ANTHROPIC,
+        provider=provider,
         input_messages=get_input_messages(params.messages) if capture_content else [],
         system_instruction=get_system_instruction(params.system) if capture_content else [],
         attributes=attributes,
diff --git a/test/instrumentation/anthropic/test_anthropic.py b/test/instrumentation/anthropic/test_anthropic.py
index 6cacc8c..0a94767 100644
--- a/test/instrumentation/anthropic/test_anthropic.py
+++ b/test/instrumentation/anthropic/test_anthropic.py
@@ -11,11 +11,12 @@
 
 pytest.importorskip("anthropic")
 
-from anthropic import Anthropic, AsyncAnthropic
+from anthropic import Anthropic, AnthropicVertex, AsyncAnthropic
 from anthropic.resources.messages import AsyncMessages, Messages
 
 from harness_sdk.plugins.control import ControlResult, get_control_registry
 from harness_sdk.gen_ai.exceptions import ControlEvaluationBlocked
+from harness_sdk.instrumentation import anthropic as anthropic_instrumentation
 from harness_sdk.instrumentation.anthropic import AnthropicInstrumentorWrapper
 
 
@@ -48,6 +49,34 @@ def _fake_messages_create(_self, *_args, **_kwargs):
     return _FakeMessage()
 
 
+def test_resolve_provider_detects_anthropic_vertex():
+    vertex_client = type("AnthropicVertex", (SimpleNamespace,), {})()
+    messages = SimpleNamespace(_client=vertex_client)
+
+    assert anthropic_instrumentation._resolve_provider(messages) == "gcp.vertex_ai"
+
+
+def test_resolve_provider_defaults_to_anthropic():
+    anthropic_client = type("Anthropic", (SimpleNamespace,), {})()
+    messages = SimpleNamespace(_client=anthropic_client)
+
+    assert anthropic_instrumentation._resolve_provider(messages) == "anthropic"
+
+
+def test_apply_vertex_client_attributes():
+    vertex_client = type("AnthropicVertex", (SimpleNamespace,), {})(
+        project_id="my-proj",
+        region="us-east5",
+    )
+    messages = SimpleNamespace(_client=vertex_client)
+    attributes = {}
+
+    anthropic_instrumentation._apply_vertex_client_attributes(attributes, messages)
+
+    assert attributes["gcp.project"] == "my-proj"
+    assert attributes["gcp.location"] == "us-east5"
+
+
 def test_anthropic_span_has_gen_ai_attributes(agent, exporter, anthropic_instrumentor):
     with patch.object(Messages, "create", new=_fake_messages_create):
         anthropic_instrumentor.instrument()
@@ -63,6 +92,7 @@ def test_anthropic_span_has_gen_ai_attributes(agent, exporter, anthropic_instrum
     assert len(spans) == 1
     attrs = spans[0].attributes
     assert attrs.get("gen_ai.system") == "anthropic"
+    assert attrs.get("gen_ai.provider.name") == "anthropic"
     assert attrs.get("gen_ai.operation.name") == "chat"
     assert attrs.get("gen_ai.request.model") == "claude-3-haiku-20240307"
     assert attrs.get("gen_ai.response.id") == "msg_test"
@@ -70,6 +100,27 @@ def test_anthropic_span_has_gen_ai_attributes(agent, exporter, anthropic_instrum
     assert attrs.get("gen_ai.usage.output_tokens") == 4
 
 
+def test_anthropic_vertex_span_has_provider_and_gcp_attributes(
+    agent, exporter, anthropic_instrumentor
+):
+    with patch.object(Messages, "create", new=_fake_messages_create):
+        anthropic_instrumentor.instrument()
+        client = AnthropicVertex(project_id="my-proj", region="us-east5")
+        client.messages.create(
+            model="claude-3-5-sonnet@20240620",
+            max_tokens=10,
+            messages=[{"role": "user", "content": "hello"}],
+        )
+
+    spans = exporter.get_finished_spans()
+    exporter.clear()
+    assert len(spans) == 1
+    attrs = spans[0].attributes
+    assert attrs.get("gen_ai.provider.name") == "gcp.vertex_ai"
+    assert attrs.get("gcp.project") == "my-proj"
+    assert attrs.get("gcp.location") == "us-east5"
+
+
 async def test_async_messages_create_span_has_gen_ai_attributes(agent, exporter, anthropic_instrumentor):
     async def _fake(_self, *_args, **_kwargs):
         return _FakeMessage()