diff --git a/chatkit/server.py b/chatkit/server.py
index 12f13ca..4ad02ad 100644
--- a/chatkit/server.py
+++ b/chatkit/server.py
@@ -1,4 +1,5 @@
 import asyncio
+import base64
 from abc import ABC, abstractmethod
 from collections.abc import AsyncIterator
 from contextlib import contextmanager
@@ -41,6 +42,7 @@
     ErrorEvent,
     FeedbackKind,
     HiddenContextItem,
+    InputTranscribeReq,
     ItemsFeedbackReq,
     ItemsListReq,
     NonStreamingReq,
@@ -69,6 +71,7 @@
     ThreadStreamEvent,
     ThreadsUpdateReq,
     ThreadUpdatedEvent,
+    TranscriptionResult,
     UserMessageInput,
     UserMessageItem,
     WidgetComponentUpdated,
@@ -319,6 +322,14 @@ async def add_feedback(  # noqa: B027
         """Persist user feedback for one or more thread items."""
         pass
 
+    async def transcribe(  # noqa: B027
+        self, audio_bytes: bytes, mime_type: str, context: TContext
+    ) -> TranscriptionResult:
+        """Transcribe speech audio to text. Override this method to support dictation."""
+        raise NotImplementedError(
+            "transcribe() must be overridden to support the input.transcribe request."
+        )
+
     def action(
         self,
         thread: ThreadMetadata,
@@ -446,6 +457,12 @@ async def _process_non_streaming(
                     request.params.attachment_id, context=context
                 )
                 return b"{}"
+            case InputTranscribeReq():
+                audio_bytes = base64.b64decode(request.params.audio_base64)
+                transcription_result = await self.transcribe(
+                    audio_bytes, request.params.mime_type, context=context
+                )
+                return self._serialize(transcription_result)
             case ItemsListReq():
                 items_list_params = request.params
                 items = await self.store.load_thread_items(
diff --git a/chatkit/types.py b/chatkit/types.py
index cbb5900..217deec 100644
--- a/chatkit/types.py
+++ b/chatkit/types.py
@@ -174,6 +174,29 @@ class AttachmentCreateParams(BaseModel):
     mime_type: str
 
 
+class InputTranscribeReq(BaseReq):
+    """Request to transcribe an audio payload into text."""
+
+    type: Literal["input.transcribe"] = "input.transcribe"
+    params: InputTranscribeParams
+
+
+class InputTranscribeParams(BaseModel):
+    """Parameters for speech transcription."""
+
+    audio_base64: str
+    """Base64-encoded audio bytes."""
+
+    mime_type: str
+    """MIME type for the audio payload (e.g. 'audio/webm', 'audio/wav')."""
+
+
+class TranscriptionResult(BaseModel):
+    """Input speech transcription result."""
+
+    text: str
+
+
 class ItemsListReq(BaseReq):
     """Request to list items inside a thread."""
 
@@ -236,6 +259,7 @@ class ThreadDeleteParams(BaseModel):
     | AttachmentsDeleteReq
     | ThreadsUpdateReq
     | ThreadsDeleteReq
+    | InputTranscribeReq
 )
 """Union of request types that yield immediate responses."""
 
diff --git a/tests/test_chatkit_server.py b/tests/test_chatkit_server.py
index f6797fa..e0d03eb 100644
--- a/tests/test_chatkit_server.py
+++ b/tests/test_chatkit_server.py
@@ -1,4 +1,5 @@
 import asyncio
+import base64
 import sqlite3
 from contextlib import contextmanager
 from datetime import datetime
@@ -38,6 +39,8 @@
     FileAttachment,
     ImageAttachment,
     InferenceOptions,
+    InputTranscribeParams,
+    InputTranscribeReq,
     ItemFeedbackParams,
     ItemsFeedbackReq,
     ItemsListParams,
@@ -75,6 +78,7 @@
     ThreadUpdatedEvent,
     ThreadUpdateParams,
     ToolChoice,
+    TranscriptionResult,
     UserMessageInput,
     UserMessageItem,
     UserMessageTextContent,
@@ -156,6 +160,7 @@ def make_server(
     ]
     | None = None,
     file_store: AttachmentStore | None = None,
+    transcribe_callback: Callable[[bytes, str, Any], TranscriptionResult] | None = None,
 ):
     global server_id
     db_path = f"file:{server_id}?mode=memory&cache=shared"
@@ -203,6 +208,13 @@ async def add_feedback(
                 return
             handle_feedback(thread_id, item_ids, feedback, context)
 
+        async def transcribe(
+            self, audio_bytes: bytes, mime_type: str, context: Any
+        ) -> TranscriptionResult:
+            if transcribe_callback is None:
+                return await super().transcribe(audio_bytes, mime_type, context)
+            return transcribe_callback(audio_bytes, mime_type, context)
+
         async def process_streaming(
             self, request_obj, context: Any | None = None
         ) -> list[ThreadStreamEvent]:
@@ -1843,6 +1855,36 @@ async def responder(
         assert any(e.type == "thread.item.done" for e in events)
 
 
+async def test_input_transcribe_decodes_base64_and_passes_mime_type():
+    audio_bytes = b"hello audio"
+    audio_b64 = base64.b64encode(audio_bytes).decode("ascii")
+    seen: dict[str, Any] = {}
+
+    def transcribe_callback(
+        audio: bytes, mime: str, context: Any
+    ) -> TranscriptionResult:
+        seen["audio"] = audio
+        seen["mime"] = mime
+        seen["context"] = context
+        return TranscriptionResult(text="ok")
+
+    with make_server(transcribe_callback=transcribe_callback) as server:
+        result = await server.process_non_streaming(
+            InputTranscribeReq(
+                params=InputTranscribeParams(
+                    audio_base64=audio_b64,
+                    mime_type="audio/wav",
+                )
+            )
+        )
+        parsed = TypeAdapter(TranscriptionResult).validate_json(result.json)
+        assert parsed.text == "ok"
+
+    assert seen["audio"] == audio_bytes
+    assert seen["mime"] == "audio/wav"
+    assert seen["context"] == DEFAULT_CONTEXT
+
+
 async def test_retry_after_item_passes_tools_to_responder():
     pass