fix(policy_engine): keep a policy-added guardrail's other stages when a pipeline steps it

A policy that both adds a guardrail and steps it in a post_call pipeline
used to drop the guardrail from the request's guardrail list outright, so
its pre_call stage never ran. The per-hook loops already skip guardrails
by pipeline mode, so the mode-agnostic subtraction only lost coverage

litellm/proxy/litellm_pre_call_utils.py

@@ -3079,10 +3079,9 @@ def _apply_resolved_guardrails_to_metadata(
     if metadata_variable_name not in data:
         data[metadata_variable_name] = {}
 
-    # Track pipeline-managed guardrails to exclude from independent execution
-    pipeline_managed_guardrails: set = set()
+    # Record the pipelines and the guardrails they step; the hook loops skip those per pipeline mode
     if pipelines:
-        pipeline_managed_guardrails = PolicyResolver.get_pipeline_managed_guardrails(pipelines)
+        pipeline_managed_guardrails: Final = PolicyResolver.get_pipeline_managed_guardrails(pipelines)
         data[metadata_variable_name]["_guardrail_pipelines"] = pipelines
         data[metadata_variable_name]["_pipeline_managed_guardrails"] = pipeline_managed_guardrails
         verbose_proxy_logger.debug(
@@ -3099,10 +3098,8 @@ def _apply_resolved_guardrails_to_metadata(
         existing_guardrails = []
 
     # Combine existing guardrails with policy-resolved guardrails (no duplicates)
-    # Exclude pipeline-managed guardrails from the flat list
     combined = set(existing_guardrails)
     combined.update(resolved_guardrails)
-    combined -= pipeline_managed_guardrails
     data[metadata_variable_name]["guardrails"] = list(combined)
 
     verbose_proxy_logger.debug("Policy engine: added guardrails to request metadata: %s", list(combined))

tests/test_litellm/proxy/test_litellm_pre_call_utils.py

@@ -4148,6 +4148,48 @@ async def test_add_guardrails_from_policy_engine():
     attachment_registry._initialized = False
 
 
+@pytest.mark.asyncio
+async def test_add_guardrails_from_policy_engine_keeps_a_policy_added_guardrail_its_pipeline_also_steps():
+    from litellm.proxy.policy_engine.attachment_registry import get_attachment_registry
+    from litellm.proxy.policy_engine.policy_registry import get_policy_registry
+    from litellm.types.proxy.policy_engine import (
+        GuardrailPipeline,
+        PipelineStep,
+        Policy,
+        PolicyAttachment,
+        PolicyGuardrails,
+    )
+
+    data = {"model": "gpt-4", "messages": [{"role": "user", "content": "Hello"}], "metadata": {}}
+    policy_registry = get_policy_registry()
+    policy_registry._policies = {
+        "response-governance": Policy(
+            guardrails=PolicyGuardrails(add=["pii_blocker"]),
+            pipeline=GuardrailPipeline(mode="post_call", steps=[PipelineStep(guardrail="pii_blocker")]),
+        ),
+    }
+    policy_registry._initialized = True
+    attachment_registry = get_attachment_registry()
+    attachment_registry._attachments = [PolicyAttachment(policy="response-governance", scope="*")]
+    attachment_registry._initialized = True
+
+    try:
+        await add_guardrails_from_policy_engine(
+            data=data,
+            metadata_variable_name="metadata",
+            user_api_key_dict=UserAPIKeyAuth(api_key="test-key"),
+        )
+    finally:
+        policy_registry._policies = {}
+        policy_registry._initialized = False
+        attachment_registry._attachments = []
+        attachment_registry._initialized = False
+
+    assert data["metadata"]["guardrails"] == ["pii_blocker"]
+    assert data["metadata"]["_pipeline_managed_guardrails"] == {"pii_blocker"}
+    assert [pipeline.mode for _policy_name, pipeline in data["metadata"]["_guardrail_pipelines"]] == ["post_call"]
+
+
 @pytest.mark.asyncio
 async def test_add_guardrails_from_policy_engine_accepts_dynamic_policies_and_pops_from_data():
     """