diff --git a/nanobot/channels/base.py b/nanobot/channels/base.py
index 30fcd1a..3a5a785 100644
--- a/nanobot/channels/base.py
+++ b/nanobot/channels/base.py
@@ -105,8 +105,9 @@ class BaseChannel(ABC):
         """
         if not self.is_allowed(sender_id):
             logger.warning(
-                f"Access denied for sender {sender_id} on channel {self.name}. "
-                f"Add them to allowFrom list in config to grant access."
+                "Access denied for sender {} on channel {}. "
+                "Add them to allowFrom list in config to grant access.",
+                sender_id, self.name,
             )
             return
         
diff --git a/nanobot/channels/dingtalk.py b/nanobot/channels/dingtalk.py
index b7263b3..09c7714 100644
--- a/nanobot/channels/dingtalk.py
+++ b/nanobot/channels/dingtalk.py
@@ -58,7 +58,8 @@ class NanobotDingTalkHandler(CallbackHandler):
 
             if not content:
                 logger.warning(
-                    f"Received empty or unsupported message type: {chatbot_msg.message_type}"
+                    "Received empty or unsupported message type: {}",
+                    chatbot_msg.message_type,
                 )
                 return AckMessage.STATUS_OK, "OK"
 
@@ -126,7 +127,8 @@ class DingTalkChannel(BaseChannel):
             self._http = httpx.AsyncClient()
 
             logger.info(
-                f"Initializing DingTalk Stream Client with Client ID: {self.config.client_id}..."
+                "Initializing DingTalk Stream Client with Client ID: {}...",
+                self.config.client_id,
             )
             credential = Credential(self.config.client_id, self.config.client_secret)
             self._client = DingTalkStreamClient(credential)
diff --git a/nanobot/channels/slack.py b/nanobot/channels/slack.py
index 79cbe76..4fc1f41 100644
--- a/nanobot/channels/slack.py
+++ b/nanobot/channels/slack.py
@@ -84,11 +84,24 @@ class SlackChannel(BaseChannel):
             channel_type = slack_meta.get("channel_type")
             # Only reply in thread for channel/group messages; DMs don't use threads
             use_thread = thread_ts and channel_type != "im"
-            await self._web_client.chat_postMessage(
-                channel=msg.chat_id,
-                text=self._to_mrkdwn(msg.content),
-                thread_ts=thread_ts if use_thread else None,
-            )
+            thread_ts_param = thread_ts if use_thread else None
+
+            if msg.content:
+                await self._web_client.chat_postMessage(
+                    channel=msg.chat_id,
+                    text=self._to_mrkdwn(msg.content),
+                    thread_ts=thread_ts_param,
+                )
+
+            for media_path in msg.media or []:
+                try:
+                    await self._web_client.files_upload_v2(
+                        channel=msg.chat_id,
+                        file=media_path,
+                        thread_ts=thread_ts_param,
+                    )
+                except Exception as e:
+                    logger.error("Failed to upload file {}: {}", media_path, e)
         except Exception as e:
             logger.error("Error sending Slack message: {}", e)
 
diff --git a/nanobot/providers/litellm_provider.py b/nanobot/providers/litellm_provider.py
index edeb5c6..58c9ac2 100644
--- a/nanobot/providers/litellm_provider.py
+++ b/nanobot/providers/litellm_provider.py
@@ -111,7 +111,7 @@ class LiteLLMProvider(LLMProvider):
     def _supports_cache_control(self, model: str) -> bool:
         """Return True when the provider supports cache_control on content blocks."""
         if self._gateway is not None:
-            return False
+            return self._gateway.supports_prompt_caching
         spec = find_by_model(model)
         return spec is not None and spec.supports_prompt_caching
 
diff --git a/nanobot/providers/registry.py b/nanobot/providers/registry.py
index 445d977..ecf092f 100644
--- a/nanobot/providers/registry.py
+++ b/nanobot/providers/registry.py
@@ -100,6 +100,7 @@ PROVIDERS: tuple[ProviderSpec, ...] = (
         default_api_base="https://openrouter.ai/api/v1",
         strip_model_prefix=False,
         model_overrides=(),
+        supports_prompt_caching=True,
     ),
 
     # AiHubMix: global gateway, OpenAI-compatible interface.