diff --git a/litellm/proxy/guardrails/guardrail_hooks/prompt_security/__init__.py b/litellm/proxy/guardrails/guardrail_hooks/prompt_security/__init__.py
index fa1f9f3d36d..121c38c80a1 100644
--- a/litellm/proxy/guardrails/guardrail_hooks/prompt_security/__init__.py
+++ b/litellm/proxy/guardrails/guardrail_hooks/prompt_security/__init__.py
@@ -20,6 +20,7 @@ def initialize_guardrail(litellm_params: "LitellmParams", guardrail: "Guardrail"
         guardrail_name=guardrail.get("guardrail_name", ""),
         event_hook=litellm_params.mode,
         default_on=litellm_params.default_on,
+        streaming_transform_mode=getattr(litellm_params, "streaming_transform_mode", None),
     )
     litellm.logging_callback_manager.add_litellm_callback(_prompt_security_callback)
 
diff --git a/litellm/proxy/guardrails/guardrail_hooks/prompt_security/prompt_security.py b/litellm/proxy/guardrails/guardrail_hooks/prompt_security/prompt_security.py
index 809d5e0fb31..cfa21064d11 100644
--- a/litellm/proxy/guardrails/guardrail_hooks/prompt_security/prompt_security.py
+++ b/litellm/proxy/guardrails/guardrail_hooks/prompt_security/prompt_security.py
@@ -79,6 +79,7 @@ class PromptSecurityGuardrail(CustomGuardrail):
         user: str | None = None,
         system_prompt: str | None = None,
         check_tool_results: bool | None = None,
+        streaming_transform_mode: Literal["block_only", "incremental_diff"] | None = None,
         **kwargs,
     ):
         kwargs.setdefault("supported_event_hooks", list(self.get_supported_event_hooks()))
@@ -105,6 +106,10 @@ class PromptSecurityGuardrail(CustomGuardrail):
             )
             raise PromptSecurityGuardrailMissingSecrets(msg)
 
+        self.streaming_transform_mode: Literal["block_only", "incremental_diff"] = (
+            "block_only" if streaming_transform_mode is None else streaming_transform_mode
+        )
+
         # Configuration for file sanitization
         self.max_poll_attempts = 30  # Maximum number of polling attempts
         self.poll_interval = 2  # Seconds between polling attempts
diff --git a/tests/test_litellm/proxy/guardrails/test_prompt_security_guardrails.py b/tests/test_litellm/proxy/guardrails/test_prompt_security_guardrails.py
index 26beaa78a46..beb01f20b02 100644
--- a/tests/test_litellm/proxy/guardrails/test_prompt_security_guardrails.py
+++ b/tests/test_litellm/proxy/guardrails/test_prompt_security_guardrails.py
@@ -637,3 +637,35 @@ async def test_check_tool_results_enabled(monkeypatch: pytest.MonkeyPatch):
 
     assert "indirect_prompt_injection" in str(excinfo.value.detail)
 
+
+def test_prompt_security_streaming_transform_mode_from_config(monkeypatch: pytest.MonkeyPatch):
+    """streaming_transform_mode in litellm_params must reach the guardrail instance,
+    otherwise the unified streaming hook stays in block_only and drops redactions."""
+    monkeypatch.setattr(litellm, "guardrail_name_config_map", {})
+    monkeypatch.setattr(litellm, "callbacks", [])
+    monkeypatch.setenv("PROMPT_SECURITY_API_KEY", "test-key")
+    monkeypatch.setenv("PROMPT_SECURITY_API_BASE", "https://test.prompt.security")
+
+    init_guardrails_v2(
+        all_guardrails=[
+            {
+                "guardrail_name": "prompt_security_streaming",
+                "litellm_params": {
+                    "guardrail": "prompt_security",
+                    "mode": "post_call",
+                    "default_on": True,
+                    "streaming_transform_mode": "incremental_diff",
+                },
+            }
+        ],
+        config_file_path="",
+    )
+
+    registered = [c for c in litellm.callbacks if isinstance(c, PromptSecurityGuardrail)]
+    assert len(registered) == 1
+    assert registered[0].streaming_transform_mode == "incremental_diff"
+
+
+def test_prompt_security_streaming_transform_mode_defaults_block_only():
+    guardrail = PromptSecurityGuardrail(api_key="k", api_base="https://test.prompt.security")
+    assert guardrail.streaming_transform_mode == "block_only"