diff --git a/unstract/sdk1/src/unstract/sdk1/adapters/base1.py b/unstract/sdk1/src/unstract/sdk1/adapters/base1.py
index c78fe5c43d..467b1ff253 100644
--- a/unstract/sdk1/src/unstract/sdk1/adapters/base1.py
+++ b/unstract/sdk1/src/unstract/sdk1/adapters/base1.py
@@ -6,6 +6,7 @@
 from abc import ABC, abstractmethod
 from importlib import import_module
 from typing import TYPE_CHECKING
+from urllib.parse import urlparse
 
 if TYPE_CHECKING:
     from typing import Any
@@ -372,6 +373,16 @@ def _is_openai_reasoning_model(model: str) -> bool:
     return bool(_OPENAI_REASONING_MODEL_PATTERN.match(model.lower()))
 
 
+def _is_openai_api_endpoint(api_base: str | None) -> bool:
+    """Return True when api_base points at OpenAI's own HTTPS API host."""
+    if not api_base:
+        return False
+    parsed = urlparse(api_base)
+    return (
+        parsed.scheme == "https" and (parsed.hostname or "").lower() == "api.openai.com"
+    )
+
+
 class OpenAICompatibleLLMParameters(BaseChatCompletionParameters):
     """See https://docs.litellm.ai/docs/providers/openai_compatible/."""
 
@@ -463,6 +474,14 @@ def validate(adapter_metadata: dict[str, "Any"]) -> dict[str, "Any"]:
         else:
             validated.pop("reasoning_effort", None)
 
+        # The custom_openai/ prefix has no entry in the cost price map. Strip
+        # it only for OpenAI's own endpoint; other gateways price the same
+        # model name differently, so leave their cost unresolved.
+        if _is_openai_api_endpoint(validated.get("api_base")):
+            validated["cost_model"] = validated["model"][
+                len(_CUSTOM_OPENAI_PROVIDER_PREFIX) :
+            ]
+
         return validated
 
     @staticmethod
diff --git a/unstract/sdk1/tests/test_openai_compatible_adapter.py b/unstract/sdk1/tests/test_openai_compatible_adapter.py
index fb7da31658..d1dd631d2b 100644
--- a/unstract/sdk1/tests/test_openai_compatible_adapter.py
+++ b/unstract/sdk1/tests/test_openai_compatible_adapter.py
@@ -303,6 +303,56 @@ def test_openai_compatible_validate_no_reasoning_unchanged() -> None:
     assert "reasoning_effort" not in validated
 
 
+def test_openai_compatible_validate_sets_cost_model_for_openai_endpoint() -> None:
+    # On OpenAI's endpoint, cost_model drops the prefix so pricing resolves.
+    validated = OpenAICompatibleLLMParameters.validate(
+        {
+            "api_base": "https://api.openai.com/v1",
+            "api_key": "test-key",
+            "model": "gpt-4o",
+        }
+    )
+
+    assert validated["model"] == "custom_openai/gpt-4o"
+    assert validated["cost_model"] == "gpt-4o"
+
+
+def test_openai_compatible_validate_cost_model_keeps_openai_subprefix() -> None:
+    validated = OpenAICompatibleLLMParameters.validate(
+        {
+            "api_base": "https://api.openai.com/v1",
+            "model": "custom_openai/openai/gpt-4o",
+        }
+    )
+
+    assert validated["cost_model"] == "openai/gpt-4o"
+
+
+def test_openai_compatible_validate_no_cost_model_for_other_gateway() -> None:
+    # Non-OpenAI gateways price the same name differently; leave it unresolved.
+    validated = OpenAICompatibleLLMParameters.validate(
+        {
+            "api_base": "https://gateway.example.com/v1",
+            "model": "gpt-4o",
+        }
+    )
+
+    assert "cost_model" not in validated
+
+
+def test_openai_compatible_validate_cost_model_stable_on_revalidation() -> None:
+    # validate() may run on its own previous output; cost_model must survive.
+    first = OpenAICompatibleLLMParameters.validate(
+        {
+            "api_base": "https://api.openai.com/v1",
+            "model": "gpt-4o",
+        }
+    )
+    second = OpenAICompatibleLLMParameters.validate(first)
+
+    assert second["cost_model"] == "gpt-4o"
+
+
 def test_openai_compatible_adapter_uses_distinct_description_and_icon() -> None:
     metadata = OpenAICompatibleLLMAdapter.get_metadata()