diff --git a/tests/e2e/coverage_registry/mgmt.yaml b/tests/e2e/coverage_registry/mgmt.yaml
index 4fbaac0a2054..a43e71035239 100644
--- a/tests/e2e/coverage_registry/mgmt.yaml
+++ b/tests/e2e/coverage_registry/mgmt.yaml
@@ -66,3 +66,4 @@
 - {id: mgmt.config_override.hashicorp_vault.happy_path, module: mgmt, tier: P2, surface: api, assertions: [happy_path], source: "config_override_endpoints.py", rationale: "Vault integration (smoke)"}
 - {id: mgmt.workflow.list.happy_path, module: mgmt, tier: P2, surface: api, assertions: [happy_path], source: "workflow_management_endpoints.py", rationale: "Workflow tracking (smoke)"}
 - {id: mgmt.credential_migration.check.happy_path, module: mgmt, tier: P2, surface: api, assertions: [happy_path], source: "key_management_endpoints.py:4252", rationale: "Encryption migration (smoke)"}
+- {id: mgmt.credential.new.serves_request, module: mgmt, tier: P1, surface: api, assertions: [serves_request], source: "credential_endpoints/endpoints.py:42", rationale: "Stored credential resolves into a deployment and serves a live /messages request"}
diff --git a/tests/e2e/llm_translation/test_credential_messages_e2e.py b/tests/e2e/llm_translation/test_credential_messages_e2e.py
new file mode 100644
index 000000000000..49ea748430e7
--- /dev/null
+++ b/tests/e2e/llm_translation/test_credential_messages_e2e.py
@@ -0,0 +1,49 @@
+"""Live e2e: stored credentials resolve into a deployment serving /v1/messages."""
+
+from __future__ import annotations
+
+import os
+
+import pytest
+
+from e2e_config import unique_marker
+from e2e_http import require_successful_call
+from endpoints_client import EndpointsClient, MessagesResult
+from lifecycle import ResourceManager
+from models import CredentialCreateBody, LiteLLMParamsBody
+
+pytestmark = pytest.mark.e2e
+
+
+class TestCredentialBackedMessages:
+    @pytest.mark.covers("mgmt.credential.new.serves_request")
+    def test_credential_backed_messages(self, endpoints_client: EndpointsClient, resources: ResourceManager) -> None:
+        marker = unique_marker()
+        credential_name = f"e2e-cred-{marker}"
+        model = f"e2e-cred-messages-{marker}"
+        anthropic_api_key = os.getenv("ANTHROPIC_API_KEY")
+        assert anthropic_api_key, "ANTHROPIC_API_KEY must be set for this live e2e test"
+
+        endpoints_client.proxy.create_credential(
+            CredentialCreateBody(
+                credential_name=credential_name,
+                credential_values={"api_key": anthropic_api_key},
+            )
+        )
+        resources.defer(lambda: endpoints_client.proxy.delete_credential(credential_name))
+
+        model_id = endpoints_client.create_model(
+            model,
+            LiteLLMParamsBody(
+                model="anthropic/claude-haiku-4-5",
+                litellm_credential_name=credential_name,
+            ),
+        )
+        resources.defer(lambda: endpoints_client.delete_model(model_id))
+
+        key = resources.key()
+        result = endpoints_client.messages(key, model, "reply with one word")
+        require_successful_call(result)
+        parsed = MessagesResult.model_validate_json(result.body)
+        assert parsed.role == "assistant", f"unexpected role: {result.body[:300]}"
+        assert parsed.text.strip(), f"/v1/messages returned no text: {result.body[:300]}"
diff --git a/tests/e2e/models.py b/tests/e2e/models.py
index 8d19e2f8965a..ebc0a122721c 100644
--- a/tests/e2e/models.py
+++ b/tests/e2e/models.py
@@ -492,6 +492,7 @@ class LiteLLMParamsBody(BaseModel):
 
     model: str
     api_key: str | None = None
+    litellm_credential_name: str | None = None
     api_base: str | None = None
     api_version: str | None = None
     realtime_protocol: str | None = None
@@ -556,6 +557,16 @@ class ModelDeleteBody(BaseModel):
     id: str
 
 
+class CredentialCreateBody(BaseModel):
+    credential_name: str
+    credential_values: dict[str, str]
+    credential_info: dict[str, str] = {}
+
+
+class CredentialCreateResponse(BaseModel):
+    success: bool
+
+
 # ---------- key / team / user / organization management ----------
 
 
diff --git a/tests/e2e/proxy_client.py b/tests/e2e/proxy_client.py
index 7eb860463757..f10392571936 100644
--- a/tests/e2e/proxy_client.py
+++ b/tests/e2e/proxy_client.py
@@ -31,6 +31,8 @@
     ChatResponse,
     CountTokensBody,
     CountTokensResponse,
+    CredentialCreateBody,
+    CredentialCreateResponse,
     CustomerDeleteBody,
     EmbedBody,
     EmbedResponse,
@@ -219,6 +221,26 @@ def delete_model(self, model_id: str) -> None:
         if not is_ok(result):
             warnings.warn(f"delete_model({model_id!r}) failed: {result}", stacklevel=2)
 
+    def create_credential(self, body: CredentialCreateBody) -> None:
+        unwrap(
+            self.transport.post(
+                "/credentials",
+                headers=self.transport.master,
+                json=body,
+                response_type=CredentialCreateResponse,
+            )
+        )
+
+    def delete_credential(self, credential_name: str) -> None:
+        result = self.transport.delete(
+            f"/credentials/{credential_name}",
+            headers=self.transport.master,
+            json=NoBody(),
+            response_type=NoBody,
+        )
+        if not is_ok(result):
+            warnings.warn(f"delete_credential({credential_name!r}) failed: {result}", stacklevel=2)
+
     # ---- LLM calls ------------------------------------------------------
 
     def chat(self, key: str, body: ChatBody) -> Result[ChatResponse]: