diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2d0b55c..637a028 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,10 +2,15 @@
 
 Notable additions, fixes, or breaking changes to the Freeplay SDK.
 
-## [0.5.11]
+## [0.5.12] - 2026-03-11
 
 ### Fixed
 
+- **`openai_responses` adapter**: Content blocks now use Responses API native types (`input_text`, `input_image`, `input_file`) instead of Chat Completions types (`text`, `image_url`, `file`) which OpenAI rejects.
+
+## [0.5.11]
+
+### Fixed
 - **`tool` role support for OpenAI adapters**: `OpenAIAdapter` and `OpenAIResponsesAdapter` now accept `tool` role messages in history. Previously, tool-use conversation history would crash with `ValueError: role 'tool' is not supported`.
 
 ## [0.5.10]
diff --git a/pyproject.toml b/pyproject.toml
index f8752e0..a5bae49 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "freeplay"
-version = "0.5.11"
+version = "0.5.12"
 description = ""
 authors = [
     {name = "Freeplay Engineering", email = "support@freeplay.ai"},
diff --git a/src/freeplay/resources/adapters.py b/src/freeplay/resources/adapters.py
index 5f2ecb1..4c4d3a0 100644
--- a/src/freeplay/resources/adapters.py
+++ b/src/freeplay/resources/adapters.py
@@ -327,7 +327,7 @@ def __translate_role(role: str) -> str:
             raise ValueError(f"Gemini formatting found unexpected role {role}")
 
 
-class OpenAIResponsesAdapter(OpenAIAdapter):
+class OpenAIResponsesAdapter(LLMAdapter):
     role_support = RoleSupport(
         supported=frozenset({"system", "user", "assistant", "developer", "tool"}),
         coerce_map={},
@@ -336,9 +336,51 @@ class OpenAIResponsesAdapter(OpenAIAdapter):
     def to_llm_syntax(
         self, messages: List[Dict[str, Any]]
     ) -> Union[str, List[Dict[str, Any]]]:
-        formatted = super().to_llm_syntax(messages)
-        assert isinstance(formatted, list)
-        return [{"type": "message", **m} for m in formatted if m["role"] != "system"]
+        result: List[Dict[str, Any]] = []
+        for message in messages:
+            if message["role"] == "system":
+                continue
+            if "has_media" in message and message["has_media"]:
+                result.append(
+                    {
+                        "type": "message",
+                        "role": message["role"],
+                        "content": [
+                            OpenAIResponsesAdapter._map_responses_content(content)
+                            for content in message["content"]
+                        ],
+                    }
+                )
+            else:
+                msg = copy.deepcopy(message)
+                result.append({"type": "message", **msg})
+        return result
+
+    @staticmethod
+    def _map_responses_content(
+        content: Union[TextContent, MediaContentBase64, MediaContentUrl],
+    ) -> Dict[str, Any]:
+        if isinstance(content, TextContent):
+            return {"type": "input_text", "text": content.text}
+        if content.type == "audio":
+            raise ValueError("Audio content is not yet supported by the Responses API")
+        if isinstance(content, MediaContentUrl):
+            if content.type != "image":
+                raise ValueError(
+                    "Message contains a non-image URL, but the Responses API only supports image URLs."
+                )
+            return {"type": "input_image", "image_url": content.url}
+        # Must be MediaContentBase64 at this point
+        if content.type == "file":
+            return {
+                "type": "input_file",
+                "filename": f"{content.slot_name}.{content.content_type.split('/')[-1]}",
+                "file_data": f"data:{content.content_type};base64,{content.data}",
+            }
+        return {
+            "type": "input_image",
+            "image_url": f"data:{content.content_type};base64,{content.data}",
+        }
 
 
 class BedrockConverseAdapter(LLMAdapter):
diff --git a/tests/test_adapters.py b/tests/test_adapters.py
index d40cb2b..302a8cf 100644
--- a/tests/test_adapters.py
+++ b/tests/test_adapters.py
@@ -577,14 +577,51 @@ def test_openai_responses_media(self) -> None:
                     "type": "message",
                     "role": "user",
                     "content": [
-                        {"type": "text", "text": "Take a look at these images!"},
+                        {"type": "input_text", "text": "Take a look at these images!"},
                         {
-                            "type": "image_url",
-                            "image_url": {"url": "https://localhost/image.png"},
+                            "type": "input_image",
+                            "image_url": "https://localhost/image.png",
                         },
                         {
-                            "type": "image_url",
-                            "image_url": {"url": "data:image/png;base64,some-data"},
+                            "type": "input_image",
+                            "image_url": "data:image/png;base64,some-data",
+                        },
+                    ],
+                },
+            ],
+        )
+
+    def test_openai_responses_file_media(self) -> None:
+        messages: List[Dict[str, Any]] = [
+            {
+                "role": "user",
+                "has_media": True,
+                "content": [
+                    TextContent("Check this file"),
+                    MediaContentBase64(
+                        type="file",
+                        content_type="application/pdf",
+                        data="pdf-data",
+                        slot_name="report",
+                    ),
+                ],
+            },
+        ]
+
+        formatted = OpenAIResponsesAdapter().to_llm_syntax(messages)
+
+        self.assertEqual(
+            formatted,
+            [
+                {
+                    "type": "message",
+                    "role": "user",
+                    "content": [
+                        {"type": "input_text", "text": "Check this file"},
+                        {
+                            "type": "input_file",
+                            "filename": "report.pdf",
+                            "file_data": "data:application/pdf;base64,pdf-data",
                         },
                     ],
                 },
diff --git a/uv.lock b/uv.lock
index 8b3a95c..088781a 100644
--- a/uv.lock
+++ b/uv.lock
@@ -353,7 +353,7 @@ wheels = [
 
 [[package]]
 name = "freeplay"
-version = "0.5.11"
+version = "0.5.12"
 source = { editable = "." }
 dependencies = [
     { name = "click", version = "8.1.8", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version < '3.10'" },