diff --git a/README.md b/README.md
index 0b93cba..81eed51 100644
--- a/README.md
+++ b/README.md
@@ -468,6 +468,19 @@ print(response.output_text)
 for item in response.output:
     print(item.type)
 
+# Structured input uses the Responses API part types
+response = client.responses.create(
+    model="gpt-5.4",
+    input=[{
+        "type": "message",
+        "role": "user",
+        "content": [
+            {"type": "input_text", "text": "What is in this image?"},
+            {"type": "input_image", "image_url": "https://example.com/cat.png"},
+        ],
+    }],
+)
+
 # With reasoning
 response = client.responses.create(
     model="gpt-5.4",
@@ -606,6 +619,12 @@ the `publish` confirmation value.
 
 ## Changelog
 
+### Unreleased
+- Type Responses API input parts: `ResponseInputText` (`input_text`),
+  `ResponseInputImage` (`input_image`) and `ResponseInputFile` (`input_file`). The old
+  `text` / `image` part types still type-check.
+- Add `budget_tokens` to `ThinkingConfig`.
+
 ### v0.4.0
 - Add `client.audio`: `speech.create()` (binary audio with `write_to_file()`),
   `transcriptions.create()` and `translations.create()` (multipart uploads).
diff --git a/apertis/types/__init__.py b/apertis/types/__init__.py
index 7772b49..34915e1 100644
--- a/apertis/types/__init__.py
+++ b/apertis/types/__init__.py
@@ -59,6 +59,9 @@
     ResponseReasoningContent,
     ResponseUsage,
     ResponseInputItem,
+    ResponseInputText,
+    ResponseInputImage,
+    ResponseInputFile,
     ResponseOutputItem,
     ResponseOutputMessage,
     ResponseOutputText,
@@ -143,6 +146,9 @@
     "ResponseReasoningContent",
     "ResponseUsage",
     "ResponseInputItem",
+    "ResponseInputText",
+    "ResponseInputImage",
+    "ResponseInputFile",
     "ResponseOutputItem",
     "ResponseOutputMessage",
     "ResponseOutputText",
diff --git a/apertis/types/chat.py b/apertis/types/chat.py
index 15275a9..14cb401 100644
--- a/apertis/types/chat.py
+++ b/apertis/types/chat.py
@@ -106,9 +106,13 @@ class ReasoningConfig(TypedDict, total=False):
 
 
 class ThinkingConfig(TypedDict, total=False):
-    """Extended thinking configuration for Gemini models."""
+    """Extended thinking configuration.
+
+    ``budget_tokens`` is read when the request goes to a Claude model.
+    """
 
     type: Literal["enabled", "disabled", "auto"]
+    budget_tokens: int
 
 
 class GeminiThinkingConfig(TypedDict, total=False):
diff --git a/apertis/types/responses.py b/apertis/types/responses.py
index 65a1bfb..e0090a7 100644
--- a/apertis/types/responses.py
+++ b/apertis/types/responses.py
@@ -166,12 +166,46 @@ class ResponseInputImageContent(TypedDict, total=False):
     source: Required[Dict[str, Any]]  # {"type": "base64", "media_type": "...", "data": "..."}
 
 
-ResponseInputContent = Union[ResponseInputTextContent, ResponseInputImageContent]
+class ResponseInputText(TypedDict):
+    """Text part of a Responses API input message."""
+
+    type: Required[Literal["input_text"]]
+    text: Required[str]
+
+
+class ResponseInputImage(TypedDict, total=False):
+    """Image part of a Responses API input message: an ``image_url`` or a ``file_id``."""
+
+    type: Required[Literal["input_image"]]
+    image_url: str  # URL or data URL
+    file_id: str
+    detail: Literal["low", "high", "auto"]
+
+
+class ResponseInputFile(TypedDict, total=False):
+    """File part of a Responses API input message."""
+
+    type: Required[Literal["input_file"]]
+    file_id: str
+    file_data: str  # data URL, e.g. "data:application/pdf;base64,..."
+    file_url: str
+    filename: str
+
+
+# The first three are the Responses API part types; the last two are kept for
+# code written against SDK 0.4.0 and earlier.
+ResponseInputContent = Union[
+    ResponseInputText,
+    ResponseInputImage,
+    ResponseInputFile,
+    ResponseInputTextContent,
+    ResponseInputImageContent,
+]
 
 
 class ResponseInputItem(TypedDict, total=False):
     """Input item for responses."""
 
     type: Required[Literal["message"]]
-    role: Required[Literal["user", "assistant"]]
+    role: Required[Literal["user", "assistant", "system", "developer"]]
     content: Required[Union[str, List[ResponseInputContent]]]
diff --git a/tests/test_responses.py b/tests/test_responses.py
index b020612..135d702 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -2,14 +2,20 @@
 
 from __future__ import annotations
 
+import json
+from typing import List
+
 import httpx
 import pytest
 import respx
 from pydantic import ValidationError
 
 from apertis import Apertis, AsyncApertis
+from apertis.types.chat import ThinkingConfig
 from apertis.types.responses import (
     Response,
+    ResponseInputContent,
+    ResponseInputItem,
     ResponseFunctionToolCall,
     ResponseOutputMessage,
     ResponseOutputRefusal,
@@ -295,3 +301,28 @@ def test_message_with_bad_content_still_fails(self) -> None:
                     "output": [{"type": "message", "id": "m", "role": "assistant"}],
                 }
             )
+
+
+class TestTypedInputParts:
+    """Spec part types are accepted and sent unchanged."""
+
+    @respx.mock
+    def test_input_parts_sent_unchanged(self, client: Apertis) -> None:
+        route = respx.post("https://api.apertis.ai/v1/responses").mock(
+            return_value=httpx.Response(200, json=_REAL_SHAPE)
+        )
+        content: List[ResponseInputContent] = [
+            {"type": "input_text", "text": "Describe both."},
+            {"type": "input_image", "image_url": "https://example.com/cat.png", "detail": "low"},
+            {"type": "input_file", "file_data": "data:application/pdf;base64,JVBERi0=", "filename": "a.pdf"},
+            {"type": "text", "text": "legacy part"},
+        ]
+        item: ResponseInputItem = {"type": "message", "role": "user", "content": content}
+
+        client.responses.create(model="gpt-5.4", input=[item])
+
+        assert json.loads(route.calls[0].request.content)["input"] == [item]
+
+    def test_thinking_budget_tokens_type_checks(self) -> None:
+        thinking: ThinkingConfig = {"type": "enabled", "budget_tokens": 2048}
+        assert thinking["budget_tokens"] == 2048